JP6766545B2 - Fixing device, image forming device - Google Patents

Description

The present invention relates to an image forming apparatus in a copier, a printer, a facsimile, or a multifunction device thereof provided with a fixing device and a fixing device.

In an image forming apparatus in a copying machine, a printer, a facsimile, or a multifunction device thereof, a fixing device for fixing an image formed on a recording medium such as paper is provided. In the fixing device, for example, the fixing member heated by the heating member heats and pressurizes the surface of the recording medium, so that the image can be fixed on the recording medium.

In such a fixing device, if the temperature of the fixing member rises excessively, problems such as accelerated deterioration of the fixing member and influence on the quality of the formed image occur. Therefore, a temperature detecting means for the fixing member is provided. The temperature of the fixing member is kept below a predetermined level by various measures such as controlling the temperature of the fixing member.

Further, when the temperature of the fixing member rises excessively, there is a problem of excessive temperature rise in the non-paper-passing region. That is, when small-sized paper is continuously passed through the fixing device, heat is consumed in the paper-passing area of the fixing member to fix the paper and toner on the paper, but non-passing paper. In the region, heat is not taken from the fixing member, so that the temperature of the fixing member rises excessively mainly in the non-paper-passing region at the widthwise end of the fixing member. Particularly in recent years, a fixing member having a low heat capacity has been used from the viewpoint of speeding up the image forming operation and saving energy, and the temperature rise of the fixing member in the non-paper-passing region tends to become a problem.

In response to such a problem, for example, in Patent Document 1 (Japanese Unexamined Patent Publication No. 63-218984), when a predetermined number or more of the minimum size papers are continuously passed, an image is formed for a certain period of time thereafter. The image forming operation of the device is prohibited, and the temperature of the fixing device is prevented from rising excessively.

The temperature rise in the non-passing region is not limited to the case where the small-sized paper described above is passed through the fixing device, but also occurs due to the misalignment of the heating region. That is, in consideration of the thermal expansion of the heating member and the dimensional error, the heating member is supported by providing a certain amount of play with respect to the support member in the axial direction thereof. Therefore, the position of the heating member moves within the range of this backlash, and the heating region also shifts by that amount. Due to such a positional deviation, a non-paper-passing region is generated in the heating region, and the temperature of the fixing member rises excessively at a position corresponding to the non-paper-passing region.

From such a situation, it is an object of the present invention to provide a fixing device capable of accurately positioning a heating member in its axial direction.

In order to solve the above problems, the present invention has a rotating fixing member, a pressure member that rotates in contact with the fixing member, and a heat generating member , and heats the fixing member or the pressure member. A first support member provided on one end side in the axial direction of the heating member and supporting the heating member, and a second support member provided on the other end side in the axial direction of the heating member and supporting the heating member. A fixing device including an urging member that abuts on the other end side in the axial direction of the heating member and urges the heating member toward one end side in the axial direction , and a conducting wire that conducts the heat generating member. The other end in the axial direction of the heating member is provided so as to project from the other end in the axial direction with respect to the second support member, and the lead wire is inserted into the heating member from the other end in the axial direction of the heating member. The urging member is connected to the heat generating member and has an elastic portion that can be elastically deformed, and an insulating member that covers one end side of the elastic portion and abuts on the other end portion in the axial direction of the heating member. It is characterized by.

In the present invention, the urging member abutting on the other end side in the axial direction of the heating member urges the heating member toward one end side in the axial direction. By this urging force, even when the heating member is arranged with play in the axial direction, the heating member can be accurately positioned at a predetermined position in the axial direction.

It is a schematic block diagram of an image forming apparatus. It is sectional drawing which shows the structure of the fixing device. It is a perspective view which shows the structure of a heater and its surroundings. It is a figure which shows the structure of a heater, and the temperature distribution of a fixing belt in an axial direction. It is an enlarged view which shows the detailed structure of the axial end portion of a heater. It is a figure which shows the structure of a heater, and the temperature distribution of a fixing belt in an axial direction. It is sectional drawing which shows the fixing apparatus of 1st Embodiment of this invention. It is sectional drawing which shows the fixing apparatus of 2nd Embodiment of this invention. It is sectional drawing which shows the fixing apparatus of 3rd Embodiment of this invention. It is sectional drawing which shows the fixing apparatus of 4th Embodiment of this invention. It is an enlarged view which shows the detailed structure of the axial end portion of a heater in the said embodiment. It is sectional drawing which shows the fixing apparatus of 5th Embodiment of this invention. It is sectional drawing which shows the fixing device of a different structure.

Hereinafter, embodiments according to the present invention will be described with reference to the drawings. In each figure, the same or corresponding parts are designated by the same reference numerals, and the duplicated description thereof will be appropriately simplified or omitted.

In the center of the color image forming apparatus 1 shown in FIG. 1, an image forming unit 2 to which four process units 9Y, 9M, 9C, and 9Bk are detachably provided is arranged. Each process unit 9Y, 9M, 9C, 9Bk accommodates developers of different colors of yellow (Y), magenta (M), cyan (C), and black (Bk) corresponding to the color separation components of the color image. It has the same configuration except that it is.

Specific process units 9 include a photoconductor drum 10 which is a drum-shaped rotating body capable of carrying toner as a developing agent on the surface, and a charging roller 11 which uniformly charges the surface of the photoconductor drum 10. And a developing device 12 having a developing roller 13 that supplies toner to the surface of the photoconductor drum 10. In FIG. 1, only the photoconductor drum 10, the charging roller 11, and the developing device 12 included in the black process unit 9K are designated by reference numerals, and the reference numerals are omitted in the other process units 9Y, 9M, and 9C. There is.

