JP2012128333A - Belt device, fixing device, and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a belt device which can be downsized by shortening a distance between a fixed rotor and a movable rotor.SOLUTION: A belt device comprises: a fixed rotor fixed at a prescribed position; a movable rotor movable in a direction to come close to or separate from the fixed rotor; an endless belt stretched and laid by the fixed rotor and the movable rotor; and an energization member 51 energizing the movable rotor in the direction to separate from the fixed rotor to apply tension to the belt. Bearings 21a, 23a disposed on the same end sides of the fixed rotor and the movable rotor, respectively, are held on a same surface of one holding member 31. Furthermore, the energization member 51 is disposed in a position avoiding the area between the respective bearings 21a, 23a of the fixed rotor and the movable rotor.

Description

  The present invention relates to a belt device, a fixing device including the belt device, and an image forming apparatus.

  In an image forming apparatus using an electrophotographic system such as a copying machine, a printer, a facsimile machine, or a complex machine of these, an electrostatic latent image is formed on the surface of a photosensitive drum as an image carrier, and a static image on the photosensitive drum is formed. The electrostatic latent image is developed and visualized with toner as a developer, the developed image is transferred to a recording medium such as paper by a transfer device, the image is transferred, and the recording medium is recorded with a fixing device using pressure and heat. Fix the upper toner image. Generally, a fixing device sandwiches a recording medium by a pair of opposed rotating members such as rollers or belts, a fixing member such as a pressure pad, or a combination thereof, and applies heat and / or pressure to place a toner image on the recording medium. It is configured to fix.

  As a fixing device, a fixing device including a fixing roller including a heater as a heating unit and a pressure roller that contacts the fixing roller is known (see Patent Document 1). In this fixing device, a recording medium carrying an unfixed toner image is introduced into a fixing nip that is a contact portion between a fixing roller and a pressure roller, whereby the toner image is heated and pressed to form a recording medium. It is fixed.

  However, the fixing device configured to form the fixing nip with the pair of rollers as described above has a limit to cope with the recent increase in the speed of the image forming apparatus. When the speed is increased, the roller linear speed increases, so it is necessary to expand the fixing nip width to supply the same amount of heat necessary for fixing. However, in the roller type fixing device, a heater is provided on the fixing roller. Since it is included, the roller becomes large and the image forming apparatus becomes large. Further, when the roller is enlarged, the heat capacity of the roller is increased, the temperature raising time (standby time) is increased, and the power consumption is increased, which is contrary to energy saving.

  Thus, conventionally, a belt-type fixing device using a belt instead of a roller has been proposed. The belt-type fixing device includes a heat-resistant endless fixing belt supported by a fixing roller, a heating roller, and a tension roller, and the pressure roller contacts the belt portion extending from the heating roller to the fixing roller for fixing. A nip is formed (see Patent Document 2). As described above, the belt-type fixing device can ensure a larger nip width than the roller-type fixing device, and can efficiently apply a sufficient amount of heat from the fixing roller to the unfixed image. Yes.

  Some belt-type fixing devices use a heating roller as a tension roller (see Patent Document 3). Specifically, a tension is applied to the fixing belt by urging the heating roller toward the fixing belt with a spring disposed between the fixing roller and the heating roller. In this configuration, since the tension roller can be eliminated, the number of parts is reduced and the cost is reduced as compared with the fixing device having the tension roller.

  However, in the configuration in which the tension is applied by the heating roller as described above, a spring is disposed between the fixing roller and the heating roller, so that a space is required between the rollers, and the distance between the rollers is shortened to reduce the size. It was difficult to make it easier.

  SUMMARY OF THE INVENTION In view of such circumstances, the present invention is intended to provide a belt device that can reduce the distance between rotating members that stretch a belt, and a fixing device and an image forming apparatus that include the belt device. To do.

  According to a first aspect of the present invention, there is provided a fixed rotating body fixed at a predetermined position, a moving rotating body movable in a direction approaching and separating from the fixed rotating body, and the fixed rotating body and the moving rotating body. A belt device comprising: an endless belt that is mounted; and a biasing member that biases the moving rotating body in a direction away from the fixed rotating body and applies tension to the belt. Each bearing disposed on the same end side of the fixed rotator and the moving rotator is held on the same surface by one holding member, and the urging member includes the fixed rotator and the moving rotator. These are disposed at locations other than between the bearings.

  By disposing the urging member at a place other than between the bearings of the fixed rotator and the moving rotator, there is no need for a space for disposing the urging member between the bearings. Can be shortened. As a result, the distance between the fixed rotating body and the moving rotating body is shortened, and the size can be reduced.

