JP7210893B2 - Fixing device and image forming apparatus provided with same - Google Patents

Description

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

In general, a fixing device provided in an image forming apparatus heats and presses a toner image formed on a sheet of paper to fix the image on the sheet of paper. A fixing device may use a member called a fixing pad. A heating belt runs along the fuser pad. If the shape of the heating belt on the upstream side of the fixing nip portion is inappropriate, there is a possibility that the sheet will not be conveyed properly to the fixing nip portion, that is, the sheet will not enter the fixing nip portion.

An example of a fixing device used in an image forming apparatus is described in Japanese Patent Application Laid-Open No. 2016-161849 (Patent Document 1). This device includes a heater member, a heat transfer member for transferring heat from the heater member, and a heater holder that supports them. The heat transfer member includes an extension portion extending upstream of the belt from the fixing nip portion. The extending portion of the heat transfer member has an R shape to guide the paper to the fixing nip portion.

Another example of a fixing device used in an image forming apparatus is described in Japanese Patent Application Laid-Open No. 2017-3606 (Patent Document 2). In this device, the fixing pad is supported by a reinforcing stay. Except for the fixing nip portion, the shoulder portion of the fixing pad and the fixing belt are not in contact with each other.

JP 2016-161849 A Japanese Unexamined Patent Application Publication No. 2017-3606

In the fixing device disclosed in Japanese Patent Application Laid-Open No. 2002-200001, the extending portion projecting upstream from the heater holder is provided with a rounded shape, but in this case, the size of the entire fixing device increases.

In the fixing device disclosed in Patent Document 2, the shoulder portion of the fixing pad has an R shape. This R shape is provided in a portion protruding upstream from the reinforcing stay. Since the shoulder portion of the fixing pad and the fixing belt are not in contact with each other, and the fixing belt wraps around the outside of the shoulder portion of the fixing pad while being separated from the shoulder portion of the fixing pad, the size of the entire fixing device increases.

In both of the fixing devices disclosed in Patent Documents 1 and 2, the size of the fixing device as a whole is increased, resulting in a lack of compactness. If the entire size of the fixing device increases, the heat capacity increases, and the efficiency of utilization of the heat energy supplied from the heat source also deteriorates.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a fixing device capable of smoothly receiving a recording medium in a fixing nip portion and having a compact structure, and an image forming apparatus having the same.

To achieve the above object, a fixing device according to the present invention comprises an endless belt circulatable for conveying a recording medium from upstream to downstream, and directing the belt from the inner side of the belt to at least a first side. and a support member for supporting the first member from the side opposite to the belt. The first member overhangs the upstream end of the support member toward the upstream side and overhangs the first side end of the support member toward a side opposite to the first side. and a second portion on the downstream side of the upstream end of the support member and on the first side of the support member. The first member has a continuous curved shape from the first portion to the second portion, with a convex side away from the support member.

According to the present invention, it is possible to smoothly receive the recording medium in the fixing nip portion, to achieve a compact configuration, and to provide a highly reliable product as an image forming apparatus.

1 is a conceptual diagram of an image forming apparatus according to Embodiment 1 of the present invention; FIG. FIG. 5 is a cross-sectional view of a fixing device according to Embodiment 2 of the present invention; FIG. 9 is an explanatory diagram of how a recording medium is guided in a fixing device according to Embodiment 2 of the present invention; FIG. 11 is a first explanatory diagram of how the pressure member is attached to the support member; FIG. 11 is a second explanatory diagram of how the pressure member is attached to the support member; FIG. 4 is a cross-sectional view of a state in which the pressure member is attached to the support member; FIG. 10 is an explanatory diagram regarding the positional relationship in the vicinity of the pressurizing member; FIG. 4 is an explanatory view in which a reference straight line is drawn on the pressing member and the supporting member; FIG. 10 is a diagram of a first comparative example; It is a figure of the 2nd comparative example. FIG. 4 is a first explanatory diagram of the configuration of the first portion of the first member; FIG. 4B is a second explanatory diagram of the configuration of the first portion of the first member; It is explanatory drawing regarding the thickness of a 1st member. FIG. 4 is an explanatory diagram of the relationship between the first member and the fixing nip portion; It is explanatory drawing regarding the shape of a 1st member. FIG. 11 is a conceptual diagram of a structure near a first member of a fixing device according to Embodiment 3 of the present invention;

(Embodiment 1)
(Image forming device)
An image forming apparatus according to Embodiment 1 of the present invention will be described with reference to FIG.