An exposure unit 3 is arranged below the process unit 9. The exposure unit 3 is configured to emit laser light based on the image data.

Toner bottles 26Y, C, M, and K filled with toners of each color of yellow, cyan, magenta, and black are detachably provided in the bottle accommodating portion 29 at the upper part of the image forming apparatus 1. Then, the toner of each color is replenished to the developing device 12 of each color through the replenishment path provided between the toner bottles 26Y, C, M, K and the developing device 12.

A transfer unit 4 is arranged above the image forming unit 2. The transfer unit 4 includes an endless intermediate transfer belt 16, a primary transfer roller 17 arranged at a position opposite to the photoconductor drum 10 of each process unit 9 with the intermediate transfer belt 16 interposed therebetween, and a secondary transfer roller. It includes 18, a secondary transfer backup roller 14, a cleaning backup roller 15, a tension roller 27, and a belt cleaning device 28.

The intermediate transfer belt 16 is an endless belt, and is stretched by a secondary transfer backup roller 14, a cleaning backup roller 15, and a tension roller 27. Here, by rotationally driving the secondary transfer backup roller 14, the intermediate transfer belt 16 orbits (rotates) in the direction indicated by the arrow in the figure.

Each of the four primary transfer rollers 17 sandwiches an intermediate transfer belt 16 with each of the photoconductor drums 10 to form a primary transfer nip. A power supply is connected to each primary transfer roller 17, and a predetermined direct current voltage (DC) and / or alternating current voltage (AC) is applied to each primary transfer roller 17.

The secondary transfer roller 18 sandwiches the intermediate transfer belt 16 with the secondary transfer backup roller 14 to form a secondary transfer nip. Further, similarly to the primary transfer roller 17, a power supply is also connected to the secondary transfer roller 18, and a predetermined DC voltage (DC) and / or AC voltage (AC) is applied to the secondary transfer roller 18. It has become like.

The belt cleaning device 28 has a cleaning brush and a cleaning blade arranged so as to come into contact with the intermediate transfer belt 16. The waste toner collected by the belt cleaning device 28 is stored in the waste toner container via the waste toner transfer hose.

The paper feed unit 5 is located at the lower part of the image forming apparatus 1, and includes a paper feed cassette 19 containing the paper P as a recording medium, a paper feed roller 20 for carrying out the paper P from the paper feed cassette 19, and the like. ing.

The transport path 6 is a transport path for transporting the paper P carried out from the paper feed section 5, and the transport roller pair is in the middle of the transport path 6 up to the paper discharge section 8 described later in addition to the pair of resist rollers 21. It is arranged appropriately in.

The fixing device 7 has a fixing belt 22 as a fixing member heated by a heating source, a pressure roller 23 as a pressure member capable of pressurizing the fixing belt 22, and the like.

The paper ejection unit 8 is provided at the most downstream side of the transport path 6 of the image forming apparatus 1. The paper ejection unit 8 is provided with a pair of paper ejection rollers 24 for ejecting the paper P to the outside and a paper ejection tray 25 for stocking the ejected paper P.

Hereinafter, the basic operation of the image forming apparatus 1 will be described with reference to FIG.

When the image forming operation is started in the image forming apparatus 1, an electrostatic latent image is formed on the surface of the photoconductor drum 10 of each process unit 9Y, 9C, 9M, 9Bk. The image information exposed by the exposure unit 3 on each photoconductor drum 10 is monochromatic image information obtained by decomposing a desired full-color image into yellow, cyan, magenta, and black color information. An electrostatic latent image is formed on each photoconductor drum 10, and the toner stored in each developing device 12 is supplied to the photoconductor drum 10 by a drum-shaped developing roller 13, so that the electrostatic latent image is formed. It is visualized as a visible toner image (developer image).

In the transfer unit 4, the intermediate transfer belt 16 is driven to travel in the direction of the arrow in FIG. 1 by the rotational drive of the secondary transfer backup roller 14. Further, a constant voltage or a constant current controlled voltage having a polarity opposite to the charging polarity of the toner is applied to each primary transfer roller 17. As a result, a transfer electric field is formed at the primary transfer nip, and the toner images formed on each photoconductor drum 10 are sequentially superimposed and transferred on the intermediate transfer belt 16 at the primary transfer nip.

On the other hand, when the image forming operation is started, in the lower part of the image forming apparatus 1, the paper feeding roller 20 of the paper feeding unit 5 is rotationally driven, so that the paper P housed in the paper feeding cassette 19 is moved to the transport path 6. Be sent out. The paper P sent out to the transport path 6 is timed by the resist roller 21 and sent to the secondary transfer nip between the secondary transfer roller 18 and the secondary transfer backup roller 14. At this time, a transfer voltage having a polarity opposite to the toner charging polarity of the toner image on the intermediate transfer belt 16 is applied, and a transfer electric field is formed in the secondary transfer nip. The toner image on the intermediate transfer belt 16 is collectively transferred onto the paper P by the transfer electric field formed in the secondary transfer nip.