  Moreover, since each bearing is hold | maintained on the same surface with one holding member, further size reduction can be achieved. That is, in the case of a configuration in which the bearings of the fixed rotating body and the moving rotating body are fixed to separate holding members, and the holding member on the moving rotating body side is moved toward and away from the holding member on the fixed rotating body side, the holding The distance between the bearings can only be reduced to the point where the members interfere with each other, but by holding each bearing with one holding member, the distance between them can be reduced to the point where the bearings interfere with each other. . For this reason, in the case of a configuration in which each bearing is held on the same surface by one holding member, the distance between the fixed rotating body and the moving rotating body can be further reduced, and further miniaturization can be achieved.

  According to a second aspect of the present invention, in the noble belt device according to the first aspect, the belt device includes a pressing member that receives the urging force of the urging member and presses the moving rotator in a direction away from the fixed rotator. The pressing member has a pressing portion that contacts and presses the bearing of the moving rotating body, and among the constituent parts of the pressing member, only the pressing portion is interposed between the bearings of the moving rotating body and the fixed rotating body. Are arranged.

  Of the constituent parts of the pressing member, by disposing only the pressing portion between the bearings of the movable rotating body and the fixed rotating body, it is possible to prevent an increase in the space between the bearings.

  A third aspect of the present invention is the belt device according to the second aspect, wherein the pressing member has a plurality of the pressing portions.

  When the pressing member has a plurality of pressing portions, the bearing can be pressed stably.

  The invention of claim 4 is the belt device according to claim 2 or 3, wherein the holding member and the pressing member are made of a cold rolled steel plate, an electrogalvanized steel plate, or a hot dip galvanized steel plate.

  As a material for the holding member and the pressing member, a cold rolled steel plate, an electrogalvanized steel plate, or a hot dip galvanized steel plate can be applied.

  According to a fifth aspect of the present invention, in the belt device according to any one of the first to fourth aspects, the biasing member is a compression coil spring or a tension coil spring.

  As the biasing member, a compression coil spring or a tension coil spring can be applied.

  The invention of claim 6 is the belt device according to any one of claims 1 to 5, wherein each bearing of the fixed rotating body and the movable rotating body is a ball bearing, a sintered bearing, or a resin bearing. Is.

  As the bearing, a ball bearing, a sintered bearing, or a resin bearing can be applied.

  According to a seventh aspect of the present invention, there is provided a fixing rotator fixed at a predetermined position, a heating rotator movable in a direction approaching and separating from the fixing rotator, and the fixing rotator and the heating rotator. A fixed fixing belt, an urging member that urges the heating rotator in a direction away from the fixing rotator to apply tension to the fixing belt, and the fixing via the fixing belt. 7. A fixing device comprising: a counter member that forms a fixing nip in contact with a rotating body; and a fixing device that passes a recording medium through the fixing nip and fixes a developer image on the recording medium. The belt device according to claim 1 is used, wherein the fixed rotator of the belt device is the fixing rotator, the moving rotator is the heating rotator, and the endless belt is the fixing belt. is there.

  When the fixing device uses the belt device according to any one of claims 1 to 6, the above-described effects of these belt devices can be obtained.

  According to an eighth aspect of the present invention, in the fixing device according to the seventh aspect, temperature detecting means for detecting the temperature of the fixing belt is disposed on the outer peripheral side of the fixing belt and is configured integrally with the pressing member. It is a thing.

  In this case, since the temperature detecting means is disposed on the outer peripheral side of the belt, the distance between the fixed rotating body and the moving rotating body can be reduced. Further, since the temperature detecting means is integrally formed with the pressing member, when the pressing member moves following the moving rotating body, the temperature detecting means can also move together. As a result, the temperature detection means can maintain a constant relative positional relationship with the belt displaced by the movement of the moving rotating body, and can perform accurate temperature detection.

  A ninth aspect of the invention is an image forming apparatus including the belt device according to any one of the first to sixth aspects.

  When the image forming apparatus includes the belt device according to any one of claims 1 to 6, the above-described effects of these belt devices can be obtained.

  According to the present invention, the urging member is disposed at a place other than between the bearings of the fixed rotator and the moving rotator, and each bearing on the same end side is arranged on the same plane by one holding member. The distance between the fixed rotator and the moving rotator can be greatly reduced, and the apparatus can be downsized.

1 is a schematic cross-sectional view illustrating a configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a perspective view illustrating an overall configuration of a fixing device mounted on the image forming apparatus. It is a figure which shows the periphery structure of one side plate shown to the near side in FIG. It is a figure which shows only the said one side plate. It is the figure which expanded the principal part of FIG. FIG. 3 is a diagram when the fixing device is viewed from a direction indicated by an arrow C in FIG. 2. FIG. 6 is a schematic diagram illustrating a configuration of a fixing device according to another embodiment of the present invention.

