Fixing device and image forming apparatus

Abstract

To provide an inexpensive, space-saving fixing device that satisfies safety standards. [Solution] The device comprises a film 3, a pressure roller 4, and an apparatus frame 100 having an entrance section 100Hi and an exit section 100Ho, and the apparatus frame 100 has an opening 101H in an area (apparatus frame 101) other than the entrance section 100Hi and the exit section 100Ho, the opening 101H having a length in the rotational axis direction of the pressure roller 4 longer than the length in the rotational axis direction of the rubber layer 4b.

Description

[Technical Field]

[0001] The present invention relates to a fixing device used in an image forming apparatus employing an electrophotographic system or an electrostatic recording system, such as a copying machine, a printer, or a facsimile, for heat-fixing an unfixed toner image on a recording material, and to an image forming apparatus equipped with the fixing device. [Background technology]

[0002] Film-heating type fixing devices have been known for use in electrophotographic copiers and printers. A film-heating type fixing device includes a cylindrical film, a heater that contacts the inner surface of the film, and a pressure roller that forms a nip with the heater via the film. The heater, which may be a planar heater with a planar heating element mounted on a ceramic substrate, is supported by a resin guide member. The guide member is reinforced with a metal reinforcing member. A through-hole is provided along a portion of the guide member's length, and a temperature detection element located in the space between the guide member and the reinforcing member detects the heater temperature through the through-hole. The heater is controlled based on the temperature detected by the temperature detection element. Similarly, a protective element such as a thermostat or thermal fuse is provided in the space between the guide member and the reinforcing member, and the protective element also detects the heater heat through another through-hole in the guide member. The protective element cuts off the power supply to the heater when the heater reaches an excessive temperature. This type of heating unit is brought into contact with a pressure member called a pressure roller at a desired pressure to form a nip. A sheet carrying an unfixed toner image passes through the nip, which is heated by the driving force of the pressure roller, thereby fixing the unfixed toner image to the sheet. Generally, these heating unit materials and pressure roller are held in a metal frame to prevent the frame from being significantly deformed by thermal expansion, thermal deformation, or pressure force, forming a fixing device.

[0003] On the other hand, the heater generates heat by passing an AC current through the heating element formed on the heater substrate, and therefore, safety standards stipulate that the film in contact with the heater and the pressure roller in contact with the heater via the film must be configured at a desired distance from the safety earth. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-013780 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in recent years, there has been a demand for high-speed, compact, and low-cost fixing devices. Therefore, it is necessary to increase the diameter of the pressure roller to increase speed, and to downsize the device frame to reduce size. Simply narrowing the distance between the device frame and the pressure roller would result in the pressure roller and device frame being closer than the distance required for insulation by safety standards. Therefore, to ensure an insulation distance between the pressure roller and device frame, it is necessary to ensure a creepage distance, and an insulating resin or sheet material must be used between the pressure roller and device frame to ensure the insulation distance. However, this method has the problem of increasing costs.

[0006] The present invention has been made under these circumstances, and has as its object to provide an inexpensive, space-saving fixing device that satisfies safety standards. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems, the present invention has the following configuration.

[0008] (1) A fixing device comprising: a heating unit having a cylindrical flexible rotating body and a heating element in contact with the inner surface of the rotating body; a pressure roller having a core and a rubber layer covering the core and in contact with the outer surface of the rotating body, the pressure roller sandwiching the rotating body together with the heating element to form a nip portion with the rotating body; an entrance portion having an opening for transporting a recording material to the nip portion, and an exit portion having an opening for transporting a recording material from the nip portion to the outside, and a metal frame that holds the pressure roller; wherein the frame has an opening in an area other than the entrance portion and the exit portion, the opening having a length in the direction of the rotational axis of the pressure roller that is longer than the length in the direction of the rotational axis of the rubber layer.

[0009] (2) An image forming apparatus comprising: an image forming means for forming a toner image on a recording material; and a fixing device according to (1) above for fixing the toner image formed by the image forming means onto the recording material. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a fixing device that satisfies safety standards, is inexpensive, and saves space. [Brief explanation of the drawings]