The paper P on which the toner image is transferred is conveyed to the fixing device 7, and the paper P is heated and pressed by the fixing belt 22 and the pressurizing roller 23 to fix the toner image on the paper P. Then, the paper P on which the toner image is fixed is separated from the fixing belt 22, is conveyed by the transport roller pair, and is discharged to the paper output tray 25 by the paper discharge roller 24 at the paper discharge unit 8.

The above description is an image forming operation when forming a full-color image on paper P, but a single-color image can be formed by using any one of four process units 9Y, 9C, 9M, and 9Bk. It is also possible to use two or three process units 9 to form a two-color or three-color image.

As shown in FIG. 2, the fixing device 7 includes a belt-shaped fixing belt 22, a nip forming member 30, a heat transfer member 31, a reinforcing member 32 that supports the nip forming member 30, and a heating member that heats the fixing belt 22. The heater 33 is provided. Further, the paper P is separated from the pressure roller 23, the temperature sensor 45, the contact / detachment mechanism 35 for bringing the pressure roller 23 into contact with the fixing belt 22, and the fixing belt 22 provided so as to face the fixing belt 22. It is provided with a separating plate 36 and the like.

The fixing belt 22 is a thin, flexible, endless belt that rotates in the direction of arrow B1 (counterclockwise) in FIG. Further, in the fixing belt 22, the base material layer, the elastic layer, and the release layer are sequentially laminated from the inner peripheral surface side which is the surface in sliding contact with the nip forming member 30, and the total thickness thereof is 1 [mm]. It is set as follows.

The base material layer of the fixing belt 22 has a layer thickness of 30 [μm] to 100 [μm] and is formed of a metal material such as nickel or stainless steel or a resin material such as polyimide. The elastic layer of the fixing belt 22 has a layer thickness of 100 [μm] to 300 [μm] and is made of a rubber material such as silicone rubber, foamable silicone rubber, and fluororubber. By providing the elastic layer, minute irregularities on the surface of the fixing belt 22 are not formed in the fixing nip N, heat is uniformly transferred to the toner image D on the paper P, and the generation of a yuzu skin image is suppressed. The release layer of the fixing belt 22 has a layer thickness of 10 [μm] to 50 [μm]. Further, this release layer is formed of a material such as PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer), PTFE (polytetrafluoroethylene), polyimide, polyetherimide, PES (polyether sulfide) and the like. There is. By providing the release layer, the release property (release property) with respect to the toner is ensured. The diameter of the fixing belt 22 is set in the range of 15 [mm] to 120 [mm], and is set to about 30 [mm] in the present embodiment.

A nip forming member 30, a heat transfer member 31, a reinforcing member 32, a heater 33, a reflecting member 34, and the like are provided on the inner peripheral surface side of the fixing belt 22.

As an example of the heater 33, a halogen heater is used in this embodiment, but an IH, a resistance heating element, a carbon heater, or the like may be used in addition to the halogen heater.

The surface of the nip forming member 30 on the pressure roller 23 side is formed in a concave shape along the curvature of the pressure roller 23. As a result, the paper P passes through the fixing nip N so as to follow the surface of the pressure roller 23, and after the fixing operation, is easily separated from the fixing belt 22 without being adsorbed on the fixing belt 22.

The heat transfer member 31 is a tubular pipe-shaped member obtained by bending a sheet metal having a thickness of 0.1 [mm] into a substantially C shape so that one end and the other end face each other. The heat transfer member 31 is formed so as to face the inner peripheral surface of the fixing belt 22 at a position other than the fixing nip N. Further, the portion facing the fixing nip N is formed in a concave shape toward the inner diameter side of the fixing belt 22, and is provided with an opening in which the nip forming member 30 is arranged.

Both ends of the heat transfer member 31 in the width direction are fixedly supported by the first support member 37 and the second support member 38 (see FIG. 3), respectively. Further, as shown in FIG. 2, the heat transfer member 31 transmits radiant heat (radiant light) from the heater 33 to the fixing belt 22. That is, the fixing belt 22 is heated from the heater 33 via the heat transfer member 31.

As the material of the heat transfer member 31, a metal thermal conductor (metal having thermal conductivity) such as aluminum, iron, and stainless steel can be used. Further, by setting the thickness of the heat transfer member 31 to 0.2 [mm] or less, the heating efficiency of the heat transfer member 31 and the fixing belt 22 can be improved. In the present embodiment, the heat transfer member 31 is made of a stainless steel plate having a thickness of 0.1 [mm].

The fixing belt 22 is heated by the radiant heat of the heater 33 via the heat transfer member 31. Then, at the fixing nip N, the heat of the fixing belt 22 is applied to the paper P and the toner image D on the paper P. A temperature sensor 45 such as a thermistor is provided on the surface of the fixing belt 22 so as to face each other, and the output of the heater 33 is controlled based on the detection result of the surface temperature of the fixing belt 22 by the temperature sensor 45. By controlling the output of the heater 33 in this way, the temperature of the fixing belt 22 (fixing temperature) can be set to a desired temperature.

The heat transfer member 31 can transmit the radiant heat from the heater 33 in the circumferential direction of the fixing belt 22, and can transfer the heat over the entire circumferential direction of the fixing belt 22 except for the fixing nip N. Therefore, even when the speed of the device is increased by shortening the heating time of the fixing belt 22, the fixing belt 22 can be sufficiently heated to prevent the occurrence of fixing failure.

