Patent Application
20230324839
This disclosure relates to a fixing member used for an induction heating type fixing unit and a fixing unit including the fixing member.
In electrophotographic image forming apparatuses, fixing units which heat fixing members by the principle of induction heating and fix an image on a recording material by the heated fixing members are brown. This type of the fixing members includes a circumferentially continuous conductive layer, and generates heat by Joule heat which is generated when an induction current circulates around the conductive layer in response to an alternating magnetic field formed by a magnetic field generation member such as a coil.
In Japanese Patent Application Laid Open No. 2015-118232, it is described that; by dividing a heating layer (conductive layer) of a tubular fixing member into a plurality of areas (segments) in a longitudinal direction, even if damage such as cracks have occurred in the heating layer, an abnormal temperature rise is made less likely to occur in adjacent arms of the damaged portion.
In a case such as continuous image formation on a plurality of sheets of the recording material, a phenomenon (called as a temperature rise in a non-sheet passing portion) may occur. When the temperature rise in the non-sheet passing portion occurs, a temperature of an end portion area (i.e., non-sheet passing portion) where the fixing member does not came into contact with the recording material becomes higher in comparison with an area where the fixing member comes into contact with the recording material. Ina case where an extent of the temperature rise in the non-sheet passing portion is remarkable, there is a possibility that, since deterioration such as wear or changes in physical properties of surfaces of the fixing member and members adjacent to the fixing member will be caused by the heat; performance or durability of the fixing unit will decrease. Further, since the occurrence of the temperature rise in the non-sheet passing portion means energy consumption in a form of not contributing to the fixation of the image, the temperature rise in the non-sheet passing portion is preferably kept to be as little as possible.
The present disclosure provides a fixing member and a fixing unit in which a conductive layer of the fixing member includes a plurality of segments and which can reduce temperature rise in a non-sheet passing portion.
According to an aspect of the present disclosure, a fixing member includes a conductive layer configured to generate heat in a case where a circulation current in a circumferential direction of the fixing member having a tubular shape is induced, wherein the conductive layer includes a plurality of segments arranged in a row in a longitudinal direction of the tubular shape and electrically separated from each other, where each of the plurality of segments is formed continuously over an entire circumference of the tubular shape in the circumferential direction, and wherein the conductive layer is configured such that a heat generation amount in an end portion of the fixing member in the longitudinal direction is less than a heat generation amount in a central portion of the fixing member in the longitudinal direction in a case where an alternating magnetic field is applied to a whole area of the fixing member in the longitudinal direction in a state where a temperature of the central portion of the fixing member is equal to a temperature of the end portion of the fixing member.
Further features of the present disclosure will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
Hereinafter, embodiments of this disclosure will be described with reference to drawings.
With reference to
The image forming apparatus 100 includes an image forming unit 1A for forming a toner image (hereinafter simply referred to as an image) on the recording material P and a fixing unit 1F for fixing the image on the recording material P The image forming unit 1A includes a photosensitive drum 1, serving as an image bearing member, a charge unit 2, a laser scanner 3, serving as an exposing unit, a developing unit 4, a cleaner 5, and a transfer member 6. The photosensitive drum 1 is a photoconductor (electrophotographic photoconductor) formed in a drum shape. A configuration of the fixing unit 1F will be described below.
An image forming operation of the image forming apparatus 100 will be described. When a control unit of the image forming apparatus has received the image data, the image forming operation is started. When the image forming operation has been started, the photosensitive drum 1 is rotatably driven, and a surface of the photosensitive drum 1 is uniformly charged by the charge unit 2. The laser scanner 3 irradiates the photosensitive drum 1 with a laser beam in accordance with a video signal generated based on the image data, and performs an exposure step of writing an electrostatic latent image on the surface of the photosensitive drum 1. The developing unit 4 performs a development step using the toner as the developer, and visualizes the electrostatic latent image as the image (toner image).
Concurrently with the operation described above, the recording material P stored in a cassette Tin an interior of an image forming apparatus body is fed one sheet at a time by the rotation of a feed roller 8. The recording material P is conveyed to a transfer nip Nt (transfer portion) formed between the photosensitive drum 1 and the transfer member 6 by a registration roller 9. The image which has been formed on the photosensitive drum 1 and conveyed to the transfer Trip Nt by the rotation of the photosensitive drum 1 is transferred onto the recording material P at the transfer nip Nt.
The recording material P which has passed through the transfer nip Nt is sent to the fixing unit 1F via a conveyance guide 10. By heating the image on the recording material P, the fixing unit 1F fixes the image on the recording material P The recording material P which has passed through the fixing unit 1F is discharged to an exterior of the apparatus body by a sheet discharge roller 11, and stacked on a tray 12.
The image forming apparatus 100 described above is an example of image forming apparatuses. It is acceptable that the image forming unit 1A is an image forming apparatus of an intermediate transfer system in which the image formed on the image bearing member is transferred onto the recording material via an intermediate transfer member such as an intermediate transfer belt. Further, it is acceptable that the image forming unit 1A is configured to be capable of forming monochromatic images of respective colors on a plurality of photosensitive drums using a plurality of colors of toner, and configured to be capable of forming a color image by superimposing the monochromatic images of the respective colors on the intermediate transfer member or the recording material.
