JP7127402B2 - Fixing device and image forming device - Google Patents

Description

The present invention relates to fixing devices and image forming apparatuses.

In a conventional electrophotographic image forming apparatus, there is disclosed a technique of detecting the temperature of a fixing sleeve using a thermopile, which is a non-contact temperature detection sensor, in a fixing device that fixes toner on a sheet of paper (for example, , Patent Document 1).

In Patent Document 1, airflow is sent from the thermopile to the fixing sleeve as a countermeasure against toner adhesion to the thermopile. Occur.
SUMMARY OF THE INVENTION It is an object of the present invention to provide a fixing device capable of suppressing the occurrence of poor fixing caused by a temperature drop of a fixing member.

A fixing device according to the present invention comprises: a first rotating body having a fixing member; non-contact temperature detecting means for detecting temperature of the first rotating body; In the fixing device for fixing the toner image carried on the recording medium by the nip, the non-contact temperature detecting means is formed after the nip formed in the circumferential direction of the first rotator. An airflow guide member is installed so as to cover the first rotating body in the area up to and is configured not to cover the first rotating body at the position of the non-contact temperature detection means. is configured as a fixing device.

According to the present invention, it is possible to suppress the occurrence of poor fixing caused by the temperature drop of the fixing member.

2 is a diagram for explaining the configuration and operation of the entire image forming apparatus; FIG. FIG. 3 is a diagram illustrating the configuration of a fixing device; It is a figure explaining the thermopile dew condensation problem. It is a figure explaining the countermeasure example (known technique) of the thermopile dew condensation. FIG. 10 is a diagram illustrating a countermeasure configuration (part 1) against a local decrease in the surface temperature of the fixing belt; FIG. 10 is a diagram illustrating a countermeasure configuration (part 2) against a local decrease in the surface temperature of the fixing belt; It is a figure explaining Example 1 of a guide member. It is a figure explaining Example 2 of a guide member. It is a figure explaining Example 3 of a guide member.

Embodiments of a fixing device and an image forming apparatus will be described in detail below with reference to the accompanying drawings. The fixing device and the image forming apparatus according to the present embodiment have the following features with respect to airflow around the thermopile and fixing belt. In short, in the conventional technology, the airflow flowing out from the thermopile hits the fixing belt directly, but in the present embodiment, since the airflow flows from the fixing belt side toward the thermopile, the airflow from the thermopile hits the fixing belt directly. It is characterized by being able to prevent

FIG. 1 is a diagram for explaining the configuration and operation of the entire image forming apparatus according to this embodiment. As shown in FIG. 1, the image forming apparatus 1 in this embodiment is a tandem color printer.

Four toner bottles 102Y, 102M, 102C, and 102K corresponding to respective colors (yellow, magenta, cyan, and black) are detachably (exchangeably) installed in the bottle storage unit 101 above the image forming apparatus main body 1. ing. An intermediate transfer unit 85 is arranged below the bottle accommodating portion 101 . Imaging units 4Y, 4M, 4C, and 4K corresponding to respective colors (yellow, magenta, cyan, and black) are arranged side by side so as to face the intermediate transfer belt 78 of the intermediate transfer unit 85 . Photoreceptor drums 5Y, 5M, 5C and 5K are arranged in the image forming units 4Y, 4M, 4C and 4K, respectively.

Further, a charging section 75, a developing section 76, a cleaning section 77, a neutralizing section (not shown), and the like are arranged around each of the photosensitive drums 5Y, 5M, 5C, and 5K.
Then, an image forming process (charging process, exposure process, development process, transfer process, cleaning process) is performed on each of the photoreceptor drums 5Y, 5M, 5C, and 5K, and each photoreceptor drum 5Y, 5M, 5C, An image of each color is formed on 5K.

The photosensitive drums 5Y, 5M, 5C, and 5K are rotated clockwise in FIG. 1 by a driving motor (not shown). Then, the surfaces of the photosensitive drums 5Y, 5M, 5C, and 5K are uniformly charged at the position of the charging section 75 (charging step). After that, the surfaces of the photosensitive drums 5Y, 5M, 5C, and 5K reach the irradiation position of the laser light L emitted from the exposure unit 3, and an electrostatic latent image corresponding to each color is formed by exposure scanning at this position. (This is the exposure process.)
After that, the surfaces of the photosensitive drums 5Y, 5M, 5C, and 5K reach a position facing the developing device 76, and the electrostatic latent image is developed at this position to form a toner image of each color (developing process is.).