FIG. 1 shows a conceptual diagram of an image forming apparatus 801 according to this embodiment. An image forming apparatus 801 includes a housing 1 and a cassette 40 arranged below the housing 1 . Inside the housing 1, a photosensitive member 44, a charger 46, a transfer belt 47, an image exposure device 48, a developing roller 45, a primary transfer roller 42, a secondary transfer roller 43, a fixing device 101, and the like are arranged. . One or more recording media 2 are stored in the cassette 40 . The recording medium 2 may be paper, for example, but may be other than paper. The transfer belt 47 is endless and arranged so as to circulate.

In the image forming apparatus 801, the surface of the photoreceptor 44 is uniformly charged by the charger 46 to a predetermined potential. The image exposure device 48 applies image exposure corresponding to the document image to the charged area. An electrostatic latent image is thereby formed on the surface of the photoreceptor 44 . This electrostatic latent image is developed into a visible toner image by a developing roller 45 to which a developing bias is applied. A bias for attracting toner is applied to the primary transfer roller 42 , and the visible toner image on the surface of the photosensitive member 44 is transferred to the transfer belt 47 .

On the other hand, the recording medium 2 is taken out one by one from the cassette 40 by the paper feed roller 41 and conveyed to the secondary transfer roller 43 . A voltage is applied to the secondary transfer roller 43 as well as the primary transfer roller 42 . The transfer belt 47 is sandwiched between the secondary transfer roller 43 and the pressure roller 49 , and this portion serves as a nip portion 38 . When the recording medium 2 passes through the nip portion 38 , the recording medium 2 and the transfer belt 47 are sandwiched and pressed between the secondary transfer roller 43 and the pressure roller 49 . The visible toner image conveyed by the transfer belt 47 is transferred to the recording medium 2 at the nip portion. The recording medium 2 bearing the visible toner image is sent to the fixing device 101 . A detailed configuration of the fixing device 101 is as described in one of the embodiments described later. That is, the image forming apparatus 801 includes any fixing device described below. The fixing device applies heat and pressure to fix the toner onto the recording medium 2 . The recording medium 2 on which image formation has been completed in this way is ejected from the outlet 39 .

(action/effect)
In this embodiment, since a fixing device as described in one of the embodiments to be described later is provided, it is possible to smoothly receive the recording medium in the fixing nip portion and to have a compact configuration. Therefore, the image forming apparatus can be a highly reliable product.

(Embodiment 2)
(fixing device)
A fixing device according to a second embodiment of the present invention will be described with reference to FIGS. 2 to 10. FIG.

As shown in FIG. 2 , the fixing device 101 includes an endless belt 51 , a pressure roller 58 , and a pressure member 52 fixed inside the belt 51 . The pressure member 52 is also called a "pad". The pressure member 52 corresponds to a "first member" described later. A pressure member 52 and a pressure roller 58 are positioned so as to sandwich the belt 51 , thereby forming a fixing nip portion 50 . The pressure member 52 defines the route of the belt 51 . The belt 51 is fed along the shape of the pressing member 52 .

The pressure member 52 is supported by a support member 54 . A heat source 56 is arranged inside the heating member 57 . The belt 51 is stretched between a heating member 57 and a pressure member 52 . The pressure roller 58 is rotated at a predetermined rotational speed by a motor (not shown). The belt 51 is thereby fed.