Next, an overview of the fixing unit 1F of the present embodiment will be described.
Hereinafter, rotational axis directions of a fixing film 20 and a press roller 22 are referred to as a longitudinal direction D1 of the fixing unit 1F or simply the longitudinal direction D1. The longitudinal direction D1 is a longitudinal direction (direction of the generatrix) of the fixing film 20 having a tubular shape. Further, the longitudinal direction D1 of the fixing unit 1F is a direction (width direction of the recording material) perpendicularly intersecting with a conveyance direction of the recording material at a fixing nip Nf. Further, the longitudinal direction D1 of the fixing unit 1F is substantially the same direction as a main scanning direction at a time of image formation in the image forming unit 1A.
Further, a circumferential direction D2 of the fixing film 20 is a direction circulating along a surface of the fixing film 20 in a direction perpendicularly intersecting with the longitudinal direction 1. In a case where the fixing film 20 is assumed to be in a cylindrical shape, the circumferential direction D2 can be a direction along a virtual circle having its center at a virtual rotational axis X of the fixing film 20. The rotational axis X is a straight line extending in the longitudinal direction D1 along a geometric center of the fixing film 20 when viewed in the longitudinal direction D1.
As illustrated in
The nip formation member 21 is made of a heat resistant material such as a heat resistant resin, and is inserted into an inner space of the fixing film 20. The nip formation member 21 faces the press roller 22 across the fixing film 20 in a vertical direction perpendicularly intersecting with both of the longitudinal direction D1 and the conveyance direction of the recording material P Part of a surface of the nip formation member 21 of this example, on a side of the press roller 22, is formed as a flat surface portion 21a extending in the longitudinal direction D1 and the conveyance direction of the recording material P The fixing nip Nf is formed between the flat surface portion 21a of the nip formation member 21 and the press roller 22.
The press roller 22 includes a core metal 22a, an elastic layer 22b formed on an outer circumferential surface of the core metal 22a, and a release layer 22c formed on an outer circumferential surface of the elastic layer 22b. An outside diameter of the press roller 22 in this example is 30 millimeters (mm).
A support configuration of the fixing unit 1F will be described. Both end portions of the nip formation member 21 in the longitudinal direction D1 are supported by a frame of the fixing unit 1F via flange members 60, described below. The frame of the fixing unit 1F is fixed to a frame of the image forming apparatus 100. A shaft portion of the core metal 22a of the press roller 22 is supported, via bearings, in a manner rotatable with respect to the frame of the fixing unit 1F and movable with respect to the nip formation member 21 in the abovementioned vertical direction. The press roller 22 comes into pressure contact with the nip formation member 21 by an urging force of an urging member such as a spring. In this example, the bearings at both sides of the press roller 22 in the longitudinal direction D1 are pressed by a pressing force of approximately 196 newtons (N) to 392N (approximately 20 kilogram farce (Kgf) to 40 (Kgf) in terms of a total pressure (sum). Thereby, the elastic layer 22b of the press roller 22 is elastically deformed, so that the fixing nip Nf in which surfaces of the fixing film 20 and the press roller 22 come into contact with each other with a predetermined width in the conveyance direction of the recording material is formed.
Next, the fixing film 20 of this example will be described. It is possible to form the fixing film 20 in the tubular shape with a diameter of 10 mm to 100 mm. An outside diameter of the fixing film 20 of this example is 30 mm. The fixing film 20 is made of a material having flexibility and heat resistance.
Cross-sectional views of the fixing film 20 are illustrated in
As illustrated in
As illustrated in
The segments 20b1 included in the conductive layer 20b are electrically separated from each other with respect to the longitudinal direction D1. In other words, the conductive layer 20b is configured such that conductive materials included in the conductive layer 20b are electrically separated from each other in the longitudinal direction D1. In this example, the plurality of segments 20b1 are electrically insulated from each other by disposing the segments 20b1 adjacent to each other at predetermined intervals. That is, the conductive layer 20b intermittently exists in the longitudinal direction D1. To be noted, it is acceptable to dispose the plurality of segments 20b1 closely adjacent to each other.
In this example, an occupying ratio of the conductive layer 20b is different depending on a position in the longitudinal direction D1. In particular, presence or absence of the segments 20b1 of the conductive layer 20b is different between a central area A1 (first area) of the fixing film 20 positioned in a central portion in the longitudinal direction D1 and end areas A2 (second area) positioned on both outside of the central area A1 and on end portions of the fixing film 20. An arrangement pattern of the segments 20b1 and its action will be described below.
