Patent Application
20210072676
This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2019-162127, filed on Sep. 5, 2019, the entire contents of which are incorporated herein by reference.
The present disclosure generally relates to image forming apparatuses and fixing devices in image forming apparatuses.
An image forming apparatus, such as a multifunctional peripheral (MFP) or a laser printer, includes a fixing device used for fixing a toner image to a sheet. The fixing device transfers heat from a heater to the sheet working in conjunction with, for example, a fixing belt. Printing of an image, text or the like on the sheet is realized by fixing the toner image to sheet.
In fixing devices for this purpose, a pressing pad located on one side of the fixing belt presses against the fixing belt a position corresponding to a pressure roller to thereby form a nip between the fixing belt and the pressure roller. Therefore, when the fixing belt and the pressure roller rotate as the sheet passes through the nip, the inner peripheral surface of the fixing belt, against which the pressing pad presses, must slide while contacting the pressing pad. Therefore, a lubricant, such as silicone oil, is typically applied to the inner peripheral surface of the fixing belt. This reduces the frictional resistance of the fixing belt with respect to pressing pad.
However, it is known that such a lubricant (e.g., the silicone oil) may leak out from the edges of the fixing belt, or also may eventually evaporate with heating/use. As a result, the sliding performance of the fixing belt tends to gradually decrease. Therefore, there have been proposed various techniques for suppressing such deterioration in the performance of the fixing belt by supplying additional lubricant to the inner peripheral surface of the fixing belt even during the operation of the image forming apparatus.
In the conventional technique, since the additional lubricant is applied to the inner peripheral surface of the fixing belt by a lubricant supply member, it is possible to suppress the deterioration in the sliding performance of the fixing belt. However, when the lubricant is heated, its viscosity is concomitantly decreased, and this additional lubricant will more easily leak from the inner peripheral surface of the fixing belt. Therefore, when the operation time of the fixing device is extended in duration, the lubricant that is initially present may be insufficient. If a grease or the like having a high viscosity is used as a lubricant, it is possible to suppress this potential outflow of lubricant, but there is a problem with use of such a higher viscosity lubricant since such a material provides increased the viscous resistance and thus frictional resistance during operation is increased.
According to at least one embodiment, a fixing device for fixing a toner image to a sheet is provided. The fixing device includes a rotatable heated body with a length dimension in a first direction. The rotatable heated body has an inner facing surface and an outer facing surface. A heater is provided for heating the rotatable heated body. The heater has a length dimension in the first direction corresponding to the length dimension of the rotatable heated body. A pressing member contacts the inner facing surface of the rotatable heated body at a first position. A pressing roller presses against the outer facing surface of the rotatable heated body at a position corresponding to the pressing member. A lubricant holding member has a length dimension in the first direction and a lubricating surface contacting the inner facing surface of the rotatable heated body at a second position. The lubricant holding member has a plurality of recesses in the lubricating surface that are spaced from each other along the length dimension of the lubricant holding member.
Hereinafter, an image forming apparatus according to example embodiments will be described with reference to the accompanying drawings. In the description, an XYZ coordinate system consisting of an X-axis, a Y-axis, and a Z-axis orthogonal to each other is used as appropriate for the purposes of explanation.
A scanner 15 for reading a document is provided below the platen 12. The scanner 15 reads an original document fed by the auto document feeder 13 or an original document that has been manually placed on the platen 12 to generate image data. The scanner 15 includes an image sensor 16.
The image sensor 16 reads an image from the document while moving in the +X direction along the platen 12. The image sensor 16 is used when reading an image from a document that has been placed on the platen 12. Furthermore, when reading a document supplied by the auto document feeder 13, the image sensor 16 can be fixed to the position shown in
An image forming section 17 is arranged inside the main body 11. The image forming section 17 forms a toner image on a recording medium, such as sheet of paper fed from a sheet cassette 18, based on image data read by the scanner 15 and image data generated by a personal computer or the like.