After that, the surfaces of the photoreceptor drums 5Y, 5M, 5C, and 5K reach positions facing the intermediate transfer belt 78 and the first transfer bias rollers 79Y, 79M, 79C, and 79K. , 5C, and 5K are transferred onto the intermediate transfer belt 78 (primary transfer step). At this time, a small amount of untransferred toner remains on the photosensitive drums 5Y, 5M, 5C, and 5K. After that, the surfaces of the photosensitive drums 5Y, 5M, 5C, and 5K reach a position facing the cleaning portion 77, and at this position the untransferred toner remaining on the photosensitive drums 5Y, 5M, 5C, and 5K is removed by the cleaning portion. It is mechanically recovered by the cleaning blade of 77 (cleaning process).

Finally, the surfaces of the photoreceptor drums 5Y, 5M, 5C, and 5K reach a position facing the static elimination unit (not shown), and the residual potential on the photoreceptor drums 5Y, 5M, 5C, and 5K is removed at this position. be. Thus, a series of image forming processes performed on the photosensitive drums 5Y, 5M, 5C, and 5K are completed. After that, the toner images of each color formed on each photosensitive drum through the development process are superimposed and transferred onto the intermediate transfer belt 78 . A color image is thus formed on the intermediate transfer belt 78 .

Here, the intermediate transfer unit 85 includes an intermediate transfer belt 78, four primary transfer bias rollers 79Y, 79M, 79C, and 79K, a secondary transfer backup roller 82, a cleaning backup roller 83, a tension roller 84, and an intermediate transfer cleaning section 80. , etc. The intermediate transfer belt 78 is stretched and supported by three rollers 82 to 84, and is endlessly moved in the direction of the arrow in FIG.

The four primary transfer bias rollers 79Y, 79M, 79C and 79K sandwich the intermediate transfer belt 78 with the photosensitive drums 5Y, 5M, 5C and 5K respectively to form primary transfer nips. A transfer bias opposite in polarity to the toner is applied to the primary transfer bias rollers 79Y, 79M, 79C, and 79K. The intermediate transfer belt 78 runs in the direction of the arrow and sequentially passes through the primary transfer nips of the primary transfer bias rollers 79Y, 79M, 79C, and 79K. In this way, the toner images of the respective colors on the photosensitive drums 5Y, 5M, 5C, and 5K are superimposed on the intermediate transfer belt 78 and primarily transferred. After that, the intermediate transfer belt 78 on which the toner images of each color have been superimposed and transferred reaches a position facing the secondary transfer roller 89 .

At this position, the secondary transfer backup roller 82 sandwiches the intermediate transfer belt 78 with the secondary transfer roller 89 to form a secondary transfer nip. The four-color toner image formed on the intermediate transfer belt 78 is transferred onto the recording medium P conveyed to the position of the secondary transfer nip. At this time, untransferred toner that has not been transferred to the recording medium P remains on the intermediate transfer belt 78 . After that, the intermediate transfer belt 78 reaches the position of the intermediate transfer cleaning station 80 . At this position, untransferred toner on the intermediate transfer belt 78 is collected. Thus, a series of transfer processes performed on the intermediate transfer belt 78 are completed. Here, the recording medium P transported to the position of the secondary transfer nip is transported from the paper feeding unit 12 disposed below the apparatus main body 1 via the paper feeding roller 97, the pair of registration rollers 98, and the like. It is a thing.

Specifically, a plurality of recording media P such as transfer paper are stored in the paper feeding unit 12 in a piled manner. When the paper feed roller 97 is rotated counterclockwise in FIG. 1, the uppermost recording medium P is fed between the rollers of the registration roller pair 98 . The recording medium P conveyed to the registration roller pair 98 temporarily stops at the roller nip position of the registration roller pair 98 whose rotational drive is stopped. Then, the registration roller pair 98 is rotationally driven in time with the color image on the intermediate transfer belt 78, and the recording medium P is conveyed toward the secondary transfer nip. A desired color image is transferred onto the recording medium P in this manner.

After that, the recording medium P onto which the color image has been transferred at the position of the secondary transfer nip is conveyed to the position of the fixing device 20 . At this position, the color image transferred to the surface is fixed on the recording medium P by heat and pressure from the fixing belt 21 and pressure roller 31 . After that, the recording medium P passes between the rollers of the paper ejection roller pair 99 and is ejected to the outside of the apparatus. The recording medium P ejected to the outside of the apparatus by the paper ejection roller pair 99 is sequentially stacked on the stack section 100 as an output image. Thus, a series of image forming processes in the image forming apparatus are 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 FIG.

