JP2020101618A - Fixing device and image forming apparatus - Google Patents

Abstract

To prevent a movement of a belt along a longitudinal direction, compared with a case where a tensile force of the belt along the longitudinal direction is made the same.SOLUTION: A fixing device comprises: a rotating endless belt 42; fixing means 41 that is in contact with the belt 42 to form a fixing nip part N; pressing means that is arranged inside the belt 42 and presses the belt 42 against the fixing means 41; support means 45 that is arranged inside the belt 42 and supports a center part of the belt along a longitudinal direction on the outside of both ends, along a direction intersecting the longitudinal direction of the belt 42; and guide means 48, 49 that guide both ends of the belt 42 along the longitudinal direction on the outside of the position supported by the support means 45, along the direction intersecting the longitudinal direction of the belt 42.SELECTED DRAWING: Figure 3

Description

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

Conventionally, as a fixing device, there is a fixing device that employs an endless belt as at least one of a pressure member and a heating member. The endless belt, unlike the heating roll and the pressure roll, can move along the longitudinal direction, and has a technical problem that it is difficult to control the fixing property including the movement along the longitudinal direction of the belt. There is. As a technique relating to a fixing device using such a belt, the one described in Patent Document 1 has already been proposed.

In Patent Document 1, a belt tension member is wound around a heating roller with a heat-resistant belt so as to form a nip, and the nip formed between the heating roller and the heating roller has an end in the axial center part. It is formed to have a convex shape larger than the portion.

JP, 2005-258108, A

An object of the present invention is to suppress the movement of the belt along the longitudinal direction, as compared with the case where the tension along the longitudinal direction of the belt is the same.

The invention described in claim 1 is a rotating endless belt,
A fixing unit that forms a fixing nip portion in contact with the belt;
Pressurizing means disposed inside the belt to press the belt against the fixing means,
Supporting means disposed inside the belt, for supporting a central portion along the longitudinal direction of the belt outside from both ends along a direction intersecting the longitudinal direction of the belt,
Means for guiding both ends of the belt along the longitudinal direction, the guide for guiding outside both ends of the supporting means along the longitudinal direction of the belt along a direction intersecting the longitudinal direction of the belt. Means and
And a fixing device.

In the invention described in claim 2, the guide means guides inside from a central portion of the support means along the longitudinal direction of the belt, along a direction intersecting the longitudinal direction of the belt. It is the fixing device described.

In the invention described in claim 3, the guide means has a tubular guide portion for guiding both end portions along the longitudinal direction of the belt,
2. The fixing device according to claim 1, wherein the guide portion guides the belt supported by the supporting means outside both ends in the longitudinal direction of the belt along a direction intersecting the longitudinal direction of the belt.

The invention described in claim 4 is the fixing device according to claim 1, wherein the supporting unit supports the belt on an upstream side in the rotation direction of the belt with respect to the fixing nip portion.

The invention described in claim 5 is the fixing device according to claim 1, wherein the supporting means supports the belt at a central portion along the longitudinal direction of the belt with a tension higher than both end portions.

In the invention described in claim 6, the guide means guides the belt with a tension smaller than a central portion of the supporting means along the longitudinal direction of the belt and larger than both end portions. It is a fixing device.

The invention described in claim 7 is the fixing device according to claim 1, wherein the guide means guides the belt upstream of the support means in the rotation direction of the belt.

The invention described in claim 8 is an image forming unit for forming an unfixed toner image on a recording medium,
A fixing unit for fixing the unfixed toner image formed on the recording medium;
An image forming apparatus using the fixing device according to claim 1 as the fixing unit.

According to the invention described in claim 1, the movement of the belt along the longitudinal direction can be suppressed as compared with the case where the tensions along the longitudinal direction of the belt are the same.

According to the invention described in claim 2, as compared with the case where the guiding means guides outside the central portion along the longitudinal direction of the belt of the supporting means, the outer side along the direction intersecting the longitudinal direction of the belt. It is possible to avoid applying excessive tension to both ends.

According to the invention described in claim 3, the guide means guides the belt by the tubular guide portion as compared with the case where the guide means does not have the tubular guide portion for guiding both end portions along the longitudinal direction of the belt. While tension can be applied.

According to the invention described in claim 4, the supporting means effectively moves the belt along the longitudinal direction as compared with the case where the belt is not supported on the upstream side in the rotation direction of the belt in the fixing nip portion. Can be suppressed.

According to the invention described in claim 5, the supporting means can apply a larger tension to the central portion along the longitudinal direction of the belt than the both end portions.

According to the invention described in claim 6, the guide means can suppress the movement of the belt along the longitudinal direction without applying excessive tension to the end portion along the longitudinal direction of the belt.

According to the invention described in claim 7, the belt can be more reliably guided along the supporting means as compared with the case where the belt is guided on the downstream side of the supporting means.

According to the invention described in claim 8, as compared with the case where the fixing device according to any one of claims 1 to 7 is not used as the fixing means, the movement of the belt along the longitudinal direction can be suppressed, The life of the belt can be extended.

1 is a schematic configuration diagram showing an image forming apparatus to which a fixing device according to Embodiment 1 of the present invention is applied. 1 is a schematic configuration diagram showing a fixing device according to Embodiment 1 of the present invention. 1 is a cross-sectional configuration diagram showing a fixing device according to Embodiment 1 of the present invention. 1 is a front configuration diagram showing a fixing device according to Embodiment 1 of the present invention. It is a perspective view showing a pressure belt. It is a perspective view showing a pressure support member. It is a perspective view showing the first and second holding members. It is a perspective view showing each guide member. It is a side view which shows a guide member. It is a side view which shows an arm member. FIG. 3 is a cross-sectional configuration diagram illustrating a state in which the nip of the fixing device according to the first embodiment of the present invention is released. FIG. 3 is a schematic diagram illustrating a main part of a fixing device. It is a cross-sectional block diagram which shows a pressure support member. FIG. 3 is a schematic diagram showing a positional relationship between a pressure support member and a fixing nip portion. It is a block diagram which shows the positional relationship between a guide member and a pressure support member. FIG. 3 is a schematic diagram showing a main part of the fixing device according to the first embodiment of the present invention. FIG. 3 is a schematic diagram showing an operation of a main part of the fixing device according to the first embodiment of the present invention. It is a schematic block diagram which shows the principal part of the fixing device which concerns on Embodiment 2 of this invention. FIG. 6 is a schematic sectional view showing a fixing device according to Embodiment 3 of the present invention.

Embodiments of the present invention will be described below with reference to the drawings.

[Embodiment 1]
1 and 2 show an image forming apparatus to which the fixing device according to the first embodiment is applied. FIG. 1 shows an outline of the entire image forming apparatus, and FIG. 2 shows an enlarged main part (image forming apparatus etc.) of the image forming apparatus. In the figure, arrow X indicates the depth direction along the horizontal direction, Y indicates the vertical direction, and Z indicates the width direction along the horizontal direction.

<Overall configuration of image forming apparatus>
The image forming apparatus 1 according to the first embodiment is configured as, for example, a monochrome printer. As shown in FIG. 1, the image forming apparatus 1 includes an image forming apparatus 10 as an example of an image forming unit that forms a toner image developed with toner constituting a developer, and a transfer position of the image forming apparatus 10. A sheet feeding device 20 that accommodates and feeds a recording sheet 5 as an example of a recording medium to be fed to the sheet, and the recording sheet 5 fed from the sheet feeding device 20 is conveyed along a conveying path indicated by a chain line in the figure. And a fixing device 40 according to the present embodiment for fixing the toner image transferred on the recording paper 5 transferred by the image forming device 10.