The belt 51 has, for example, a three-layer structure of base layer/elastic layer/release layer. Although the outer diameter of the belt 51 is arbitrary, it is preferably 10 mm or more and 100 mm or less. A base layer of the belt 51 is made of, for example, polyimide, SUS, or Ni electroforming. The thickness of the base layer is, for example, 5 μm or more and 100 μm or less. The elastic layer of the belt 51 is preferably made of a highly heat-resistant material such as silicone rubber or fluororubber. The thickness of the elastic layer is preferably 10 μm or more and 300 μm or less. It is preferable that the release layer of the belt 51 has a release property such as a fluorine tube and a fluorine-based coating. The thickness of the release layer is preferably 5 μm or more and 100 μm or less.

The pressure member 52 may be made of resin such as polyphenylene sulfide, polyimide, or liquid crystal polymer. Instead of resin, the pressure member 52 may be made of metal such as aluminum or iron, ceramic, or the like. good too. The pressure member 52 may include a fixing member made of silicone rubber, fluororubber, or the like. The pressure member 52 may be configured by a combination of two or more parts.

The heating member 57 is a member made of metal such as aluminum or SUS, and has a substantially cylindrical shape. Although the outer diameter of the heating member 57 is arbitrary, it is preferably 10 mm or more and 100 mm or less. The thickness is preferably 0.1 mm or more and 5 mm or less. When a halogen heater is used as the heat source 56, the inner surface of the heating member 57 is preferably black. The outer surface of heating member 57 may be coated with PTFE, for example, in order to prevent the outer surface of heating member 57 from being scratched due to the entry of foreign matter or the like.

The pressure roller 58 has a three-layer structure of a metal core/elastic layer/release layer. The outer diameter of the pressure roller 58 is arbitrary, but preferably 20 mm or more and 100 mm or less. The elastic layer is preferably made of a material having high heat resistance such as silicone rubber or fluororubber. The thickness of the elastic layer is preferably 1 mm or more and 20 mm or less. The core metal is preferably made of metal such as aluminum or iron. The core bar may be pipe-shaped and may have a thickness of 0.1 mm or more and 10 mm or less. The core bar may have a solid shape, or may have an irregular cross-sectional shape such as a three-arrow shape. It is preferable that the release layer is formed of a fluorine tube or has a release property such as a fluorine-based coating. The thickness of the release layer is preferably 5 μm or more and 100 μm or less.

Heat source 56 may be a halogen heater. Alternatively, the heat source 56 may be of a type that heats the heating member 57 and/or the belt 51 with IH. A method of forming the heating member 57 and/or the belt 51 from a resistance heating element and generating heat by itself may be employed.

The recording medium 2 to which the toner image has been transferred is conveyed to the fixing nip portion 50 and passes through the fixing nip portion 50 with the surface to which the toner image has been transferred facing the heated belt 51 . The recording medium 2 passing through the fixing nip portion 50 is pressed and heated by being sandwiched between the belt 51 and the pressure roller 58 . Thereby, the toner image is fixed on the recording medium 2 .

FIG. 3 shows an enlarged view of the vicinity of the pressure member 52. As shown in FIG. In this figure, the recording medium 2 is fed from bottom to top as indicated by arrows 91 and 92, so the bottom is the upstream side and the top is the downstream side.

In order to reduce the angle formed by the recording medium 2 entering the fixing nip portion 50 and the belt 51 and to convey the recording medium 2 as intended when entering the fixing nip portion 50, the curvature radius R of the pressure member 52, that is, the upstream side of the pad is It's getting bigger. As the radius of curvature R increases, the probability of occurrence of jamming when the recording medium 2 rushes in decreases, and the recording medium 2 can be conveyed smoothly. However, there is also a balance with the space, and as a guideline, it is preferable that R on the upstream side of the pad≈R of the pressure roller, or R on the upstream side of the pad≧R of the pressure roller.

