Patent Grant
11906916
This patent application is based on and claims priority pursuant to 35 U.S.C. § 119(a) to Japanese Patent Application No. 2021-091417, filed on May 31, 2021, in the Japan Patent Office, the entire disclosure of which is hereby incorporated by reference herein.
Embodiments of the present disclosure generally relate to a heating device, a fixing device, a drying device, a laminator, and an image forming apparatus.
A heating device in a fixing device includes a fixing belt as a rotator and a pressure roller as a pressure rotator. While a sheet passes through a fixing nip formed between the fixing belt and the pressure roller, toner on the sheet is heated and pressed.
This specification describes an improved heating device that includes a planar heater, a rotator, a pressure rotator, a heating device frame, a resistor, and a discharger. The pressure rotator has a conductive outer surface and presses the rotator. The heating device frame holds the pressure rotator. The discharger is in contact with the conductive outer surface of the pressure rotator and grounded via the resistor and the heating device frame.
This specification also describes a fixing device that includes the heating device. This specification further describes a dryer including the heating device.
This specification further describes a laminator including the heating device.
This specification further describes an image forming apparatus including the heating device.
A more complete appreciation of the disclosure and many of the attendant advantages and features thereof can be readily obtained and understood from the following detailed description with reference to the accompanying drawings, wherein:
The accompanying drawings are intended to depict embodiments of the present invention and should not be interpreted to limit the scope thereof. The accompanying drawings are not to be considered as drawn to scale unless explicitly noted. Also, identical or similar reference numerals designate identical or similar components throughout the several views.
In describing embodiments illustrated in the drawings, specific terminology is employed for the sake of clarity. However, the disclosure of this specification is not intended to be limited to the specific terminology so selected and it is to be understood that each specific element includes all technical equivalents that have a similar function, operate in a similar manner, and achieve a similar result.
Referring now to the drawings, embodiments of the present disclosure are described below. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. Identical reference numerals are assigned to identical components or equivalents and a description of those components is simplified or omitted. Hereinafter, a fixing device incorporated in an image forming apparatus is described as a heating device according to an embodiment of the present disclosure.
The image forming apparatus 100 illustrated in
The image forming apparatus 100 includes an exposure device 6, a sheet feeder 7, a transfer device 8, a fixing device 9, and a sheet ejection device 10. The exposure device 6 exposes the surface of the photoconductor 2 to form an electrostatic latent image on the surface of the photoconductor 2. The sheet feeder 7 supplies a sheet P as a recording medium to a sheet conveyance path 14. The transfer device 8 transfers the toner images formed on the photoconductors 2 onto the sheet P. The fixing device 9 fixes the toner image transferred onto the sheet P to the surface of the sheet P. The sheet ejection device 10 ejects the sheet P outside the image forming apparatus 100. The image forming units 1Y, 1M, 1C, and 1Bk including photoconductors 2 and the charging devices 3, the exposure devices 6, the transfer device 8, and the like configures an image forming device that forms an image on the sheet P.
The transfer device 8 includes an intermediate transfer belt 11 having an endless form and serving as an intermediate transferor, four primary transfer rollers 12 serving as primary transferors, a secondary transfer roller 13 serving as a secondary transferor. The intermediate transfer belt 11 is stretched by a plurality of rollers. Each of the four primary transfer rollers 12 transfers the toner image on each of the photoconductors 2 onto the intermediate transfer belt 11. The secondary transfer roller 13 transfers the toner image transferred onto the intermediate transfer belt 11 onto the sheet P. The four primary transfer rollers 12 are in contact with the respective photoconductors 2 via the intermediate transfer belt 11. Thus, the intermediate transfer belt 11 contacts each of the photoconductors 2, forming a primary transfer nip therebetween. On the other hand, the secondary transfer roller 13 contacts, via the intermediate transfer belt 11, one of the plurality of rollers around which the intermediate transfer belt 11 is stretched. Thus, the secondary transfer nip is formed between the secondary transfer roller 13 and the intermediate transfer belt 11.
A timing roller pair 15 is disposed between the sheet feeder 7 and the secondary transfer nip defined by the secondary transfer roller 13 in the sheet conveyance path 14.