The image forming apparatus 10 includes a rotating photosensitive drum 11 as an example of an image holding unit. The following devices are mainly arranged around the photosensitive drum 11. The main devices include a charging device 12 that charges a peripheral surface (image holding surface) of the photosensitive drum 11 on which an image can be formed to a required electric potential, and image information on the charged peripheral surface of the photosensitive drum 11 ( An exposure device 13 that irradiates light based on a signal) to form an electrostatic latent image having a potential difference; a developing device 14 that develops the electrostatic latent image with toner of a black developer to form a toner image; A transfer device 15 that transfers the toner image to the recording paper 5, and a drum cleaning device 16 that removes and cleans adhered substances such as toner remaining on the image holding surface of the photosensitive drum 11 after the transfer.

The photoconductor drum 11 is formed by forming an image holding surface having a photoconductive layer (photosensitive layer) made of a photosensitive material on the peripheral surface of a cylindrical or cylindrical base material to be grounded. The photoconductor drum 11 is supported so as to rotate in a direction indicated by an arrow A when power is transmitted from a driving device (not shown).

The charging device 12 is composed of a contact-type charging roll that is arranged in contact with the photosensitive drum 11. A charging voltage is supplied to the charging device 12. When the developing device 14 performs reversal development, a voltage or current having the same polarity as the charging polarity of the toner supplied from the developing device 14 is supplied as the charging voltage. As the charging device 12, a non-contact type charging device such as a scorotron arranged in a non-contact state on the surface of the photosensitive drum 11 may be used.

The exposure device 13 irradiates the photoconductor drum 11 with light according to image information by using LEDs (Light Emitting Diodes) as a plurality of light emitting elements arranged along the axial direction of the photoconductor drum 11 to form an electrostatic latent image. Forming an LED print head. The exposure device 13 can be moved to an exposure position close to the photoconductor drum 11 and a retracted position shown by a broken line in FIG. As the exposure device 13, a device that deflects and scans laser light configured according to image information along the axial direction of the photosensitive drum 11 may be used. When an exposure device that deflects and scans laser light is used as the exposure device 13, it is not necessary to retract the exposure device 13 because it can be exposed from a position separated from the peripheral surface of the photoconductor drum 11.

The developing device 14 is an example of a developer holding unit that holds the developer 4 and conveys the developer 4 to a developing area facing the photoconductor drum 11 inside a housing 140 in which an opening and a storage chamber for the developer 4 are formed. Developing roller 141, agitating/conveying members 142 and 143 such as two screw augers for conveying the developer 4 while agitating the developer 4, and the amount of the developer held on the developing roller 141 (layer thickness ) Of the layer thickness regulating member 144 and the like are arranged. A developing bias voltage is supplied to the developing device 14 between the developing roll 141 and the photosensitive drum 11 from a power supply device (not shown). Further, the developing roll 141 and the stirring/conveying members 142, 143 are rotated in a desired direction by the transmission of power from a driving device (not shown). Further, as the developer 4, a two-component developer containing a non-magnetic toner and a magnetic carrier is used.

The transfer device 15 is a contact-type transfer device that includes a transfer roll that is in contact with the periphery of the photosensitive drum 11 via the recording paper 5 during image formation and rotates and is supplied with a transfer voltage. As the transfer voltage, a DC voltage having a polarity opposite to the charging polarity of the toner is supplied from a power supply device (not shown).

The drum cleaning device 16 is arranged so as to come into contact with the peripheral surface of the photosensitive drum 11 after the primary transfer with a required pressure, and removes adhered substances such as residual toner to clean the container-shaped main body having an opening. The cleaning plate and a delivery member such as a screw auger that collects and removes adhered substances such as toner removed by the cleaning plate and sends them to a collection container (not shown). A plate-shaped member (for example, a blade) made of a material such as rubber is used as the cleaning plate.

As shown in FIG. 1, the fixing device 40 is rotated in the direction indicated by the arrow inside the device housing 43 in which the inlet and outlet of the recording paper 5 are formed, and the surface temperature is maintained at a predetermined temperature. Heating roller 41 as an example of a heating rotator (fixing means) that is heated by a heating means, and a pressing rotator that rotates in contact with a predetermined pressure in a state substantially along the axial direction of the heating roller 41. A pressure belt 42 as an example of (endless belt) is arranged and configured. In the fixing device 40, the contact portion where the heating roll 41 and the pressure belt 42 contact each other serves as a fixing nip portion N that performs a required fixing process (heating and pressing). The configuration of the fixing device 40 will be described in detail later.

The paper feeding device 20 is arranged so as to be present at a lower position along the vertical direction Y of the image forming device 10. The paper feeding device 20 includes a single (or a plurality of) paper accommodating body 22 for accommodating the recording paper 5 of a desired size and type in a state of being stacked on a stacking plate 21, and the recording paper 5 from the paper accommodating body 22. It is mainly composed of a sending device 23 for sending out one by one. The paper feeding device 20 is attachable/detachable to/from the device main body 1 a of the image forming apparatus 1 by manually grasping and pulling out the grasping portion 24 provided in the paper container 22.

Examples of the recording paper 5 include thin paper such as plain paper and tracing paper used in electrophotographic copying machines and printers, and OHP sheets. In order to further improve the smoothness of the image surface after fixing, it is preferable that the surface of the recording paper 5 is also as smooth as possible. For example, coated paper obtained by coating the surface of plain paper with resin or the like, art paper for printing, etc. So-called thick paper having a relatively large grammage can also be suitably used.

Between the sheet feeding device 20 and the transfer device 15, as shown in FIG. 1, a plurality (or a single) pair of sheet conveying rolls 31a for conveying the recording sheet 5 delivered from the sheet feeding device 20 to the transfer position, A sheet feeding/conveying path 32 including a conveying guide 31b and a conveying guide (not shown) is provided in a shape that is curved upward toward the inside (X direction) of the apparatus main body 1a toward the upper side along the vertical direction Y of the apparatus main body 1a. Has been. The paper transport roll pair 31b arranged immediately before the transfer position in the paper feed transport path 32 is configured as, for example, a roll (registration roll) that adjusts the transport timing of the recording paper 5. Further, from the transfer device 15 to the fixing device 40, a paper transport path 33 for transporting the transferred recording paper 5 delivered from the transfer device 15 to the fixing device 40 is provided along the horizontal direction X.

Further, obliquely above the fixing device 40, one of the two pairs of conveying rolls 34 and 35 having one conveying roll in common is conveyed to one of the sheet discharging units 36 via one of the pair of conveying rolls 34 and discharged. A discharge/transport path 37 is provided. The paper discharge unit 36 is provided in a state of being inclined to the upper end surface of the apparatus body 1a.

At the exit 37a of the discharge/conveyance path 37, a pair of discharge rolls 37b for discharging the recording paper 5 and reversing the front and back are arranged. The rotation direction of the discharge roll pair 37b can be switched between the forward rotation direction and the reverse rotation direction.

Further, a switching gate (not shown) for switching the transport direction of the recording paper 5 is provided in front of the discharge roll pair 37b. When images are formed on both sides of the recording paper 5, the conveyance direction of the recording paper 5 is switched from the discharge conveyance path 37 to the double-sided conveyance path 38 by a switching gate (not shown). At this time, after the trailing edge of the recording sheet 5 conveyed in the discharge direction passes through a switching gate (not shown), the rotation direction of the discharge roll pair 37b is switched from the normal rotation direction (discharge direction) to the reverse rotation direction. The recording sheet 5 conveyed in the reverse direction by the discharge roll pair 37b has its conveyance path switched downward in the vertical direction Y by a switching gate (not shown), and the rear surface of the apparatus main body 1a of the image forming apparatus 1 via the conveyance roll pair 35. Is conveyed from the vertical direction Y to the double-sided conveyance path 38 which is formed so as to be curved along the horizontal direction X. The double-sided transport path 38 is provided with a pair of paper transport rolls 39a and 39b for transporting the recording paper 5 to the paper transport roll pair 31b with the front and back reversed, a transport guide (not shown), and the like.