  Hereinafter, the present invention will be described with reference to the accompanying drawings. In the drawings for explaining the present invention, components such as members and components having the same function or shape are denoted by the same reference numerals as much as possible, and once described, the description will be given. Omitted.

First, an overall configuration and operation of an image forming apparatus to which the present invention is applied will be described with reference to FIG.
The image forming apparatus shown in FIG. 1 is a color laser printer, and four process units 1Y, 1M, 1C, and 1Bk as image forming units are detachably mounted on the apparatus main body 100. Each process unit 1Y, 1M, 1C, 1Bk contains toners of different colors of yellow (Y), magenta (M), cyan (C), and black (Bk) corresponding to the color separation components of the color image. Other than that, the configuration is the same.

  Specifically, each of the process units 1Y, 1M, 1C, and 1Bk includes a drum-shaped photosensitive member 2 as an image carrier, a charging device that includes a charging roller 3 that charges the surface of the photosensitive member 2, and a photosensitive device. The image forming apparatus includes a developing device 4 that supplies toner (developer) to the surface of the body 2 and a cleaning device that includes a cleaning blade 5 for cleaning the surface of the photoreceptor 2. In FIG. 1, only the photoconductor 2, the charging roller 3, the developing device 4, and the cleaning blade 5 included in the yellow process unit 1 </ b> Y are denoted by reference numerals, and the other process units 1 </ b> M, 1 </ b> C, and 1 </ b> Bk are denoted by reference numerals. Omitted.

  In FIG. 1, an exposure device 6 as an exposure means for exposing the surface of the photoreceptor 2 is disposed above each process unit 1Y, 1M, 1C, 1Bk. The exposure device 6 includes a light source, a polygon mirror, an f-θ lens, a reflection mirror, and the like, and irradiates the surface of each photoreceptor 2 with laser light based on image data.

  A transfer device 7 is disposed below each process unit 1Y, 1M, 1C, 1Bk. The transfer device 7 has an intermediate transfer belt 8 constituted by an endless belt as a transfer body. The intermediate transfer belt 8 is stretched around a driving roller 9 and a driven roller 10 as support members. When the driving roller 9 rotates counterclockwise in the figure, the intermediate transfer belt 8 is in the direction indicated by the arrow in the figure. It is comprised so that it may run around (rotate).

  Four primary transfer rollers 11 as primary transfer means are disposed at positions facing the four photoconductors 2. Each primary transfer roller 11 presses the inner peripheral surface of the intermediate transfer belt 8 at each position, and a primary transfer nip is formed at a location where the pressed portion of the intermediate transfer belt 8 and each photoconductor 2 are in contact with each other. ing. Each primary transfer roller 11 is connected to a power source (not shown), and a predetermined direct current voltage (DC) and / or alternating current voltage (AC) is applied to the primary transfer roller 11.

  A secondary transfer roller 12 as a secondary transfer unit is disposed at a position facing the drive roller 9. The secondary transfer roller 12 presses the outer peripheral surface of the intermediate transfer belt 8, and a secondary transfer nip is formed at a location where the secondary transfer roller 12 and the intermediate transfer belt 8 are in contact with each other. Similar to the primary transfer roller 11, the secondary transfer roller 12 is connected to a power source (not shown) so that a predetermined direct current voltage (DC) and / or alternating current voltage (AC) is applied to the secondary transfer roller 12. It has become.

  A belt cleaning device 13 for cleaning the surface of the intermediate transfer belt 8 is disposed on the outer peripheral surface on the right end side of the intermediate transfer belt 8 in the drawing. A waste toner transfer hose (not shown) extending from the belt cleaning device 13 is connected to an entrance of a waste toner container 14 disposed below the transfer device 7.

  A paper feed cassette 15 that accommodates a sheet-like recording medium P such as paper or OHP is disposed below the apparatus main body 100. The paper feed cassette 15 is provided with a paper feed roller 16 for feeding out the stored recording medium P. On the other hand, a pair of paper discharge rollers 17 for discharging the recording medium to the outside and a paper discharge tray 18 for stocking the discharged recording medium are disposed on the upper part of the apparatus main body 100.

  In the apparatus main body 100, a transport path R for transporting the recording medium P from the paper feed cassette 15 through the secondary transfer nip to the paper discharge tray 18 is disposed. In the conveyance path R, a pair of registration rollers 19 are disposed upstream of the position of the secondary transfer roller 12 in the recording medium conveyance direction. A fixing device 20 is disposed downstream of the position of the secondary transfer roller 12 in the recording medium conveyance direction.

