CN214409588U - Fixing device and image forming apparatus - Google Patents

Abstract

The utility model provides a photographic fixing device and image forming device. The fixing device of the embodiment comprises: a rotating body formed as an annular body extending in a longitudinal direction; a heater provided inside the rotating body, the heater including a plurality of heating elements arranged in sequence at a predetermined distance along the longitudinal direction; and a heat equalizer provided inside the rotating body, the heat equalizer having a long groove extending in the longitudinal direction, the heat equalizer having a plurality of spaced grooves extending in a longitudinal direction orthogonal to the longitudinal direction, the spaced grooves corresponding to the positions of the heat generating elements in the longitudinal direction. Through the utility model discloses, can avoid the record medium low temperature stained and the inhomogeneous phenomenon of gloss to appear.

Description

Fixing device and image forming apparatus

Technical Field

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

Background

In the related art, a fixing device for fixing a toner image on a recording medium by heating and pressing is known. The fixing device can fix recording media of different sizes. In order to alleviate the temperature rise of the non-sheet-passing portion when the fixing device fixes a small-sized recording medium, the heater in the fixing device may be divided, and the fixing device may operate only the heater in the sheet-passing portion depending on the size of the recording medium. The soaking member is in contact with the divided heaters in order to alleviate the temperature rise on the back side of the heaters and to reduce the temperature unevenness in the longitudinal direction of the fixing device. In addition, it is sometimes employed to provide a groove along the length direction of the soaking member to increase the amount of heat applied to the fixing belt of the fixing device.

However, since there are spaced portions between the divided heaters, the temperature of the spaced portions is lower than that of the other portions, low-temperature offset is likely to occur in the region on the recording medium to be fixed corresponding to the spaced portions, and uneven gloss on the recording medium is likely to be caused due to uneven temperature at the time of heating.

SUMMERY OF THE UTILITY MODEL

The utility model provides a prevent that recording medium from appearing low temperature stained photographic fixing device and image forming device.

The fixing device of the embodiment comprises: a rotating body formed as an annular body extending in a longitudinal direction; a heater provided inside the rotating body, the heater including a plurality of heating elements arranged in sequence at a predetermined distance along the longitudinal direction; and a heat equalizer provided inside the rotating body, the heat equalizer having a long groove extending in the longitudinal direction, the heat equalizer having a plurality of spaced grooves extending in a longitudinal direction orthogonal to the longitudinal direction, the spaced grooves corresponding to the positions of the heat generating elements in the longitudinal direction.

An image forming apparatus of another embodiment includes: an original conveying portion that conveys an original to be transferred; a scanner section that reads the original to generate image data of the original; a transfer section that forms a toner image on a recording medium according to the image data; and a fixing device that fixes the toner image on the recording medium, wherein the fixing device includes: a rotating body formed as an annular body extending in a longitudinal direction; a heater provided inside the rotating body, the heater including a plurality of heating elements arranged in sequence at a predetermined distance along the longitudinal direction; and a heat equalizer provided inside the rotating body, the heat equalizer having a long groove extending in the longitudinal direction, the heat equalizer having a plurality of spaced grooves extending in a longitudinal direction orthogonal to the longitudinal direction, the spaced grooves corresponding to the positions of the heat generating elements in the longitudinal direction.

Through the utility model discloses, can avoid the record medium low temperature stained and the inhomogeneous phenomenon of gloss to appear.

Drawings

FIG. 1 is a schematic view of an image forming apparatus according to the present invention;

FIG. 2 is a schematic view of a fixing device of an image forming apparatus according to the present invention;

FIG. 3 is a schematic view of a fixing device according to the present invention, in which a heater is divided into a plurality of heating regions;

FIG. 4 is a schematic view showing a temperature distribution when a rotary body of the fixing device of the present invention is heated;

fig. 5 is a schematic structural view of a heater and a soaking part of the fixing device according to the present invention.

Detailed Description

Hereinafter, a fixing device and an image forming apparatus according to an embodiment will be described with reference to the drawings. In the drawings, the same components are denoted by the same reference numerals.