FIG. 2 is a diagram for explaining the configuration of the fixing device. As shown in FIG. 2, the fixing device 20 includes a fixing belt 21 as a belt member, a nip forming member 26, a heating member 22, a reinforcing member 23 (supporting member), a heater 25 (heat source), and a heating member as a pressure rotating body. It is composed of the pressure roller 31, the temperature sensor 40, the contact/separation mechanisms 51 and 52, and the like. Here, the fixing belt 21 is a thin flexible endless belt, and rotates (runs) in the direction of the arrow (counterclockwise) in FIG.

The fixing belt 21 has a substrate layer, an elastic layer, and a release layer which are sequentially laminated from the inner peripheral surface side, and the total thickness is set to 1 mm or less. The base layer of the fixing belt 21 has a layer thickness of 30 to 100 μm, and is made of a metal material such as nickel or stainless steel or a resin material such as polyimide. The elastic layer of the fixing belt 21 has a layer thickness of 100 to 300 μm and is made of a rubber material such as silicone rubber, foamed silicone rubber, fluororubber, or the like. By providing the elastic layer, minute irregularities are not formed on the surface of the fixing belt 21 at the nip portion, and heat is evenly transferred to the toner image T on the recording medium P, thereby suppressing the generation of the orange peel image.

The release layer of the fixing belt 21 has a layer thickness of 10 to 50 μm and is made of PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer), PTFE (polytetrafluoroethylene), polyimide, polyetherimide, PES ( polyether sulfide), etc. By providing the release layer, the releasability (releasability) of the toner T (toner image) is ensured. Further, the diameter of the fixing belt 21 is set to be 15 to 120 mm. Incidentally, in this embodiment, the diameter of the fixing belt 21 is set to about 30 mm.

Further, the pressure roller 31 as a pressure rotating member that contacts the outer peripheral surface of the fixing belt 21 at the position of the nip portion has a diameter of about 30 to 40 mm, and has an elastic layer 33 on a core metal 32 having a hollow structure. It is formed. The elastic layer 33 of the pressure roller 31 is made of a material such as foamed silicone rubber, silicone rubber, or fluororubber. A thin release layer made of PFA, PTFE, or the like may be provided on the surface layer of the elastic layer 33 . The pressure roller 31 presses against the fixing belt 21 to form a desired nip portion between the two members.

The nip forming member 26 is made of a heat-resistant resin material such as liquid crystal polymer. By providing an elastic member such as silicone rubber or fluororubber between the nip forming member 26 and the fixing belt 21, the belt surface follows minute unevenness on the surface of the recording medium P at the nip portion, thereby The heat is evenly transferred to the toner image T on the P, which is effective in preventing the yuzu-skin image. The nip forming member 26 has a concave cross-sectional shape so that the surface on the pressure roller 31 side follows the curvature of the pressure roller 31 . As a result, since the recording medium P is delivered from the nip part so as to follow the curvature of the pressure roller 31, it is possible to prevent the problem that the recording medium P after the fixing process is attracted to the fixing belt 21 and is not separated. be able to.

In FIG. 2, the cross-sectional shape of the nip forming member 26 that forms the nip portion is concave, but the shape of the nip forming member 26 that forms the nip portion may be formed in a flat shape, or the concave shape may continue from a flat surface. It can also be formed so as to change dynamically. By setting the nip shape to an arbitrary shape, when the shape of the nip portion is substantially parallel to the image surface of the recording medium P, there is an effect of preventing wrinkles from occurring on the recording medium. Further, by approximating the cross-sectional shape to a concave shape, the adhesion between the fixing belt 21 and the recording medium is increased, and the fixability is improved. Furthermore, since the curvature of the fixing belt 21 on the exit side of the nip portion is large, the recording medium fed from the nip portion can be easily separated from the fixing belt 21 .

The heating member 22 is a pipe-shaped member with a thickness of 0.2 mm or less. As a material of the heating member 22, a metal thermal conductor (a metal having thermal conductivity) such as aluminum, iron, stainless steel, etc. can be used. By setting the thickness of the heating member 22 to 0.2 mm or less, the heating efficiency of the fixing belt 21 (heating member 22) can be improved. The heating member 22 is formed so as to be close to or in contact with the inner peripheral surface of the fixing belt 21 at a position other than the nip portion. is provided. Here, the gap A between the fixing belt 21 and the heating member 22 at room temperature (the gap at the position excluding the nip portion) is preferably greater than 0 mm and less than or equal to 1 mm (0 mm<A≦1 mm). .