As a result, when the recording medium 2 enters the fixing nip portion 50, the angle formed by the recording medium 2 and the belt 51 can be made acute, thereby preventing conveyance failure. When the recording medium 2 enters the fixing nip portion 50, it is possible to secure a wide area in which the recording medium 2 can enter without being jammed. In particular, in the case of the recording medium 2 having low stiffness such as thin paper, the recording medium 2 may be fed into the fixing nip portion 50 in an undesirably deformed state. For example, in the example shown in FIG. 3, the recording medium 2 is fed in a state deviated in the direction of the arrow 93 from the correct advancing direction of the recording medium 2 indicated by the arrows 91 and 92 . Also in this case, the movement path of the recording medium 2 is naturally corrected by the running belt 51, and the recording medium 2 is correctly guided to the fixing nip portion 50. FIG. In this manner, even when the recording medium 2 moves away from the fixing nip portion 50 , it can be properly guided to the fixing nip portion 50 . In this manner, the recording medium 2 can be conveyed without jamming.

Attachment of the pressure member 52 to the support member 54 will be described with reference to FIGS. 4 to 6. FIG. The support member 54 may be made of sheet metal. As shown in FIGS. 4 and 5, the support member 54 is provided with a hole 54a for mounting the pressure member 52 thereon. As shown in FIG. 5, a pin 52b is provided on the surface of the pressure member 52 on the support member 54 side for attachment to the support member 54. As shown in FIG. The pressure member 52 can be attached to the support member 54 by fitting the pin 52b into the hole 54a. FIG. 6 shows a cross-sectional view of the completed installation.

The positional relationship in the vicinity of the pressing member 52 will be described with reference to FIG. A straight line extending toward the pressure roller 58 in contact with the upstream end 54 e of the support member 54 is drawn and designated as a straight line 21 . The curved shape 5 of the pressure member 52 is provided so as to straddle the upstream side and the downstream side of the straight line 21, as shown in FIG.

For a more detailed explanation, FIG. 8 shows a state in which the pressure member 52 and the support member 54 are taken out and the reference straight lines 21 and 22 are drawn. The straight line 21 is the same as that previously described with respect to FIG. A straight line 22 is a straight line that contacts the end 54f of the support member 54 on the pressure roller 58 side and extends vertically in the figure. In FIG. 8 the first side 95 is indicated by an arrow. In FIG. 8, the bottom is the upstream side and the top is the downstream side. In FIG. 8, the curved surface shape 5 of the pressing member 52 is represented by a thick line.

Although the description has been made with reference to FIGS. 2, 3, 7, and 8, the configuration of fixing device 101 in the present embodiment can be expressed as follows.

The fixing device 101 includes an endless belt 51 that can be circulated to convey the recording medium 2 from upstream to downstream, and a first member that presses the belt 51 toward at least a first side 95 from the inside of the belt 51 . and a support member 54 that supports the first member from the side opposite to the belt 51 . The first member protrudes upstream from the upstream end 54e of the support member 54, and is located on the side opposite to the first side 95 from the end 54f of the first side 95 of the support member 54. and a second portion 12 located on the downstream side of the upstream end 54 e of the support member 54 and on the first side 95 of the support member 54 . The pressure member 52 as the first member has a continuous curved surface shape 5 extending from the first portion 11 to the second portion 12 and convex on the side away from the support member 54 .

In the fixing device 101 according to the present embodiment, the positional relationship of the pressure member 52, the support member 54, etc. is as shown in FIG. 8, but comparative examples are shown in FIGS. . In FIG. 9 , the entire curved surface shape 5 is on the upstream side of the straight line 21 . In FIG. 10 , the entire curved shape 5 is on the pressure roller 58 side of the straight line 22 . The configuration shown in FIG. 8 is different from the configuration shown in FIG. 9 and is also different from the configuration shown in FIG.