A toner cartridge 145, which is an example of a developer container that contains a developer containing at least toner to be supplied to the developing device 14, is arranged above the developing device 14. Below the toner cartridge 145, a toner supply device (not shown) having a supply roll for supplying the toner contained in the toner cartridge 145 to the developing device 14 is provided.

In this embodiment, the photosensitive drum 11, the charging device 12, the developing device 14, and the drum cleaning device 16 are integrally mounted to form the process cartridge 300. As shown in FIG. 1, the process cartridge 300 is attachable to and detachable from the apparatus body 1a of the image forming apparatus 1 with the exposure device 13 moved to the retracted position. In addition to the process cartridge 300, the toner cartridge 145 that is frequently attached and detached is configured to be independently attachable to and detachable from the apparatus main body 1a of the image forming apparatus 1.

In addition, reference numeral 200 in FIG. 1 denotes a control device that integrally controls the operation of the image forming apparatus 1. The control device 200 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory) (not shown), a bus connecting these CPU and ROM, and a communication interface.

<Basic operation of image forming apparatus>
Hereinafter, a basic image forming operation of the image forming apparatus 1 will be described.

The image forming apparatus 1 is controlled by the control device 200, and receives command information of a monochrome image forming operation (printing) request from an operation panel (not shown) attached to the apparatus main body 1a, a user interface (not shown), a printer driver, or the like. Then, the image forming device 10, the paper feeding device 20, the conveying device 30, the fixing device 40, etc. are started.

Then, in the image forming device 10, as shown in FIG. 1, the photosensitive drum 11 first rotates in the direction indicated by the arrow A, and the charging device 12 causes the surface of the photosensitive drum 11 to have a desired polarity (embodiment). (1 is negative polarity) and the electric potential is charged. Then, the exposure device 13 irradiates the surface of the photosensitive drum 11 after charging with light emitted based on the information of the image input to the image forming apparatus 1, and the surface is formed with a required potential difference. Electrostatic latent image is formed.

Then, the developing device 14 electrostatically supplies the electrostatic latent image formed on the photosensitive drum 11 with black toner charged to a required polarity (negative polarity) from the developing roller 141. Attach and develop. By this development, the electrostatic latent image formed on the photosensitive drum 11 is visualized as a toner image developed with black toner. Toner is supplied from the toner cartridge 145 to the developing device 14 of the process cartridge 300 at a required timing via a toner supply device (not shown).

Subsequently, when the toner image formed on the photosensitive drum 11 is conveyed to the transfer position, the transfer device 15 transfers the toner image onto the recording paper 5.

Further, in the image forming apparatus 10 after the transfer is completed, the drum cleaning device 16 cleans the surface of the photoconductor drum 11 by scraping off the adhering substances. As a result, the image forming device 10 is brought into a state in which the next image forming operation is possible.

The paper feeding device 20 sends out the required recording paper 5 to the paper feeding and conveying path 32 in accordance with the image forming operation. In the paper feed transport path 32, a pair of paper transport rolls 31b serving as registration rolls sends the recording paper 5 to a transfer position at the transfer timing and supplies the recording paper 5.

Then, the recording sheet 5 to which the toner image is transferred is conveyed to the fixing device 40 via the sheet conveying path 33. In the fixing device 40, the recording paper 5 after transfer is introduced into and passed through the fixing nip portion N between the rotating heating roll 41 and the pressure belt 42, so that the necessary fixing process (heating and pressing) is performed. Then, the unfixed toner image is fixed on the recording paper 5. After the fixing, the recording sheet 5 is provided on the upper end portion of the apparatus main body 1a by the discharge roll pair 37b along the discharge conveyance path 37 during the image forming operation of only forming an image on one side thereof. And is discharged to the paper discharge unit 36.

When images are formed on both sides of the recording sheet 5, the recording sheet 5 having an image formed on one side is conveyed to the discharge roll pair 37b by a switching gate (not shown), and the recording sheet 5 is temporarily moved by the discharge roll pair 37b. It is transported in the discharge direction. After that, the direction of rotation of the discharge roll pair 37b is reversed with the discharge roll pair 37b holding the rear end of the recording paper 5, and the front and back sides of the recording paper 5 are reversed. The toner image is transferred to the transfer device 15 and the toner image is transferred to the back surface of the recording paper 5. The recording paper 5 having the toner image transferred on the back surface is conveyed to the fixing device 40 via the paper conveyance path 33, is subjected to fixing processing (heating and pressure) by the fixing device 40, and is ejected by the ejection roll pair 37b. It is discharged to the part 36.

By the above operation, the recording paper 5 on which a monochrome image is formed on one side or both sides is output.

<Structure of fixing device>
FIG. 2 is a sectional configuration diagram showing the fixing device according to the first embodiment.

The fixing device 40 employs a so-called free belt nip system. As shown in FIG. 2, the fixing device 40 includes a device housing 43 formed in an elongated box shape having a substantially rectangular cross section. A pressure belt 42, which is an example of a rotating endless belt, and a heating roll 41, which is an example of a fixing unit that contacts the pressure belt 42 to form a fixing nip portion N, are pressed inside the apparatus housing 43. It is arranged in a closed state. The device housing 43 has an inlet 431 below the left side surface thereof for introducing the recording paper 5 to which the unfixed toner image t is transferred. Inside the introduction port 431, a guide plate 432 for guiding the recording paper 5 to the fixing nip portion N where the heating roll 41 and the pressure belt 42 are in pressure contact with each other is arranged in a state of being inclined obliquely upward. Further, the apparatus housing 43 has a discharge port 433 for discharging the recording paper 5 fixed by the heating roll 41 and the pressure belt 42 to the outside above the right side surface thereof. The discharge port 433 is rotatably provided with a pair of exit rolls 434 for discharging the recording paper 5 to the outside of the apparatus housing 43. The recording sheet 5 is conveyed with the center (a so-called center register) along the direction intersecting the conveying direction as a reference.

An actuator 436 as an example of a detection unit that detects passage of the recording paper 5 is rotatably provided at the upper end as a fulcrum in a conveyance path 435 formed between the fixing nip portion N of the fixing device 40 and the exit roll pair 434. Has been. The rotation operation of the actuator 436 is detected as the passage of the recording paper 5 by an optical sensor or the like (not shown).

As shown in FIG. 2, the fixing device 40 is roughly provided with a heating roll 41 and a pressure unit 44 having a pressure belt 42 that is provided so as to be able to come into contact with and separate from the heating roll 41.

As shown in FIG. 3, the heating roll 41 includes a cylindrical core metal 411 made of metal such as stainless steel, aluminum, iron (thin-wall high-strength steel pipe), and a silicone rubber coated on the outer periphery of the core metal 411. An elastic layer 412 made of a heat-resistant elastic body such as fluororubber, and a mold release layer made of polytetrafluoroethylene (PTFE) or perfluoroalkoxyalkane (PFA) thinly coated on the surface of the elastic layer 412. It has a layer 413. Inside the heating roll 41, two halogen lamps 414a and 414b having different outer diameters are arranged as an example of heating means (heating source).