A substance which is non-magnetic and has a high volumetric resistivity and excellent heat resistance is suitable for a material of the base layer 20a. Such a substance includes, for example, the heat resistant resin such as polyimide (PI) and polyamideimide (PAI), a fiber reinforced resin such as carbon fiber reinforced plastics (CFRP) and a glass fiber reinforced resin (GFRP), and the like. In a case of using the heat resistant resin, the thickness of the base layer 20a is preferably a thickness with which the strength of the fixing film 20, sliding properties of the fixing nip N and the rotational stability of the fixing film 20 are easily obtained, and, for example, thicknesses of 20 to 200 micrometers (μm) are suitable. In this example, the base layer is formed of the PI, and the thickness is set at 50 μm.
For a material of the conductive layer 20b, for example, metal having a low volume resistivity, such as gold, silver, copper, iron, platinum, tin, stainless steel, titanium, aluminum, and nickel, are suitable. In this example, copper is used as the material of the conductive layer 20b, and the thickness is set at 3 μm. Further, in this example, the width and thickness of each conductive layer 20b in the longitudinal direction D1 are set to be constant.
An example of a method for forming the conductive layer 20b will be described. A coating film is formed by preparing paint containing a microparticle of the abovementioned metal and a polyimide precursor solution and, then, coating an outer surface of the base layer 20a, which has been prepared in advance, with the abovementioned paint in a manner of blade coating screen printing or the like. In the coating process, by a common technique (such as a masking process), dividing portions (uncoated portions) dividing the segments 20b1 into each other are formed in portions corresponding to the non-heat generating area so as to form the segments 20b1 at the predetermined intervals in the longitudinal direction D1. Thereafter, the coating film described above is gradually heated and dried to and at about 300° C. to 500° C. so as to progress an imidation, so that the segments 20b1 are formed and strongly adhered to the base layer 20a Besides the method described above, it is acceptable to form the segments 20b1 by a technique such as laser etching or chemical etching after having plated the outer surface of the base layer 20a with the metal.
The protective layer 20c is formed on an outer circumferential side of the conductive layer 20b. The protective layer 20c protects the conductive layer 20b. As with the base layer 20a, a substance which is non-magnetic and has high volume resistivity and excellent heat resistance is suitable for a material of the protective layer 20c. Such a substance includes, for example, the heat resistant resin such as the polyimide (PI) and the polyamideimide (PAI), the fiber reinforced resin such as the carbon fiber reinforced plastics (CFRP) and the glass fiber reinforced resin (GFRP), and the like. For the protective layer 20c, thicknesses of 20 to 200 μm which are the thicknesses with which the rotational stability of the fixing film 20 is easily obtained is suitable. In this example, the protective layer 20c is formed of the PI, and the thickness is set at 50 μm.
The elastic layer 20d is formed on an outer circumferential side of the protective layer 20c. The elastic layer 20d is formed of a heat resistant elastic body such as a silicone rubber. In this example, the elastic layer 20d is formed of a good thermal conductivity silicone rubber with a thickness of 200 μm.
The release layer 20e is formed on an outer circumferential side of the elastic layer 20d. The release layer 20e reduces the adhesion of the toner onto the surface of the fixing film 20 and the occurrence of image defects. A material which is excellent in non-adhesiveness is suitable for the release layer 20e, and it is possible to use a fluororesin. For example, a perfluoroalkylvinylether (PFA), a polytetrafluoroethylene(PTFE), a tetrafluoroethylene-hexafluoropropylene (FEP), or a tetrafluoroethylene-ethylene (ETFE) can be used. In this example, the PFA with a thickness of 15 μm is used for the release layer 20e.
Here, as illustrated in
Next, a configuration for generating a magnetic field so as to allow the fixing film 20 to generate heat will be described. As described above, the fixing unit 1F includes the magnetic core 30 and the exciting coil 31 (refer to
The magnetic core 30 is preferably formed of a material that has a small hysteresis loss and a high relative permeability. As a material of the magnetic core 30, a ferromagnetic material including a high permeability oxide or alloy material, such as a sintered ferrite, a ferrite resin, an amorphous alloy, or a permalloy is preferred. Further, it is preferred to enlarge the cross-section of the magnetic core 30 as much as possible to the extent that a diameter of the magnetic core 30 can be fitted into the interior of the fixing film 20. In this example, the sintered ferrite with a diameter of 15 mm is used. The shape of the magnetic core 30 is not limited to the cylindrical shape, and it is possible to select a prismatic shape and the like.
In this example, the magnetic core 30 is disposed only in the interior of the fixing film 20, and forms an open magnetic circuit. As a modified example, it is acceptable to dispose a member which forms the magnetic circuit also in the exterior of the fixing film 20. Further, it is acceptable to form a closed magnetic circuit by the magnetic circuit forming member described above and the magnetic core 30.
The exciting coil 31 includes a helical portion L in which a single-conductor wire of a copper wire rod with a diameter of 1 to 2 mm coated with the heat resistant polyamideimide is wound over the magnetic core 30 in a helical shape with a number of windings of approximately 10 to 30. An axis of the helical portion L is substantially parallel to the rotational axis X of the fixing film 20. Further, the magnetic core 30 over which the helical portion L is wound overlaps the rotational axis X.