As a result, the problem of accelerated wear of the fixing belt 21 due to an increase in the area of sliding contact between the heating member 22 and the fixing belt 21 can be prevented, and the heating of the fixing belt 21 due to excessive separation between the heating member 22 and the fixing belt 21 can be prevented. It is possible to prevent the problem that the efficiency is lowered. Furthermore, since the heating member 22 is arranged close to the fixing belt 21, the circular posture of the flexible fixing belt 21 is maintained to some extent, so deterioration and breakage due to deformation of the fixing belt 21 can be reduced. . In order to reduce the sliding resistance between the heating member 22 and the fixing belt 21, the sliding contact surface of the heating member 22 is made of a material with a low coefficient of friction, or the inner peripheral surface 21a of the fixing belt 21 contains fluorine. A surface layer made of material can also be formed.

In FIG. 2, the heating member 22 is formed to have a substantially circular cross-sectional shape, but the heating member 22 can also be formed to have a polygonal cross-sectional shape. Further, if a means for uniformly transmitting heat from the heating source to the belt member and ensuring the running stability of the belt member during driving is separately prepared, the heating member 22 may not be provided and the belt may be operated. It is also possible to construct a fixing device of a direct heating type. In this case, the heat capacity of the heating member 22 is excluded from the heat capacity of the fixing device as a whole.

The reinforcing member 23 (supporting member) serves to reinforce and support the nip forming member 26 that forms the nip portion, and is fixed to the inner peripheral surface of the fixing belt 21 .

Both longitudinal ends of the heating member 22 are fixedly supported by side plates (not shown) of the fixing device 20 . The heating member 22 is heated by radiant heat (radiant light) from the heater 25 to heat the fixing belt 21 . That is, the heating member 22 is directly heated by the heater 25 (heating means), and the fixing belt 21 is indirectly heated by the heater 25 via the heating member 22 . The output control of the heater 25 is performed based on the detection result of the belt surface temperature by a temperature sensor 40 such as a thermopile or a thermistor facing the surface of the fixing belt 21 . Further, the temperature of the fixing belt 21 (fixing temperature) can be set to a desired temperature by controlling the output of the heater 25 in this manner.

Thus, in the fixing device 20, the fixing belt 21 is not only partially heated locally, but the heating member 22 heats the fixing belt 21 almost entirely in the circumferential direction. Even if the speed of the apparatus is increased, the fixing belt 21 is sufficiently heated to prevent the occurrence of defective fixing. Although a halogen heater is used as an example of the heater 25 in FIG. 2, the type of heat source is not limited to the halogen heater, and a fixing device having an induction heating type heat source, for example, may be used.

The reinforcing member 23 is formed to have the same longitudinal length as the nip forming member 26 , and both longitudinal ends thereof are fixedly supported by side plates (not shown) of the fixing device 20 . Further, the reinforcing member 23 contacts the pressure roller 31 via the nip forming member 26 and the fixing belt 21, so that the nip forming member 26 receives the pressure of the pressure roller 31 at the nip portion and is greatly deformed. are deterring. In order to satisfy the functions described above, the reinforcing member 23 is preferably made of a metal material having high mechanical strength such as stainless steel or iron.

Further, when the heater 25 is a heat source such as a halogen heater that uses radiant heat, a heat insulating member may be provided on a part or the whole of the surface of the reinforcing member 23 facing the heater 25, or BA treatment may be performed. A mirror polishing treatment can also be applied. Since the radiant heat (heat for heating the reinforcing member 23) directed from the heater 25 to the reinforcing member 23 is used for heating the heating member 22, the heating efficiency of the fixing belt 21 (heating member 22) is further improved. Become.

The pressure roller 31 is provided with a gear that meshes with a drive gear of a drive mechanism (not shown), and the pressure roller 31 is rotationally driven in the direction of the arrow (clockwise) in FIG. The pressure roller 31 is rotatably supported by side plates (not shown) of the fixing device 20 at both ends in the longitudinal direction via bearings. A heat source such as a halogen heater may be provided inside the pressure roller 31 . Further, when the elastic layer 33 of the pressure roller 31 is formed of a sponge-like material such as foamed silicone rubber, the pressure acting on the nip portion can be reduced, so that the nip forming member 26 is prevented from bending. can be mitigated. Furthermore, the heat insulation of the pressure roller 31 is enhanced, and the heat of the fixing belt 21 is less likely to move to the pressure roller 31 side, so that the heating efficiency of the fixing belt 21 is improved.