[0011] [Figure 1] Schematic cross-sectional view of a fixing device according to a first embodiment [Figure 2] Schematic diagram of fixing devices in Examples 1 to 3 [Figure 3] Schematic diagram of heaters in Examples 1 to 3 [Figure 4] Schematic cross-sectional view of a fixing device of a comparative example [Figure 5] Schematic diagram of a fixing device of a comparative example [Figure 6] Schematic perspective view of a fixing device according to a first embodiment of the present invention. [Figure 7] Schematic cross-sectional view of a fixing device according to a second embodiment [Figure 8] Schematic perspective view of a fixing device according to a second embodiment of the present invention. [Figure 9]Schematic cross-sectional view of an image forming apparatus according to a third embodiment. [Figure 10] Schematic cross-sectional view of a fixing device according to a third embodiment [Figure 11] 10 is a schematic perspective view of a fixing device according to a third embodiment of the present invention; DETAILED DESCRIPTION OF THE INVENTION

[0012] The following describes embodiments of the present invention with reference to the drawings. Note that the following embodiments do not limit the scope of the invention as claimed, and not all of the combinations of features described in the embodiments are necessarily essential to the solution of the invention. [Example]

[0013] A first embodiment of the present invention will be described below.

[0014] <Fixing device> The schematic configuration of a fixing device 1 of Example 1 will be described with reference to FIGS. 1 to 6. FIG. 1 is a schematic cross-sectional view of the fixing device 1. The fixing device 1 includes a heating unit 2 having a film 3 as a flexible, rotatable cylindrical rotating body containing a heater 5 having a heat generating element, and a pressure roller 4 that presses the heating unit 2 with a pressure means (not shown) to form a nip portion N. The pressure roller 4 abuts against the outer peripheral surface of the film 3. By nipping and conveying a recording material P in the nip portion N, an unfixed toner image (not shown) on the recording material P can be heated and fixed. The heating unit 2 and the pressure roller 4 are housed in a device frame 100.

[0015] 2 is a schematic diagram of the heating unit 2 and pressure roller 4 of the fixing device 1. Here, the direction perpendicular to the conveying direction Dt of the recording material P, in other words, the rotational axis direction or longitudinal direction of the film 3 and pressure roller 4, is designated as Dr. The heating unit 2 and pressure roller 4 are supported at both ends by the device frame 100 of the fixing device 1 (see FIG. 1), and the pressure roller 4 is configured to rotate in the rotation direction Drt by transmitting a driving force from a driving source (not shown) to a driving gear 28. The pressure roller 4 has a core 4a made of iron or the like and a rubber layer 4b covering the periphery of the core 4a.

[0016] The film 3, which is in pressure contact with the pressure roller 4, is configured to rotate in response to the rotation of the pressure roller 4. A heater 5 serving as a heating member is provided inside the film 3, and the inner circumferential surface of the film 3 and the heater 5 are in slidable contact with each other, with both ends held by flanges 29. Note that the heating member may also be configured to have a sliding contact member (such as a metal plate) and the sliding contact member contacting the inner surface of the film 3.

[0017] Grease is applied between the heater 5 and the film 3 to improve sliding. The heater 5 is configured to generate heat when power is supplied from a power supply (not shown) via a connector 30, which serves as an electrical contact. The heater 5 is held inside the film 3 by a heater holder 7 (FIG. 1). It is preferable that the nip N formed by the film 3 and the pressure roller 4 has a uniform width in the direction of the rotation axis (Dr) of the film 3. Therefore, to improve the strength against the pressure force, a metal reinforcing member 8 (FIG. 1) is attached to the heater holder 7 at the position shown in FIG. 1. The reinforcing member 8 receives a pressing force F from a pressure means (not shown) via flanges 29 attached to both ends of its longitudinal direction. The heating unit 2 is attached to the device frame 100 by inserting the flanges 29 into the device frame 100.

[0018] <Heater> Next, the configuration of the heater 5 will be described using Figure 3. Figure 3(a) is a plan view showing the configuration of the heater 5, and Figure 3(b) is a cross-sectional view taken along the line AA in Figure 3(a). A planar heating element 5H is disposed on a ceramic heater substrate 5Ce, and the heating element 5H is covered with a glass layer 5G. The heater 5 has a heater contact portion 5C at its end, which is a contact portion with the connector 30, and the heating element 5H generates heat by supplying an AC current to the heating element 5H via the connector 30. Note that the heater contact portion 5C is not covered with the glass layer 5G.

[0019] The heating unit 2 has a temperature detection unit (not shown) that detects the temperature of the heater 5. During the transport of the recording material P, the temperature detection is used to control the supply of AC current to maintain the heater 5 at the desired temperature. Because AC current flows through the heating element 5H of the heater 5, the glass layer 5G provides basic insulation, and the film 3 in contact with the heater 5 and the pressure roller 4 in contact with the film 3 are at basic insulation potential. Therefore, the metal device frame 100 (frame), which also serves as a safety earth, must ensure the necessary clearance and creepage distances to ensure supplemental insulation from the film 3 and pressure roller 4, in accordance with safety standards, to ensure supplemental insulation from components at basic insulation potential. In Example 1, a clearance distance of 2.3 mm and a creepage distance of 2.5 mm are ensured between the pressure roller 4 and the device frame 100, as specified in the IEC 62368 safety standard.