To be noted, as described above, a dimension (longitudinal width) of the magnetic core 30 in the longitudinal direction D1 is longer than the maximum width of the recording material P on which the fixing unit 1F can fix the image. The magnetic core 30 forms the magnetic circuit substantially over the whole length of the fixing film 20 in the longitudinal direction D1. It is suitable that an extension range of the magnetic core 30 in the longitudinal direction D1 includes the central area A1 described above. Further, it is suitable that the extension range of the magnetic core 30 in the longitudinal direction D1 includes an area where the segments 20b1 of the conductive layer 20b are disposed. Further, it is suitable that the extension range of the magnetic core 30 in the longitudinal direction D1 includes the sheet passing portion, and acceptable that the extension range of the magnetic core 30 in the longitudinal direction D1 includes the whole length of the fixing film 20.
Power supply contact portions 31a and 31b which are both ends of the exciting coil 31 are electrically coupled to a high frequency converter 51, serving as an alternating current generation circuit Based on a command from a control circuit 50, the high frequency converter 51 supplies a high-frequency anent (alternating anent) to the exciting coil 31. The high-frequency anent flowing through the helical portion L of the exciting coil 31 generates the alternating magnetic field around the fixing film 20.
With reference to
In
A moment when the electrical current is increasing in the exciting coil 31 in an arrow I direction in
Since the induced electromotive force is generated in a circulating direction of the conductive layer 20b, the circulation current J uniformly flows in the inside of the conductive layer 20b. Then, since the magnetic field generated by the exciting coil 31 repeats generation/extinction and a direction reversal by a high frequency anent, the circulation current J flows in a manner of repeating the generation/extinction and the direction reversal in synchronization with the high frequency current. When the electrical current flows in the conductive layer 20b, the Joule heat is generated in accordance with electrical resistance of the material (for example, metal) of the conductive layer 20b.
The magnetic field lines B in and B out of the magnetic field generated by the exciting coil 31 are substantially parallel to the longitudinal direction D1, and directions become opposite to each other in the inside and the outside of the fixing film 20. Therefore, the circulation current J flows in the circumferential direction D2 of the fixing film 20. As illustrated in
As described above, in the fixing film 20 of this example, because the high frequency current is made to flow in the exciting coil 31, the circulation current J, serving as an induced current, flows in each of the segments 20b1 of the conductive layer 20b. Since the circulation current J flows, the conductive layer 20b generates the heat.
Using
The high frequency converter 51 (refer to
When the recording material P onto which the image T was transferred by the operation of the image forming unit 1A described above has reached the fixing Trip N the recording material P is conveyed by being Tripped between the fixing film 20 and the press roller 22. Then, during time when the recording material P passes through the fixing nip N an image T on the recording material P is thermally fixed to the recording material P by receiving the heat and pressure from the fixing film 20.
Next, details of a division pattern of the conductive layer 20b of the fixing film 20 in this example will be described using
As illustrated in
In this example, a longitudinal width Sa of the fixing film 20 is 240 mm. On the other hand, an area where the conductive layer 20b exists is only an area in the central portion having a longitudinal width Sb which is narrower than the longitudinal width Sa of the whole film. The longitudinal width Sb is preferably set wider than a maximum sheet passable width of the recording material. In this example, the maximum sheet passable width of the recording material is the letter (LTR) size of 215.9 mm, and Sb is 220 mm. That is, the conductive layer 20b does not exist in a 10-mm area at both end portions of the fixing film 20.
The central area A1 whose longitudinal width is Sb and in which the conductive layer 20b is disposed is the first area of this example, and the end areas A2 on both outside of the central area A1 in the longitudinal direction D1 are the second area of this example. So as to secure fixing stability for the maximum size recording material over the whole area in the longitudinal direction D1, the central area A1 preferably includes the sheet passing portion (matching the sheet passing portion, or extending to the outside of the sheet passing portion). In this example, all of the plurality of segments 20b1 included in the conductive layer 20b are disposed in the central area A1, and the segments 20b1 do not exist in the end areas A2. Further, the central area A1 and the end areas A2 of this example are disposed symmetrically with respect to the central position of the fixing film 20.
It will be described that it is possible to reduce a temperature rise in the non-sheet passing portion by not disposing the conductive layer 20b in the end areas A2. In this example, in the central area A1 of the fixing film 20, the segments 20b1 with the width of 300 μm are disposed at intervals of 200 μm. Therefore, when the alternating magnetic field is generated by supplying the high frequency current to the exciting coil 31 at a time of the image formation, the central area A1 generates the heat by the heat generation principle described above. Further, the distribution of heat generation in the longitudinal direction D1 is substantially uniform in the inside of the central area A1. On the other hand, since the conductive layer 20b does not exist in the end areas A2 of the fixing film 20, the circulation current does not flow even in the inside of the alternating magnetic field, so that the end areas A2 do not generate the heat.