As shown in FIG. 4, both ends of the heating roll 41 in the longitudinal direction (axial direction) are rotatably supported by the frame 438 of the device housing 43 via bearing members 439. The heating roll 41 is rotationally driven at a required speed in the direction of arrow C (see FIG. 3) by a driving device (not shown) via a driving gear G attached to one end in the axial direction. The pressure belt 42 is pressed against the heating roll 41 that is driven to rotate and is driven to rotate.

As shown in FIG. 2, the surface temperature of the heating roll 41 is detected by the temperature sensor 437. The heating roll 41 controls the energization of the halogen lamps 414a and 414b based on the detection result of the temperature sensor 437 by a temperature control circuit (not shown), so that the surface thereof has a required fixing temperature (for example, about 170° C.). To be heated.

On the other hand, as shown in FIG. 3, the pressurizing unit 44 is disposed inside the pressurizing belt 42 and the pressurizing belt 42, and is an example of pressurizing means for pressing the pressurizing belt 42 against the surface of the heating roll 41. The pressure unit 451 of the pressure supporting member 45, which is also the pressure supporting member 45, is an example of a supporting unit that is disposed inside the pressure belt 42 and that supports the pressure belt 42 in a part of the orbit of the pressure belt 42. The support portion 452 of the pressure support member 45, the first and second holding members 46 and 47 as an example of holding means for holding the pressure support member 45, and both end portions of the pressure belt 42 along the longitudinal direction are provided. Guide members 48 and 49 as examples of guide means for rotatably guiding, and a sliding sheet 50 as an example of a sheet interposed between the pressure belt 42 and the pressure support member 45 to reduce sliding resistance. And first and second felt members 51 and 52, which are arranged inside the pressure belt 42 and serve as an example of a lubricant holding unit that holds a lubricant applied to the inner peripheral surface of the pressure belt 42. ing.

As shown in FIG. 5, the pressure belt 42 is made of a flexible material, and is configured as an endless belt having a thin-walled cylindrical free shape before being mounted. The pressure belt 42 includes a base material layer, an elastic body layer coated on the surface of the base material layer, and a release layer coated on the surface of the elastic body layer. Further, the pressure belt 42 may be composed of a base material layer and a release layer directly coated on the surface of the base material layer. The base material layer is formed of a heat-resistant synthetic resin such as polyimide, polyamide, or polyimideamide, or a metal such as stainless steel, nickel, or copper. The elastic layer is made of a heat-resistant elastic material such as silicone rubber or fluororubber. The release layer is formed of polytetrafluoroethylene (PTFE), perfluoroalkoxyalkane (PFA), or the like. The pressure belt 42 can be set to have a thickness of, for example, about 50 to 200 μm.

In the first embodiment, as described above, the pressurizing unit 451 is disposed inside the pressurizing belt 42 and serves as a pressurizing unit that pressurizes the pressurizing belt 42 against the heating roll 41, and also the pressurizing belt 42. A support portion 452, which is disposed inside and serves as a support unit that supports the pressure belt 42, is integrally configured as the pressure support member 45.

As shown in FIG. 6, the pressure support member 45 is made of heat-resistant synthetic resin integrally molded into a desired shape by, for example, injection molding. Examples of the heat-resistant synthetic resin include liquid crystal polymer (LCP), polyether ether ketone (PEEK), polyphenylene sulfide (PPS), polyether sulfone (PES), polyamide imide (PAI), polytetrafluoroethylene (PTFE). ), polychlorotrifluoroethylene (PCTFE), polyvinylidene fluoride (PVDF), or composite materials thereof.

As shown in FIG. 3, the pressure support member 45 is disposed at the downstream end of the fixing nip portion N along the rotation direction of the pressure belt 42, and the pressure belt 42 is attached to the surface of the heating roll 41. It is provided with a pressurizing unit 451 for pressurizing. The pressure unit 451 is arranged along the longitudinal direction of the pressure belt 42 over substantially the entire length. As shown in FIG. 3, the pressurizing unit 451 includes a pressurizing wall 451a having a pressurizing surface 451a′ that is pressed against the heating roll 41 via the pressurizing belt 42 and the sliding sheet 50, and the pressurizing wall 451a. The plate-shaped side walls 451b and 451c arranged in parallel to each other at both ends of the 451a are formed into a substantially semi-cylindrical or semi-cylindrical shape with an open rear surface. As shown in FIG. 6, the pressing surface 451a′ has a flat surface 451a″ along the rotation direction of the pressing belt 42 and a curved surface 451a″′ along the rotation direction of the pressing belt 42. Each is formed. As shown in FIG. 3, the pressure unit 451 is arranged to press the pressure belt 42 toward the center O of the heating roll 41 by the pressure wall 451a.

As shown in FIGS. 3 and 6, a plurality of reinforcing ribs 451d are provided inside the pressing portion 451 in parallel with each other along the longitudinal direction of the pressing support member 45. The plurality of reinforcing ribs 451d are provided with fixing slits 451e for fixing the tips of the first holding members 46 in a fitted state.

The first and second holding members 46 and 47 are made of, for example, a metal plate material such as stainless steel, aluminum, or steel. As shown in FIGS. 3 and 7, the first holding member 46 has a vertical plate portion 461 arranged substantially perpendicular to the surface of the heating roll 41 and a base end portion of the vertical plate portion 461. The horizontal plate portion 462 bent in the intersecting direction is formed into an L-shaped cross section. The vertical plate portion 461 of the first holding member 46 is arranged along a first straight line L1 extending in the radial direction through the center O of the heating roll 41. The second holding member 47 is bent in a direction intersecting the vertical plate portion 471 arranged in parallel with the vertical plate portion 461 of the first holding member 46 and the base end portion of the vertical plate portion 471. The horizontal plate portion 472 is formed into an L-shaped cross section. The horizontal plate portion 462 of the first holding member 46 and the horizontal plate portion 472 of the second holding member 47 are arranged to face each other with a slight gap.

As shown in FIG. 7, the first and second holding members 46 and 47 are convex portions for positioning and fixing the guide members 48 and 49 at both end portions along the longitudinal direction of the vertical plate portions 461 and 471. It has 463, 464, 473, 474.

As shown in FIG. 3, on the horizontal plate portions 462 and 472 of the first and second holding members 46 and 47, the first and second felt members 51 and 52 are attached to their outer side surfaces by means such as adhesion. It is provided. The first and second felt members 51, 52 are relatively thick so as to elastically deform and support the pressure belt 42 when tension is applied to the pressure belt 42. Note that FIG. 3 shows a state before the deformation of the first and second felt members 51 and 52 for convenience.

The first and second felt members 51, 52 are impregnated with a predetermined amount of lubricant for supplying the inner peripheral surface of the pressure belt 42 in a coated state. As the lubricant, for example, amino-modified silicone oil having a viscosity of 100 to 350 cs is used. The lubricant is applied and supplied to the inner peripheral surface of the pressure belt 42 by impregnating the first and second felt members 51 and 52 in advance, but the present invention is not limited to this and is initially applied. The pressure belt 42 may be supplied in a state of being coated on the inner peripheral surface thereof.

Further, as shown in FIGS. 3 and 6, the pressure support member 45 is arranged on the upstream side in the rotation direction of the pressure belt 42 with respect to the fixing nip portion N so as to be separated from the pressure portion 451. A supporting portion 452 that supports the pressure belt 42 is provided. The support part 452 is formed integrally with the pressurizing part 451 via a connecting part 453 located in the middle.

As shown in FIG. 3, the connecting portion 453 is formed in a flat plate shape between the pressing portion 451 and the supporting portion 452. On the back side of the connecting portion 453, a flat plate-shaped reinforcing plate 453a that intersects the connecting portion 453 and is arranged along the longitudinal direction of the pressure supporting member 45, and pressurizes and supports in a direction that intersects with the reinforcing plate 453a. A plurality of reinforcing ribs 453b are arranged in parallel with each other along the longitudinal direction of the member 45. Fitting slits 453c are formed on the plurality of reinforcing ribs 453b, and are attached to the vertical plate portions 471 of the second holding member 47 in a fitted state.

