Patent Grant
9952542
Field of the Invention
The present invention relates to a fixing apparatus having a heating unit for heating a recording material by using a cylindrical rotating member having flexibility, and relates to an image forming apparatus having this fixing apparatus.
Description of the Related Art
Image forming apparatuses based on an electrophotographic system include an apparatus for fixing a toner image onto a recording material by heating and pressurizing the toner image formed on the recording material.
The recording material 206 is conveyed from the right side of
However, in this configuration, there is a movement of heat from the fixing belt 201 to the fixing member 203, and because of this movement of heat, it is difficult to increase the temperature of the fixing belt 201, and there is a problem in that the fixing apparatus cannot be started in a short time.
According to a first aspect of the present invention, a fixing apparatus comprises a heating rotating member having a cylindrical shape, a nip portion forming member which includes a first surface and a second surface opposite to the first surface, and which is provided in a hollow portion of the heating rotating member so that the first surface faces an inner surface of the heating rotating member, and a pressure member which, together with the first surface of the nip portion forming member, sandwiches the heating rotating member to form a nip portion, wherein the nip portion is a contact area between the pressure member and an external surface of the heating rotating member, and a recording material is conveyed at the nip portion, wherein a recording material on which an image is formed is heated while being conveyed at a nip portion, and the image is fixed on the recording material, and wherein a plurality of recessed portions is provided on the first surface of the nip portion forming member, so that an area size where the first surface of the nip portion forming member is in contact with the heating rotating member is smaller in an upstream area of the nip portion than in a downstream area of the nip portion with respect to a center of the nip portion in a rotation direction of the heating rotating member.
Further features of the present invention will become apparent from the following description of exemplary embodiments (with reference to the attached drawings).
Hereinafter, modes for carrying out this invention will be described in details in an exemplary manner on the basis of embodiments with reference to drawings. However, a size, a material, a shape, and a relative position of components described in the embodiments may be changed as necessary in accordance with the configuration and various conditions of the apparatus to which the invention is applied, and therefore, it is to be understood that, unless otherwise specifically described, the scope of the invention is not be limited thereto. In a configuration of a later embodiment, the same constituent elements as those of a previous embodiment are denoted with the same reference numerals of the previous embodiment, so that the explanations in the previous embodiment are considered to be incorporated therein by reference.
[First Embodiment]
<The Entire Configuration of Image Forming Apparatus>
The photosensitive drum 101 is rotated and driven at a predetermined process speed (circumferential velocity) in a clockwise direction indicated by an arrow. The photosensitive drum 101 is charged in charging processing in a uniform manner to attain a predetermined polarity and potential with the charging roller 102 in its rotation process.
The laser beam scanner 103 serving as an image exposure unit outputs laser light 113 which is ON-OFF modulated in accordance with a digital pixel signal received from an external device such as a computer, not illustrated, and scans and exposes a charging processing surface of the photosensitive drum 101. With this scanning and exposure, an electrical charge on an exposure bright portion of the surface of the photosensitive drum 101 is removed, and an electrostatic latent image corresponding to image information is formed on the surface of the photosensitive drum 101.
The developing apparatus 104 receives a developer (toner) onto the surface of the photosensitive drum 101 from the developing roller 104a, so that the electrostatic latent image on the surface of the photosensitive drum 101 has been developed successively as toner images which are transferrable images.
A cassette 105 accommodates recording materials 114. A feeding roller 106 is driven on the basis of a feeding start signal, and the recording materials 114 in the cassette 105 are separated and fed sheet by sheet. Then, the recording material 114 is introduced with predetermined timing by way of a pair of registration rollers 107 into a transfer portion 108T which is a contact nip portion between the photosensitive drum 101 and a transfer roller 108 driven and rotated by coming into contact with the photosensitive drum 101. More specifically, the pair of registration rollers 107 controls the conveying operation of the recording material 114 so that the leading edge portion of the toner image on the photosensitive drum 101 and the leading edge portion of the recording material 114 reach the transfer portion 108T at the same time.
Thereafter, the recording material 114 is sandwiched and conveyed in the transfer portion 108T, during which time a transfer bias application power supply, not illustrated, applies a transfer voltage (transfer bias), which is controlled to attain a predetermined voltage, to the transfer roller 108. A transfer bias having a polarity opposite to the toner is applied to the transfer roller 108, and at the transfer portion 108T, the toner image at the surface side of the photosensitive drum. 101 is electrostatically transferred to the surface of the recording material 114.