2, the diameter of the fixing belt 21 is equal to the diameter of the pressure roller 31, but the diameter of the fixing belt 21 may be smaller than the diameter of the pressure roller 31. can. In this case, since the curvature of the fixing belt 21 at the nip portion is smaller than the curvature of the pressure roller 31 , the recording medium P delivered from the nip portion is easily separated from the fixing belt 21 . Further, the diameter of the fixing belt 21 can be formed to be larger than the diameter of the pressure roller 31. However, regardless of the relationship between the diameter of the fixing belt 21 and the diameter of the pressure roller 31, , does not act on the heating member 22 .

Further, the fixing device 20 is provided with contact/separation mechanisms 51 to 53 for contacting/separating the pressure roller 31 from/to the fixing belt 21 . Specifically, the contact/separation mechanism is composed of a pressure lever 51, an eccentric cam 52, a pressure spring 53, and the like. The pressure lever 51 is rotatably supported by a side plate (not shown) of the fixing device 20 around a support shaft 51a provided at one end.

A central portion of the pressure lever 51 abuts on a bearing of the pressure roller 31 (not shown; movably held in an elongated hole formed in a side plate). A pressure spring 53 is connected to the other end of the pressure lever 51, and a holding plate of the pressure spring 53 is engaged with an eccentric cam 52 (which is rotatable by a drive motor (not shown)). are in agreement. With this configuration, the rotation of the eccentric cam 52 causes the pressure lever 51 to rotate about the support shaft 51a, thereby moving the pressure roller 31 in the direction of the dashed arrow in FIG.

That is, during a normal fixing process, the eccentric cam 52 is in the state shown in FIG. 2, and the pressure roller 31 presses the fixing belt 21 to form a desired nip portion. On the other hand, in times other than the normal fixing process (during jam processing, standby, etc.), the posture of the eccentric cam 52 is rotated 180 degrees from the state shown in FIG. The roller 31 is separated from the fixing belt 21 (or the pressure of the fixing belt 21 is reduced).

The normal operation of the fixing device 20 configured as described above will be briefly described below. When the power switch of the apparatus main body 1 is turned on, power is supplied to the heater 25 and the pressure roller 31 is started to rotate in the direction of the arrow in FIG. As a result, the fixing belt 21 is also driven (rotated) in the direction of the arrow in FIG. After that, the recording medium P is fed from the paper feeding unit 12 , and the unfixed color image is carried (transferred) on the recording medium P at the position of the secondary transfer roller 89 .

The recording medium P bearing the unfixed image T (toner image) is conveyed in the direction of arrow Y10 in FIG. 2 while being guided by a guide plate (not shown). It is fed into the nip. Then, due to the heating by the fixing belt 21 heated by the heating member 22 (heater 25) and the pressing force between the nip forming member 26 reinforced by the reinforcing member 23 and the pressure roller 31, the toner is deposited on the surface of the recording medium P. An image T is fixed. After that, the recording medium P delivered from the nip portion is conveyed in the direction of arrow Y11.

FIG. 3 is a diagram for explaining the thermopile dew condensation problem. In the process of fixing the toner image T onto the recording medium P by the fixing belt 21 and pressure roller 31 heated to a high temperature, water contained in the recording medium P is also heated at the same time and released from the recording medium P as water vapor. Part of the released water vapor is accompanied by the rotation of the fixing belt 21 and fills the inside of the fixing cover 60 covering the fixing belt 21, as shown in FIG. On the other hand, the fixing cover 60 has a hole so that the thermopile 40 does not block the area where the temperature of the fixing belt 21 is read. come.

The temperature of the thermopile 40 gradually rises due to the heat emitted by the fixing device 20 during the printing operation. However, when the printing operation is started first thing in the morning, the temperature of the thermopile 40 is close to room temperature. A difference occurs between the actual temperature of the belt 21 and the detected temperature detected by the thermopile 40 . This causes problems such as poor image quality and, in the worst case, damage due to overheating of the member.