Next, a description is given of a series of print operations of the image forming apparatus 100 with reference to
When the image forming apparatus 100 receives an instruction to start printing, a driver drives and rotates the photoconductor 2 clockwise in
The toner image formed on each of the photoconductors 2 reaches the primary transfer nip at each of the primary transfer rollers 12 in accordance with rotation of each of the photoconductors 2. The toner images are sequentially transferred and superimposed onto the intermediate transfer belt 11 that is driven to rotate counterclockwise in
After the full color toner image is transferred onto the sheet P, the sheet P is conveyed to the fixing device 9 to fix the toner image on the sheet P. Subsequently, the sheet ejection device 10 ejects the sheet P outside the image forming apparatus 100, and the series of print operations are completed.
Next, a configuration of the fixing device 9 is described.
As illustrated in
The fixing belt 20 includes, for example, a tubular base 20b (a base layer 20b) made of polyimide (PI), and the tubular base has an outer diameter of 25 mm and a thickness of from 40 to 120 μm. The fixing belt 20 further includes a release layer serving as an outermost surface layer. The release layer is made of fluororesin, such as tetrafluoroethylene-perfluoroalkylvinylether copolymer (PFA) or polytetrafluoroethylene (PTFE) and has a thickness in a range of from 5 μm to 50 μm to enhance durability of the fixing belt 20 and facilitate separation of the sheet P and a foreign substance from the fixing belt 20. An elastic layer made of rubber having a thickness of from 50 to 500 μm may be interposed between the base and the release layer. The base of the fixing belt 20 may be made of heat resistant resin such as polyetheretherketone (PEEK) or metal such as nickel (Ni) and steel use stainless (SUS), instead of polyimide. The inner circumferential surface of the fixing belt 20 may be coated with polyimide or polytetrafluoroethylene (PTFE) as a slide layer.
The pressure roller 21 having, for example, an outer diameter of 25 mm, includes a solid iron core 21a, an elastic layer 21b on the surface of the core 21a, and a release layer 21c formed on the outside of the elastic layer 21b. The elastic layer 21b is made of silicone rubber and has a thickness of 3.5 mm, for example. Preferably, the release layer 21c is formed by a fluororesin layer having, for example, a thickness of approximately 40 μm on the surface of the elastic layer 21b to improve releasability.
The release layer 21c of the pressure roller 21 is a conductive layer made of perfluoroalkoxy alkane (PFA) with a conductive filler such as carbon. The outer peripheral surface (that is, an outer surface) of the release layer 21c (that is a surface layer) forms the outer surface of the pressure roller 21.
The heater 22 is disposed to contact the inner circumferential surface of the fixing belt 20. The heater 22 in the present embodiment contacts the pressure roller 21 via the fixing belt 20 and serves as a nip formation pad to form the fixing nip N between the pressure roller 21 and the fixing belt 20. The fixing belt 20 is a heated member heated by the heater 22.
The heater 22 may not contact the fixing belt 20 or may contact the fixing belt 20 indirectly via, e.g., a low-friction sheet. When the heater 22 is brought into direct contact with the fixing belt 20, the heat transfer efficiency to the fixing belt 20 is improved.
The heater 22 includes a base 50, a conductor layer 51 including a resistive heat generator 60, and an insulation layer 52.
The heater holder 23 and the stay 24 are disposed inside a loop of the fixing belt 20. The stay 24 is configured by a channeled metallic member, and both side plates of the fixing device 9 support both end portions of the stay 24. The stay 24 supports a stay side face of the heater holder 23. The stay side face faces the stay 24 and is opposite a heater side face of the heater holder 23. The heater side face faces the heater 22. Accordingly, the stay 24 retains the heater 22 and the heater holder 23 to be immune from being bent substantially by pressure from the pressure roller 21. Thus, the fixing nip N is stably formed between the fixing belt 20 and the pressure roller 21.
Since the heater holder 23 is subject to temperature increase by heat from the heater 22, the heater holder 23 is preferably made of a heat resistant material. The heater holder 23 made of heat-resistant resin having low thermal conduction, such as a liquid crystal polymer (LCP) or polyether ether ketone (PEEK), reduces heat transfer from the heater 22 to the heater holder 23. Thus, the heater 22 can effectively heat the fixing belt 20.