The tip ends of the vertical plate portions 461 and 471 of the first and second holding members 46 and 47 are arranged such that the first holding member 46 is closer to the heating roll 41 than the second holding member 47. .. The first and second holding members 46 and 47 oppose the reaction force received when the pressure support member 45 presses the pressure belt 42 against the heating roll 41 and supports the pressure belt 42, and applies the force. It is a member that holds the pressure support member 45. The first holding member 46 faces the reaction force directly received from the heating roll 41, and the second holding member 47 mainly faces the reaction force received from the heating roll 41 via the pressure belt 42. ..

A leaf spring 60, which is an example of an auxiliary pressurizing unit, is arranged on the surface of the connecting portion 453. As shown in FIG. 3, the leaf spring 60 is made of a thin spring material such as metal, and is provided on the surface of the heating roll 41 via a flat base end portion 601 and one end of the base end portion 601 through a curved portion 602. It is formed in a substantially V-shaped cross-section from the distal end portion 603 that is formed along the curved shape. The tip portion 603 of the leaf spring 60 is provided with a thin felt 604 on its surface by means such as adhesion. The base end portion 601 of the leaf spring 60 is mounted in a state of being fitted into a recess 454 provided on the surface of the connecting portion 453 of the pressure support member 45. Further, the tip end portion 603 of the leaf spring 60 is divided by a plurality of slits (not shown) along the longitudinal direction so that the spring property can be maintained for a long time.

The leaf spring 60 presses the pressure belt 42 against the surface of the heating roll 41 via the sliding sheet 50, so that heat transfer from the heating roll 41 causes heat transfer from the heating roll 41 in the upstream region of the fixing nip portion N. Is for heating efficiently.

As shown in FIG. 3, the support portion 452 of the pressure support member 45 has a first straight line L1 along the vertical plate portion 461 of the first holding member 46 and a second straight line L2 parallel to the first straight line L1. It is arranged so as to project toward the heating roll 41 side from substantially the same positions as the rear end portions of the both side walls 451b and 451c of the pressurizing portion 451. The tip 452d of the support portion 452 is located at a position projecting from a perpendicular line L3 that is downward with respect to the first straight line L1 passing through the center O of the heating roll 41. In other words, the tip 452d of the support portion 452 is provided at a position that makes a central angle α greater than 90 degrees with the first straight line L1. The leading end 452d of the support portion 452 defines the winding length of the pressure belt 42 arranged in a wound state along the outer peripheral surface of the heating roll 41.

As shown in FIGS. 3 and 6, the support portion 452 of the pressure support member 45 is formed in a relatively thick flat plate shape. An outer surface of the support portion 452 (a surface opposite to the heating roll 41) has a base end portion 452a inclined toward the second felt member 52 side along the circular orbit of the pressure belt 42, and a first holding portion. The member 46 includes an intermediate portion 452b arranged substantially in parallel with the vertical plate portion 461, and a tip portion 452c inclined toward the heating roll 41 side. As shown in FIG. 6, the outer surface of the support portion 452 including the base end portion 452a, the intermediate portion 452b, and the tip end portion 452c is not a flat surface to reduce sliding resistance with the pressure belt 42, but a pressure belt. It is constituted by the surfaces of a plurality of ribs (projections) 452a, 452b, 452c formed along the moving direction of 42. Further, the boundary between the base end portion 452a and the intermediate portion 452b and the boundary between the intermediate portion 452b and the distal end portion 452c of the support portion 452 are the first and the second portions provided along the direction intersecting the moving direction of the pressure belt 42. It is partitioned by the second partition parts 452e and 452f.

As shown in FIG. 3, the tip end 452d of the support portion 452 is formed in a curved surface shape such as a substantially arc shape in cross section. The front end 452d of the support portion 452 is a portion around which the pressure belt 42 is wound via the sliding sheet 50, and the moving direction of the pressure belt 42 moving along the outer surface of the support portion 452 is set to the fixing nip portion N. It is a part that changes in the direction toward. The front end 452d of the support portion 452 is arranged apart from the fixing nip portion N on the upstream side in the rotation direction of the pressure belt 42.

The sliding sheet 50 is made of an elongated flat rectangular sheet. The sliding sheet 50 is made of, for example, a base layer made of a fluororesin such as polytetrafluoroethylene (PTFE), and a woven or knitted fabric made of glass fibers or aramid fibers laminated on the front surface or the front and back surfaces of the base layer. Those equipped with tissues are used. Further, the sliding sheet 50 may be composed of only a single layer made of a woven fabric or a knitted fabric made of glass fiber, aramid fiber or the like. The thickness of the sliding sheet 50 can be set to about 100 to 200 μm.

In the sliding sheet 50, a plurality of oval-shaped locking holes (not shown) are opened along the longitudinal direction at the upper end in the rotational direction of the pressure belt 42. As shown in FIG. 3, the sliding sheet 50 is mounted by engaging a plurality of locking holes (not shown) with the locking projections 455 provided on the back surface of the support part 452 of the pressure support member 45. It In the sliding sheet 50, the tip end 452d of the support portion 452 of the pressure support member 45 is arranged with the upstream side along the rotation direction of the pressure belt 42 along the outer surface of the support portion 452 of the pressure support member 45. It is arranged so as to reach the fixing nip portion N via. Further, the sliding sheet 50 is required to exceed the side wall 451c of the pressing portion 451 of the pressing support member 45 after the downstream end of the pressing belt 42 in the rotation direction passes through the fixing nip portion N. It is arranged to extend for the length of.

As shown in FIG. 4, the guide members 48 and 49 are arranged at both ends of the pressure belt 42 along the longitudinal direction. The guide members 48 and 49 are formed in a bilaterally symmetrical shape, as shown in FIGS. The guide members 48 and 49 have a shape following the circular orbit of the pressure belt 42, and the outer peripheral ends of the guide members 48 and 49 extend in a direction intersecting the longitudinal direction of the pressure belt 42 from the circular orbit of the pressure belt 42. It has flat plate-shaped side plate portions 481 and 491 that project outward.

Here, the direction intersecting the longitudinal direction of the pressure belt 42 means, as shown in FIG. 5, when the center axis of the cylindrical pressure belt 42 before mounting is assumed, the direction intersects the center axis. It means the direction along the radial direction of the pressure belt 42, which is the direction in which the pressure belt 42 moves. Even in the deformed pressure belt 42 after being mounted, when the axis along the longitudinal direction is assumed inside thereof, it means the direction intersecting with the axis.

In other words, the direction intersecting the longitudinal direction of the pressure belt 42 can be said to be the direction from the inner peripheral surface side to the outer peripheral surface side along the thickness direction of the pressure belt 42.

As shown in FIG. 8, the side plate portions 481 and 491 of the guide members 48 and 49 are wound around the inner surface of the pressure belt 42, which is an inner surface along the longitudinal direction of the pressure belt 42. Guide portions 482 and 492 (an example of a guide portion), which have a shape following the track and project inward in the longitudinal direction of the pressure belt 42, are provided integrally.

As shown in FIG. 5, the pressure belt 42 is rotatably (circulatingly) guided with both ends along the longitudinal direction thereof being inserted into the guide portions 482 and 492 of the guide members 48 and 49. .. In addition, as shown in FIGS. 8A and 8B and FIG. 9, the guide portions 482 and 492 of the guide members 48 and 49 have the pressing portion 451 of the pressing support member 45 in the fixing nip portion N. Notches 483 and 493 are provided to allow direct contact with the surface of the heating roll 41 via the pressure belt 42.