(action/effect)
In this embodiment, since the curved shape 5 is on the upstream side of the fixing nip portion 50 , the recording medium 2 conveyed from the upstream side is guided to the fixing nip portion 50 by the curved shape 5 . Moreover, since the curved shape 5 is provided from the first portion 11 to the second portion 12 as shown in FIG. 8, it does not require a very large space. Therefore, the fixing device 101 according to the present embodiment can smoothly receive the recording medium 2 in the fixing nip portion 50, and can have a compact configuration.

As shown in this embodiment, the fixing device 101 includes a second member that presses the belt 51 from the outside in at least part of the region where the pressure member 52 as the first member presses the belt 51 . is preferred. Here, the pressure roller 58 corresponds to the second member. Since the second member presses the belt 51 from the outside, fixing can be performed efficiently. Although the first member is the pad-like pressure member 52 and the second member is the pressure roller 58 in this embodiment, the combination may be reversed. That is, the first member may be some kind of roller and the second member may be a pad-like member.

Preferably, the first portion 11 of the first member abuts the upstream surface 54b of the support member 54, as shown in FIG. By adopting this configuration, the posture of the first member can be reliably fixed, and the recording medium can be conveyed stably.

On the other hand, as shown in FIG. 12, a configuration in which the first portion 11 is not in contact with the surface 54b is also conceivable. In this case, since the contact area between the pressure member 52 as the first member and the support member 54 is small, the degree of heat escape from the first member to the support member 54 can be reduced. As a result, it leads to energy saving.

As shown in the present embodiment, the curved shape 5 extends upstream of the fixing nip portion 50 as the region where the pressure roller 58 as the second member presses the belt 51 . As a result, even if the recording medium deviates slightly to the upstream side, the contact between the belt 51 and the recording medium can be made at a small angle, and the recording medium can enter the fixing nip portion 50 without jamming.

As shown in this embodiment, the fixing device is preferably provided with a guide plate 35 (see FIG. 3 or FIG. 7) that is arranged so as to face the curved shape 5 from the upstream side and guides the recording medium 2. . By adopting this configuration, the recording medium 2 can be reliably brought into contact with the curved shape 5 .

As shown in the present embodiment, the thickness of pressure member 52 as the first member may vary depending on the location. In this fixing device, as shown in FIG. 13, the thickness T1 of the first portion 11 is greater than the thickness T2 of the pressure member 52 at the corners of the support member 54 . By adopting this configuration, the first member can easily come into contact with the upstream side surface 54b of the support member 54 while realizing the R shape, and the recording medium 2 can be conveyed stably. can be done.

As shown in FIG. 14, a pressure member 52 as a first member and a pressure roller 58 as a second member press against a portion where the upstream surface 54b of the support member 54 is extended toward the second member. It is preferable that they do not match. 14, it is preferable that the straight line 21 extending from the surface 54b toward the second member is upstream of the most upstream end of the fixing nip portion 50. As shown in FIG.

Further, in the example shown in FIG. 14, the straight line 23 extending the downstream surface of the support member 54 toward the second member passes through the downstream end of the fixing nip portion 50 as is apparent from the Z2 section. ing. Straight line 23 preferably passes through fusing nip 50 . By adopting this configuration, it is possible to apply sufficient pressure to the recording medium and perform good fixing.

As shown in FIG. 13, an outlet peak portion 52d, which is a slightly overhanging portion, is provided in the vicinity of the downstream end portion of the pressure member 52. Sufficient pressure can be applied to the passing recording medium, and good fixing can be performed.

The first member, that is, the pressure member 52 is preferably made of resin. If it is made of resin, even a complicated shape can be easily produced. A desired shape suitable for the fixing operation can be easily produced.

As shown in FIG. 15 , the pressure member 52 as the first member has a third portion 13 downstream of the second portion 12 , and the third portion 13 has a planar shape 6 continuously connected to the curved shape 5 . It is preferred to have By providing the planar shape 6 on the first member in this manner, the pressure and the amount of heat applied to the toner can be easily controlled to desired values, the toner can be sufficiently melted, and sufficiently good fixing can be performed.