A spring serving as a biasing member causes the fixing belt 20 and the pressure roller 21 to press against each other. Thus, the fixing nip N is formed between the fixing belt 20 and the pressure roller 21. As a driving force is transmitted to the pressure roller 21 from a driver disposed in the image forming apparatus 100 (see
When printing starts, the driver drives and rotates the pressure roller 21, and the fixing belt 20 starts rotation in accordance with rotation of the pressure roller 21. Additionally, as power is supplied to the heater 22, the heater 22 heats the fixing belt 20. When the temperature of the fixing belt 20 reaches a predetermined target temperature called a fixing temperature, as illustrated in
As illustrated in
Each of the side walls 28 includes an insertion slot 28b through which a rotation shaft and the like of the pressure roller 21 are inserted. The insertion slot 28b opens toward the rear wall 29 and closes at a portion opposite the rear wall 29, and the portion of the insertion slot 28b opposite the rear wall 29 serves as a contact portion. A bearing 30 is disposed at an end of the contact portion to support the rotation shaft of the pressure roller 21. As both sides of the rotation shaft of the pressure roller 21 are attached to the corresponding bearings 30, the side walls 28 rotatably support the pressure roller 21.
A driving force transmission gear 31 serving as a drive transmitter is disposed at one side of the rotation shaft of the pressure roller 21 in an axial direction thereof. In a state in which the side walls 28 support the pressure roller 21, the driving force transmission gear 31 is exposed outside the side wall 28. Accordingly, when the fixing device 9 is installed in the body of the image forming apparatus 100 (see
A pair of flanges 32 as end holders that support the fixing belt 20 and the like is disposed at both sides of the fixing belt 20 in the longitudinal direction thereof, respectively. The flange 32 is a part of the fixing device frame 40 of the fixing device 9. The flanges 32 support the fixing belt 20 in a state in which the fixing belt 20 is not basically applied with tension in a circumferential direction thereof while the fixing belt 20 does not rotate, that is, by a free belt system. Each flange 32 has a guide groove 32a. As edges of the insertion slot 28b of the side wall 28 enter the guide grooves 32a, respectively, the flange 32 is attached to the side wall 28.
A pair of springs 33 serving as a pair of biasing members is interposed between the rear wall 29 and each of the flanges 32. As the springs 33 bias the flanges 32 and the stay 24 toward the pressure roller 21, respectively, the fixing belt 20 is pressed against the pressure roller 21 to form the fixing nip between the fixing belt 20 and the pressure roller 21.
As illustrated in
As illustrated in
In addition to the guide grooves 32a described above, each of the pair of flanges 32 includes a belt support 32b, a belt restrictor 32c, and a supporting recess 32d. The belt support 32b is C-shaped and inserted into the loop of the fixing belt 20, thus contacting the inner circumferential surface of the fixing belt 20 to support the fixing belt 20. The belt restrictor 32c has a flange shape and contacts an edge face of the fixing belt 20 to restrict motion (e.g., skew) of the fixing belt 20 in the longitudinal direction of the fixing belt 20. One ends of the heater holder 23 and the stay 24 are inserted into the supporting recess 32d of one of the flanges 32, and the other ends of the heater holder 23 and the stay 24 are inserted into the supporting recess 32d of the other one of the flanges 32. As a result, the flanges 32 support the heater holder 23 and the stay 24.
As illustrated in
As illustrated in
The stay 24 is not positioned with respect to the flange 32 in the longitudinal direction of the stay 24. As illustrated in
As illustrated in
The base 50 is made of an insulating material such as glass or ceramic such as alumina or alumina nitride. Alternatively, the base 50 may be made of metal such as steel use stainless (SUS), iron, copper, or aluminum, and an insulation layer may be disposed between the base 50 and the conductor layer 51 to surely insulate the conductor layer 51.
Since metal has an enhanced durability against rapid heating and is easy to process, metal is preferably used to reduce manufacturing costs. Among metals, aluminum and copper are preferable because aluminum and copper have high thermal conductivity and are less likely to cause uneven temperature. Stainless steel is advantageous because stainless steel is manufactured at reduced costs compared to aluminum and copper.