The basic operation of the image forming apparatus will be described below with reference to FIG.
When the image forming operation is started, the photoconductors 2 of the process units 1Y, 1M, 1C, and 1Bk are rotationally driven clockwise in the drawing, and the surface of each photoconductor 2 is made uniform to a predetermined polarity by the charging roller 3. Is charged. Based on the image information of the document read by a reading device (not shown), the exposure device 6 irradiates the charged surface of each photoconductor 2 with laser light, and an electrostatic latent image is formed on the surface of each photoconductor 2. . At this time, the image information to be exposed on each photoconductor 2 is single-color image information obtained by separating a desired full-color image into color information of yellow, magenta, cyan, and black. As the electrostatic latent image formed on the photosensitive member 2 is supplied with toner by each developing device 4, the electrostatic latent image is visualized (visualized) as a toner image.

  A drive roller 9 that stretches the intermediate transfer belt 8 is driven to rotate, causing the intermediate transfer belt 8 to run in the direction of the arrow in the figure. Also, a primary transfer nip between each primary transfer roller 11 and each photoreceptor 2 is applied to each primary transfer roller 11 by applying a constant voltage or a voltage controlled by a constant current opposite to the charging polarity of the toner. A transfer electric field is formed. Then, the toner images of the respective colors on the respective photoconductors 2 are sequentially superimposed and transferred onto the intermediate transfer belt 8 by the transfer electric field formed in the primary transfer nip. Thus, the intermediate transfer belt 8 carries a full-color toner image on its surface. Further, the toner on each photoreceptor 2 that could not be transferred to the intermediate transfer belt 8 is removed by the cleaning blade 5.

  When the image forming operation is started, the paper feed roller 16 rotates and the recording medium P is carried out from the paper feed cassette 15. The unloaded recording medium P is timed by the registration roller 19 and sent to the secondary transfer nip between the secondary transfer roller 12 and the intermediate transfer belt 8. At this time, a transfer voltage having a polarity opposite to the toner charging polarity of the toner image on the intermediate transfer belt 8 is applied to the secondary transfer roller 12, thereby forming a transfer electric field in the secondary transfer nip. Then, the toner image on the intermediate transfer belt 8 is collectively transferred onto the recording medium P by the transfer electric field formed in the secondary transfer nip. Thereafter, the recording medium P is sent to the fixing device 20 and the toner image is fixed on the recording medium P. Then, the recording medium P is discharged to the paper discharge tray 18 by the pair of discharge rollers 17.

  The above description is an image forming operation when a full-color image is formed on a recording medium. A single color image is formed using any one of the four process units 1Y, 1M, 1C, and 1Bk, and 2 Two or three process units can be used to form a two or three color image.

Next, the configuration and operation of the fixing device 20 installed in the image forming apparatus main body 100 will be described in detail.
As shown in FIG. 1, the fixing device 20 includes a fixing roller 21 as a fixing rotator, a heating roller 23 as a heating rotator including a heater 25 as a heating source, and stretches between these rollers 21 and 23. The endless fixing belt 24 and the pressure roller 22 as an opposing member (or pressure rotator) that forms a fixing nip by contacting the fixing roller 21 via the fixing belt 24 are configured.

  Here, the fixing roller 21 is formed of a heat-resistant elastic material such as silicone rubber, fluorine rubber, and foamable silicone rubber on a cylindrical body (wall thickness: 1 mm, outer diameter: 30 mm) made of a metal material such as aluminum or iron. (Thickness is about several mm). The heating roller 23 is reduced in capacity by using a small diameter and thin metal pipe in order to shorten the warm-up time of the fixing device. The metal pipe is made of aluminum, iron, stainless steel or the like. Here, aluminum having excellent heat conductivity is used, and the pipe having an outer diameter of 20 mm and a wall thickness of 1 mm is used.

  The fixing belt 24 is formed of a heat-resistant elastic material such as silicone rubber, fluorine rubber, or foamable silicone rubber (thickness 150 μm) on a heat-resistant resin film (thickness 60 μm) such as a nickel electroformed sheet or polyimide. On the surface layer, PFA (tetrafluoroethylene perfluoroalkyl vinyl ether copolymer resin) and PTFA (polytetrafluoroethylene) are formed with a thickness of several tens of μm as a release layer.

  The heater 25 disposed inside the heating roller 23 is a halogen heater, and both ends thereof are fixed to the frame of the fixing device 20. Then, the cylindrical body made of the metal material is heated by the radiant heat from the heater 25 whose output is controlled by the power supply unit (AC power supply) of the apparatus main body 100, and the heat is further transmitted to the elastic material and the release layer, so that Heat is applied to the toner image.