Further, by providing the heat transfer member 31 along the shape of the inner peripheral surface thereof, the fixing belt 22 can be supported from the inside, and the peripheral shape of the flexible fixing belt 22 can be maintained. it can. In order to reduce the sliding resistance between the heat transfer member 31 and the fixing belt 22, a material having a low friction coefficient with respect to the fixing belt 22 of the sliding contact surface of the heat transfer member 31 that is in sliding contact with the inner peripheral surface of the fixing belt 22 is used. The thermal member 31 may be formed. Further, a surface layer made of a material containing fluorine may be formed on the inner peripheral surface of the fixing belt 22.

The reinforcing member 32 supports the nip forming member 30 from the side opposite to the fixing nip N. As a result, in the fixing nip N, it is possible to prevent the nip forming member 30 from being significantly deformed by receiving the pressing force of the pressure roller 23.

The reinforcing member 32 is preferably formed of a metal material having high mechanical strength such as stainless steel or iron in order to satisfy the above functions. Further, a heat insulating member may be provided on a part or all of the surface of the reinforcing member 32 facing the heater 33, or a BA treatment (bright baking treatment) or a mirror polishing treatment may be performed. As a result, the radiant heat of the heater 33 is less likely to be absorbed by the reinforcing member 32, and the fixing belt 22 can be heated more efficiently.

The reflection member 34 is provided between the reinforcing member 32 and the heater 33. The reflective member 34 can efficiently heat the fixing belt 22 by reflecting a part of the radiant heat radiated from the heater 33 to the side of the reinforcing member 32 to the fixing belt 22. As the material of the reflective member 34, for example, aluminum, stainless steel, or the like can be used.

The pressure roller 23 is formed by forming an elastic layer 23b on a core metal 23a having a hollow structure. In the present embodiment, the diameter of the pressure roller 23 is set to about 30 [mm]. The elastic layer 23b is made of a material such as silicone rubber, foamable silicone rubber, or fluororubber. When the elastic layer 23b of the pressure roller 23 is formed of a sponge-like material such as foamable silicone rubber, the pressing force acting on the fixing nip N can be reduced, and the bending generated in the nip forming member 30 can be reduced. At the same time, the heat insulating property of the pressure roller 23 is enhanced, and the heat of the fixing belt 22 is less likely to move to the pressure roller 23 side, so that the heating efficiency of the fixing belt 22 is improved. A thin mold release layer made of PFA, PTFE, or the like can be provided on the surface layer of the elastic layer 23b. Further, a heating member such as a halogen heater can be provided inside the core metal 23a.

The pressure roller 23 presses against the fixing belt 22 to form a desired fixing nip N between both members. Further, the pressurizing roller 23 is provided with a gear that meshes with the drive gear of the drive mechanism. The pressurizing roller 23 is rotationally driven in the direction of arrow B2 (clockwise) in FIG. 2 by a rotational driving force transmitted from the driving mechanism.

In the present embodiment, the diameters of the fixing belt 22 and the pressure roller 23 are set to the same size. However, it is also possible to set the diameter of the fixing belt 22 to be smaller than the diameter of the pressurizing roller 23 so that the paper P can be easily separated from the fixing belt 22 at the fixing nip N.

Next, the normal operation of the fixing device 7 configured as described above will be briefly described.

When the power is turned on to the image forming apparatus 1, the heater 33 is supplied with electric power, and the rotary drive of the pressurizing roller 23 in the direction of arrow B2 in FIG. 2 is started. Due to the rotation of the pressure roller 23, the fixing belt 22 that is in pressure contact with the pressure roller 23 is driven to rotate in the direction of arrow B1. The drivenly rotating fixing belt 22 is heated over the entire circumference by heating the heater 33.

The paper P that has been conveyed to the fixing device 7 through the image forming step or the like is conveyed in the direction of the arrow C1 in FIG. 2 and guided to the fixing nip N. Then, in the fixing nip N, the toner image D is fixed on the surface of the paper P by heating and pressurizing. After that, the paper P that has passed through the fixing nip N is conveyed in the direction of arrow C2, separated from the fixing belt 22 by the separation plate 36, and further conveyed to the downstream process. In this way, a series of fixing processes in the fixing device 7 is completed.

Next, the configuration of the heater 33 and its surroundings will be specifically described with reference to FIGS. 3 and 4. In FIG. 3, only the heater 33 and its support structure are described, and the description of other members such as the fixing belt 22 and the pressure roller 23 is omitted. The Y direction shown in FIG. 3 is the axial direction of the heater 33 and the like. Hereinafter, the Y direction is simply the axial direction, the left side of the paper surface in the Y direction is the one end side in the axial direction, and the right side of the paper surface in the Y direction is the other end side in the axial direction. Call each.

As shown in FIG. 3, at both ends in the axial direction of the heater 33, a first support member 37 that supports one end side in the axial direction of the heater 33, a second support member 38 that supports the other end side in the axial direction of the heater 33, and a second support member 38. A side plate 39 to which the one support member 37 and the second support member 38 are attached is provided.

The side plate 39 includes one end side vertical plate 39a to which the first support member 37 is attached, the other end side vertical plate 39b to which the second support member 38 is attached, and a connecting portion 39c for axially connecting these vertical plates. The first support member 37 and the second support member 38 are attached to one end side vertical plate 39a and the other end side vertical plate 39b, respectively, by screws or the like. One end side vertical plate 39a is provided with one end side insertion holes 39d and 39e into which one end side of a fixing belt 22 and a pressure roller 23 (see FIG. 2) is inserted, and the other end side vertical plate 39b is provided with a fixing belt 22. The other end side insertion holes 39f and 39g for inserting the other end side of the pressure roller 23 are provided. Both ends of the fixing belt 22 and the pressure roller 23 are inserted into the insertion holes of the side plate 39 and supported by the side plate 39.