The image forming section 17 includes image forming sections 20Y, 20M, 20C, and 20K for forming latent images using toners of the respective colors yellow (Y), magenta (M), cyan (C), and black (K). Scanning heads 19Y, 19M, 19C, and 19K are provided corresponding to of the image forming sections 20Y, 20M, 20C, and 20K. The image forming section 17 in this embodiment includes an intermediate transfer belt 21.
The image forming sections 20Y, 20M, 20C, and 20K are disposed below the intermediate transfer belt 21. In image forming section 17, image forming sections 20Y, 20M, 20C, and 20K are arranged from the −X side to the +X side. Scanning heads 19Y, 19M, 19C, and 19K are disposed under image forming sections 20Y, 20M, 20C, and 20K, respectively.
Image forming section 20K has a photosensitive drum 22. A charger 23, a developing device 24, a primary transfer roller 25, a cleaner 26, and the like are disposed around the photosensitive drum 22 in the state order along the direction indicated by the arrow t. The photosensitive drum 22 is irradiated with laser light from the scanning head 19K at an exposure position. When the surface of the rotating photosensitive drum 22 is irradiated with laser light, an electrostatic latent image is formed on the surface of the photosensitive drum 22.
The charger 23 in the image forming section 20K uniformly charges the surface of the photosensitive drum 22. The developing device 24 supplies toner to the photosensitive drum 22 via the developing roller 24a to which the developing bias is applied, thereby developing the electrostatic latent image. The cleaner 26 separates and removes residual toner left on the surfaces of photo sensitive drum 22 by using the blade 27. The toner separated by the blade 27 is collected in the cleaner 26.
As shown in
A secondary transfer roller 33 is disposed opposite to the drive roller 31 that can be used for stretching/tensioning the intermediate transfer belt 21. When the sheet P passes between the drive roller 31 and the secondary transfer roller 33, the secondary transfer roller 33 applies a secondary transfer bias to the sheet P. Thus, the toner image formed on the intermediate transfer belt 21 is transferred onto the sheet P (referred to as a secondary transfer). As shown in
As shown in
A fixing device 50 is provided above the secondary transfer roller 33. A sheet discharge roller 37 is provided above the fixing device 50. The sheet P that has been passed through the intermediate transfer belt 21 and the secondary transfer roller 33 is heated by the fixing device 50. Thus, the toner image is fixed to the sheet P by heat. The sheet P that has passed through the fixing device 50 is then discharged to the sheet discharge unit 38 (e.g., a discharge tray) by the sheet discharge roller 37.
The base member 80 is long in the Y-axis direction and has U-shaped cross section in the XZ plane. The base member 80 is made of, for example, iron, stainless steel, or the like. The base member 80 is substantially equal in length to the heating roller 60 and is supported horizontally so as to be parallel to the Y-axis.
The pressing pad 81 is similarly long in direction of the Y-axis direction. Pressing pad 81 has a length substantially equal to that of the length of the heating roller 60. The material of the pressing pad 81 is, for example, a silicone rubber, a fluorine rubber or other elastic material, or a polyimide resin, polyphenylene sulfone resin (PPS), polyether sulfone (PES), a liquid crystal polymer (LCP), or a heat-resistant resin such as a phenol resin (PF). For example, as shown in
The fixing belt 51 is an annular belt formed into a cylindrical shape having a longitudinal direction in the Y-axis direction. The length of the fixing belt 51 in the Y-axis direction is substantially equal to the length of the heating roller 60, and is greater than the width (the dimension in the Y-axis direction) of the sheet P. The fixing belt 51 is wound around a heating roller 60 and a pressing pad 81. The fixing belt 51 is stretched with a constant tension when pressed in the −X direction by the heating roller 60.
Fixing belt 51 has a thickness of about 300 μm. The fixing belt 51 is made of, for example, a polyimide film having a high heat resistance and a thickness of 70 μm as a base material. A metal layer, a composite functional layer, an elastic layer, and a protective layer are laminated on the surface of this base material.