In a case where the LTR size recording material having the maximum width size is continuously passed through the fixing unit 1F, the heat of the fixing film 20 is taken by the recording material in the sheet passing portion, but the heat is not taken in the non-sheet passing portion. Therefore, in the comparative example illustrated in
In contrast, since, in the fixing film 20 of this example, the conductive layer 20b is not disposed in the end areas A2, a heat generation amount in the non-sheet passing portion is reduced. Consequently, it is possible to reduce the temperature rise in the non-sheet passing portion in comparison with the comparative example illustrated in
Next, an evaluation experiment which confirmed reduction in temperature rise in the non-sheet passing portion will be described. In the experiment, the fixing film 20 of this example illustrated in
As a measurement condition, Vitality (trade name, manufactured by Xerox Corporation) which is the LTR size paper having a grammage of 75 gram/square meter (g/m2) is used as the recording material. The abovementioned paper was set in the image forming apparatus 100, and a print operation was performed continuously on 50 sheets of paper at a sheet conveyance speed of 350 millimeters/second (mm/s), at a thruput of 70 sheets per minute.
In the print operation, so as to fix the image on the paper, the control circuit 50 controlled the high frequency converter 51 such that the detection result of the temperature detection unit 40 (refer to
During this print operation, a surface temperature of the non-sheet passing portion of the fixing film 20 was measured, and this example was compared with the comparative example. Here, the surface temperature of the non-sheet passing portion of the fixing film 20 is a surface temperature of the fixing film 20 in a position which is inside of the non-sheet passing portion which is outside of the sheet passing portion corresponding to the maximum width of the recording material, and in the position which is adjacent to end faces of the fixing film 20 in the longitudinal direction D1 and is not likely to be affected by a shape variation such as a twist. In this experiment, the surface temperature of the end portion of the fixing film 20 was measured in a position at a distance of 5 mm from the end face to the central side in the longitudinal direction D1.
The measured results are illustrated in
In a case of the comparative example (refer to
As described above, in this example, in a case where the alternating magnetic field is applied to the fixing film 20 (fixing member) at a time of the fixing operation, the heat generation amount in the end areas A2 (second area) of the fixing film 20 is smaller than the heat generation amount in the central area A1 (first area) of the fixing film 20. As illustrated in
As depicted in the results of the evaluation experiment illustrated in
To be noted, in this example, the configuration in which the conductive layer 20b is not disposed at both end portions of the fixing film 20 at all is illustrated. However, it is not limited to this, and, as illustrated in
Here, the occupying ratio of the conductive layer 20b in the central area A1 is a ratio of the sum of longitudinal widths of the segments 20b1 positioned in the central area A1 with respect to an overall width of the central area A1 in the longitudinal direction D1. Similarly, the occupying ratio of the conductive layer 20b in the end areas A2 is a ratio of the sum of the longitudinal widths of the segments 20b1 positioned in the end areas A2 with respect to an overall width of the end areas A2 (the sum of widths of two end areas A2) in the longitudinal direction D1.
Further, as illustrated in
As described above, it is possible to reduce the temperature rise in the non-sheet passing portion of the fixing film 20 of this example by applying the arrangement pattern of the segments 20b1 of the conductive layer 20b so as to lower the heat generation amount in both end portions of the fixing film 20 in the longitudinal direction D1 than the heat generation amount in the central portion. Further, thereby, it is possible to reduce the deterioration of the durability of the fixing film 20 due to the excessive temperature rise in the non-sheet passing portion and wasteful energy consumption accompanying the temperature rise in the non-sheet passing portion.
Next, an example 2 will be described. Configurations of the image forming apparatus 100 and the fixing unit 1F except for the fixing film 20 are the same as the example 1. Hereinafter, assuming that elements on which reference characters common to the example 1 are put have substantially the same configurations and functions as the example 1, portions different from the example 1 will be mainly described.
In the example 2, a configuration which can increase the mechanical strength of the end areas A2 of the fixing film 20 by increasing adhesion between the base layer 20a and the protective layer 20c will be described. To be noted, the base layer 20a is an example of an inner layer formed on the inner circumferential side of the conductive layer 20b in the fixing film 20, and the protective layer 20c is an example of an outer layer formed on the outer circumferential side of the conductive layer 20b in the fixing film 20.
In the example 1 (refer to
In a case where the adhesion between the base layer 20a and the protective layer 20c in the end areas A2 of the fixing film 20 is low, if a lateral-shift force is applied to the fixing film 20 in the longitudinal direction D1, there is a possibility that damage (break) may occur around the end face of the fixing film 20. Here, the lateral-shift force is a force which is applied with respect to the fixing film 20 in the longitudinal direction D1, and, for example, is generated when the user pulls out the recording material stuck in the fixing nip Nf because of a sheet jam or the like, obliquely with respect to the conveyance direction of the recording material. Further, other than a time of treating the sheet jam, the lateral-shift force is generated in a case where a left-right difference exists in a conveyance force due to unevenness in the temperature distribution of the press roller 22 in the longitudinal direction D1 and also in a case where rotational axes of the fixing film 20 and the press roller 22 are not parallel to each other.