As shown in FIG. 4, the heater 33 includes a glass tube 33a, a heat generating member 33b, a first holding member 33c on one end side of the glass tube 33a, and a second holding member 33c on the other end side of the glass tube 33a. A member 33e is provided. Further, a lead wire 50 is connected to one end side in the axial direction of the heater 33, and a lead wire 51 is connected to the other end side in the axial direction. The first holding member 33c and the second holding member 33e are held so as to cover one end side in the axial direction and the other end side in the axial direction of the glass tube 33a, respectively, and are provided integrally with the glass tube 33a. Further, as a material for the first holding member 33c and the second holding member 33e, for example, ceramic can be used.

One end in the axial direction of the heater 33 is inserted into the insertion hole 37a of the first support member 37, the other end in the axial direction of the heater 33 is inserted into the insertion hole 38a of the second support member 38, and each support member is inserted into both ends in the axial direction of the heater 33. Each side is supported.

The first support member 37 and the second support member 38 have tubular protrusions 37b and 38b that project toward the central side in the axial direction (the central side in the axial direction of the heater 33), respectively. The projecting portions 37b and 38b support both ends of the heat transfer member 31 (see FIG. 2) in the axial direction from the inner peripheral surface side thereof, and maintain the cross-sectional shape of the heat transfer member 31.

As shown in FIG. 5, a sealing portion in which 33 g of metal foil is embedded is formed at the end portion of the glass tube 33a. The second holding member 33e is from the base 33e1 that holds the glass tube 33a so as to cover the sealing portion provided at the end portion, and the insertion portion 33e2 that is inserted into the insertion hole 38a of the second support member 38 described above. Become. Further, the lead wire 51 has a configuration in which the lead wire 51a is covered with an insulating coating 51b. Although the other end side of the heater 33 is illustrated in FIG. 5, the same configuration is also provided for one end side of the heater 33.

An internal line 33b1 extends to the axial end side of the heat generating member 33b, and is connected to the metal foil 33g at the axial end. Further, the lead wire 51a is connected to the metal foil 33g at one end thereof. The heat generating member 33b is electrically connected to the conducting wire 51a via the internal wire 33b1 and the metal foil 33g.

As shown in FIG. 4, the width H1 of the support region (range from the base 33c1 on one end side of the heater 33 to the base 33e1 on the other end side) supported by each support member of the heater 33 is the width H1 of the first support member 37. The distance G1 is smaller than the distance H2 between the inner surface and the inner surface of the second support member 38. In other words, the heater 33 is supported by the two support members by providing a play of a distance G1 between the two support members. This backlash G1 is provided in consideration of the dimensional error of each member, the thermal expansion of the heater 33 due to the heat generated by the heat generating member 33b, and the like.

By the way, the paper P passed through the fixing nip N is passed through the paper P at a position corresponding to the heat generating region HA of the heat generating member 33b in the axial direction, and the heat is transferred from the fixing belt 22 heated by the heater 33. .. In the present embodiment, the heater 33 is moved to the left side of FIG. 4, and the heater 33 is supported by the first support member 37 at a position where the first holding member 33c is in contact with the first support member 37. With this position as a reference position, the heat generation region HA and the paper passing region PA are aligned. However, the present invention is not limited to this, and the center position or the position moved to the right side of the figure can be used as a reference.

In the configuration of FIG. 4, since the heat generating region HA of the heater 33 is provided in a slightly larger range than the paper passing range PA, non-paper passing regions PB are generated at both ends of the heat generating region HA.

The lower side of FIG. 4 shows the distribution of the temperature T of the fixing belt 22 in the axial direction. In the axial direction, in the paper passing region PA, the heat of the fixing belt 22 is taken away by the paper P and the toner image D on the paper P, so that the temperature T drops. On the other hand, in the above-mentioned region PB, the heat of the fixing belt 22 is not taken away by the paper P and the toner image D, and the temperature T rises.

As shown in FIG. 4, when the heater 33 is arranged at the target position and the range of the region PB is small, the rate of temperature rise in the region PB is also small, and the temperature can be controlled stably.

However, since the heater 33 has the above-mentioned backlash G between the first support member 37 and the second support member 38, the heater 33 is not necessarily arranged at the target position. For example, as shown in FIG. 6, when the heater 33 moves to a position where it abuts on the second support member 38, the deviation between the heat generation region HA and the paper passing region PA becomes large, and the other end side of the heat generation region HA in the axial direction (FIG. 6). A large area PB is formed on the right side of 6). In this case, the temperature T of the fixing belt 22 locally rises excessively in the region PB. If the temperature of the fixing belt 22 rises locally excessively in this way, problems such as accelerated deterioration of the fixing belt 22 and affecting the quality of the image formed on the paper P occur. Further, in the region PC at one end in the axial direction of the paper passing region PA, the paper P is separated from the heat generation region HA, and the toner image D is not sufficiently heated, resulting in image defects.