The metal layer is a layer made of a metal such as copper or stainless steel (SUS), and the composite functional layer is a layer made of nickel. The elastic layer is a layer made of silicone rubber having a thickness of about 200 μm. The elastic layer can be covered with a protective layer made of a PFA resin (perfluoroalkoxy polymeric resin) or the like. The elastic layer and the protective layer are adjusted in thickness so that the heat capacity does not become too large in order to shorten the warm-up time of fixing device 50. A silicone oil is applied as a lubricant to the inner peripheral surface of the fixing belt 51.
As shown in
The pressure roller 52 is supported so as to be rotatable about the core member 52a, and is biased in the −X direction by, for example, elastic force of a spring. As a result, pressure roller 52 rests against pressing pad 81 with the fixing belt 51 interposed therebetween. The pressure roller 52 presses against the pressing pad 81, via the fixing belt 51, so as to form a nip between the pressure roller 52 and the fixing belt 51.
The lubricant holding member 90 is made of a material that has a property of high liquid absorbency or retention properties and can be elastically deformed. The lubricant holding member 90 is adhered to a lower surface of the base member 80 (a surface on the −Z side) by an adhesive, for example. The lubricant holding member 90 has a longitudinal direction along the Y-axis direction, and a length in the Y-axis direction that is equal to the length of the fixing belt 51. The width of the lubricant holding member 90 (the dimension in the X-axis direction) is, for example, about 1 cm to about 2 cm, and the thickness thereof is about 3 mm to about 5 mm, for example. The lubricant holding member 90 is made of, for example, a material having high liquid absorbency and high heat resistance, such as aramid fiber, melamine resin, glass fiber, and the like.
A rectangular recess 91 and slit 92 are formed from the outer edge on the +X side extending along the X direction towards the center portion of the lubricant holding member 90. Except for the slits 92 formed at both ends in the Y-axis direction of the lubricant holding member 90, the recesses 91 and the slits are alternately formed with each other along the Y-axis direction.
As the first lubricant, silicone oil having a viscosity of about 100 centistokes (cSt) at 100° C. can be used. As the second lubricant, a lubricant having a viscosity of about 200 cSt to 300 cSt (at 100° C.), such as a grease having a synthetic oil as a base oil, can be used.
As shown in
In the fixing device 50, the heating roller 60 is heated by energy from the heater 61. The heating roller 60 heats the fixing belt 51 to raise the temperature of the fixing belt 51 to the appropriate fixing temperature. By rotating the pressure roller 52, the sheet P is conveyed through the nip between the pressure roller 52 and the fixing belt 51. As a result, the sheet P is heated by the heated fixing belt 51, and the toner image formed on the sheet P is fixed to the sheet P.
As the fixing belt 51 rotates, the first lubricant impregnated in the lubricant holding member 90 is applied to the entire inner peripheral surface of the fixing belt 51. The second lubricant added to the recess 91 is applied only to the area(s) A1 (see
The ROM 120 stores control programs and control data for specifying the basic operations of the image forming process.
The RAM 121 functions as a working memory serving as a working area of the CPU 100.
The CPU 100 executes a program stored in the ROM 120, for example. Accordingly, the various components of the image forming apparatus 10 are controlled by the CPU 100, and the processing associated with forming an image on the sheet are sequentially executed.
The interface 122 communicates with an apparatus such as a user terminal, such as a personal computer or the like. The input/output control circuit 123 functions to display information on the operation panel 14 for the user and accepts user input from the operation panel 14. The user of the image forming apparatus 10 can designate, for example, the sheet size, the number of copies of the document, and the like by operating the operation panel 14.
The conveyance control circuit 130 is a unit for controlling a motor group 131 for driving the pickup roller 18a, the sheet feed roller 35, the sheet discharge roller 37, and the like. The conveyance control circuit 130 controls the motor group 131 in accordance with a control signal from the CPU 100 or the detection results of various sensors 132 provided along the sheet conveyance path, the vicinity of the sheet cassette 18, or the like.