The recording material 114 having the toner image transferred thereon is separated from the surface of the photosensitive drum 101, and passes through a conveying guide 109 to be introduced into the fixing apparatus 115 serving as a heating apparatus. In the fixing apparatus 115, the recording material 114 is subjected to thermal fixing processing of the toner image.
On the other hand, after the toner image is transferred onto the recording material 114, a cleaning apparatus 110 removes transfer residual toner and paper particles from the surface of the photosensitive drum 101, so that the surface of the photosensitive drum 101 is made into a clean surface, and so that the photosensitive drum 101 is capable of being repeatedly used for image formation. The recording material 114 having passed through the fixing apparatus 115 is discharged from a discharge port 111 to a discharge tray 112.
<Fixing Apparatus>
A fixing sleeve (fixing film) 1 serving as a cylindrical rotating member as illustrated in
In the configuration according to the present embodiment, SUS having a thickness 50 μm is employed as the base layer 1a. The material of the elastic layer 1b can be made of a material having a high heat-resistance, and the elastic layer 1b has a thickness 50 μm to 150 μm, and is made of silicone rubber or fluorine rubber. The separation layer 1c is made of PFA tube having a thickness of about 50 μm.
The halogen heater 2 serving as a heating unit for increasing the temperature of the fixing sleeve 1 is disposed inside of the fixing sleeve 1. The fixing sleeve 1 is heated by radiant heat generated by the halogen heater 2. The radiant heat of the halogen heater 2 should not be radiated to portions other than the fixing sleeve 1 in order to efficiently heat the fixing sleeve 1 with the radiant heat of the halogen heater 2. Therefore, a reflection plate 5 is provided between the sliding member 3 and the halogen heater 2. This reflection plate 5 is made of heat-resistant resin, and has metal deposited on the reflection surface in order to increase the reflection rate of radiation.
The pressure roller 4 serving as the pressure member includes a cored bar 4a and an elastic layer 4b having heat-resistant property such as silicone rubber, fluorine rubber, and fluorine resin formed around the cored bar 4a to cover the cored bar 4a in a coaxial manner, and is provided with a separation layer 4c on a surface layer thereof. A material having a high separation property and a high heat-resistant property such as PFA, PTFE, and FEP is selected for the separation layer 4c.
Both end portions of the cored bar 4a are held and arranged so as to be able to rotate with bearings. The pressure roller 4 rotates in a counterclockwise direction of
The sliding member 3 is required to have a heat-resistant property, a sliding property, and a low heat conductivity. Therefore, in the configuration according to the present embodiment, the sliding member 3 employs PPS resin (Poly Phenylene Sulfide) as its material. However, the material of the sliding member 3 is not limited to PPS resin. Other heat-resistant resins or metals may be employed. The shape of the sliding member 3 will be described below in detail.
<Surface Shape of Sliding Member>
In a case in which the length of the fixing external surface nip N is longer than the length of the fixing inner surface nip N′, the following problems may occur. A pressure locally increases at an edge portion of the sliding member 3 at the upstream side in the conveying direction of the recording material, and this accelerates abrasion of the sliding member 3. Since cut powders generated at that moment are interposed at the fixing nip, this may make it difficult for the fixing sleeve 1 to rotate, and as a result, the torque of the pressure roller 4 may increase. Therefore, the fixing inner surface nip N′ can be longer than the fixing external surface nip N. In the configuration according to the present embodiment, the length of the fixing external surface nip N is 11 mm, and the length of the fixing inner surface nip N′ is 14 mm.
In the fixing external surface nip N, an area of the sliding member surface 3a at the upstream side in the rotation direction of the fixing sleeve 1 will be denoted as an area N1, and an area at the downstream side will be denoted as an area N2. In the configuration according to the present embodiment, countersunk holes J are provided in the area N1, a countersunk hole width X1 is 0.9 mm, a non-countersunk hole width X0 is 0.9 mm, and a countersunk hole depth Z is 0.5 mm. In this case, the countersunk hole J means a recessed portion having a bottom. In the present embodiment, multiple recessed portions are formed in the sliding member surface 3a. In the area N1 of the contact area (fixing inner surface nip N′) in which the fixing sleeve 1 and the sliding member 3 are in contact with each other, the sliding member surface 3a serves as a portion in which an uneven shape is formed on the surface of the sliding member 3, and the fixing sleeve 1 and the sliding member 3 are locally in contact with each other. The sliding member surface 3a is a surface facing the inner surface of the fixing sleeve 1, and is a curved surface that is in a shape protruding in a direction away from the pressure roller 4. Instead of the countersunk holes J formed in the recessed portion having the bottom, the portion of the recessed portion may be configured to be a penetration hole.