  The output control of the heater 25 is performed based on the detection result by detecting the surface temperature of the fixing belt 24 by a thermistor (not shown) as temperature detecting means that contacts and faces the surface of the fixing belt 24. Specifically, the AC voltage is applied to the heater 25 for the energization time determined based on the detection result of the thermistor. By such output control of the heater 25, the temperature (fixing temperature) of the fixing belt 24 can be adjusted and controlled to a desired temperature (target control temperature). A thermostat (not shown) is also provided as a temperature detecting means for detecting when the fixing belt 24 becomes abnormally hot and forcibly stopping the heating of the heater 25.

  Subsequently, the pressure roller 22 is formed by forming a heat-resistant elastic material having a thickness of 4 mm made of silicone rubber, fluorine rubber, foamable silicone rubber or the like on a metal core. The pressure roller 22 has an outer diameter set to about 35 mm. A release layer made of PFA, PTFE, or the like can be provided on the surface layer of the elastic material.

  The pressure roller 22 is brought into pressure contact with the fixing roller 21 through the fixing belt 24 by a pressure unit. Thus, a desired nip portion (fixing nip) is formed between the pressure roller 22 and the fixing roller 21. Here, the fixing roller 21 is rotationally driven by a drive motor (not shown).

  In the present embodiment, a heating unit such as a heater that directly heats the pressure roller 22 can be installed, or a thermopile that faces the surface of the fixing belt 24 in a non-contact manner for output control of the heater 25. It can also be used.

  A guide plate for guiding the conveyance of the recording medium is disposed on the entrance side of the contact portion (fixing nip) between the fixing roller 21 and the pressure roller 22. In addition, a separation plate for preventing a problem that the recording medium after the fixing process sent from the fixing nip is wound around the fixing roller 21 is installed at a position in contact with the fixing roller 21 and in the vicinity of the exit side of the fixing nip. ing.

The fixing device 20 configured as described above operates as follows.
When the power switch of the apparatus main body 100 is turned on, an AC voltage is applied (powered) from the AC power source to the heater 25, and the fixing roller 21 is started to rotate by a drive motor (not shown) and simultaneously pressurized. The roller 22 is driven to rotate. Thereafter, the recording medium is fed from the paper feed cassette 15 and an unfixed image is carried on the recording medium at the position of the secondary transfer nip. The recording medium carrying the unfixed image (toner image) is conveyed to the fixing device 20 and fed into the fixing nip between the fixing roller 21 and the pressure roller 22 in a pressure contact state. The toner image is fixed on the surface of the recording medium by the heating by the fixing belt 24 and the pressing force of the fixing roller 21 and the pressure roller 22. Thereafter, the recording medium sent from the fixing nip by the rotating fixing roller 21 and the pressure roller 22 is conveyed and discharged to the paper discharge tray 18 by the paper discharge roller 17.

Hereinafter, the configuration and operation of the fixing device 20 that are characteristic of the present embodiment will be described with reference to FIGS.
FIG. 2 is a perspective view showing the overall configuration of the fixing device of the present embodiment.
In FIG. 2, reference numerals 21a and 21b denote bearings that rotatably support both ends of the fixing roller, reference numerals 23a and 23b denote bearings that rotatably support both ends of the heating roller, and reference numerals 31 and 32 denote fixing rollers. And side plates as a pair of holding members that hold the bearings 21a, 21b, 23a, and 23b of the heating roller. Rotating members 41 and 42 are attached to the side plates 31 and 32 so as to be rotatable around fulcrums 410 and 420, respectively. The rotating members 41 and 42 hold bearings 22a and 22b that rotatably support both ends of the pressure roller 22, and the rotating members 41 and 42 rotate around the fulcrums 410 and 420, The pressure roller 22 can contact and separate from the fixing belt 24. Furthermore, the other end portions of the tension coil springs (pressurizing means) 43 and 44 whose one end portions are attached to the side plates 31 and 32 are attached to the rotating members 41 and 42, respectively. The pressure roller 22 is pressed against the fixing belt 24 by the force to form a fixing nip.

  In this embodiment, the bearings of the fixing roller, the heating roller, and the pressure roller are high-reliability ball bearings that can withstand high loads. However, inexpensive sintered bearings and resin bearings that are excellent in mass productivity are used. Is also possible. Which bearing is to be selected may be selected as appropriate in consideration of the balance of load conditions and cost.

3 is a view showing a peripheral structure of one side plate shown on the near side in FIG. 2, FIG. 4 is a view showing only the side plate, and FIG. 5 is an enlarged view of a main part of FIG.
Since the pair of side plates 31 and 32 and their peripheral configurations are symmetrical with each other, only the peripheral structure of one of the side plates shown in FIGS. 3 to 5 will be described in order to simplify the description.