In particular, in recent years, a fixing belt 22 having a low heat capacity has been used from the viewpoint of speeding up the image forming operation and saving energy, and the above-mentioned problems are likely to occur. That is, such a fixing belt 22 having a low heat capacity not only tends to have a high temperature, but also has a small heat flux inside the member, so that heat is difficult to diffuse, and if local temperature unevenness occurs, it takes time to eliminate it. Therefore, a local temperature rise is particularly likely to occur. Further, in the case of the configuration in which the fixing belt 22 is heated by one heat generating member 33b as in the present embodiment, the amount of heat generated per heat generating member is larger than that of the fixing device including a plurality of heat generating members. Therefore, the above problem is particularly likely to occur.

Therefore, as a fixing device of the present embodiment for solving the above problems, as shown in FIG. 7, the fixing device 7 includes a spring 40 as an urging member that abuts on the other end side in the axial direction of the heater 33. There is. In the following description, points different from the above-described configuration will be described, and similar configurations will be omitted as appropriate.

One end of the spring 40 is in contact with the base 33e1 on the other end side of the heater 33, and the heater 33 is urged toward the other end side in the axial direction (in the direction of the arrow in the figure). The other end of the spring 40 is fixed to the second support member 38. Due to the urging force of the spring 40, the side surface of the base 33c1 on one end side in the axial direction is in contact with the first support member 37, and the heater 33 can be positioned with respect to the first support member 37. it can.

As described above, in the present embodiment, the spring 40 is directly in contact with the heater 33. Further, the first support member 37 comes into contact with the base 33e1 provided on one end side of the heater 33 to support the heater 33.

In this embodiment, a stainless steel spring is used as the spring 40. By using stainless steel for the spring 40, the spring 40 can be constructed at a relatively low cost. Further, stainless steel is excellent in heat resistance and durability over time, and has an advantage that the urging force of the spring 40 is not easily lowered or damaged. Further, a nickel alloy can be used as the spring 40, and for example, Inconel (registered trademark) can be used. By using a nickel alloy for the spring 40, it is possible to construct the spring 40 which has better heat resistance than stainless steel and does not impair the urging force even in an environment of several hundred degrees. As described above, by using the spring as the urging member, it is possible to form the urging member having excellent heat resistance.

Here, the coefficient of linear expansion in the axial direction of the glass tube 33a is α, the cross-sectional area of the cross section orthogonal to the axial direction is A, the Young's modulus is E, the temperature rise due to heat generation of the heat generating member 33b is ΔT, and the heater 33 is normal. Assuming that the urging force of the spring 40 arranged at the position with respect to the heater 33 is F, the urging force F of the spring 40 is adjusted so that F <αΔTAE. As a result, when the glass tube 33a tries to thermally expand due to the heat generated by the heat generating member 33b, it can expand to the other end side in the axial direction against the urging force of the spring 40. In the present embodiment, the state in which the heater 33 is in the normal position is a state in which the base 33c1 of the heater 33 is in contact with the first support member 37. When the pressing force on the spring 40 due to the axial expansion of the base 33c1 and the base 33e1 is not negligible with respect to the pressing force due to the axial expansion of the glass tube 33a, in addition to the above αΔTAE, The pressing force toward the other end side in the axial direction due to the thermal expansion of the bases 33c1 and 33e1 may be considered.

As described above, in the present embodiment, the heater 33 is urged toward one end in the axial direction by the spring 40, and the heater 33 is positioned at a position where the base 33c1 abuts on the first support member 37. Therefore, even if the heater 33 is supported by providing a constant backlash G between the first support member 37 and the second support member 38, the heater 33 can be reliably positioned at the above position. it can. Therefore, as shown in FIG. 6, it is possible to prevent the heater 33 from being displaced within the range of the backlash G1 and increasing the region PB, so that the temperature of the fixing belt 22 locally rises excessively. Further, by providing the backlash G and adjusting the urging force of the spring 40 as described above, the heater 33 can be accurately positioned, and the thermal expansion of the glass tube 33a due to the heat generated by the heat generating member 33b can be allowed. .. Further, the first support member 37 and the second support member 38 are attached to the side plates 39 that support both ends of the fixing belt 22 and the pressure roller 23 in the axial direction. Therefore, by positioning the heater 33 with respect to the first support member 37 and the second support member 38, the heater 33 can be positioned with respect to the side plate 39, and the positional relationship with each member attached to the side plate 39 is determined. You can also do it.

In the present embodiment, the spring 40 abuts on the base 33e1 made of ceramic among the heaters 33, and urges the heater 33 toward one end in the axial direction. On the other hand, the spring 40 may be brought into contact with the glass tube 33a, but in this case, the glass tube 33a is damaged by the urging force of the spring 40, or the spring 40 becomes hot due to the heat generated by the heat generating member 33b. Heat is transferred from the glass tube 33a, which may lead to deterioration or breakage of the spring 40. Further, when the spring 40 is brought into contact with the lead wire 51, the lead wire 51 may be broken due to the urging force of the spring 40. Therefore, the configuration of this embodiment is more preferable.

FIG. 8 is a diagram illustrating a second embodiment of the present invention. As shown in FIG. 8, in the present embodiment, assuming that the spring 40 is the first urging member, the spring 41 as the second urging member is provided on the other end side of the heater 33 in the axial direction.

One end of the spring 41 is fixed to the first support member 37, and the other end of the spring 41 is in contact with the base 33c1 on one end side of the heater 33. The spring 41 comes into contact with the base 33c1 and urges the heater 33 toward the other end in the axial direction.