The insulation layer 52 is made of heat-resistant glass. Alternatively, ceramic, polyimide (PI) or the like may be used as the material of the insulation layer 52.
The resistive heat generator 60 is produced by, for example, mixing silver-palladium (AgPd), glass powder, and the like into a paste. The paste is coated on the base 50 by screen printing or the like. Thereafter, the base 50 is fired to form the resistive heat generator 60. Alternatively, the resistive heat generator 60 may be made of a resistive material such as a silver alloy (AgPt) and ruthenium oxide (RuO2).
The power supply lines 62 are made of conductors having an electrical resistance value smaller than the electrical resistance value of the resistive heat generator 60. Silver (Ag), silver palladium (AgPd) or the like may be used as a material of the power supply lines 62 and the electrodes 61. Screen-printing such a material forms the power supply lines 62 and the electrodes 61.
Although the resistive heat generator 60 are disposed on the front side of the base 50 in the present embodiment, alternatively, the resistive heat generator 60 may be disposed on the back side of the base 50. In this case, since the heat of the resistive heat generator 60 is transmitted to the fixing belt 20 through the base 50, it is preferable that the base 50 be made of a material with high thermal conductivity such as aluminum nitride. Making the base 50 with the material having high thermal conductivity enables to sufficiently heat the fixing belt even if the resistive heat generator 60 is disposed on the back side of the base 50.
According to the present embodiment, the resistive heat generator 60, the electrodes 61, and the power supply lines 62 are made of an alloy of silver, palladium, or the like to attain a positive temperature coefficient (PTC) property, that is, to have a positive temperature coefficient of resistance. The PTC characteristic is a characteristic in which the resistance value increases as the temperature increases, for example, a heater output decreases under a constant voltage.
The resistive heat generator 60 having the PTC property quickly starts heat generation with an increased output at low temperatures and prevents overheating because high temperatures decrease output. For example, if a temperature coefficient of resistance (TCR) of the PTC property is in a range of from about 300 ppm/° C. to about 4,000 ppm/° C., the heater 22 is manufactured at reduced costs while retaining a resistance value needed for the heater 22.
The TCR is preferably in a range of from about 500 ppm/° C. to about 2,000 ppm/° C. The TCR is calculated by measuring the resistance value at 25° C. and 125° C. For example, if the temperature increases by 100° C. and the resistance value increases by 10%, the TCR is 1,000 ppm/° C.
According to the present embodiment, the resistive heat generator 60 includes three resistive heat generators arranged in a longitudinal direction of the base 50. One of the three resistive heat generators is a central heat generator 65A as a first heat generator disposed at the center of the base 50 in the longitudinal direction, and the remaining two resistive heat generators are end heat generators 65B as second heat generators disposed adjacent to both ends of the central heat generator 65A in the longitudinal direction. The central heat generator 65A and the end heat generators 65B are configured to be independently controlled with respect to heat generation.
The plurality of electrodes 61 are referred to as a first electrode 61A, a second electrode 61B, a third electrode 61C, and a fourth electrode 61D in order from the left side in
In addition, the first electrode 61A and the third electrode 61C are coupled in parallel outside the heater 22 and configured to be able to apply the voltage at the same time. Applying the voltage between the second electrode 61B and each of the first electrode 61A and the third electrode 61C enables both end heat generators 65B to generate heat at the same time. Each of Arrows in
When a width of the sheet passing through the fixing device 9 is equal to or shorter than the width L1 of the central heat generator 65A, the central heat generator 65A generates heat. When the width of the sheet passing through the fixing device 9 is longer than the width L1 of the central heat generator 65A, the end heat generators 65B generate heat in addition to the central heat generator 65A. As a result, the heater 22 can generate heat in a heat generation area corresponding to a size of a sheet conveyance area. Additionally, the width L1 of the central heat generator 65A is set to a width of a small sheet (for example, a width corresponding to A4 sheet: 215 mm). The width L2 of the heat generation area from one end heat generator 65B to the other end heat generator 65B is set to a width of a large sheet (for example, a width corresponding to A3 sheet: 301 mm). In the above-described configuration, turning off the end heat generators 65B prevents an excessive temperature rise in a non-sheet conveyance portion caused by many small sheets P passing through the fixing device. The above-described configuration can improve the productivity of printing because the above-described configuration does not need to reduce a print speed to prevent the excessive temperature rise.