  As shown in FIG. 4, the side plate 31 includes a fixing bearing holding hole 31a for holding the fixing roller bearing 21a, a heating bearing holding hole 31b for holding the heating roller bearing 23a, and a pressure roller. A shaft insertion hole 31c for inserting the rotation shaft is formed.

  The fixing bearing holding hole 31a is formed in a circular shape that can be fitted to the outer periphery of the bearing 21a of the fixing roller. The fixing roller is fixed to the side plate 31 by fitting the fixing roller bearing 21 a into the fixing bearing holding hole 31 a.

  The heating bearing holding hole 31b is formed to be long in the horizontal direction (the direction of arrow A in the figure), and the bearing 23a of the heating roller inserted into the hole 31b extends to the bearing 21a of the fixing roller 21 along the hole 31b. On the other hand, it can move in the direction of approaching and separating (horizontal direction). Further, the vertical width of the heating bearing holding hole 31b is formed substantially equal to the outer diameter of the heating roller bearing 23a, and the heating roller bearing 23a moves in the vertical direction within the heating bearing holding hole 31b. Is regulated. In addition, the side plate 31 is provided with a claw portion 31d for preventing the dropping of the heating roller to lock the bearing 23a of the heating roller so that the bearing 23a of the heating roller does not move and drop off with respect to the side plate 31. is there.

  The shaft insertion hole 31c is formed as an arc-shaped long hole along a locus (in the direction of arrow B in the drawing) along which the shaft of the pressure roller moves when the rotating members 41 and 42 rotate. Thereby, the contact / separation operation of the pressure roller with respect to the fixing belt is allowed.

  In FIG. 3, reference numeral 50 denotes a pressing member that receives a biasing force of a tension coil spring 51 as a biasing member and presses the bearing 23a of the heating roller. Both end portions 51a and 51b of the tension coil spring 51 are hooked and attached to a claw-like attachment portion 50a provided on the pressing member 50 and a claw-like attachment portion 31e (see FIG. 4) provided on the side plate 31. The pressing member 50 is pulled in the horizontal direction by the tension coil spring 51. Thereby, the bearing 23a of the heating roller is pressed by the pressing member 50 in the direction away from the bearing 21a of the fixing roller along the longitudinal direction of the pressure bearing holding hole 31b, and tension is applied to the fixing belt.

  Moreover, in this embodiment, the pressing member 50 and the side plate 31 are produced by press sheet metal working of a cold rolled steel plate (SPCC or the like), an electrogalvanized steel plate (SECC or the like), or a hot dip galvanized steel plate (SGCC or the like). Is used.

  As shown in FIG. 5, the pressing member 50 has a claw-shaped pressing portion 50b that abuts on the outer peripheral surface of the bearing 23a of the heating roller 23. The pressing portion 50b presses the bearing 23a of the heating roller 23. ing. In the present embodiment, only one pressing portion 50b is provided for one pressing member 50. However, a plurality of pressing portions 50b may be provided so that the bearing 23a can be stably pressed.

  Further, as shown in FIG. 5, two tension coil springs 51 that bias the pressing member 50 are provided. Accordingly, the pressing member 50 is provided with two attachment portions 50a for attaching the one end portion 51a of each tension coil spring 51, and the side plate 31 also has two attachment portions 31e for attaching the other end portion 51b of each tension coil spring 51. It is provided. In FIG. 5, the side plate 31 is not shown. The two coil springs 51 are disposed at positions symmetrical to each other with the axial center of the heating roller 23 interposed therebetween, and springs having the same tensile force are used. In the present embodiment, a tension coil spring 51 having an urging force of 10 N is used, and the heating roller 23 is urged by a force of 20 N by two tension coil springs 51 on one side plate side and both by 40 N. However, the biasing force of the tension coil spring 51 is not limited to this, and can be set as appropriate.

  The pressing member 50 holds and fixes the end portion of the heating roller 23 and the insertion hole 50c through which the heater 25 included in the heating roller is inserted, and the end portion of the heater 25 inserted through the insertion hole 50c. And an arm-shaped fixing portion 50d.