[0020] <Device frame and task description> FIG. 4 is a schematic cross-sectional view of a fixing device 1′ of a comparative example, and FIG. 5(a) is a schematic diagram showing the relationship between a device frame 100′ of the comparative example, a heating unit 2, and a pressure roller 4 in the longitudinal direction Dr. Here, one end in the longitudinal direction Dr is defined as the left, and the other end as the right. The left side of the metal device frame 100′ will be referred to as device frame 103′, and the right side will be referred to as device frame 104′. The surface (first surface) of the device frame 100′ on the pressure roller 4 side (lower side) extending in the longitudinal direction Dr will be referred to as device frame 101′, and the surface (second surface) of the device frame 100′ on the film 3 side (upper side) extending in the longitudinal direction Dr will be referred to as device frame 102′. The device frame 101′ is the surface facing the pressure roller 4, and the device frame 102′ is the surface facing the film 3.

[0021] As shown in FIG. 4, when viewed in the direction of the rotation axis (Dr) of the film 3 and the pressure roller 4, the device frame 101' has a U-shaped cross section, with its upstream end in the conveying direction Dt designated as end 101'i and its downstream end designated as end 101'o. The device frame 102' also has a U-shaped cross section, with its upstream end in the conveying direction Dt designated as end 102'i and its downstream end designated as end 102'o. The end 101'i of the device frame 101' and the end 102'i of the device frame 102' are spaced a predetermined distance apart as shown in FIG. 4, and form an opening (hereinafter referred to as inlet portion 100'Hi) so that the leading edge of the recording material P is guided to the nip portion N of the fixing device 1. An end 101'o of the device frame 101' and an end 102'o of the device frame 102' are also spaced a predetermined distance apart, and form an opening (hereinafter referred to as an exit portion 100'Ho) so that the leading edge of the recording material P can be guided from the nip portion N of the fixing device 1 to the outside of the fixing device 1. The device frames 101' and 102' do not have to have a U-shaped cross section, as long as they are shaped to surround the film 3 and the pressure roller 4, respectively, and are provided with an entrance portion 100'Hi and an exit portion 100'Ho, which are the entrance and exit for the recording material P.

[0022] The device frames 103' and 104' are fastened and fixed to the device frames 101' and 102', respectively, by fastening means (not shown). As a result, as shown in FIG. 5(a), the cross section of the device frame 100' in a direction perpendicular to the conveying direction Dt is rectangular. The heating unit 2 and the pressure roller 4 are supported at both ends by the device frames 103' and 104', respectively.

[0023] <Clearance and creepage distance> In this configuration, the film 3 and pressure roller 4, which are at basic insulation potential, are positioned at a clearance SD of 2.3 mm or more and a creepage distance CD of 2.5 mm or more from the equipment frame 100'. The ends of the film 3 and pressure roller 4 are secured with a creepage distance CD greater than the supplemental insulation distance by insulating resin members 3L, 3R, 4L, and 4R. Here, at the left end of the film 3, the creepage distance CD is the distance from the surface of the film 3 to the equipment frame 103' via the resin member 3L. At the right end of the film 3, the creepage distance CD is the distance from the surface of the film 3 to the equipment frame 104' via the resin member 3R. The creepage distance CD between the film 3 and the equipment frame 103' (104') is set so that the smaller creepage distance on either the left or right side satisfies the safety standard. At the left end of the pressure roller 4, the creepage distance CD is the distance from the core metal 4a of the pressure roller 4 to the equipment frame 103' via the resin member 4L. On the right end side of the pressure roller 4, the creepage distance CD is the distance from the core metal 4a of the pressure roller 4 to the device frame 104' via the resin member 4R. The creepage distance CD of the pressure roller 4 is set so that the smaller value of the creepage distance on either the left or right side satisfies the safety standard.

[0024] Meanwhile, the spatial distance SD between the film 3 and the device frame 102' and the spatial distance SD between the pressure roller 4 and the device frame 101' are both 2.3 mm or more to ensure the additional insulation distance. In other words, the spatial distance SD is also configured to be greater than the insulation distance (a specified distance) specified by the safety standard. Here, the spatial distance SD is the distance between the surface of the film 3 and the device frame 102'. The spatial distance SD is the distance between the surface of the pressure roller 4 and the device frame 101'.