The guide members 48 and 49 are also provided on the upstream side of the cutouts 483 and 493 along the rotation direction of the pressure belt 42. The pressure belt 42, as shown in FIG. In the portion N, it is pressed against the surface of the heating roll 41 while being separated from the guide portions 482 and 492.

More specifically, in the pressure support member 45, as shown in FIG. 6, the width W1 of the support portion 452 along the longitudinal direction of the pressure belt 42 substantially corresponds to the length of the guide portions 482 and 492. The width is set to be shorter than the width W2 of the pressurizing portion 451. As shown in FIG. 8A, the support portion 452 of the pressure support member 45 is arranged adjacent to the guide portions 482 and 492 of the guide members 48 and 49 along the longitudinal direction of the pressure belt 42. .. Further, the leaf spring 60 is also set to have substantially the same length as the supporting portion 452 of the pressure supporting member 45.

As shown in FIG. 8, the guide portions 482, 492 of the guide members 48, 49 have regulating portions 484, 485, 494, 495 for partially regulating both end portions along the longitudinal direction of the pressure belt 42. The pressure belt 42 is provided so as to project inward in the longitudinal direction.

In addition, as shown in FIG. 9, the side plate portions 481 and 491 of the guide members 48 and 49 are in a state where the convex portions 463, 464, 473, and 474 of the first and second holding members 46 and 47 penetrate. Through holes 486, 487, 496, 497 to be mounted are opened.

As shown in FIG. 4, arm members 71 and 72 for holding the guide members 48 and 49 are arranged on the outer surfaces of the guide members 48 and 49 along the longitudinal direction of the pressure belt 42, respectively. As shown in FIG. 10, the arm members 71 and 72 are formed to have a substantially L-shaped side surface. The arm members 71 and 72 are rotatably attached to the frame 438 of the fixing device 40 about fulcrums 712 and 722 provided on the base end portions 711 and 721 thereof. A coil spring 73 having one end fixed to the tip portions 713 and 723 of the arm members 71 and 72 as an example of a biasing unit that biases the pressure unit 44 in the direction of pressing against the heating roll 41. , 74 are connected. One ends of the coil springs 73 and 74 are locked in locking holes 714 and 724 provided in the tip portions 713 and 723 of the arm members 71 and 72. The other ends of the coil springs 73 and 74 are fixed to the frame 438 of the fixing device 40. Further, eccentric cams 75 and 76 as an example of a retracting means for moving the tip portions 713 and 723 of the arm members 71 and 72 in a direction of moving the tip portions 713 and 723 toward and away from the heating roll 41 are brought into contact with each other. Has been done. The eccentric cams 75 and 76 are rotationally driven by a drive motor (not shown).

The pressure unit 44 rotationally drives the eccentric cams 75 and 76 to press the pressure unit 44 against the surface of the heating roll 41 by the biasing force of the coil springs 73 and 74, and a fixing position (FIG. 3). The pressure unit 44 is configured to be movable to a retracted position (FIG. 11) separated from the surface of the heating roll 41 against the biasing force of the coil springs 73 and 74.

As shown in FIG. 11, the pressure belt 42 is not tensioned at the retracted position. Although the pressure belt 42 is in contact with the surface of the heating roll 41 at the retracted position, it is freely deformable because no tension is applied, and the recording paper 5 in which the conveyance failure (jam) has occurred in the fixing nip portion N occurs. Can be easily removed.

On the other hand, as shown in FIG. 3, the pressure belt 42 is moved to the fixing position and brought into pressure contact with the surface of the heating roll 41 at a required fixing pressure to apply tension. The reason why tension is applied to the pressure belt 42 at the fixing position is that the length of the orbit of the pressure belt 42 at the fixing position is set longer than the length of the pressure belt 42 in the free state. ..

The tension T applied to the pressure belt 42 may be a large value (T>0) as compared with the free state (T=0) of the pressure belt 42, and is always a significantly large value (T>>0). Does not have to be.

As shown in FIG. 3, the pressure belt 42 is stretched along the outer surface of the support portion 452 of the pressure support member 45, and the tension direction is changed by the tip 452d of the support portion 452 of the pressure support member 45. The direction is changed to the fixing nip portion N.

The support portion 452 of the pressure support member 45 is a member that comes into contact with the inner peripheral surface of the pressure belt 42 on the upstream side of the fixing nip portion N in the rotation direction of the pressure belt 42. This greatly affects the behavior, particularly the behavior of the pressure belt 42 moving along the longitudinal direction of the pressure belt 42.

When the tip of the support portion 452 of the pressure support member 45 is formed linearly along the longitudinal direction of the pressure belt 42, a constant tension acts on the pressure belt 42 along the longitudinal direction.

The pressure belt 42 is usually arranged such that the pressure distribution along the axial direction of the heating roll 41, the alignment of the heating roll 41 and the pressure belt 42, the outer diameter and the wall thickness of the heating roll 41 and the pressure belt 42. Due to various factors such as variations (tolerances), a so-called walk phenomenon of moving toward the end portion along the longitudinal direction occurs as shown in FIG. The walk phenomenon that occurs in the pressure belt 42 is also influenced and changed by disturbance such as skew of the recording paper 5.

When the walk phenomenon occurs in the pressure belt 42, the end portion of the pressure belt 42 hits one of the guide members 48 and 49, and the end portion of the pressure belt 42 is deformed such as buckling or bending inward. If it occurs, or in an extreme case, the bent end of the pressure belt 42 may be broken, and the fixing device 40 may become unusable.

Therefore, in the fixing device 40 according to the first embodiment, in order to prevent or suppress the occurrence of a walk phenomenon in the pressure belt 42, tension is applied to the pressure belt 42 so that the pressure belt 42 moves in the longitudinal direction. A portion that is in contact with the central portion along the longitudinal direction of the pressure belt 42 is provided with supporting means that is supported outside so as to be outside the both ends along the longitudinal direction of the pressure belt 42. It is possible.

In the fixing device 40, the tip end 452d of the supporting portion 452 of the pressure supporting member 45 is applied to the central portion of the pressure belt 42 along the longitudinal direction with a greater tension than the both ends, as schematically shown in FIG. By supporting, the forces F1 and F2 from the central portion along the longitudinal direction of the pressure belt 42 toward both ends are applied, respectively, and the forces F1 and F2 from the central portion toward both ends are balanced (F1= F2) prevents or suppresses the walk phenomenon from occurring in the pressure belt 42.

However, the tension is applied to the pressure belt 42 in this way, and the portion in contact with the central portion along the longitudinal direction of the pressure belt 42 is closer to the center of the pressure belt 42 than the both ends along the longitudinal direction of the pressure belt 42. When the support portion 452 of the pressurizing support member 45 located outside along the direction intersecting the longitudinal direction is provided, the following problems may occur.

That is, in the case where the pressure belt 42 is configured to suppress the occurrence of the walk phenomenon by applying a force to the pressure belt 42 from the central portion along the longitudinal direction to both ends, the pressure belt 42 moves in the longitudinal direction for some reason. If it is attempted to move to one end along the above, it is impossible to exert a force in the direction of returning from the end toward the center, or a force that prevents movement to the one end, with respect to the pressure belt 42.

Further, since the tension at both ends along the longitudinal direction of the pressure belt 42 is smaller than that at the central portion, sufficient tension cannot be applied to both ends of the pressure belt 42 and the pressure belt 42 is pressed. Deformation such as buckling easily occurs at both ends of the belt 42.