FIG. 4 is a diagram for explaining an example (a known technique) of countermeasures against thermopile condensation. In order to prevent air containing a lot of water vapor from flowing into the thermopile 40, a duct member 70 is provided so that the air flows from the thermopile 40 side to the fixing belt 21 side. As described above, there is already known a technique for causing an airflow generated by an airflow generating device (not shown) or the like to flow from the thermopile 40 side to the fixing belt 21 side. However, in this method, since the airflow from the thermopile 40 directly hits the fixing belt 21, the surface temperature of the fixing belt 21 is locally lowered. This may cause problems such as image defects.

FIG. 5 is a diagram illustrating a configuration (part 1) for countermeasures against a local decrease in the surface temperature of the fixing belt 21. As shown in FIG. As shown in FIG. 5, a guide member 61 that guides the air flowing from the fixing belt 21 is installed on the fixing cover 60 . The guide member 61 is installed so as to guide the airflow generated by the rotation of the fixing belt 21 toward the thermopile 40 . Likewise, from the thermopile 40 side, the airflow generating device generates an airflow toward the fixing belt 21 side. As a result, the airflow from the thermopile 40 side does not directly hit the fixing belt 21 and is discharged outside the unit as indicated by arrow D in FIG.

Specifically, the duct member 70 is provided on the fixing belt 21 side of the thermopile 40 , and the guide member 61 is provided on the thermopile 40 side of the fixing belt 21 . The duct member 70 has a fixing belt 21 side guide 70a and an outer guide 70b provided outside the fixing belt 21 side guide 70a substantially at right angles to the fixing belt 21 side guide 70a. The guide member 61 has such a shape that the air current flowing out from the thermopile 40 through the duct member 70 and the air current flowing along the guide member 61 due to the rotation of the fixing belt 21 are opposed to each other. That is, the guide member 61 includes a fixing belt 21 side guide 61a formed along the fixing belt 21 at substantially the same interval with respect to the fixing belt 21 on the upstream side of the rotation direction of the fixing belt 21, and one end of the guide member 61a. The duct member 70 is fixedly connected to the fixing belt 21 side guide 70a of the duct member 70 at a predetermined angle with the guide 61a and substantially parallel to the fixing belt 21 side guide 70a of the duct member 70, and the other end is fixedly connected to the fixing cover 60. side guide 61b (upstream side).

Thus, the first rotating body having the fixing belt 21, the thermopile 40 which is a non-contact temperature detecting means for detecting the temperature of the first rotating body, and the second rotating body forming a nip with the first rotating body. In the fixing device 20 for fixing a toner image carried on a recording medium by a nip, the thermopile 40 is formed after the nip formed in the circumferential direction of the first rotary body. The fixing belt 21 is provided with an airflow guide member 61 which is installed so as to cover the first rotating body in the area of , and is configured so as not to cover the first rotating body at the position of the thermopile 40 . It is possible to suppress the occurrence of defective fixing caused by the temperature drop of the thermopile 40 , and to prevent condensation on the thermopile 40 without causing the temperature drop of the fixing belt 21 .

That is, the air current flowing out from the thermopile 40 via the duct member 70 and the air current flowing along the guide member 61 due to the rotation of the fixing belt 21, that is, the direction of the fixing belt 21 side guide 70a and the duct member 70 side guide 61b (upstream side). , collide and cancel each other between the thermopile 40 and the fixing belt 21 , and flow out in the D direction, which is the direction of the gap between the duct member 70 and the fixing cover 60 . Therefore, the temperature of the fixing belt 21 is not lowered, and the accuracy of the temperature of the thermopile 40 can be maintained.

Further, the duct member 70 side guide 61b (downstream side) is provided on the downstream side in the rotation direction of the fixing belt 21, and the fixing belt 21 side guide 61a is not provided. By omitting the fixing belt 21 side guide 61a in this way, the weight of the fixing device itself can be reduced.

If the airflow from the thermopile 40 is too strong, it reaches the fixing belt 21 and causes the temperature of the fixing belt 21 to drop. Condensation occurs on the lens of the Therefore, in an airflow generating device (not shown in the drawing) that generates an airflow from the thermopile 40, the airflow from the thermopile 40 is adjusted so that the strength of the airflow from the fixing belt 21 is approximately the same as that from the fixing belt 21. It is desirable to

Further, in order to stably obtain the desired effect at all times, it is necessary to stabilize the air volume from the fixing belt 21 . For this reason, the guide member 61 is provided along the entire longitudinal direction of the fixing belt 21, and the holes through which the air flow flowing out along the guide member 61 due to the rotation of the fixing belt 21 can escape are the same as those of the thermopile 40 in the longitudinal direction and the circumferential direction. position. With such an arrangement, the airflow can stably flow from the fixing belt 21 to the thermopile 40 .