For convenience of explanation, coordinate axes are shown in the drawings. The X-axis direction is a lateral direction (hereinafter also referred to as a horizontal direction) of the fixing device and the image forming apparatus. The Y-axis direction is a longitudinal direction (hereinafter also referred to as a vertical direction) of the fixing device and the image forming apparatus. The Z-axis direction is a depth direction (hereinafter also referred to as a longitudinal direction) of the fixing device and the image forming apparatus. The X, Y and Z directions are orthogonal to each other. The direction of the fixing device and the image forming apparatus along the X-axis arrow is the right side, the direction of the fixing device and the image forming apparatus along the Y-axis arrow is the upper side, and the direction of the fixing device and the image forming apparatus along the Z-axis arrow (toward the back side in fig. 1) is the rear side, and the left side, the lower side, and the front side are opposite to the above. In the drawings, the structure is shown enlarged, reduced, or omitted as appropriate for convenience of explanation. When the orientations of the + X (+ Y, + Z) direction and the-X (-Y, -Z) direction are not considered or both directions are included, the directions are simply referred to as the X (Y, Z) directions.

Fig. 1 is a schematic configuration diagram of an image forming apparatus 1 according to the present invention.

As shown in fig. 1, the image forming apparatus 1 of the present embodiment is, for example, a multifunction peripheral (MFP), a printer, a copier, or the like. The image forming apparatus 1 forms an image on a recording medium based on image data read on a document. Next, a case where the image forming apparatus 1 is a multifunction peripheral will be described.

The image forming apparatus 1 has a main body 11. An image reading portion 12 is provided on an upper portion of the main body 11, and the image reading portion 12 is used to read an original to generate image data of the original. The image reading portion 12 is composed of a document conveying portion 13 and a scanner portion 14.

A scanner unit 14 is provided below the document conveying unit 13. The original conveying portion 13 conveys an original to be transferred to the scanner portion 14. The scanner section 14 has an optical mechanism 15, and the scanner section 14 reads the original to be transferred conveyed by the original conveying section 13 or the original to be transferred placed directly on a platen glass of the scanner section 14 through the optical mechanism 15 to generate image data of the original.

The optical mechanism 15 moves in the lateral direction along the platen glass when reading an image of an original directly placed on the platen glass of the scanner section 14. The optical mechanism 15 reads an original image on one original page line by line. When reading an image of a document conveyed by the document conveying portion 13, the optical mechanism 15 reads the conveyed document at a fixed position shown in fig. 1.

An operation display unit 16 is provided on the front side of the scanner unit 14 and above the main body 11. The operation display unit 16 has a function of receiving an operation by an operator and displaying a state of the image forming apparatus 1. The operation display unit 16 is, for example, a touch-enabled liquid crystal display.

The main body 11 has a transfer portion 17 at the center in the longitudinal direction. The main body 11 includes a plurality of paper feed cassettes 18 in a lower portion thereof for supplying a recording medium to the transfer unit 17. The plurality of paper feed cassettes have substantially the same configuration and are arranged so as to overlap one another in order from the upper side toward the lower side.

The sheet feeding cassette 18 has a sheet feeding mechanism 19. The paper feed mechanism 19 takes out the recording media P one by one from the paper feed cassette 18 and conveys the recording media P to a conveyance path. For example, the paper feeding mechanism 19 may include a pickup roller, a separation roller, and a paper feeding roller.

The paper feed cassette 18 accommodates recording media (paper sheets) P of various sizes.

The transfer portion 17 forms a toner image on the recording medium P using toner from the image data read by the scanner portion 14, or image data made by a personal computer or the like.

The transfer portion 17 has a plurality of image forming units 51 that form images using different color toners (e.g., yellow, magenta, cyan, black, etc.), an exposer 52, and an intermediate transfer belt 53. The transfer unit 17 converts the image data into color signals of the respective colors, and controls the exposure unit 52 based on the color signals of the respective colors.

The configuration of the transfer section 17 is not limited to this, and the transfer section may have two or three image forming units, or the transfer section may have five or more image forming units.

The image forming units 51 are arranged in parallel below the intermediate transfer belt 53 (in a direction from the left side to the right side in fig. 1).

The exposure unit 52 irradiates exposure light L to each image forming unit 51. The exposer 52 may generate a laser scanning beam as the exposure light. The exposure unit 52 may be configured to include a solid-state scanning element such as a light-emitting diode that generates exposure light.