In a case where the lateral-shift force described above has been strongly generated, the end areas A2 of the fixing film 20 is strongly pressed to the flange members 60 (refer to
Separately from the segments 20b1 which generate the heat by allowing the circulation current J to flow, the conductive layer 20b of this example includes dummy segments 20b2, each of which is formed electrically discontinuously in at least one place in the circumferential direction D2 so as not to allow the circulation-current J to flow. The dummy segments 20b2 can be also referred to as anon heat generating area in which the conductive layer 20b exists.
As illustrated in
A layer configuration of the fixing film 20 in a longitudinal position where the dummy segments 20b2 exist (non-heat generating area including the conductive layer 20b) will be described using
So as to form the gap portion G1, it is possible to use a method similar to the method used for forming the non-heat generating area in the gap between each neighboring two of the segments 20b1 in course of the preparation of the conductive layer 20b. That is, when coating paint for forming the conductive layer 20b on the base layer 20a, a dividing portion (non-coating portion) can be formed in advance in a portion corresponding to the gap portion G1 by the common technique such as the masking process. Besides the method described above, it is acceptable to form the gap portion G1, after having plated the outer surface of the base layer 20a with metal, by removing a part of the plated metal in the circumferential direction D2 using a technique such as laser etching and chemical etching.
As described above, since each dummy segment 20b2 does not form the closed electric circuit, even if the alternating magnetic field is generated around the dummy segment 20b2 by the exciting coil 31 to which the high frequency current is supplied, the circulation anent does not flow in the dummy segment 20b2. Therefore, in the longitudinal position where the dummy segments 20b2 exist, the fixing film 20 does not generate the heat.
Therefore, as with the example 1, the fixing film 20 of this example can reduce the temperature rise in the non-sheet passing portion.
Further, according to this example, since the conductive layer 20b also exists in the end areas A2 in a form of the dummy segments 20b2, the adhesion between the base layer 20a and the protective layer 20c is improved by the anchor effect. Thereby, in comparison with the example 1, the breaking strength of the end portions of the fixing film 20 is improved, and the durability and robustness of the fixing unit 1F are improved.
Next, an evaluation experiment by which an effect of improving the breaking strength of the fixing film 20 by this example was confirmed will be described. In the experiment, the breaking strength against the lateral-shift force was compared between the fixing film 20 of the example 1 illustrated in
As an evaluation method, while rotating the fixing film 20 attached to the fixing unit 1F, the lateral-shift force was intentionally generated in the longitudinal direction D1, and the lateral-shift force at which an end portion of the fixing film 20 breaks was compared. So as to generate the lateral-shift force, an angle (intersection angle) formed between the rotational axes of the fixing film 20 and the press roller 22 was gradually increased from 0 degree. The larger the intersection angle becomes, the stronger the lateral-shift force is generated and the stronger the end portion of the fixing film 20 is pressed to the flange member. The lateral-shift force at each intersection angle was measured by a load cell disposed to the flange member. Then, the lateral-shift force was gradually increased, and the breaking strength was measured based on whether or not the end portion of the fixing film 20 was broken at each lateral-shift force.
Results of the evaluation experiment are shown in Table 1. In Table 1, a case where the break of the end portion of the fixing film 20 occurred at each lateral-shift force is indicated as “no good”, and a case where the break of the end of the fixing film 20 did not occur at each lateral-shift force is indicated as “good”.
As shown in Table 1, in the fixing film 20 of the example 1, the break of the end portion of the fixing film 20 did not occur up to the lateral-shift force of 800 gf. However, when the lateral-shift force of 1200 gf was applied, the end portion of the fixing film 20 was deformed and bent, and finally led to the break.
On the other hand, in the fixing film 20 of this example, the break of the end portion did not occur when the lateral-shift force of 1600 gf was applied. It is considered that, since the conductive layer 20b exists also in the end areas A2 in this example, the breaking strength is high because of high adhesion between the base layer 20a and the protective layer 20c in comparison with the example 1 in which the conductive layer 20b does not exist in the end areas A2.
To be noted, in this example, the whole of the conductive layer 20b in the end areas A2 is formed by using the dummy segments 20b2 including the gap portions G1. Instead of this, for example, as illustrated in
That is, it is acceptable that the occupying ratio of the segments 20b1 in the central area A1 (first area) is higher than the occupying ratio of the segments 20b1 in the end areas A2 (second area) and the occupying ratio of the segments 20b2 in the end areas A2 (second area) is higher than the occupying ratio of the dummy segments 20b2 in the central area A1 (first area). To be noted, the occupying ratio of the segments 20b1 in the central area A1 is a ratio of the sum of the longitudinal widths of the segments 20b1 positioned in the central area A1 with respect to the overall width of the central area A1, and the same also applies to the other occupying ratios. With this configuration, while generating the heat in the central area A1 at the time of the fixing operation, it is possible to suppress the temperature rise in the non-sheet passing portion. Also in this example, it is preferred that the arrangement pattern of the segments in the conductive layer 20b is examined so as to, depending on the configuration of the fixing unit 1F, while satisfying the performance such as the fixing stability, reduce the temperature rise in the non-sheet passing portion.