The image forming control circuit 140 controls the photosensitive drum 22, the charger 23, the scanning heads 19Y, 19M, 19C, 19K, the developing device 24, and the primary transfer roller 25 based on the control signal from the CPU 100.
The fixing control circuit 150 controls the driving motor 151 for rotating the pressure roller 52 of the fixing device 50 based on the control signal from the CPU 100, and drives the heater 61 based on the output from the sensor 152 provided for detecting the temperature of the fixing belt 51, the size of the sheet P notified from the CPU 100, or the like. The fixing control circuit 150 also stops the operation of the fixing device 50 based on a signal from the thermostat 153 that monitors for overheating of the fixing belt 51.
In the image forming apparatus 10, an image forming process for performing printing on the sheet P is performed by using a print command from a user as a trigger. The image forming process is performed, for example, when image data received via the interface 122 is instructed to be printed, or when image data generated by the scanner 15 is to be printed.
The image forming process of the image forming apparatus 10 will now be described. When the image forming apparatus 10 receives a print command from the user, the image forming apparatus 1 executes an image forming process for forming an image on the sheet P. In the image forming process, as shown in
In parallel with the above operation, toner images are formed on the respective photosensitive drums 22 in the image forming sections 20Y, 20M, 20C, and 20K. The toner images formed on photosensitive drum 22 in each image forming section 20Y, 20M, 20C, and 20K are sequentially transferred to intermediate transfer belt 21. As a result, a composite toner image composed of yellow (Y) toner, magenta (M) toner, cyan (C) toner, and black (K) toner is formed on the intermediate transfer belt 21.
When the sheet P passes through the nip formed between intermediate transfer belt 21 and the secondary transfer roller 33, the toner image formed on the intermediate transfer belt 21 is transferred to the sheet P. As a result, a toner image composed of yellow (Y), magenta (M), cyan (C), and black (K) toners is on the sheet P.
The sheet P then passes through the fixing device 50. During this time, the fixing control circuit 150 controls the output of the heater 61 in accordance with the size of the sheet P. The sheet P is heated by passing through the fixing device 50. Thus, the toner image previously transferred to the sheet P is fixed to the sheet P, and an image is printed on the sheet P. The sheet P is then discharged to the sheet discharge unit 38 by the sheet discharge roller 37. In the image forming process, the above-described processing can be executed in accordance with the number of copies or sheets to be printed.
As described above, in the fixing device 50, as shown in
Therefore, movement of the first lubricant along the Y-axis direction toward an outer edge portion of the fixing belt 51 is reduced after being applied to the inner peripheral surface of the fixing belt 51 by the presence of the higher viscosity second lubricant also on the inner peripheral surface of the fixing belt 51. Accordingly, it is possible to suppress the outflow of the first lubricant from the fixing belt 51. As a result, the friction between the fixing belt 51 and pressing pad can be kept low for a long period without significantly increasing the viscous resistance. In addition, when a cushioning material such as a sliding sheet 81a is provided between the pressing pad 81 and the fixing belt 51, the friction between the cushioning member and the fixing belt 51 can be kept low for a long period.
Accordingly, wear on the various contacting materials such as fixing belt 51 and pressing pad 81 or fixing belt 51 and sliding sheet 81a can be suppressed, and the performance of fixing device 50 can be maintained for a long period.
When the fixing device is assembled, a significant amount of lubricant, such as silicone oil, is typically applied to the inner peripheral surface of the fixing belt. However, due to the rotation and use of the fixing belt, the lubricant flows out beyond the edges of the fixing belt and eventually the amount of remaining lubricant becomes insufficient to reduce friction and wear. As a result, the sliding performance between the fixing belt and the pressing pad will be reduced. Even if the amount of lubricant applied at the time of assembling the fixing device is increased, the amount of lubricant flowing out during of operation or assembly of the apparatus will generally be increased as well, so that any effect of increasing the amount of lubricant applied at device assembly is relatively limited. In a fixing device according to the present disclosure, lubricant can be continuously supplied during operation, so that the lubrication of the fixing belt can be maintained over a long period.