  Thus, although the pressing member 50 is comprised by the attaching part 50a, the press part 50b, the insertion hole 50c, the fixing | fixed part 50d, and the main-body part 50e which provided these, among these structural parts, a press part Only 50 b is disposed between the bearing 23 a of the heating roller and the bearing 21 a of the fixing roller 21. In FIG. 5, the bearing 21a of the fixing roller 21 is not shown. That is, components other than the pressing portion 50 b are not disposed between the bearing 23 a of the heating roller and the bearing 21 a of the fixing roller 21. Specifically, the main body portion 50e, the insertion hole 50c, the attachment portion 50a, and the fixing portion 50d provided in the main body portion 50e are disposed at positions facing the axial direction of the bearing 23a of the heating roller. Accordingly, the tension coil springs 51 attached to the respective attachment portions 50a are also arranged at positions facing the axial direction of the bearing 23a of the heating roller, and between the bearing 23a of the heating roller and the bearing 21a of the fixing roller 21. Not arranged.

6 is a view of the fixing device as seen from the direction indicated by the arrow C in FIG.
A pair of pressing members 50 shown on the left side and the right side in FIG. 6 are connected to each other via a longitudinal connecting member 60 disposed to face the outer peripheral surface of the fixing belt 24. The connecting member 60 and each pressing member 50 are fastened by a plurality of screws 61, respectively. The connecting member 60 is provided with a plurality of thermistors 71 and one thermostat 72 as temperature detecting means for detecting the temperature of the fixing belt 24.

  As described above, in the fixing device 20 according to the present embodiment, among the portions constituting the pressing member 50, most of the portions other than the pressing portion 50b, the tension coil spring 51, the bearing 23a of the heating roller 23, and the fixing roller. Therefore, the distance between the heating roller 23 and the fixing roller 21 can be reduced, and the size can be reduced. Moreover, although the press part 50b is arrange | positioned between each bearing 23a, 21a, since the press part 50b is comprised by the nail | claw-shaped small member, it causes the expansion of the space between each bearing 23a, 21a. There is nothing.

  Further, in the fixing device 20 according to the present embodiment, the bearings 23a and 21a on the same end side of the heating roller 23 and the fixing roller 21 are held on the same surface by the one side plate 31, so that it is further increased. Can be miniaturized. That is, in the case of a configuration in which the bearings of the heating roller and the fixing roller are fixed to separate side plates and the side plate on the heating roller side is moved closer to and away from the side plate on the fixing roller side, until the side plates interfere with each other. However, the distance between the bearings can be reduced, but by holding each bearing with one side plate as in the present embodiment, the distance between the bearings can be reduced until just before they interfere with each other. For this reason, in the case of a configuration in which each bearing is held on the same surface by one side plate, the distance between the heating roller and the fixing roller can be further reduced, and further miniaturization can be achieved.

  Further, in the present embodiment, the thermistor 71 and the thermostat 72 are disposed on the outer peripheral side of the fixing belt 24 and are not disposed between the heating roller 23 and the fixing roller 21. It is possible to reduce the distance between the rollers 23 and 21.

  Further, since the thermistor 71 and the thermostat 72 are disposed on the connecting member 60 that connects the pressing members 50 to each other, when the pressing member 50 moves following the heating roller 23, the thermistor 71 and the thermostat 72 are also the pressing members. 50 can move together. As a result, the thermistor 71 and the thermostat 72 can maintain a constant relative positional relationship with the fixing belt 24 that is displaced by the movement of the heating roller 23, and can perform accurate temperature detection.

  Further, since the pressing member 50 and the connecting member 60 can be separated by removing the screw 61, the pressing member 50 is easily inserted into the heating bearing holding holes 31b of the side plates 31 and 32 when the fixing device is assembled. Can be assembled. If the pair of pressing members 50 and the connecting member 60 are integrally configured, the heating bearing holding hole 31b needs to be formed large, leading to an increase in the size of the apparatus.

  In addition, since two tension coil springs 51 are provided for biasing each pressing member 50, the length of the spring can be shortened compared to biasing by one tension coil spring 51. Miniaturization in the direction can be achieved. If a spring with a strong urging force is used, even the single tension coil spring 51 can be shortened. However, in this case, there is a problem that it is difficult to manufacture and assemble because the urging force is strong.

FIG. 7 is a schematic diagram illustrating a configuration of a fixing device according to another embodiment of the present invention.
As shown in FIG. 7, in this embodiment, a pair of spring receiving members 52 extending from the bearings 23 a, 21 a side to the outer peripheral side of the rollers 23, 21 are provided on the bearings 23 a, 21 a of the heating roller 23 and the fixing roller 21. The compression coil spring 45 is disposed between the spring receiving members 52. As a result, the heating roller 23 is urged away from the fixing roller 21, and tension is applied to the fixing belt 24.

  In the embodiment shown in FIG. 7, as in the above embodiment, the bearings 23a and 21a on the same end side of the heating roller 23 and the fixing roller 21 are arranged on the same surface by one side plate (not shown). Although being held, the side plate, the heating roller and the like are not shown.