As illustrated in
As illustrated in
As illustrated in
Since the connector 70 serving as a power supply member also functions as a clamping member that clamps and holds the heater 22 and the heater holder 23 together, the fixing device 9 in the present embodiment does not need to have another clamping member. As a result, the number of components can be reduced. Note that the connector 70 is similarly attached to the other end of the heater 22 opposite to the end of the heater 22 illustrated in
In the above-described fixing device 9, the surface of the pressure roller 21 illustrated in
To prevent the pressure roller 21 from charging, for example, a discharger may be brought into contact with the core 21a of the pressure roller 21. The discharger removes the charge on the outer peripheral surface of the pressure roller 21 from the release layer 21c to the core 21a via the conductive elastic layer 21b to prevent the fixing failure and the electrostatic offset.
However, the above-described configuration needs the elastic layer 21b having conductivity. A method of making the elastic layer 21b having conductivity is, for example, mixing a conductive filler into the silicone rubber of the elastic layer 21b. However, this method impairs the elasticity and expansibility of the elastic layer 21b, which reduces the width of the fixing nip N. In order to secure a sufficient width of the fixing nip N, a load applied to the fixing belt 20 by the pressure roller 21 (hereinafter referred to as a fixing load) needs to be increased. Increase the fixing load increases frictional force generated between the fixing belt 20 and the pressure roller 21. As a result, the fixing belt 20 is likely to be worn and easily damaged. In particular, since a high-speed image forming apparatus prints a large number of sheets per job, charge in the pressure roller 21 of the fixing device 9 increases. In order to secure a sufficient discharge ability with respect to the pressure roller 21, increasing the amount of filler mixed in the silicone rubber to further reduce the electric resistance of the elastic layer 21b is needed, which increases the fixing load. Accordingly, the above-described configuration causes the problem of wear and breakage of the fixing belt 20.
As described above, the occurrence of the problem of wear and breakage of the fixing belt 20 in the above-described configuration causes difficulty in achieving both speed-up of the fixing device 9 and reduction of the electrostatic offset and the fixation failure.
To prevent the pressure roller 21 from charging, the fixing device 9 according to the present embodiment includes a discharging brush 35 as the discharger as illustrated in FIG. 10. The discharging brush 35 is in contact with the release layer 21c that is a surface layer of the pressure roller 21. The discharging brush 35 is grounded via a first resistor 36.
The discharging brush 35 can remove the charge on the surface layer of the pressure roller 21 to prevent the fixing failure and the electrostatic offset. In addition, since the discharging brush 35 is in contact with the release layer 21c of the pressure roller 21, the elastic layer 21b that is an intermediate layer does not need to be a conductive layer. Accordingly, the above-described configuration does not need to increase the fixing load in order to secure the width of the fixing nip N as described above and can achieve both speed-up of the fixing device 9 and reduction of the electrostatic offset and the fixation failure.
In the fixing device 9 including the planar heater 22 in contact with the inner surface of the fixing belt 20 as in this embodiment, current from an AC power source leaks to a member outside the fixing device 9 via the pressure roller 21, which may adversely affect electronic components or cause components in the image forming apparatus to be charged and toner to adhere to the components. As illustrated in
The discharging brush 35 grounded via the first resistor 36 in the present embodiment solves the above-described disadvantage in the fixing device including the planar heater, that is, prevents the above-described charging of components and the above-described adverse effects on electronic components. The first resistor 36 reduces the current flowing to the ground via the fixing device frame 40 and the apparatus main body frame 103 to prevent the adverse effect on the electronic components in the image forming apparatus and the charging of the components. The first resistor 36 may be a resistor such as a general passive element or a conductive resin component as long as the first resistor 36 has a necessary resistance value.