[0025] However, in recent years, there has been a demand for smaller, faster, and less costly image forming devices. Therefore, the cross-section of the fixing device 1 needs to be reduced, or the pressure roller 4 needs to be enlarged while the device frame 100' needs to be reduced in size. Therefore, as shown in Figure 5(b), simply narrowing the spatial distance SD0 between the pressure roller 4 and the device frame 101' results in a spatial distance SD0 of less than 2.3 mm (SD0<2.3 mm). Therefore, to ensure the additional insulation distance, a creepage distance CD0 of 2.5 mm or more is required, and an additional insulating resin or sheet material must be added between the pressure roller 4 and the device frame 101'. However, while this method achieves miniaturization, it also increases costs. The same problem arises when the spatial distance on the film 3 side is narrowed.

[0026] Note that FIG. 5(a) illustrates the spatial distance SD in the region excluding both left and right ends in the longitudinal direction Dr of the pressure roller 4. As described above, the pressure roller 4 has a core 4a and a rubber layer 4b, and the core 4a is not exposed in the region excluding both left and right ends. Therefore, the surface of the pressure roller 4 is the rubber layer 4b (or the fluororesin layer if there is a fluororesin layer on the rubber layer 4b), and the distance between the rubber layer 4b (fluororesin layer) and the device frame 101' can be considered as the spatial distance SD. However, because the core 4a is exposed at both left and right ends of the pressure roller 4 (see FIG. 2), both the core 4a and the rubber layer 4b must be considered. In other words, it is necessary to consider both the spatial distance between the core 4a and the device frame 101' and the spatial distance between the rubber layer 4b and the device frame 101', and the smallest value of the multiple spatial distances must satisfy the safety standards. Hereinafter, the spatial distance between the pressure roller 4 and the device frame 101' includes not only the spatial distance between the rubber layer 4b and the device frame 101' but also the spatial distance between the core metal 4a and the device frame 101'.

[0027] <Device frame opening> In the first embodiment shown in Fig. 1, openings are provided in areas of the device frame 100 other than the entrance section 100Hi and the exit section 100Ho (other than the entrance and exit sections). For example, in the first embodiment, an opening 101H is provided in the portion of the device frame 101 in Fig. 1 facing the pressure roller 4. Note that the configuration of the device frame 100 in the first embodiment other than the opening 101H is the same as the configuration of the device frame 100', and therefore the reference numerals in Figs. 4 and 5 are used with the "'" removed, and the description thereof will be omitted.

[0028] Fig. 6 is a schematic perspective view seen in the direction of arrow A in Fig. 1. Here, as shown in Fig. 1, of the edges of the device frame 101 that form the opening 101H, the upstream edge in the conveying direction Dt of the recording material P is referred to as edge 101u, and the downstream edge is referred to as edge 101d. Furthermore, of the edges of the device frame 101 that form the opening 101H, one end (left end) in the longitudinal direction Dr is referred to as edge 101l, and the other end (right end) is referred to as edge 101r.

[0029] The spatial distance SD1 shown in FIG. 1 is the distance between the surface of the pressure roller 4 and the edge 101u of the opening 101H, and the distance between the surface of the pressure roller 4 and the edge 101d of the opening 101H. The spatial distance SD2 shown in FIG. 6 is the distance between one end (left end) of the pressure roller 4 in the longitudinal direction Dr and the edge 101l of the opening 101H, and the distance between the other end (right end) of the pressure roller 4 and the edge 101r of the opening 101H. By positioning the opening 101H so that these spatial distances SD1 and SD2 are not less than 2.3 mm, it is possible to ensure the additional insulation distance. Thus, in Example 1, the opening 101H is provided in the portion of the device frame 101 facing the pressure roller 4 so that SD1 ≥ 2.3 mm and SD2 ≥ 2.3 mm. As shown in FIG. 6, the opening 101H is formed so that the length L1 in the longitudinal direction Dr is longer than the length L2 in the longitudinal direction Dr of the pressure roller 4, more specifically, the length L2 in the longitudinal direction Dr of the rubber layer 4b (L1>L2). In Example 1, the spatial distances SD1 and SD2 were set to 3.5 mm in consideration of variations in products.

[0030] <Variation 1> In the above-described embodiment, an opening 101H is provided in the device frame 101 facing the pressure roller 4, thereby reducing the overall area of ​​the fixing device 1 in a cross section perpendicular to the rotation axis direction (Dr) while satisfying safety standards, but this is not limited to this.