Further, the pressure belt 42 is supported at the outer side along the direction intersecting the longitudinal direction of the pressure belt 42 from the both end portions in contact with the central portion along the longitudinal direction. If the tension is weak, it becomes difficult to make the pressure belt 42 follow the shape of the central portion along the longitudinal direction of the supporting means.

In addition, the pressure belt 42 supports both ends along the longitudinal direction with a certain amount of tension, so that the central portion along the length direction extends along the direction crossing the longitudinal direction of the pressure belt 42. It is possible to favorably support the outer position.

Therefore, in this embodiment, in order to positively apply tension to both ends of the pressure belt 42 in the longitudinal direction, a means for guiding both ends of the pressure belt 42 in the longitudinal direction is provided. The support means is configured to include guide means for guiding the pressure belt 42 outside from both ends in the longitudinal direction of the pressure belt 42 along a direction intersecting the longitudinal direction of the pressure belt 42.

That is, in the first embodiment, as shown in FIGS. 6 and 13, the leading end 452d of the supporting portion 452 of the pressure supporting member 45 has the center portion along the longitudinal direction of the pressure belt 42 at both ends. In comparison, the pressure belt 42 is formed in a so-called crown shape that protrudes outwardly along a direction intersecting the longitudinal direction of the pressure belt 42.

In addition, as shown in FIG. 14, the tip end 452d of the support portion 452 of the pressure support member 45 has a central portion along the longitudinal direction of the pressure belt 42 in the rotational direction of the pressure belt 42 as compared with the both ends. Is formed in a curved shape so as to be close to the fixing nip portion N. Therefore, the central portion of the front end 452d along the longitudinal direction of the pressure belt 42 is configured such that the distance from the fixing nip portion N is shorter than that at both end portions.

Further, in the first embodiment, the guide members 48 and 49 as an example of guide means for guiding both ends of the pressure belt 42 in the longitudinal direction are configured as follows.

As shown in FIG. 15, the guide members 48 and 49 include guide portions 482a and 492a at positions corresponding to the support portion 452 of the pressure support member 45. The guide portions 482a and 492a are formed in a shape substantially following the outer surface of the support portion 452 of the pressure support member 45. The guide portions 482a and 492a include the receiving end portions 482a′ and 492a′ corresponding to the base end portion 452a of the supporting portion 452, the intermediate portions 482a″ and 492a″ corresponding to the intermediate portion 452b of the supporting portion 452, and the supporting portion 452. The front end portions 482a″′ and 492a″′ corresponding to the front end portion 452c and the front end portions 482a″″ and 492a″″ corresponding to the front end 452d of the support portion 452 are provided.

The end portions 482a' and 492a' of the guide portions 482a and 492a are formed in the same shape as the base end portion 452a of the support portion 452 including the positions thereof. Further, the intermediate portions 482a″, 492a″ and the tip portions 482a″′, 492a″′ of the guide portions 482a, 492a are in a direction intersecting the longitudinal direction of the pressure belt 42 from the tip portion 452c of the support portion 452 (pressure belt). It is arranged on the outer peripheral side in the direction from the inner peripheral surface side toward the outer peripheral surface side along the thickness direction of 42). Further, the tip ends 482a″″ and 492a″″ of the guide portions 482a and 492a are arranged on the outer peripheral side along the direction intersecting the longitudinal direction of the pressure belt 42 with respect to the tip end 452d of the support portion 452.

Further, the tip ends 482a″″ and 492a″″ of the guide portions 482a and 492a are located closer to the pressure belt 42 than the tip end 452d of the support portion 452 located at the center of the pressure support member 45 along the longitudinal direction of the pressure belt 42. Are arranged on the inner peripheral side along a direction intersecting the longitudinal direction of the.

As a result, the pressure belt 42 corresponds to the tip end 452d of the support portion 452 located at the center of the pressure support member 45 along the longitudinal direction of the pressure belt 42, as schematically shown in FIG. The tension T is greatest in the central portion along the longitudinal direction of the pressure belt 42, and then along the longitudinal direction of the pressure belt 42 corresponding to the tips 482a″″ and 492a″″ of the guide portions 482a and 492a. The tension T at both ends is large, and the regions of the pressure support member 45 located at both ends along the longitudinal direction of the pressure belt 42 have the smallest tension T corresponding to the tip 452d of the support 452.

Therefore, as shown in FIG. 16, the center portion of the pressure belt 42 is supported by the center portion of the supporting portion 452 with the largest tension T1 along the longitudinal direction thereof, and then the both ends are centered along the longitudinal direction thereof. Is supported by the tip ends 482a"", 492a"" of the guide members 48, 49 with a tension T2 smaller than that of the portion, and both end portions located inside both ends along the longitudinal direction thereof have the smallest tension by both end portions of the support portion 452. It is configured to be supported at T3 (T3<T2<T1).

<Operation of fixing device>
In the fixing device 40 according to this embodiment, the movement of the belt along the longitudinal direction is suppressed as compared with the case where the tension along the longitudinal direction of the belt is the same as described below. ..

When the fixing device 40 receives the command information of the request for the monochrome image forming operation (printing), as shown in FIG. 11, the eccentric cams 75 and 76 are rotationally driven by the drive motor (not shown), and the pressure unit 44 is moved. The mounted arm members 71 and 72 rotate counterclockwise by the urging force of the coil springs 73 and 74, and the pressure unit 44 is pressed against the heating roll 41 as shown in FIG.

At the same time, as shown in FIG. 4, the fixing device 40 is rotationally driven via the drive gear G in which the heating roll 41 is attached to one axial end thereof. The heating roll 41 is energized by the halogen lamps 414a and 414b to start heating.

As shown in FIG. 3, in the fixing device 40, as the heating roll 41 is rotated, the pressure belt 42, which is in pressure contact with the heating roll 41 in the fixing nip portion N, generates frictional force between the heating belt 41 and the heating belt 41. Followed rotation.

At this time, the pressure belt 42 is arranged such that the pressure distribution along the axial direction of the heating roll 41, the alignment of the heating roll 41 and the pressure belt 42, the outer diameter and the thickness of the heating roll 41 and the pressure belt 42. When there are various factors such as variation (tolerance) such as thickness, there is a possibility that a so-called walk phenomenon of moving toward the end along the longitudinal direction may occur, as shown in FIG.

By the way, in the fixing device 40 according to the first embodiment, as shown in FIG. 6, the leading end 452d of the supporting portion 452 of the pressure supporting member 45 has both ends at the central portion along the longitudinal direction of the pressing belt 42. It protrudes in a curved shape compared to the part. Therefore, in the pressure belt 42, as shown in FIG. 17, the tension in the central portion along the longitudinal direction of the pressure belt 42 is larger than that in both ends.

As a result, the pressure belt 42 supports the central portion along the longitudinal direction of the pressure belt 42 by the tip 452d of the support portion 452 of the pressure support member 45 with a greater tension than the both ends, and thus the pressure belt 42. Forces F1 and F2 from the center to both ends along the longitudinal direction of 42 act respectively, and the forces F1 and F2 from the center to both ends are balanced (F1=F2), whereby the pressure belt 42 The occurrence of the walk phenomenon is prevented or suppressed.

In addition, in this embodiment, as shown in FIG. 15, of the guide portions 482 and 492 of the guide members 48 and 49, the guide portion 482a″″ corresponding to the tip 452d of the support portion 452 of the pressure support member 45. , 492″″ is along the direction crossing the longitudinal direction of the pressure belt 42, rather than the tips 452d located at both ends of the supporting portion 452 of the pressure support member 45 along the longitudinal direction of the pressure belt 42. It is configured to be located on the outer peripheral side.