Therefore, a contact area size rate at the contact area (fixing inner surface nip N′) in which the fixing sleeve 1 and the sliding member 3 are in contact with each other is smaller in the area N1 at the upstream in the rotation direction L1 of the fixing sleeve 1 than in the area N2 at the downstream. A contact area size rate at the contact area (fixing external surface nip N) in which the fixing sleeve 1 and the pressure roller 4 are in contact with each other is smaller in the area N1 at the upstream of in the rotation direction L1 of the fixing sleeve 1 than in the area N2 at the downstream.
The optimum value in the countersunk hole width X1 changes in accordance with the rigidity and the pressure force of the fixing sleeve 1. More specifically, when the size of the countersunk hole width X1 is increased excessively, the fixing sleeve 1 follows the inside of the countersunk hole J to lose pressure, and an image failure occurs so that an image on the recording material 6 is scraped before it is fixed. Therefore, it is necessary to set the countersunk hole width X1 so that such image failure does not occur.
In the configuration according to the present embodiment, the countersunk hole portion and the non-countersunk hole portion are repeated in a regular manner, but it may not be necessarily in a regular manner. For example, the countersunk hole width X1 may be increased in a portion in which the pressure is lower in the area N1.
In the configuration according to the present embodiment, the countersunk holes J are provided in the area within the fixing inner surface nip N′ but not included in the fixing external surface nip N. In a non-contact area Y in which the fixing sleeve 1 and the pressure roller 4 are not in contact with each other in the contact area (fixing inner surface nip N′) in which the fixing sleeve 1 and the sliding member 3 are in contact with each other, there is a sliding member surface 3a1 serving as a portion in which an uneven shape is formed on the surface of the sliding member 3a, and the fixing sleeve 1 and the sliding member 3 are locally in contact with each other.
In this area, pressure is not applied from the pressure roller 4, and this area is an area in which contact with the sliding member 3 is made by rigidity of the fixing sleeve 1. Therefore, the pressure is low, and even if a countersunk hole J is provided in this area, the image failure is less likely to occur, and therefore, a larger countersunk hole J than those in the fixing nip N can be attached.
Therefore, this suppresses transfer of heat from the fixing sleeve 1 to the sliding member 3, so that the fixing apparatus 115 can be started in a short time. When the countersunk holes J according to the present embodiment are provided, the startup speed can be increased by about 10% as compared with a conventional configuration having no countersunk hole J. However, a shape other than that described above may be employed as the shape of the countersunk hole J, and the type of the countersunk hole shape will be described later in detail.
Hereinafter, the reason why providing many countersunk holes J in the area N1 than in the area N2 is effective for suppressing thermal transfer from the fixing sleeve 1 to the sliding member 3 will be described in detail.
In the fixing external surface nip N, heat is transferred from the fixing sleeve 1 to the pressure roller 4, to the recording material 6, and to the sliding member 3. For this reason, in the contact area (fixing external surface nip N) in which the fixing sleeve 1 and the pressure roller 4 are in contact with each other, the temperature of the fixing sleeve 1 is higher at an upstream end Nin upstream in the rotation direction L1 of the fixing sleeve 1 than at a downstream end Nout downstream in the rotation direction L1. Since the amount of thermal transfer due to heat conduction is proportional to the temperature difference, the thermal transfer from the fixing sleeve 1 to the sliding member 3 is larger in the area N1 than in the area N2.
Therefore, the heat can be insulated effectively by providing a greater number of countersunk holes J in the area N1 than in the area N2. Accordingly, in the present embodiment, since the countersunk holes J are provided in the area N1, the pressure distribution in the fixing external surface nip N is rear end pressure. More specifically, the present embodiment employs such a shape that the sliding member 3 is engaged with the pressure roller 4 more deeply at a position of a rear end portion Nt, as illustrated in
However, when the rear end pressure configuration is employed, the pressure of the area N1 is relatively reduced, and therefore, even when the countersunk holes J are provided, the abrasion level does not cause any problem. Therefore, the average value of the pressure in the contact area (fixing external surface nip N) where the fixing sleeve 1 and the pressure roller 4 are in contact with each other is lower in the area N1 at the upstream in the rotation direction L1 of the fixing sleeve 1 than in the area N2 at the downstream.