As described above, according to this example, it is possible to reduce the temperature rise in the non-sheet passing area, and also possible to improve the mechanical strength of the end area A2 of the fixing film 20.
Next, an example 3 will be described. Configurations of the image forming apparatus 100 and the fixing unit 1F except for the fixing film 20 are the same as the example 1. Hereinafter, assuming that elements on which reference characters common to the examples 1 and 2 are put have substantially the same configurations and functions as the examples 1 and 2, portions different from the examples 1 and 2 will be mainly described.
The example 3 is an example which can further improve the mechanical strength of the end area A2 of the conductive layer 20b in comparison with the example 2. In the evaluation experiment described above, when a state of the end portions of the fixing film 20 of the example 2 had been examined in detail, it was revealed that, immediately before the occurrence of the break, cracks occur along the gap portions G1 of the dummy segments 20b2.
In the example 2, the gap portions G1 of the plurality of dummy segments 20b2 are disposed in a row in the longitudinal direction D1. Therefore, when the end portion of the fixing film 20 was strongly pressed to the flange member by the lateral-shift force, stress was concentrated on a position of the gap portion G1, where the conductive layer 20b does not exist, and there was a possibility that the cracks would have become likely to occur. Then, it is considered that the break of the end portion of the fixing film 20 progressed from the cracks occurred in the gap portions G1 as the starting point Therefore, to further improve the mechanical strength of the fixing film 20, a reduction of the cracks in the gap portions G1 which becomes the starting point of the break of the end portion is considered.
Therefore, in this example, positions of the gap portions G1 in the circumferential direction D2 are disposed in a manner different from each other among the plurality of dummy segments 20b2.
The conductive layer 20b of the fixing film 20 of this example includes the segments 20b1 in which the circulation anent flows and the dummy segments 20b2 in which the circulation anent does not flow. In the central area A1 of the fixing film 20, only the segments 20b1 are provided, and, in the end areas A2, only the dummy segments 20b2 are provided.
As illustrated in
To be noted, if the positions of the gap portions G1 are not the same among all of the plurality of dummy segments 20b2, it can be said that the positions of the gap portions G1 in the circumferential direction D2 are different from each other. For example, if the positions of the gap portions G1 of a first group and a second group among the plurality of dummy segments 20b2 are different from each other, it is acceptable to position the gap portions G1 at the same position in each group.
By varying the positions of the gap portions G1 between each of adjacent dummy segments 20b2 as with this example, it is possible to more effectively mitigate the stress concentration. Further, a configuration in which any two among all of the dummy segments 20b2 do not have the gap portions G1 at the same position is also useful for more effectively mitigating the stress concentration.
Next, an evaluation experiment by which degree of improvement in the breaking strength of the end portion of the fixing film 20 by this example was confirmed will be described. An evaluation method is similar to the method described in the example 2. In the experiment, the breaking strength against the lateral-shift force was compared between the fixing film 20 of the example 2 and the fixing film 20 of this example.
Results of the evaluation experiment are shown in Table 2. In Table 2, a case where the break of the end of the fixing film 20 occurred at each lateral-shift force is indicated as “no good”, and a case where the break of the end of the fixing film 20 did not occur at each lateral-shift force is indicated as “good”.
As shown in Table 2, while, in a case of the fixing film 20 of the example 2, the break occurred when the lateral-shift force of 2000 gf was applied, in a case of the fixing film 20 of this example, the break did not occur even when the lateral-shift force of 2000 gf was applied. While, in the case where the lateral-shift force of 2000 gf was applied to the fixing film 20 of the example 2, the cracks occurred in the positions of the gap portions G1 immediately before the break, the cracks did not occur in the case of this example.
In this example, it is considered that, by varying the positions of the gap portions G1 depending on a position in the longitudinal direction D1, the stress concentration on the gap portions G1 was mitigated so as to increase the breaking strength.
To be noted, a method to vary the positions of the gap portions G1 among the dummy segments 20b2 is not limited to the method described above. For example, as illustrated in
As described above, according to this example, it is possible to reduce the temperature rise in the non-sheet passing portion, and, also, possible to further improve the mechanical strength of the end areas A2 of the fixing film 20.
Next, an example 4 will be described. Configurations of the image forming apparatus 100 and the fixing unit 1F except for the fixing film 20 are the same as the example 1. Hereinafter, assuming that elements on which reference characters common to the examples 1 to 3 are put have substantially the same configurations and functions as the examples 1 to 3, portions different from the examples 1 and 2 will be mainly described.
In the examples 1 to 3, the methods for reducing the temperature rise in the non-sheet passing portion and improving the adhesion between the base layer 20a and the protective layer 20c by the pattern of the conductive layer 20b of the fixing film 20 are described. In this example, it will be described that it is also possible to reduce the temperature rise in the non-sheet passing portion by varying the thickness, width, or material of the segment of the conductive layer 20b.