Therefore, as shown in FIG. 17, at the both ends along the longitudinal direction of the pressure belt 42 guided by the guide portions 482a″″″ and 492″″ of the guide members 48 and 49, as shown in FIG. In, a tension T that is smaller than the central portion along the longitudinal direction of the pressure belt 42 and larger than both end portions acts.

As a result, the pressure belt 42 is supported by the guide portions 482a"", 492"" of the guide members 48, 49 with a larger tension than the both ends of the support portion 452 along the longitudinal direction of the pressure belt 42. Thus, the forces F3 and F4 acting from both ends along the longitudinal direction of the pressure belt 42 toward the central portion act, respectively.

Therefore, the forces F3 and F4 directed from both ends toward the center can be constantly applied to both ends of the pressure belt 42 in the longitudinal direction, and the pressure belt 42 has one end in the longitudinal direction for some reason. Even when the pressure belt 42 is attempted to move to the end, it is possible to apply the forces F3 and F4 that prevent the pressure belt 42 from returning from the end toward the center, that is, to the end. Become.

Further, to the pressure belt 42, a certain amount of tension T2 can be applied to both ends along the longitudinal direction thereof, and it is possible to suppress deformation such as buckling at both ends of the pressure belt 42. You can

Furthermore, tension T2 can be applied to both ends of the pressure belt 42 along the longitudinal direction thereof, and the central portion of the pressure belt 42 along the longitudinal direction is supported by the support portion of the pressure support member 45. The shape of the tip 452d of 452 can be imitated.

Further, in the rotational direction of the pressure belt 42, the guide portions 482a″″ and 492a″″ of the guide members 48 and 49 are provided on the upstream side of the tip 452d of the support portion 452 of the pressure support member 45. As a result, the pressure belt 42 can be more reliably fixed as compared with the case where the guide portions 482a″″ and 492a″″ of the guide members 48 and 49 are provided on the downstream side of the tip 452d of the support portion 452 of the pressure support member 45. It can be along the tip 452d of the support portion 452 of the pressure support member 45.

[Embodiment 2]
FIG. 18 shows a fixing device according to the second embodiment. In the fixing device according to the second embodiment, as a supporting unit which is disposed inside the belt and which supports the central portion along the longitudinal direction of the belt on the outer side along the direction intersecting the longitudinal direction of the belt from both end portions, Instead of using the pressure supporting member, the felt member as the lubricant applying means also serves as a felt member.

As shown in FIG. 18, the first and second felt members 51 and 52 are set shorter than the entire length of the pressure belt 42 including the central portion along the longitudinal direction of the pressure belt 42. Has been done. Therefore, the pressure belt 42 is applied with a tension corresponding to the thickness of the first and second felt members 51 and 52 only at the central portion along the longitudinal direction thereof, and at both end portions along the longitudinal direction thereof. Is configured so that tension according to the thickness of the first and second felt members 51 and 52 does not act.

Further, in this embodiment, the tip end 452d of the support portion 452 of the pressure support member 45 is formed linearly along the longitudinal direction of the pressure belt 42.

Further, in this embodiment, as shown in FIG. 15, in the guide portions 482 and 492 of the guide members 48 and 49, the shape corresponding to the tip 452d of the support portion 452 of the pressure support member 45 is the pressure belt. It is formed in a shape located on the outer peripheral side in the direction intersecting the longitudinal direction of 42.

In the second embodiment, the tension along the longitudinal direction of the pressure belt 42 satisfies the relationship shown in FIG. 16 without forming the support portion 452 of the pressure support member 45 in a complicated shape. Can be configured.

The other configurations and operations are the same as those in the above-mentioned embodiment, and therefore their explanations are omitted.

[Third Embodiment]
FIG. 19 shows an image forming apparatus to which the fixing device according to the third embodiment is applied. In the first embodiment, the heating roll 41 is used as the fixing unit, and the pressure belt 42 is used as the endless belt. However, in the third embodiment, the pressure roll is used as the fixing unit. A heating belt is used as the endless belt.

That is, as shown in FIG. 19, the fixing device 40 according to the third embodiment includes a heating belt 81 and a pressure roll 82 as an example of an endless belt. A pressure pad 85 that forms the fixing nip portion N by pressing the heating belt 81 against the pressure roll 82 is provided inside the heating belt 81. Further, the pressure pad 85 is provided with a heating resistor 86. Further, both ends of the heating belt 81 along the longitudinal direction of the heating belt 81 are guided by guide members 83 and 84 as guide means.

A portion 85a of the pressure pad 85 on the upstream side of the fixing nip portion N in the rotation direction of the heating belt 81 has the same shape as the tip 452d of the support portion 452 of the pressure support member 45 of the first embodiment. Has been formed. Further, the guide members 83, 84 are formed such that a part of the upstream side of the fixing nip portion thereof has the same shape as the guide portions 482a"", 492a"" of the guide members 48, 49 of the first embodiment. ..

The other configurations and operations are the same as those in the above-mentioned embodiment, and therefore their explanations are omitted.

In addition, in the above-mentioned embodiment, the case where the pressurizing means and the supporting means are integrally formed has been described, but the present invention is not limited to this, and the pressurizing means and the supporting means may be separately formed. Of course.

Further, in the above embodiment, the case where the support means and the guide means are formed as separate bodies has been described, but the present invention is not limited to this, and the support means and the guide means may be integrally formed.

Further, in the above-described embodiment, the case where the image forming apparatus is applied to the monochrome image forming apparatus has been described, but each of the yellow (Y), magenta (M), cyan (C), and black (K) image forming apparatuses. Needless to say, the same can be applied to a full-color image forming apparatus having 10 (Y, M, C, K).

DESCRIPTION OF SYMBOLS 1... Image forming device 40... Fixing device 41... Heating roll 42... Pressurizing belt 45... Pressurizing support member 451... Pressurizing part 452... Supporting parts 48, 49... Guide members 482, 492... Guide part

Claims (8)

A rotating endless belt,
A fixing unit that forms a fixing nip portion in contact with the belt;
Pressurizing means disposed inside the belt to press the belt against the fixing means,
Supporting means disposed inside the belt, for supporting a central portion along the longitudinal direction of the belt outside from both ends along a direction intersecting the longitudinal direction of the belt,
Means for guiding both ends of the belt along the longitudinal direction, the guide for guiding outside both ends of the supporting means along the longitudinal direction of the belt along a direction intersecting the longitudinal direction of the belt. Means and
A fixing device including. 2. The fixing device according to claim 1, wherein the guiding unit guides the inside of the supporting unit from a central portion of the supporting unit along the longitudinal direction of the belt along a direction intersecting the longitudinal direction of the belt. The guide means has a tubular guide portion that guides both end portions along the longitudinal direction of the belt,
2. The fixing device according to claim 1, wherein the guide portion guides outside both ends of the belt supported by the support unit along the longitudinal direction of the belt along a direction intersecting the longitudinal direction of the belt. The fixing device according to claim 1, wherein the supporting unit supports the belt on an upstream side of the fixing nip portion along a rotation direction of the belt. The fixing device according to claim 1, wherein the supporting unit supports the belt at a central portion along the longitudinal direction of the belt with a tension higher than that of both end portions. The fixing device according to claim 5, wherein the guide unit guides the belt with a tension smaller than a central portion of the supporting unit along the longitudinal direction of the belt and larger than both end portions. The fixing device according to claim 1, wherein the guide unit guides the belt upstream of the support unit in the rotation direction of the belt. An image forming unit for forming an unfixed toner image on a recording medium,
A fixing unit for fixing the unfixed toner image formed on the recording medium;
An image forming apparatus using the fixing device according to claim 1 as the fixing unit.

Images