Therefore, with the rear end pressure configuration of the countersunk holes J in the area N1, while the abrasion of the sliding member 3 is suppressed, the thermal transfer from the fixing sleeve 1 to the sliding member 3 can be effectively suppressed.
The contact area and the non-contact area are defined in the following measurement. A polyimide tape 7 is adhered to the sliding member surface 3a while a tension is appropriately maintained. At this occasion, a shape with which the fixing sleeve 1 comes into contact with the sliding member 3 in the fixing apparatus 115 is reproduced by applying pressure with the pressure roller 4. Thereafter, the pressure roller 4 is separated, and a shape measurement of the polyimide tape surface 7a is performed with a measurement device such as a laser microscope. A shape of the polyimide tape adhesion surface 7b can be calculated by considering the thickness of the polyimide tape 7.
The polyimide tape adhesion surface 7b corresponds to the back surface of the fixing sleeve 1, and therefore, the sliding member 3 at the position of the polyimide tape adhesion surface 7b is considered to be in contact with the fixing sleeve 1. As described above, the contact area size rate can be calculated by obtaining the contact area and the non-contact area as described above.
<Countersunk Hole Shape and Startup Time>
In the present embodiment, the countersunk hole shape is as illustrated in
In the case of longitudinal direction grooves (three grooves), which is the configuration according to the present embodiment, the startup time is faster by about 10% as compared with the conventional case without any countersunk hole J (see
Subsequently, when a case in which countersunk holes J are increased not only in the longitudinal direction but also in a direction of 30 degrees from the conveying direction (the rotation direction L1) (
A circle can also be considered as a countersunk hole shape (
As described above, in the fixing apparatus 115 according to the present embodiment, countersunk hole processing is provided in the sliding member surface 3a. At this occasion, thermal supply from the fixing sleeve 1 to the sliding member 3 is suppressed by increasing the countersunk hole quantity at the upstream side, and as a result, the startup speed of the fixing apparatus 115 can be increased.
The halogen heater 2 is employed as the heating unit in the configuration according to the present embodiment, but any heating method may be used as the heating unit as long as it is a method for heating the fixing sleeve 1 without relying on the fixing nip portion.
[Second Embodiment]
Hereinafter, the configuration according to the second embodiment will be described. In the present embodiment, the sliding member 3 according to the first embodiment is made into two bodies, i.e., a sliding member 8 and a sliding portion holding member 9. Therefore, explanations about the configuration other than the sliding member 8 and the sliding portion holding member 9 will not be described.
The sliding portion holding member 9 is arranged at the position facing the fixing sleeve 1 with the sliding member 8 interposed therebetween, so that the sliding member 8 is fixed. The sliding portion holding member 9 is a member for backing up a thin sliding member 8, and therefore, the sliding portion holding member 9 needs to have a heat-resistant property, and have a low thermal transfer property so that the heat is not transmitted. In the configuration according to the present embodiment, PPS resin is employed as the sliding portion holding member 9.
In this configuration, there is some heat transfer from the fixing sleeve 1 to the sliding member 8, but since the heat capacity of the sliding member 8 is small, the temperature suddenly rises, and the heat transfer from the fixing sleeve 1 to the sliding member 8 is converged. Therefore, in order to start the fixing apparatus 115 in a short time, it is necessary to suppress heat transfer from the sliding member 8 to the sliding portion holding member 9.
In the configuration according to the present embodiment, countersunk holes J are provided on a holding member surface 9a. The size of a countersunk hole width X3 can be set to a relatively large size with respect to the countersunk hole width X1 according to the first embodiment. In the first embodiment, since the fixing sleeve 1 follows the inside of the countersunk hole J, the countersunk hole width X1 cannot be enlarged, but in the configuration according to the present embodiment, the sliding member 8 is configured to receive a pressure force from the pressure roller 4. Therefore, the countersunk hole width X3 may be determined within a range in which the sliding member 8 is not deformed and the pressure distribution in the fixing nip does not change.