FIG. 6 is a diagram for explaining a countermeasure configuration (part 2) for the local decrease in the surface temperature of the fixing belt 21 . As shown in FIG. 6, the fixing belt 21 side guide 61a' of the guide member 61 has a configuration in which the gap between the fixing belt 21 and the fixing belt 21 gradually widens at positions from immediately after the nip to the thermopile 40 in the circumferential direction of the fixing belt 21. As shown in FIG. ing. With such a configuration, it is possible to reduce the decrease in flow velocity due to the pressure loss of the airflow, so that more air can flow in the direction of the thermopile 40 .

In FIG. 6, on the contrary to the above, a guide member 61 similar to the guide member 61 a on the side of the fixing belt 21 is located downstream from the position of the thermopile 40 in the circumferential direction of the fixing belt 21 . A fixing belt 21 side guide 61c is provided, and the guide has a structure in which the gap between the fixing belt 21 and the fixing belt 21 gradually narrows. With such a configuration, the decrease in flow velocity due to pressure loss can be increased, so the amount of air flowing downstream of the fixing belt 21 can be reduced, and as a result, the amount of air flowing in the direction of the thermopile 40 can be increased. be able to.

That is, in FIG. 6, the guide member 61 and the fixing belt 21 are separated from each other as the portion of the fixing belt 21 closest to the thermopile 40 is approached. The amount of airflow flowing in the direction of the thermopile 40 can be adjusted accordingly.

In this way, in FIG. 6, the gap between the airflow guide member 61 and the first rotor is widened in the area from the post-nip formed in the circumferential direction of the first rotor to the position of the thermopile 40 . Since the shape gradually increases, it is possible to increase the amount of air flowing to the thermopile side by reducing the pressure loss due to the air flow guide. The airflow guide member 61 has a shape in which the gap between the first rotor and the first rotor narrows from the position of the thermopile 40 in the circumferential direction of the first rotor toward the region downstream of the first rotor. Therefore, by increasing the pressure loss caused by the airflow guide, it becomes difficult for air to flow downstream of the fixing belt, and as a result, the amount of air flowing to the thermopile side can be increased.

7A and 7B are diagrams illustrating the first embodiment of the guide member 61. FIG. As already explained, the guide member 61 is shaped to cover the fixing belt 21 . In FIG. 7 , the guide member 61 is provided with a round hole shape 71 only at a portion substantially at the same height and longitudinal position as the thermopile 40 . With such a configuration, the air flowing in the vicinity of the fixing belt 21 along with the rotation of the fixing belt 21 flows out from the hole shape 71 to the thermopile 40 side. A plurality of hole shapes 71 may be provided, but when only one position of the thermopile 40 is provided as shown in FIG.

8A and 8B are diagrams illustrating a second embodiment of the guide member 61. FIG. The hole provided in the guide member 61 is not limited to the hole shape as shown in FIG. For example, as shown in FIG. 8, the same effect as shown in FIG. 7 can be obtained even with a notch shape 81 that is cut only at a portion of the pile 40 at substantially the same height and longitudinal position. be able to.

As shown in FIGS. 7 and 8, the airflow guide member 61 does not cover the first rotor in the longitudinal direction at the position of the thermopile 40 in the circumferential direction of the first rotor. Other regions are shaped to cover the first rotating body. In this way, by providing the airflow guide member 61 with a hole or notch only at the position of the thermopile 40, the airflow is concentrated as compared with the case where the holes or notches are provided at a plurality of positions, so that a stronger airflow can be flowed to the thermopile side. In FIG. 7, the airflow guide member 61 has a hole shape 71 only at the position of the thermopile 40, and the airflow guide member is provided downstream of the fixing belt 21 from the position of the hole. 40 can reliably send a strong airflow.

9A and 9B are diagrams illustrating a third embodiment of the guide member 61. FIG. The guide member 61 can also be configured to have a protruding portion 61d on the lower side, which is the position on the downstream side of the fixing belt 21, with respect to the hole shape shown in FIG. By providing such a projecting portion 61d, the airflow entrained by the fixing belt 21 collides with the projecting portion 61d, and the airflow easily flows from the projecting portion 61d toward the hole shape, that is, toward the thermopile 40 side. , the same effects as those shown in FIGS. 7 and 8 can be obtained.