The structures of the respective image forming units 51 are the same as each other except that the colors of the toners are different. Examples of the toner include a decolorable toner which can be decolored (invisible) by an external stimulus (e.g., temperature, light having a specific wavelength, or pressure), and a normal non-decolorable toner. A toner that is decolored by temperature decolors when it reaches a specific decoloring temperature or higher, and develops color when it is equal to or lower than a specific restoration temperature.

The image forming unit 51 has a photosensitive drum as an image carrier. The photosensitive drum has a photosensitive body (e.g., an organic photoconductor) on an outer circumferential surface. Around the photosensitive drum, the image forming unit 51 is provided with a charger for uniformly charging the outer periphery of the photosensitive drum, a developing unit for developing an electrostatic latent image on the photosensitive drum, a primary transfer roller, a drum cleaner for removing residual toner on the surface of the photosensitive drum, and the like.

The exposer 52 generates exposure light L modulated according to image data. The exposure light L exposes the surface of the photosensitive drum of the image forming unit 51. The potential of the area on the photosensitive drum irradiated with light is changed to form an electrostatic latent image.

The intermediate transfer belt 53 is an endless belt member that circulates, and the intermediate transfer belt 53 is stretched over a driving roller 69 and a plurality of driven rollers 70.

The intermediate transfer belt 53 is in contact with the photosensitive drum of the image forming unit 51 from above. A primary transfer roller is disposed above the image forming unit 51 at a position facing the photosensitive drum via the intermediate transfer belt 53. The primary transfer roller is disposed inside the intermediate transfer belt 53. The primary transfer roller transfers the toner image formed on the photosensitive drum of the image forming unit 51 onto the intermediate transfer belt 53 when a primary transfer voltage is applied. After the toner images on the photosensitive drums of the plurality of image forming units are sequentially transferred onto the intermediate transfer belt 53 in such a manner as to overlap each other, toner images formed of the toners of the respective colors are formed.

The secondary transfer roller 71 faces the drive roller 69 across the intermediate transfer belt 53. The contact portion between the intermediate transfer belt 53 and the secondary transfer roller 71 constitutes a secondary transfer position. The driving roller 69 drives the intermediate transfer belt 53 to rotate. When the recording medium P passes through the secondary transfer position, a secondary transfer voltage is applied to the secondary transfer roller 71, and the secondary transfer roller 71 secondarily transfers the toner image on the intermediate transfer belt 53 onto the recording medium P.

A belt cleaner 72 is disposed at a position facing one of the driven rollers 70 across the intermediate transfer belt 53. The belt cleaner 72 removes the residual transfer toner on the intermediate transfer belt 53 from the intermediate transfer belt 53. Specifically, the belt cleaner 72 may be a resin member made of urethane or the like.

A conveying path from the paper feed cassette 18 to the secondary transfer roller 71 is provided with a pair of conveying rollers 75 and a pair of registration rollers 76. The pair of transport rollers 75 transport the recording medium P taken out of the paper feed cassette 18 by the paper feed mechanism 19.

The pair of registration rollers 76 align the positions of the leading ends of the recording medium P fed from the pair of transport rollers 75 at the positions where they abut against each other. The positions of the pair of registration rollers 76 in contact with each other constitute registration positions. The pair of registration rollers 76 conveys the recording medium P such that the leading end of the region on the recording medium P to which the toner image is to be transferred reaches the secondary transfer position when the leading end of the toner image reaches the secondary transfer position.

The fixing device 3 is disposed downstream (upper side in fig. 1) of the secondary transfer roller 71 in the conveying direction of the recording medium P. The fixing device 3 fixes the toner image on the recording medium P by applying heat and pressure.

A discharge roller pair 21 is disposed downstream (upper left side in fig. 1) of the fixing device 3 in the conveying direction of the recording medium P. The discharge roller pair 21 discharges the recording medium P to the sheet discharge portion 22.

A reverse conveyance path 10 is disposed downstream (right side in fig. 1) of the fixing device 3 in the conveyance direction of the recording medium P. The reverse conveyance path 10 reverses the recording medium P and guides the recording medium P to the secondary transfer roller 71. The reverse conveyance path 10 is used when performing duplex printing.