The fixing film 20 of this example includes the segments 20b1 in both of the central area A1 and the end areas A2 (for example, refer to
For example, when the thickness of the segments 20b1 in the end area A2 is further thinned than the thickness of the segments 20b1 in the central area A1, the circulation resistance of the segments 20b1 in the end area A2 increases, and the heat generation amount in the end area A2 decreases. Further, when the width of each segment 20b1 in the end area A2 is more decreased than the width of each segment 20b1 in the central area A1, the circulation resistance of the segments 20b1 in the end area A2 increases, and the heat generation amount in the end area A2 decreases. To be noted, since the anchor effect itself is delivered even in a case where the thickness or width of each segment 20b1 in the end area A2 is varied from the central area A1, the adhesion between the base layer 20a and the protective layer 20c in the end area A2 is improved.
It is acceptable to reduce the heat generation amount in the end areas A2 by using a material with the volume resistivity higher than the volume resistivity of a material of the segments 20b1 in the central area A1 as a material of the segments 20b1 in the end area A2.
To be noted, in a case of the dummy segments 20b2 described in the examples 2 and 3 (i.e., segments in which the circulation current does not flow due to the gap portions G1), the circulation current does not flow regardless of the volume resistivity. Therefore, in a case where the dummy segments 20b2 are disposed, regardless of the volume resistivity, it is acceptable to select a material which can improve the mechanical strength or the adhesion between the base layer 20a and the protective layer 20c of the segment itself.
As described above, according to this example, it is possible to reduce the temperature rise in the non-sheet passing portion. Further, this example can be implemented in combination with the examples 1 to 3.
In the fixing film described in the examples 1 to 3, the segments 20b1 or the dummy segments 20b2 of the conductive layer 20b is not disposed in the end faces of the fixing film 20 in the longitudinal direction D1. Instead of this, so as to increase the breaking strength of the end faces of the fixing film 20, it is acceptable to change the pattern of the conductive layer 20b so that one of the segments 20b1 or one of the dummy segments 20b2 will be exposed at the end face.
In the examples 1 to 4, as the layer configuration of the fixing film 20, a configuration of five layers including the base layer 20a, the conductive layer 20b, the protective layer 20c, the elastic layer 20d, and the release layer 20e is illustrated. The layer configuration of the fixing film 20 is not limited to this, and it is preferred to appropriately select an optimum layer configuration in consideration of such as fixability and the durability.
In the examples 1 to 4, the fixing unit 1F and the image forming apparatus 100 including a center referenced sheet passing configuration in which the center of the sheet passing portion of the recording material P matches the center of the fixing unit 1F in the longitudinal direction D1 are described. Instead of this, for example, in a case of the fixing unit 1F and the image forming apparatus 100 including a side referenced sheet passing configuration in which the end of the recording material P in the longitudinal direction D1 matches a predetermined position of the fixing unit 1F in the longitudinal direction D1, a positional relationship between the sheet passing portion and the non-sheet passing portion becomes different. In such a case, it is acceptable to configure the conductive layer 20b such that the heat generation amount in the end portion on a side of the non-sheet passing portion of the fixing film 20 becomes less than the heat generation amount in the central portion.
In the examples 1 to 4, the configuration in which the alternating magnetic field for allowing the conductive layer 20b to generate the heat is generated by the exciting coil 31 inserted into the inner space of the fixing film 20 is described. Instead of this or in addition to the exciting coil 31, it is acceptable to dispose a coil, which generates the alternating magnetic field, in the outside of the fixing film 20.
In the examples 1 to 4, as an example of the tubular fixing member, the fixing film 20 which is a flexible endless film (belt) is described. It is not limited to this, and it is acceptable to use a rigid cylindrical roller member (fixing roller) for the tubular fixing member.
Embodiments of the present disclosure can also be realized by a computer of a system or apparatus that reads out and executes computer executable instructions (e.g, one or more programs) recorded on a storage medium (which may also be referred to more fully as a ‘non-transitory computer-readable storage medium’) to perform the functions of one or more of the above-described Embodiments and/or that includes one or more circuits (e.g, application specific integrated circuit (ASIC)) for performing the functions of one or more of the above-described Embodiments, and by a method performed by the computer of the system or apparatus by, for example, reading out and executing the computer executable instructions from the storage medium to perform the functions of one or more of the above-described Embodiments and/or controlling the one or more circuits to perform the functions of one or more of the above-described Embodiments. The computer may include one or more processors (e.g, central processing unit (CPU), micro processing unit (MPU)) and may include a network of separate computers or separate processors to read cut and execute the computer executable instructions. The computer executable instructions may be provided to the computer, for example, from a network or the storage medium. The storage medium may include, for example, one or more of a hard disk, a random-access memory (RAM), a read-only memory (ROM), a storage of distributed computing systems, an optical disk (such as a compact disc (CD), digital versatile disc (DVD), or Blu-rayDisc™ (BD)), a flash memory device, a memory card, and the like.
While the present disclosure has been described with reference to exemplary embodiments, it is to be understood that the disclosure is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
This application claims the benefit of Japanese Patent Application No. 2022-063233, filed on Apr. 6, 2022, which is hereby incorporated by reference herein in its entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2022-063233 | Apr 2022 | JP | national |