On the further downstream side of the planar shape 6, an intermediate concave shape 7 and an outlet convex shape 8 are connected in this order. The pressure member 52 as the first member preferably has such a combination of shapes. As shown in FIG. 15 , a planar shape 15 may continue downstream of the outlet convex shape 8 .

As shown in FIG. 2, the fixing device 101 preferably includes a heating roller 59 which is a roller having a heat source, and the belt 51 preferably circulates around the heating roller 59 and the first member.

(Embodiment 3)
(Constitution)
A fixing device according to Embodiment 3 of the present invention will be described with reference to FIG. The fixing device in this embodiment is basically the same as that described in the second embodiment, but differs in the following points.

The fixing device comprises a sliding sheet 9 positioned over the surface 10 of the first side 95 of the first member. Up to FIG. 15, thick lines were used to emphasize the external shape of the pressure member 52 as the first member, but in FIG. 16, the actually arranged sliding sheet 9 is represented by thick lines. ing.

(action/effect)
In this embodiment, since the sliding sheet 9 covers the surface 10 of the first member, the belt 51 can be slid smoothly, so that the driving torque can be reduced.

As shown in this embodiment, the sliding sheet 9 may cover not only the surface 10 but also the surface of the first member other than the first side 95 .

It should be noted that the above embodiments disclosed this time are illustrative in all respects and are not restrictive. The scope of the present invention is indicated by the claims, and includes all changes within the meaning and range of equivalents to the claims.

REFERENCE SIGNS LIST 1 housing 2 recording medium 5 curved shape 6 planar shape 7 intermediate concave shape 8 outlet convex shape 9 sliding sheet 10 surface 11 first part 12 second part 13 third part 15 Planar shape 21, 22, 23 Straight line 35 Guide plate 38 Nip portion (for secondary transfer) 39 Exit 40 Cassette 41 Paper feed roller 42 Primary transfer roller 43 Secondary transfer roller 44 Photoreceptor 45 Developing roller 46 Charger 47 Transfer belt 48 Image exposure device 49 Pressure roller 50 Fixing nip portion 51 Belt 52 Pressure member (first member) 52b Pin 52d Exit peak portion 54 support member 54a hole 54b surface 54e, 54f edge 56 heat source 57 heating member 58 pressure roller 59 heating roller 91, 92, 93 arrow 95 first side 101 fixing device 801 image processing equipment.

Claims (7)

an endless belt that can be circulated to convey the recording medium from upstream to downstream;
a first member that presses the belt toward at least a first side from the inside of the belt;
a support member that supports the first member from a side opposite to the belt;
a second member that presses the belt from the outside in at least part of a region where the first member presses the belt,
The first member is
a first portion that overhangs the upstream end of the support member toward the upstream side and overhangs the first side end of the support member toward the side opposite to the first side;
a second portion on the downstream side of the upstream end of the support member and on the first side of the support member;
The first member has a continuous curved surface shape from the first portion to the second portion with a convex side away from the support member,
The first member includes a third portion downstream of the second portion, the third portion having a planar shape continuously connected to the curved shape,
In the first member, an intermediate concave shape, an exit convex shape, and a second planar shape are arranged in this order on the further downstream side of the planar shape,
The fixing device, wherein the second member is a pressure roller, and the radius of curvature of the first member on the upstream side of the fixing nip portion is equal to or greater than the radius of the pressure roller. The fixing device according to claim 1 , wherein the first portion is in contact with the upstream surface of the support member. 2. The fixing device according to claim 1, wherein the curved shape extends upstream of a region where the second member presses the belt. 4. The fixing device according to any one of claims 1 to 3, further comprising a guide plate arranged from the upstream side toward the curved shape and guiding the recording medium. The fixing device according to any one of claims 1 to 4, further comprising a sliding sheet arranged to cover the first side surface of the first member. 6. The fixing device according to claim 1, further comprising a heating roller that is a roller having a heat source, wherein said belt circulates while surrounding said heating roller and said first member. An image forming apparatus comprising the fixing device according to claim 1 .

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