Next, the structure of the fixing device 3 in the image forming apparatus 1 according to the present invention will be described with reference to fig. 2.

Fig. 2 is a schematic configuration diagram of the fixing device 3 in the image forming apparatus 1 according to the present invention.

As shown in fig. 2, in the present embodiment, the fixing device 3 includes a rotating body 31, a pressurizing unit 32, a heater 312, a soaking unit 313, and the like. In the following description, an exemplary pass will be described with the fixing belt as the rotating body 31, and an exemplary pass will be described with the pressure roller as the pressure section 32. The direction in which the recording medium P is conveyed in the fixing device 3 (the direction substantially parallel to the longitudinal direction) is referred to as the "conveying direction", the direction orthogonal to the recording medium conveying direction (the direction parallel to the Z axis) is referred to as the "width direction", the dimension of the recording medium P extending in the Z axis direction is referred to as the width dimension, and the dimension of the recording medium P extending in the conveying direction is referred to as the length dimension.

In the present embodiment, the fixing device 3 is surrounded by a casing, not shown, and an entrance opening through which the recording medium P enters and a discharge opening through which the recording medium P is discharged are formed in the casing of the fixing device 3. For example, the entrance opening of the fixing device 3 is provided on the lower side in the longitudinal direction (Y-axis direction) (-Y direction). The discharge opening of the fixing device 3 is provided on the upper side (+ Y direction) in the longitudinal direction (Y axis direction). In addition, guides, not shown, for guiding the recording medium P are provided at the entrance opening and the discharge opening of the fixing device 3.

As shown in fig. 2, the rotating body 31 is formed in a cylindrical shape having a small thickness, and the rotating body 31 is, for example, a fixing belt. The rotating body 31 has an annular cross section, and the fixing belt as the rotating body 31 extends in the longitudinal direction (Z-axis direction), whereby the rotating body 31 is formed into an annular body. The rotating body 31 is formed of a heat-resistant flexible material. The outer peripheral surface of the rotating body 31 has a base layer made of a polyimide base material, an elastic layer made of silicone rubber formed outside the base layer, and a release layer made of a resin material having good releasability from toner formed outside the elastic layer. The material of the release layer is, for example, polytetrafluoroethylene. In addition, an elastic layer is not necessary. The rotating body 31 extends in the longitudinal direction (Z-axis direction) to a dimension larger than the width dimension of the recording medium P having the maximum width that can pass through the fixing device 3. The rotating body 31 is supported to be rotatable about its central axis C1.

The pressing portion 32 is a columnar roller extending in the longitudinal direction (Z-axis direction), and a pressing roller as the pressing portion 32 is provided at a position facing the fixing belt as the rotating body 31 in the horizontal direction (X-axis direction). The pressurizing portion 32 is supported to be rotatable about its own center axis C2, and rotation shafts (not shown) extend from both ends in the longitudinal direction (Z-axis direction) of the pressurizing portion 32. Each rotation shaft is disposed coaxially with the center axis C2 of the pressure section 32.

The pressing portion 32 has a metal core 321 and an elastic layer 322. The metal core 321 is a cylindrical member, and is made of, for example, an aluminum alloy. Rotation shafts (not shown) extend from both ends of the metal core 321 in the longitudinal direction (Z-axis direction), and are coaxial with the center axis C2 of the metal core 321. The elastic layer 322 is stacked in a cylindrical shape on the outer peripheral surface of the metal core 321. The elastic layer 322 has a dimension in the longitudinal direction (Z-axis direction) larger than the width dimension of the recording medium P having the maximum width that can pass through the fixing device 3. The elastic layer 322 is formed of, for example, a heat-resistant rubber material or the like. The outer peripheral surfaces of both end portions of the metal core 321 in the longitudinal direction (Z-axis direction) are not covered with the elastic layer 322.