In the present embodiment, the first resistor 36 is disposed between the discharging brush 35 and the fixing device frame 40 in a direction of the current flowing from the surface layer of the pressure roller 21 to the ground via the discharging brush 35. The above-described configuration can prevent the adverse effect on electronic components around the fixing device 9 (that is, the electronic components outside the fixing device 9 in the image forming apparatus). In addition, the above-described configuration can prevent members around the fixing device 9 from charging and, as a result, can effectively prevent toner from scattering and adhering to the outside of the fixing device 9.
The resistance value of the first resistor 36 is set to an appropriate value in order to set the current flowing to the ground to a desired value or less. Specifically, the preferable current value of the current flowing through the first resistor 36 is equal to or less than 3.5 mA that is defined by International Electrotechnical Commission Japanese Industrial Standard No. 6095-1 (IEC-J60950-1). A more preferable current value is 1.0 mA or less defined in Appended table 12 of Electrical Appliance and Material Safety Act regarding Article 7 (ii) of Ministerial Order to Provide Technical Standards for Electrical Appliances and Materials in Japan. The above-described current values are measured by an ammeter when the power supply applies a voltage to the first resistor 36.
The resistance value of the first resistor 36 is calculated by E1/I1, where E1 is the voltage [V] of the power supply in the image forming apparatus, and I1 is the current value [A] flowing through the first resistor 36. Specifically, the resistance value of the first resistor 36 is set to (10/3.5)×104Ω or more by (100/3.5×10−3) in the case that the voltage E1 is 100 V, and the current I1 is the preferable current value 3.5 mA or less. Alternatively, the resistance value of the first resistor 36 may be set to 1×105Ω or more by 100/(1.0×10−3) in the case that the voltage E1 is 100 V, and the current I1 is the more preferable current value 1.0 mA or less. Setting the resistance value of the first resistor 36 as described above means setting a combined resistance on a current path to (10/3.5)×104Ω or more or 1×105Ω or more.
Preferably, a plurality of first resistors 36a and 36b are coupled in series between the discharging brush 35 and the fixing device frame 40 as illustrated in
As illustrated in
Setting the thickness of the elastic layer 21b to 2.5 mm or more ensures the creepage distance between the release layer 21c and the core 21a (that is the distance between the axial end surface of the release layer 21c and the axial end surface of the core 21a) to be 2.5 mm or more and basically insulates the release layer 21c and the core 21a each other. The above-described configuration prevents a current from flowing from the release layer 21c to the core 21a and charging the core 21a.
However, setting the thickness of the elastic layer 21b to too large increases the difference in diameters of portions of the elastic layer 21b due to thermal expansions. The too thick elastic layer 21b increases a variation in a rotation speed of the pressure roller 21 and affects a rotation speed of the fixing belt 20 in the case that the rotation of the pressure roller 21 drives and rotates the fixing belt 20. In order to suppress the variation in the rotation speed due to thermal expansion, the elastic layer 21b is preferably set to 6.0 mm or less.
In consideration of the above-described basic insulation and the variation in the rotational speeds due to thermal expansion, the thickness of the elastic layer 21b is preferably set to 2.5 mm or more and 6.0 mm or less. In addition, the thickness of the elastic layer 21b and the fixing load is more preferably set so that the thickness of the elastic layer is larger than or equal to 2.5 mm in a pressure state that the pressure roller 21 is pressed against the fixing belt 20. Note that the pressure state is defined as a state in which the pressure roller 21 is pressed against the fixing belt 20 to fix the toner image onto the sheet. As a result, the base insulation can be secured more reliably.
Setting the thicknesses of the elastic layers 21b as described above enables freely designing the bearing 30. The above-described setting enables using a ball bearing as the bearing 30 which improves safety of the fixing device and lengthen the life of the fixing device. Without setting the thickness of the elastic layer 21b as described above, a non-conductive sliding bearing may be used as the bearing 30 as another method of preventing the current from flowing from the core 21a to the ground. However, the non-conductive sliding bearing as the bearing 30 is more likely to be worn than the ball bearing in a high-speed fixing device. Alternatively, an insulating member may be inserted between the fixing device frame 40 and the ball bearing. However, inserting the insulating member deteriorates the positional accuracy of the bearing 30 and the parallelism between the fixing belt 20 and the pressure roller 21, which causes meandering or wear of the fixing belt 20. Accordingly, setting the thicknesses of the elastic layers 21b as described above and using the ball bearing as the bearing 30 improves the safety of the fixing device and lengthen the life of the fixing device.