As a result, the countersunk hole quantity can be more than that of the first embodiment. In the configuration according to the present embodiment, 1.0 mm is employed as the countersunk hole width X3. For the same reason as in the first embodiment, in the area N2, it is necessary to decrease the number of countersunk holes J as compared with the area N1. Therefore, in the configuration according to the present embodiment, countersunk holes J are not provided in the area N2. The contact area size rate between the sliding member 8 and the sliding portion holding member 9 is smaller in the area N1 serving as an “upstream portion” upstream in the rotation direction L1 of the fixing sleeve 1 than in the area N2 serving as a “downstream portion” downstream in the rotation direction L1 of the fixing sleeve 1. Accordingly, the startup speed can be increased by about 10% as compared with a conventional configuration.
In the contact area (fixing inner surface nip N′) where the sliding member 8 and the sliding portion holding member 9 are in contact with each other, the holding member surface 9a serves as a “portion” in which an uneven shape is formed on the surface of the sliding portion holding member 9 and in which the sliding member 8 and the sliding portion holding member 9 are “locally in contact with each other”. In the contact area (fixing inner surface nip N′) in which the fixing sleeve 1 and the sliding member 8 are in contact with each other, there is a portion described below in the non-contact area Y where the fixing sleeve 1 and the pressure roller 4 are not in contact with each other. More specifically, a holding member surface 9a1 serves as a “portion” in which an uneven shape is formed on the surface of the sliding portion holding member 9 and in which the sliding portion holding member 9 and the sliding member 8 “are locally in contact with each other”.
As described above, in the fixing apparatus 115 according to the present embodiment, two bodies are provided, i.e., the sliding member 8 and the sliding portion holding member 9, and the countersunk hole processing is provided on the sliding portion holding member 9. With the effect of the sliding member 8, as compared with the first embodiment, while an abnormal increase in the temperature at the end portion of the fixing sleeve 1 is suppressed, the heat supply from the sliding member 8 to the sliding portion holding member 9 is suppressed by more greatly increasing the countersunk hole quantity of the sliding portion holding member 9 at the upstream side. As a result, the fixing apparatus 115 can be started in a shorter period of time.
[Third Embodiment]
Hereinafter, the configuration of the third embodiment will be described. However, in the present embodiment, only a sliding member 10 and a sliding portion holding member 11 are different from the configuration of the second embodiment. Therefore, explanation about the configuration other than the sliding member 10 and the sliding portion holding member 11 will be omitted.
The countersunk hole width X3 needs to be determined because of the reason described in the second embodiment, and in the configuration according to the present embodiment, 6.5 mm is employed. By providing the countersunk holes J, the startup speed of the fixing apparatus 115 can be increased by about 5% as compared with the conventional configuration.
The sliding portion holding member 11 is arranged at the positon facing the fixing sleeve 1 with the sliding member 10 interposed there between, so that the sliding member 10 is fixed. Like the sliding portion holding member 9 according to the second embodiment, the sliding portion holding member 11 is required to have a heat-resistant property and have a low thermal transfer property so that heat is not transmitted. In the configuration according to the present embodiment, PPS resin is employed as the sliding portion holding member 11.
The contact area size rate between the sliding member 10 and the sliding portion holding member 11 is smaller in the area N1 serving as an “upstream portion” upstream in the rotation direction L1 of the fixing sleeve 1 than in the area N2 serving as a “downstream portion” downstream in the rotation direction L1 of the fixing sleeve 1.
In the contact area (fixing inner surface nip N′) in which the sliding member 10 and the sliding portion holding member 11 are in contact with each other, there is a sliding member back surface 10a serving as a “portion” in which an uneven shape is formed on the back surface of the sliding member 10 and in which the sliding member 10 and the sliding portion holding member 11 “are locally in contact with each other”. In the contact area (fixing inner surface nip N′) in which the fixing sleeve 1 and the sliding member 10 are in contact with each other, there is a portion described below in the non-contact area Y in which the fixing sleeve 1 and the pressure roller 4 are not in contact with each other. More specifically, like the second embodiment, there may be a portion in which an uneven shape is formed on the back surface of the sliding member 10 and in which the sliding portion holding member 11 and the sliding member 10 are locally in contact with each other.
While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention 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, equivalent structures and functions.
This application claims the benefit of Japanese Patent Application No. 2015-197957, filed Oct. 5,2015 which is hereby incorporated by reference herein in its entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2015-197957 | Oct 2015 | JP | national |
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