The rotating body 31 and the pressing portion 32 face each other in the horizontal direction (X-axis direction). The pressing portion 32 further includes a base layer and a release layer, not shown, on the outer side of the elastic layer 322, and the base layer is made of a fluorine resin such as polyimide, for example. A biasing member (not shown) is further provided on the right side (+ X direction) of the pressing portion 32 in the horizontal direction (X axis direction), and the biasing member (e.g., a spring or the like) biases the pressing portion 32 in the horizontal direction (X axis direction) so that the pressing portion 32 moves toward the rotating body 31. When the pressing portion 32 is biased, the outer peripheral surface of the rotating body 31 abutting against the pressing portion 32 is bent along the outer peripheral surface of the pressing portion 32. The inner peripheral surface of the rotating body 31 abutting against the pressure section 32 is brought close to a heater 312 described later and brought into close contact with the heater 312. A nip 33 of the fixing device 3 is formed between the rotating body 31 and the pressing portion 32, and when the recording medium P enters the nip 33 between the pressing portion 32 and the rotating body 31, the pressing portion 32 presses the recording medium P.

The pressurizing unit 32 is rotationally driven by a drive source such as a motor, not shown, provided in the main body 11. When the pressure section 32 is the driving side, when the pressure section 32 rotates about its own axis C2, the rotary body 31 is biased leftward (-X direction) in the horizontal direction (X axis direction) by the pressure section 32, so that the inner peripheral surface of the rotary body 31 is in close contact with the heater 312, the outer peripheral surface of the rotary body 31 is in contact with the outer peripheral surface of the pressure section 32, and the rotary body 31 rotates by friction with the pressure section 32. Since the driving force of the pressing portion 32 is transmitted to the rotating body 31 via the nip portion 33, the rotating body 31 rotates about its own axis C1 following the rotation of the pressing portion 32. The recording medium P entering the nip 33 is conveyed downstream in the conveyance direction by the rotation of the pressing portion 32 and the rotating body 31.

In the present embodiment, the heater 312 and the soaking section 313 are provided inside the rotating body 31. A part of the support portion 314 supporting the heater 312 is provided inside the rotating body 31.

The heater 312 is a member capable of heating the rotating body 31 inside the rotating body 31, and in the present embodiment, the heater 312 is disposed on the inner peripheral side of the rotating body 31, the heater 312 is a plate-like member extending in the longitudinal direction (Z-axis direction) and having a constant thickness in the horizontal direction (X-axis direction), the surface of the plate-like heater 312 facing the inner peripheral side of the rotating body 31 is referred to as a front surface, and the surface of the plate-like heater 312 facing away from the rotating body 31 and facing the soaking portion 313 is referred to as a rear surface. The front surface of the plate-like heater 312 faces the inner circumferential surface of the rotating body 31. The back surface of the plate-like heater 312 faces away from the inner circumferential surface of the rotating body 31. The heater 312 extends in the longitudinal direction (Z-axis direction) to a size larger than the size of the recording medium P of the maximum width that can pass through the fixing device 3 in the width direction.

The heater 312 is disposed at a position facing the pressure section 32 with the rotating body 31 interposed therebetween in the horizontal direction (X-axis direction). The surface of the heater 312 facing the pressing portion 32 through the rotating body 31 slidably abuts against the inner circumferential surface of the rotating body 31, the pressing portion 32 presses the heater 312 through the rotating body 31, and the rotating body 31 is sandwiched between the heater 312 and the pressing portion 32. When the heater 312 abuts against the rotating body 31, a region of the rotating body 31 that faces the heater 312 is heated.

When the rotating body 31 rotates, the heater 312 operates so that the temperature of the rotating body 31 reaches a fixing temperature necessary for fixing the toner image. The recording medium P reaching the nip 33 is heated in the nip 33, and the toner image is fixed to the recording medium P.

In the above description, the heater 312 is described as being in direct contact with the inner peripheral surface of the rotating body 31, but the present invention is not limited to this, and when the pressing portion 32 is biased toward the rotating body 31, the pad between the heater 312 and the inner peripheral surface of the rotating body 31 may be brought into contact with the inner peripheral surface of the rotating body 31, thereby reducing wear of the heater 312 and the rotating body 31.

Next, a structure in which the heater 312 has a plurality of heating regions will be described with reference to fig. 3.

Fig. 3 is a schematic structural view of the fixing device 3 according to the present invention in which the heater 312 is divided into a plurality of heating regions.