  As described above, also in the embodiment shown in FIG. 7, the compression coil spring 45 as the urging member is not disposed between the bearings 23 a and 21 a of the heating roller 23 and the fixing roller 21. The distance from the roller 21 can be reduced, and the size can be reduced.

  As described above, according to the present invention, the tension coil spring 51 or the compression coil spring 45 is disposed at a place excluding the space between the bearings 21a and 23a of the fixing roller 21 and the heating roller 23, and further, on the same end side. By holding the bearings 21a and 23a by one side plate 31, the distance between the shafts of the fixing roller 21 and the heating roller 23 can be greatly reduced, and the apparatus can be downsized.

  In addition, this invention is not limited to the above-mentioned embodiment, Of course, a various change can be added in the range which does not deviate from the summary of this invention. In the above-described embodiment, the case where the configuration of the present invention is applied to a fixing device having a fixing belt has been described as an example. It can be applied to other belt devices.

  That is, the configuration of the present invention is stretched between a fixed rotating body fixed at a predetermined position, a moving rotating body movable in a direction approaching and separating from the fixed rotating body, and the fixed rotating body and the moving rotating body. The present invention can be applied to a belt device including an endless belt and a biasing member that biases the moving rotating body in a direction away from the fixed rotating body and applies tension to the belt. In the above-described embodiment, the fixed rotating body is a fixing roller, the moving rotating body is a heating roller, and the endless belt is a fixing belt. However, the endless belt is a photosensitive belt, a transfer belt, or the like, and moves with the fixed rotating body. The rotating body may be a roller that stretches a photosensitive belt or a transfer belt. In this case as well, as described above, the distance between the rollers (the distance between the fixed rotating body and the moving rotating body) can be reduced, and the size can be reduced.

  The image forming apparatus according to the present invention is not limited to the color laser printer shown in FIG. The belt device according to the present invention can also be mounted on image forming apparatuses such as other printers, copiers, facsimiles, or multifunction machines thereof.

20 Fixing device 21 Fixing roller (fixed rotating body)
21a Bearing 21b Bearing 23 Heating roller (moving rotating body)
23a bearing 23b bearing 24 fixing belt 31 side plate (holding member)
32 Side plate (holding member)
51 Tensile coil spring (biasing member)
71 thermistor (temperature detection means)
72 Thermostat (temperature detection means)

Japanese Patent No. 3871198 JP-A-9-218601 JP 2009-237191 A

Claims (9)

A fixed rotating body fixed at a predetermined position, a moving rotating body movable in a direction approaching and separating from the fixed rotating body, and an endless belt stretched by the fixed rotating body and the moving rotating body And a biasing member that biases the moving rotating body in a direction away from the fixed rotating body and applies tension to the belt,
Each bearing disposed on the same end side of the fixed rotating body and the moving rotating body is held on the same surface by one holding member,
The belt device according to claim 1, wherein the urging member is disposed at a place other than between the bearings of the fixed rotating body and the moving rotating body.   A pressing member that receives the urging force of the urging member and presses the moving rotator in a direction away from the fixed rotator, and the pressing member has a pressing portion that contacts and presses a bearing of the moving rotator. 2. The belt device according to claim 1, wherein, of the constituent parts of the pressing member, only the pressing portion is disposed between the bearings of the movable rotating body and the fixed rotating body.   The belt device according to claim 2, wherein the pressing member includes a plurality of the pressing portions.   The belt device according to claim 2 or 3, wherein the holding member and the pressing member are made of a cold-rolled steel plate, an electrogalvanized steel plate, or a hot-dip galvanized steel plate.   The belt device according to any one of claims 1 to 4, wherein the biasing member is a compression coil spring or a tension coil spring.   The belt device according to any one of claims 1 to 5, wherein each bearing of the fixed rotating body and the moving rotating body is a ball bearing, a sintered bearing, or a resin bearing. A fixing rotator fixed at a predetermined position, a heating rotator movable in a direction approaching and separating from the fixing rotator, a fixing belt stretched by the fixing rotator and the heating rotator, and An urging member for urging the heating rotator in a direction away from the fixing rotator to apply tension to the fixing belt, and fixing by contacting the fixing rotator via the fixing belt. A fixing device for fixing a developer image on the recording medium by passing the recording medium through the fixing nip.
The belt device according to any one of claims 1 to 6, wherein the fixed rotating body of the belt device is the fixing rotating body, the moving rotating body is the heating rotating body, and the endless belt is A fixing device provided as the fixing belt.   The fixing device according to claim 7, wherein temperature detection means for detecting the temperature of the fixing belt is disposed on an outer peripheral side of the fixing belt and is configured integrally with the pressing member.   An image forming apparatus comprising the belt device according to claim 1.

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