In the present embodiment, the heater 33 is urged by the springs 40 and 41 at both ends in the axial direction, and the springs 40 and 41 are adjusted to have the same urging force. As a result, the heater 33 has a backlash G2 (for example, the backlash G2 is half the distance of the backlash G1) between the base 33c1 and the first support member 37, and the base 33e1 and the second support member 38, respectively. There is. By urging from both sides with equal force in this way, the heater 33 can be positioned at the center of the first support member 37 and the second support member 38. Therefore, as in the above-described embodiment, it is possible to prevent the heater 33 from being displaced within the range of play and the temperature of the fixing belt 22 from rising locally excessively. Further, also in this case, the urging force of the springs 40 and 41 is adjusted so that the force that the glass tube 33a tries to expand (the force corresponding to the above-mentioned αΔTAE) exceeds the urging force from the springs 40 and 41. Therefore, the thermal expansion of the glass tube 33a can be tolerated.

In the fixing device of the third embodiment shown in FIG. 9, a leaf spring 42 is used as an urging member for urging the heater 33. As shown in FIG. 9, one end of the leaf spring 42 is in contact with the base 33e1 on the other end side of the heater 33, and the other end is fixed to the second support member 38. In the illustrated example, the other end of the leaf spring 42 sandwiches the second support member 38. The leaf spring 42 is made of an elastic metal material in this embodiment.

The leaf spring 42 urges the heater 33 toward one end in the axial direction by a force at which the end abutting the base 33e1 tends to elastically deform toward one end in the axial direction (force in the direction of the arrow in the figure). As a result, similarly to the embodiment using the spring 40 described above, the heater 33 can be brought into contact with the first support member 37 on one end side in the axial direction, and the heater 33 can be positioned with respect to the first support member 37.

As shown in FIG. 10, in the fourth embodiment of the present invention, the leaf spring 43 as an urging member is provided on the outer side (right side in the drawing) in the axial direction with respect to the second support member 38. Hereinafter, the axial center side of the heater 33 is referred to as an axial inner side, and the axial end side of the heater 33 is referred to as an axial outer side.

The leaf spring 43 includes an elastic portion 43a that is elastically deformed and an insulating member 43b that covers one end of the elastic portion 43a.

In the heater 33, the insertion portion 33e2 on the other end side in the axial direction is inserted into the second support member 38, and a part of the insertion portion 33e2 protrudes outward in the axial direction from the second support member 38. Then, one end of the leaf spring 43 is in contact with the axially outwardly protruding portion of the insertion portion 33e2 via the insulating member 43b. Further, the other end of the leaf spring 43 is fixed to the lateral side surface of the second support member 38 in the axial direction by a screw 44. The leaf spring 43 urges the heater 33 toward one end in the axial direction by a force at which the end abutting the insertion portion 33e2 tends to elastically deform toward one end in the axial direction (in the direction of the arrow in the figure).

In the present embodiment, the leaf spring 43 is brought into contact with the axially outer (right side) end of the insertion portion 33e2 provided outside the second support member 38, so that the leaf spring 43 is formed by the heat generating member 33b. It receives almost no radiant heat and can prevent deterioration and damage of the leaf spring 43 due to thermal influence. Therefore, as the material for forming the leaf spring 43, a material having lower heat resistance can be selected, which leads to cost reduction of the member.

Further, as shown in FIG. 11, by covering the end of the leaf spring 43 on the side of contacting the heater 33 with the insulating member 43b, the insulating coating 51b of the lead wire 51 is temporarily damaged and the lead wire 51a is exposed to the outside. Even if there is, it is possible to prevent the elastic portion 43a from coming into contact with the lead wire 51a which is an active portion, and it is possible to prevent a short circuit between the metal elastic portion 43a and the lead wire 51a. Depending on the configuration that protects the lead wire 51a, the insulating member 43b can be omitted as appropriate.

Further, the mounting position of the urging member is not limited to the above-mentioned support member. For example, as shown in FIG. 12, the leaf spring 43 may be fixed to the axially outer side surface of the side plate 39 by a fixing member such as a screw 44. In this way, the optimum configuration of the fixing position of the urging member is appropriately selected in consideration of the urging force of the urging member with respect to the heater, the dimensions of each member, the thermal influence of the above-mentioned heat generating member, and the like. be able to.

In the above embodiment, the configuration in which the leaf spring is provided axially outside the second support member 38 and the side plate 39 as the urging member has been described, but the spring 40 illustrated in FIG. 7 is provided on the second support member 38 and the side plate 39. It may be provided axially outside of 39. In this case, it is necessary to provide a member for fixing the other end side of the spring 40 (the end portion opposite to the one end side that comes into contact with the heater 33).

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and it goes without saying that various modifications can be made without departing from the gist of the present invention.

The configuration of the fixing device of the present invention is not limited to the fixing device of FIG. 2 described in the above-described embodiment, and for example, the fixing device shown in FIG. 13 can be adopted as the configuration of the present invention.

Similar to the fixing device of FIG. 2, the fixing device 7 shown in FIG. 13 is provided with a thin and flexible endless fixing belt 22 and a heater 33 for heating the fixing belt 22 from the inner peripheral surface side. Further, unlike the fixing device having the configuration of FIG. 2, the fixing device 7 of the present embodiment is not provided with the heat transfer member 31 (see FIG. 2) between the heater 33 and the fixing belt 22, and the fixing belt 22 is not provided. Is directly heated by the heater 33. Therefore, in the fixing device 7 of the present embodiment, the fixing belt 22 is more easily heated even with the same amount of heat generated from the heater 33, as compared with the configuration in which the fixing belt 22 is heated via the heat transfer member 31, and the fixing device While energy saving can be realized, the temperature of the fixing belt 22 tends to rise excessively in the non-paper-passing region described above.