As shown in fig. 3, the heater 312 has a substrate 316 made of a ceramic material. The heater 312 has a plurality of heating elements 315 on a substrate 316, the plurality of heating elements 315 are sequentially arranged at a predetermined distance in a longitudinal direction (Z-axis direction), and the heating elements 315 may be, for example, thermal resistors. The heat generating element 315 functions as a member for heating the recording medium P passing through the fixing device 3.

The heater 312 in the present embodiment includes a plurality of heat generating elements 315. Each of the heat generating elements 315 is configured to be controlled by the fixing device 3 and to operate independently. The heater 312 is divided into a plurality of heating zones arranged in the longitudinal direction (Z-axis direction) by providing a plurality of heating elements 315 at intervals. The plurality of heating areas are switched to a heating state or a non-heating state (an energized state and a non-energized state) according to the width of the recording medium P being conveyed. For example, when the number of the heating elements is seven, the heating elements are divided into seven regions. Each of the heat generating elements 315 on the substrate 316 may be individually temperature controlled to generate heat. The heat of the heat generating element 315 is transferred to the rotating body 31 in contact with the heater 312 in the horizontal direction (X-axis direction).

As shown in fig. 3, in the fixing device 3 of the present embodiment, when the small-sized recording medium P1 is conveyed and fixed, it is not necessary to operate all the heat generating elements 315, but it is only necessary to selectively energize and heat some of the heat generating elements 315 depending on the size of the recording medium P1 in the width direction, that is, to operate the heat generating elements 315 covering the paper passing region N of the small-sized recording medium, and for example, when the width of the recording medium P1 is the smallest size, only three heat generating elements 315 arranged at the center in the length direction (Z-axis direction) heat. When the maximum-size recording medium P2 is conveyed for fixing, the recording medium P2 covers the entire heat generating elements 315 of the heater 312 in the width direction, and all the heat generating elements 315 located in the length direction (Z-axis direction) of the heater 312 perform heating.

The determination of the width dimension of the recording medium P by the fixing device 3 may be a setting made manually before the recording medium P is conveyed to the fixing device 3. However, in addition to this, the determination of the width dimension of the recording medium P may be automatically performed based on the detection result of the sensor.

In this way, when the fixing device fixes the small-sized recording medium P1, the heat generating element 315 of the non-sheet passing portion (portion other than the sheet passing region N) does not operate, and therefore, an excessive increase in the temperature of the non-sheet passing region can be avoided.

In order to keep the heat quantity in the longitudinal direction (Z-axis direction) uniform in the heater 312 dividing the plurality of heating regions, local temperature rise is prevented from being excessively high. The fixing device 3 of the present embodiment is further provided with a soaking section 313.

As shown in fig. 2, the soaking section 313 is a member capable of uniformizing the heat of the heater 312 along the longitudinal direction (Z-axis direction) of the rotating body 31 inside the rotating body 31. In the present embodiment, the heat equalizing portion 313 is disposed on the inner peripheral side of the rotating body 31, and the heat equalizing portion 313 is formed in a plate shape extending in the longitudinal direction (Z-axis direction) and having a constant thickness in the horizontal direction (X-axis direction). The heat equalizing portion 313 faces the pressurizing portion 32 with the heater 312 interposed therebetween. One of two side surfaces of the plate-shaped soaking section 313 orthogonal to the horizontal direction (X-axis direction) faces the back surface of the heater 312. The dimension of the heat equalizing portion 313 extending in the longitudinal direction (Z-axis direction) coincides with the dimension of the heater 312 extending in the longitudinal direction (Z-axis direction).

The entire soaking section 313 is brought into contact with the heater 312, whereby the temperature of the heater 312 can be soaked. However, when the entire rear surface of the heater 312 is in contact with the soaking section 313, the heat of the heater 312 is likely to be excessively transferred to the soaking section 313. At this time, the heating performance of the heater 312 with respect to the rotating body 31 is lowered, and the rotating body 31 is not easily heated by the heater 312.

Therefore, in order to increase the amount of heat applied to the rotating body 31, a long groove 317 extending in the longitudinal direction (Z-axis direction) is also formed in the soaking portion 313.