As illustrated in
The first diode 37 charges the pressure roller 21 to a polarity opposite to the polarity of the toner (positive in the present embodiment), that is, charges the pressure roller 21 so as to attract the toner. The above-described configuration can prevent to toner from adhering to the fixing belt 20.
In the present embodiment, the first diode 37 is disposed between the discharging brush 35 and the fixing device frame 40 in the direction of the current flowing from the release layer 21c of the pressure roller 21 to the ground. In other words, the first diode 37 is disposed between the discharging brush 35 and the fixing device frame 40 in a path of the current flowing from the release layer 21c of the pressure roller 21 to the ground. The above-described configuration attracts toner to an upstream portion from the fixing device frame 40 in the direction of the current flowing from the pressure roller 21 to the ground. As a result, the above-described configuration limits charged components to a minimum range, prevents the adverse effect on electronic components outside the fixing device, and prevents toner from scattering and adhering to the components outside the fixing device.
In addition, the base layer 20b of the fixing belt 20 may be made of conductive material, and the fixing belt 20 may be grounded via the base layer 20b as illustrated in
Grounding the fixing belt 20 via the base layer 20b sets the potential of the fixing belt 20 to 0 V, which prevents the toner from adhering to the fixing belt 20.
In
The fixing belt 20 is grounded via a second resistor 38. The second resistor 38 limits the current flowing from the base layer 20b of the fixing belt 20 to the ground and improves the safety of the fixing device. The second resistor 38 is disposed between the base layer 20b of the fixing belt 20 and the fixing device frame 40 in a direction of the current flowing from the base layer 20b of the fixing belt 20 to the ground.
The second diode 39 is set so that the direction in which current flows in the second diode 39 is opposite to the direction in which the current flows in the first diode 37. The second diode 39 charges the base layer 20b of the fixing belt 20 to the same polarity (negative in the present embodiment) as the toner, that is, charges the fixing belt so that the toner and fixing belt repel each other. The above-described configuration can prevent the toner from adhering to the fixing belt 20.
In the above, the resistor coupled in series to the release layer 21c of the pressure roller 21 to ground the release layer 21c is different from the resistor coupled in series to the base layer 20b of the fixing belt 20 to ground the base layer 20b, but the release layer 21c and the base layer 20b may be grounded via a common resistor. For example, as illustrated in
The above-described embodiments are illustrative and do not limit this disclosure. It is therefore to be understood that within the scope of the appended claims, numerous additional modifications and variations are possible to this disclosure otherwise than as specifically described herein.
The image forming apparatus according to the present embodiments of the present disclosure is applicable not only to a color image forming apparatus 100 illustrated in
The sheets P serving as recording media may be thick paper, postcards, envelopes, plain paper, thin paper, coated paper, art paper, tracing paper, overhead projector (OHP) transparencies, plastic film, prepreg, copper foil, and the like.
The embodiments of the present disclosure are also applicable to fixing devices as illustrated in
First, the fixing device 9 illustrated in
Next, a description is given of in the fixing device 9 illustrated in
Finally, the fixing device 9 illustrated in
In the fixing devices illustrated in
A heating device according to the present disclosure is not limited to the fixing device described in the above embodiments. The heating device according to the present disclosure is also applicable to, for example, a heating device such as a dryer to dry ink applied to the sheet, a coating device (a laminator) that heats, under pressure, a film serving as a covering member onto the surface of the sheet such as paper, and a thermocompression device such as a heat sealer that seals a seal portion of a packaging material with heat and pressure. Applying the present disclosure to the above heating device can prevent components around the heating device from charging.
The above-described embodiments are illustrative and do not limit the present invention. Thus, numerous additional modifications and variations are possible in light of the above teachings. For example, elements and/or features of different illustrative embodiments may be combined with each other and/or substituted for each other within the scope of the present invention.
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