Further, as shown in FIG. 13, the fixing device 7 is provided with a nip forming member 30 having a flat nip forming surface. The nip forming member 30 has a base pad 301 and a low friction sheet 302 provided on the surface of the base pad 301. Since the nip forming member 30 has a flat nip forming surface, the shape of the fixing nip N becomes substantially parallel to the image surface of the paper P, and the adhesion between the fixing belt 22 and the paper P is improved. Fixability is improved. Further, since the curvature of the fixing belt 22 on the outlet side of the fixing nip N becomes large, the paper P after the fixing operation can be easily separated from the fixing belt 22.

Similar to the fixing device of FIG. 2, the nip forming member 30 is supported by the reinforcing member 32 from behind. The reinforcing member 32 includes a base portion 32a extending in the paper transport direction and supporting the nip forming member 30, and rising portions 32b extending in a direction orthogonal to the paper transport direction at both ends of the base portion 32a in the paper transport direction. It has a U-shape with. By providing the rising portion 32b, the reinforcing member 32 has a horizontally long cross section extending in the pressurizing direction of the pressurizing roller 23, the cross section coefficient becomes large, and the mechanical strength of the reinforcing member 32 is improved. It becomes possible.

A heater 33 is provided between the two rising portions 32b. Similar to the fixing device of FIG. 2, a reflecting member 34 is provided between the heater 33 and the reinforcing member 32, and radiant heat radiated from the heater 33 to the reinforcing member 32 is reflected to the fixing belt 22. Further, a temperature sensor 45 such as a thermistor is provided on the surface of the fixing belt 22 so as to face each other.

The image forming apparatus according to the present invention is not limited to the color image forming apparatus shown in FIG. 1, and may be a monochrome image forming apparatus, a copying machine, a printer, a facsimile, or a combination machine thereof.

Recording media include paper P (plain paper), thick paper, postcards, envelopes, thin paper, coated paper (coated paper, art paper, etc.), tracing paper, transparencies, plastic films, prepregs, copper foil, etc. included.

In the above embodiment, the configuration in which the heater 33 has one heat generating member 33b has been described, but the heater 33 may have a configuration having a plurality of heat generating members 33b. Further, although the configuration in which the heater 33 is provided on the inner peripheral surface side of the fixing belt 22 to heat the fixing belt 22 has been described, the heater 33 may be provided in the pressurizing roller 23.

1 Image forming device 7 Fixing device 22 Fixing belt (fixing member)
23 Pressurizing roller (pressurizing member)
33 Heater (heating member)
33a Glass tube 33b Heat generating member 33c First holding member 33e Second holding member (holding member)
37 First support member 38 Second support member 39 Side plate 40 Spring (biasing member or first urging member)
41 Spring (second urging member)
42 Leaf spring (urging member)
43 Leaf spring (urging member)
43a Elastic part 43b Insulation member

JP-A-63-218984

Claims (8)

With a rotating fixing member
A pressure member that rotates in contact with the fixing member,
A heating member having a heat generating member and heating the fixing member or the pressurizing member,
A first support member provided on one end side in the axial direction of the heating member and supporting the heating member,
A second support member provided on the other end side in the axial direction of the heating member and supporting the heating member,
An urging member that abuts on the other end side in the axial direction of the heating member and urges the heating member toward one end side in the axial direction .
A fixing device including a conducting wire for conducting the heat generating member.
The axially opposite end of the heating member is provided so as to project axially to the other side of the second support member.
The lead wire is inserted into the heating member from the axially opposite end of the heating member and connected to the heating member.
The fixing device includes an elastic portion that can be elastically deformed, and an insulating member that covers one end side of the elastic portion and abuts on the other end portion in the axial direction of the heating member . The heating member includes a glass tube, a heat generating member provided inside the glass tube, and a holding member that holds the other end side of the glass tube in the axial direction and is provided integrally with the glass tube.
The fixing device according to claim 1 , wherein the other end in the axial direction of the heating member is the other end in the axial direction of the holding member . The heating member is arranged at a normal position, where the rising temperature of the glass tube is ΔT, the coefficient of linear expansion in the axial direction is α, the cross-sectional area of the cross section orthogonal to the axial direction is A, and the Young ratio is E. Let F be the urging force of the urging member with respect to the heating member.
The fixing device according to claim 2, which satisfies the relationship of F <αΔTAE. When the urging member is the first urging member,
The fixing device according to any one of claims 1 to 3, further comprising a second urging member that abuts on one end side in the axial direction of the heating member and urges the heating member toward the other end side in the axial direction. A side plate for supporting the fixing member and the pressurizing member from the axial end side is further provided.
The fixing device according to any one of claims 1 to 4, wherein the second support member is attached to the side plate . When the axial center side of the heating member is the axial inner side and the axial end side of the heating member is the axial outer side,
The fixing device according to claim 5, wherein the urging member is provided outside the side plate in the axial direction . The heating member is inserted into an insertion hole provided in the second support member and supported by the second support member.
The fixing device according to any one of claims 1 to 6, wherein the other end side of the urging member, which is opposite to one end side, is fixed to the other side surface of the second support member in the axial direction. .. An image forming apparatus comprising the fixing apparatus according to any one of claims 1 to 7.

Images