Since the thermal conductivity of air is smaller than that of metal, when the long groove 317 is formed in the soaking part 313, the long groove 317 is filled with air. The temperature on the back surface of the heater 312 is not easily transmitted to the long groove 317, and the heat of the heater 312 is more easily applied to the rotating body 31 through the portion in contact with the rotating body 31, and at this time, the temperature increase rate of the rotating body 31 is good. The temperature increase of the rotating body 31 can be accelerated by forming the long groove 317 in the longitudinal direction (Z-axis direction) of the soaking section 313.

The support portion 314 is a sheet metal member extending in the longitudinal direction (Z-axis direction), and the support portion 314 supports the rotating body 31, the soaking portion 313, and the heater 312. Support portions 314 support both end portions of rotating body 31 in the longitudinal direction (Z-axis direction), and support portions 314 support rotating body 31 so as to be rotatable. Heater 312 is held on support 314. The support portion 314 is parallel to the heater 312 in the longitudinal direction (Z-axis direction), and the support portion 314 is formed of, for example, a thermosetting resin.

Next, the temperature distribution when the fixing device 3 is heated will be described with reference to fig. 3 and 4.

Fig. 4 is a schematic view of the temperature distribution when the rotary body 31 of the fixing device 3 of the present invention is heated. In fig. 4, vertical lines indicate the temperature at positions on the rotary body 31 that face the respective heating elements 315 of the heater 312 at intervals in the longitudinal direction (Z-axis direction).

As shown in fig. 3 and 4, when the heat generating elements 315 of the heater 312 are spaced apart by a certain distance in the length direction (Z-axis direction), the temperature distribution of the surface of the rotating body 31 during heating is not uniform. As is clear from fig. 4, since the temperature of the position on the rotating body 31 facing the space between the respective heat generating elements 315 in the longitudinal direction (Z-axis direction) is lower than the temperature of the other positions of the rotating body 31, low-temperature offset of the recording medium heated by the fixing device 3 and fixed and uneven gloss due to temperature unevenness are likely to occur.

Next, the structure of the fixing device 3 capable of avoiding the low-temperature offset and the uneven gloss of the recording medium in the present embodiment will be described with reference to fig. 5.

Fig. 5 is a schematic structural view of the heater 312 and the soaking unit 313 in the fixing device 3 according to the present invention. In fig. 5, for the sake of clarity, the heater 312 and the soaking section 313 are shown as being shifted by a certain distance in the longitudinal direction (Y-axis direction), that is, the soaking section 313 is shown as being positioned below the normal state (-Y direction), and the heater 312 is shown as being positioned above the normal state (+ Y direction). However, the fixing device 3 is normally configured such that the heat equalizing portion 313 and the heater 312 are opposed to each other in the horizontal direction (X-axis direction) and the heat equalizing portion 313 and the heater 312 are held at the same height position in the vertical direction (Y-axis direction) as shown in fig. 2.

As shown in fig. 5, in the present embodiment, a plurality of spacing grooves 318 are further formed in the soaking section 313. Each of the spaced grooves 318 is a groove extending in the longitudinal direction (Y-axis direction) in the soaking portion 313, and each of the spaced grooves 318 penetrates the soaking portion 313 in the longitudinal direction (Y-axis direction). The plurality of spaced grooves 318 are arranged in this order at a constant distance along the longitudinal direction (Z-axis direction) of the soaking section 313. A plurality of spacing grooves 318 are formed on the surface of the soaking section 313 facing the heater 312. As shown in fig. 5, the position of the spacing groove 318 corresponds to the position of the interval between the heat generating elements 315 of the heater 312 in the longitudinal direction (Z-axis direction), and the position of each spacing groove 318 corresponds to the position of each interval between the adjacent heat generating elements 315.

In the present embodiment, by arranging a plurality of longitudinal spacing grooves 318 in this order at a fixed distance in the longitudinal direction (Z-axis direction) of the soaking section 313 and by arranging the plurality of spacing grooves 318 at positions corresponding to the positions of the plurality of heating elements 315 of the heater 312 spaced apart in the longitudinal direction (Z-axis direction), when the soaking section 313 and the heater 312 are brought into close contact in the horizontal direction (X-axis direction), since the spacing grooves 318 are filled with air, the temperature at the space formed in the longitudinal direction (Z-axis direction) of each heating element 315 on the heater 312 is not easily transmitted to the spacing grooves 318 and is more easily applied to the rotating body 31 by contact with the rotating body 31 because the thermal conductivity of air is smaller than that of metal, and therefore the temperature at the position on the rotating body 31 facing the space formed in the longitudinal direction (Z-axis direction) of each heating element 315 of the heater 312 can be increased, this can reduce temperature unevenness on the rotating body 31, and can provide effects of preventing low-temperature offset and preventing unevenness of gloss.