In a conventional fusing unit, the airflow from the thermopile flows directly to the fusing belt, which lowers the temperature of the fusing belt. At the same time, water vapor generated in the fusing unit flows to the thermopile, causing condensation on the thermopile lens, which causes a shift in the detected temperature. I had a problem. However, in the present embodiment, the airflow from the thermopile to the fixing belt can be optimized with a simple configuration in which the guide member as described above is provided, and the temperature detection accuracy can be improved. Specifically, a guide member is provided for causing the airflow that is rotated along with the rotation of the fixing belt to flow in the direction of the thermopile, and the airflow flows from the fixing belt side toward the thermopile. With such a configuration, the airflow coming from the thermopile is pushed back, and it is possible to prevent the airflow from the thermopile from hitting the fixing belt directly, thereby reducing the influence of the temperature of the fixing belt.

In addition to the configuration shown in the above embodiment, for example, the surface of the airflow guide member 61 facing the first rotor may be made of a member having an infrared reflectance of 90% or more. With such a configuration, the airflow guide member 61 does not absorb the radiant heat from the fixing belt 21, and the heat emitted from the fixing belt is less when the heat is reflected to the fixing belt 21 with higher efficiency, thereby improving energy saving. can be connected to

Further, the airflow guide member 61 may have a width equal to or larger than the passage area of the recording medium in the longitudinal direction. With such a configuration, the guide member 61 exists in the entire paper passing area, and the temperature of the paper passing area can be made uniform.

Moreover, in the area|region near the thermopile 40, it has the structure which flows an airflow toward the direction of a 1st rotating body from the thermopile 40. FIG. That is, if the thermopile 40 is directly exposed to the airflow from the fixing belt 21 , condensation may occur on the thermopile 40 . As a result, dew condensation on the thermopile 40 can be prevented.

The present invention is not limited to the above-described embodiment as it is, and in the implementation stage, the constituent elements may be modified and embodied within the scope of the gist thereof, or the plurality of constituent elements disclosed in the above-described embodiment may be modified. can be implemented in combination as appropriate.

1 Image forming apparatus 20 Fixing device 21 Fixing belt 26 Nip forming member 22 Heating member 23 Reinforcing member 25 Heater 31 Pressure roller 40 Temperature sensor 51, 52 Contact/separation mechanism 60 Fixing cover 61a Fixing belt side guide 61b Duct member side guide 61c Fixing Belt-side guide 61d Protruding portion 70 Duct member 70a Fixing-belt-side guide 70b Outer guide 71 Hole shape 81 Notch shape

JP 2005-241544 A

Claims (8)

a first rotating body having a fixing member;
Non-contact temperature detection means for detecting the temperature of the first rotating body;
Having a second rotating body forming a nip with the first rotating body,
In a fixing device that fixes a toner image carried on a recording medium by the nip,
It is installed so as to cover the first rotating body in a region from the post-nip formed in the circumferential direction of the first rotating body to the non-contact temperature detecting means, and at the position of the non-contact temperature detecting means Having an airflow guide member configured not to cover the first rotating body ,
The gap between the airflow guide member and the first rotating body gradually widens from immediately after the nip formed in the circumferential direction of the first rotating body to the position of the non-contact temperature detecting means. has a curved shape,
A fixing device characterized by: The airflow guide member does not cover the first rotating body at the position of the non-contact temperature detecting means in the circumferential direction of the first rotating body, and does not cover the first rotating body at the position other than the position in the longitudinal direction. having a shape that covers the first rotating body,
2. The fixing device according to claim 1, wherein: The airflow guide member has a hole shape at the position of the non-contact temperature detection means,
3. The fixing device according to claim 1, wherein: A gap between the airflow guide member and the first rotating body becomes narrower from the position of the non-contact temperature detecting means in the circumferential direction of the first rotating body to a downstream region of the first rotating body. has a curved shape ,
The fixing device according to any one of claims 1 to 3 , characterized in that: The surface of the airflow guide member facing the first rotating body is made of a member having an infrared reflectance of 90% or more,
5. The fixing device according to claim 1 , wherein: The airflow guide member has a width equal to or larger than the passage area of the recording medium in the longitudinal direction,
The fixing device according to any one of claims 1 to 5 , characterized in that: In a region near the non-contact temperature detection means, an air current is caused to flow from the non-contact temperature detection means toward the first rotating body.
The fixing device according to any one of claims 1 to 6 , characterized in that: An image forming apparatus comprising the fixing device according to claim 1 .

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