In addition, in the fixing device 50, the recesses 91 and the slits 92 are alternately provided on the lubricant holding member 90. By providing a slit 92, movement of the second lubricant which is added in the recess 91, is suppressed in the direction along the Y-axis. Therefore, the first lubricant and the second lubricant can be held in a separated state on lubricant holding member 90. Accordingly, it is possible to effectively suppress the outflow of the first lubricant by use of the second lubricant applied to the fixing belt 51. Therefore, abrasion wear due to the movement of the fixing belt 51 can be suppressed, and the performance of the fixing device 50 can be maintained for a long time.
In addition, with fixing device 50, even when the first lubricant flows out, the second lubricant does not flow out, but instead remains on the inner peripheral surface of the fixing belt 51. Therefore, it is possible to maintain the sliding property of fixing belt 51 for a long period.
Since an image forming apparatus 10 according to the present embodiment includes a fixing device 50 as described, it is possible to form an image in such an apparatus with high throughput (a large number of sheets can be printed in a substantially continuous process without deterioration or maintence).
The present disclosure is not limited to the example embodiments described above. For example,
In this case as well, a first lubricant having a low viscosity resistance is applied to the entire region of the inner peripheral surface of the fixing belt 51, and the second lubricant having a high viscosity is selectively applied to the annular region A1 of the inner peripheral surface of the fixing belt 51 which passes through the recess 91. Accordingly, the leakage of the first lubricant is suppressed, so that the wear due to the sliding of the fixing belt 51 is suppressed, and the performance of the fixing device 50 can be maintained for a long time.
As shown in
Further, the relative size of lubricant holding members 902 (to which the first lubricant having a low viscosity is added) may be increased to reduce the relative coverage of the lubricant holding members 901 (to which the second lubricant having a high viscosity is added) on the lubricant holding member 90. As a result, two kinds of lubricants can be efficiently held.
In one embodiment depicted in
In consideration of the fact that the lubricant flows out from both edges of the fixing belt 51 to the outside, it is also possible to arrange recesses 91 more densely proximate to the ends in the Y-axis direction of the lubricant holding member 90. That is, spacing between adjacent recesses 91 may be closer near the ends of the lubricant holding member 90. Furthermore, the dimension of the recesses 91 in the Y-axis direction may be increased for those recesses 91 nearer to the ends of the lubricant holding member 90 in the Y-axis direction relative those nearer the center.
In the above description, the first lubricant was referred to as an oil and the second lubricant was referred to as a grease. However, the first lubricant is not specifically limited to oils, and may be a grease (or referred to as being a grease) as long as its viscosity is 100 cSt or so. Similarly, the second lubricant may be a lubricant other than a grease. In general, the second lubricant can be an oil (or referred to as being an oil), as long as it has a viscosity greater than that of the first lubricant.
In the above-described example embodiment, a halogen type heater 61 is used as a heat source for heating the fixing belt 51. However, in other examples, the fixing belt 51 may be heated by using electromagnetic induction or the like by means of a heating coil or the like. Furthermore, in still other examples, the fixing belt 51 may be heated by using a ceramic heater or the like.
For example,
In fixing device 50A, the pressure roller 52 is pressed against the heating portion of the ceramic heater 62 contacting the inner peripheral surface of the fixing belt 51, whereby a nip is formed between the fixing belt 51 and the pressure roller 52. The sheet P to which the toner image has already been transferred passes through the nip, and is thereby heated. As a result, the toner image is fixed to the sheet P, and an image is formed on the sheet P.
In the above-described example embodiment, the case in which the image forming apparatus 10 is a multifunction peripheral has been described. However, the image forming apparatus 10 is not limited to this and may be a laser printer or the like.
While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the present disclosure. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the present disclosure. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the present disclosure.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2019-162127 | Sep 2019 | JP | national |