In the present embodiment, the number of the spacing grooves 318 may be adjusted to suit different situations according to the characteristics of the heater 312.

As shown in fig. 5, the shape of the spacing groove 318 is configured to be rectangular in order to better correspond to the interval in the longitudinal direction (Z-axis direction) of each of the heating elements 315 of the heater 312, but is not limited thereto, and may be other shapes such as a trapezoid, a parallelogram, or the like.

In order to make the heat transfer in the soaking section 313 as uniform as possible, the dimension of the long groove 317 formed in the horizontal direction (X-axis direction) is set to be the same as the dimension of the spacing groove 318 formed in the horizontal direction (X-axis direction), that is, the depth of the long groove 317 is the same as the depth of the spacing groove 318.

According to at least one embodiment described above, the formation of the spacer grooves in the soaking portion corresponding to the intervals between the heating elements of the heater can improve the low-temperature region of the rotating body in a targeted manner, thereby reducing temperature unevenness in the rotating body, and achieving the effects of preventing low-temperature contamination and preventing gloss unevenness.

While several embodiments of the present invention have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the invention. These new embodiments can be implemented in other various manners, and various omissions, substitutions, combinations, and changes can be made without departing from the gist of the present invention. These embodiments and modifications are included in the scope and gist of the present invention, and are included in the present invention described in the claims and the equivalent scope thereof.

Claims (10)

1. A fixing device is characterized by comprising:

a rotating body formed as an annular body extending in a longitudinal direction;

a heater provided inside the rotating body, the heater including a plurality of heating elements arranged in sequence at a predetermined distance along the longitudinal direction; and

and a heat equalizer provided inside the rotating body, the heat equalizer having a long groove formed therein and extending in the longitudinal direction, the heat equalizer having a plurality of spaced grooves formed therein and extending in a longitudinal direction orthogonal to the longitudinal direction, the spaced grooves being located at positions corresponding to positions of spaces between the heat generating elements in the longitudinal direction.

2. A fixing device according to claim 1, further comprising:

a pressing portion which abuts against the rotating body,

wherein the heat equalizing portion faces the pressure portion with the heater interposed therebetween.

3. A fixing device according to claim 1,

the depth of the long groove is the same as that of the spacing groove.

4. A fixing device according to claim 1,

the shape of the spacing groove is rectangular.

5. A fixing device according to claim 1,

the heating element is a thermal resistor.

6. An image forming apparatus, comprising:

an original conveying portion that conveys an original to be transferred;

a scanner section that reads the original to generate image data of the original;

a transfer section that forms a toner image on a recording medium according to the image data; and

a fixing device that fixes the toner image on the recording medium,

wherein the fixing device has:

a rotating body formed as an annular body extending in a longitudinal direction;

a heater provided inside the rotating body, the heater including a plurality of heating elements arranged in sequence at a predetermined distance along the longitudinal direction; and

and a heat equalizer provided inside the rotating body, the heat equalizer having a long groove formed therein and extending in the longitudinal direction, the heat equalizer having a plurality of spaced grooves formed therein and extending in a longitudinal direction orthogonal to the longitudinal direction, the spaced grooves being located at positions corresponding to positions of spaces between the heat generating elements in the longitudinal direction.

7. The image forming apparatus according to claim 6, further comprising:

a pressing portion which abuts against the rotating body,

wherein the heat equalizing portion faces the pressure portion with the heater interposed therebetween.

8. The image forming apparatus according to claim 6,

the depth of the long groove is the same as that of the spacing groove.

9. The image forming apparatus according to claim 6,

the shape of the spacing groove is rectangular.

10. The image forming apparatus according to claim 6,

the heating element is a thermal resistor.

Images