[0031] For example, an opening may be provided in the device frame 102 facing the film 3. In this case, the opening should be provided so that the spatial distance between the film 3 and the edge of the opening provided in the device frame 102 is not less than 2.3 mm. Furthermore, openings may be provided in both the device frame 101 and the device frame 102.

[0032] <Variation 2> 1, when viewed in the direction of the rotation axis (Dr) of the fixing device 1, the surface of the pressure roller 4 does not protrude from the opening 101H to the outside of the fixing device 1, but a part of the pressure roller 4 may protrude from the opening 101H to the outside of the fixing device 1. This makes it possible to further reduce the area of ​​the region surrounded by the device frame 100 when viewed in the direction of the rotation axis of the fixing device 1, and to further increase the diameter of the pressure roller 4 for higher speeds.

[0033] When an opening is provided in the device frame 102 on the film 3 side, a part of the film 3 may protrude from this opening to the outside of the fixing device 1. Furthermore, when openings are provided in both the device frame 101 and the device frame 102, both a part of the pressure roller 4 and a part of the film 3 may protrude from each opening. Even in this case, when the cross section of the fixing device 1 is viewed from the rotation axis direction (Dr), the area of ​​the region surrounded by the device frame 100 can be made smaller.

[0034] As described above, according to the configuration of the first embodiment, it is possible to reduce the cross-sectional area of ​​the fixing device 1 in order to downsize the fixing device 1. Furthermore, even if the diameter of the pressure roller 4 is increased in accordance with an increase in the speed of the fixing device 1, the cross-sectional area of ​​the fixing device 1 can be reduced, making it possible to provide an inexpensive and compact fixing device.

[0035] As described above, according to the first embodiment, it is possible to provide a fixing device that satisfies safety standards and is inexpensive and space-saving. [Example]

[0036] The configuration of Example 2 will be described. In Example 2, the same components as those described in Example 1 are denoted by the same reference numerals. Also, the description of the same components and functions as those in Example 1 will be omitted, and only the characteristic parts of Example 2 will be described.

[0037] <Device frame configuration> FIG. 7 is a schematic cross-sectional view of the fixing device 1 of Example 2, and FIG. 8 is a schematic perspective view as viewed in the direction of arrow B in FIG. 7. While Example 1 has a configuration in which an opening 101H is provided in the device frame 101, Example 2 has the device frame 101 divided into two members, and the opening is formed by spacing the two members apart. Here, in the device frame 101, the member on the upstream side of the conveying direction Dt of the recording material P is referred to as device frame 101a (first surface), and the member on the downstream side is referred to as device frame 101b (second surface). In addition, the end of the device frame 101a facing the device frame 101b is referred to as edge 101ae, and the end of the device frame 101b facing the device frame 101a is referred to as edge 101be.

[0038] 8, the device frame 101 is composed of device frames 101a and 101b, which are fastened to device frames 103 and 104, respectively. As a result, an opening 101H is formed in the portion facing the pressure roller 4. In other words, the device frames 101a, 101b, device frame 103, and device frame 104 form a frame shape.

[0039] The spatial distances SD3a and SD3b shown in FIG. 7 are the distances from the surface of the pressure roller 4 to the edge of the opening 101H. More specifically, the spatial distance SD3a is the distance between the surface of the pressure roller 4 and the edge 101ae of the device frame 101a. The spatial distance SD3b is the distance between the surface of the pressure roller 4 and the edge 101be of the device frame 101b. The spatial distance SD4L shown in FIG. 8 is the distance between the left end of the pressure roller 4 in the longitudinal direction Dr and the device frame 103. The spatial distance SD4R is the distance between the right end of the pressure roller 4 in the longitudinal direction Dr and the device frame 104. L1 and L2 are the same as in the first embodiment.

[0040] By positioning the opening 101H at a position where the spatial distances SD3a, SD3b, and SD4L, SD4R are not less than 2.3 mm, it is possible to ensure the additional insulation distance. In this way, in Example 2, the opening 101H is provided in the portion facing the pressure roller 4 so that SD3a ≥ 2.3 mm, SD3b ≥ 2.3 mm, SD4L ≥ 2.3 mm, and SD4R ≥ 2.3 mm. In Example 2, the spatial distances SD3a, SD3b, and SD4L, SD4R are set to 3.5 mm in consideration of product variations.

[0041] When an opening is provided in the device frame 102 on the film 3 side, the device frame 102 may be divided into two members (first surface and second surface) to form the opening. When openings are provided in both the device frame 101 and the device frame 102, each of the device frames may be divided into two members (first surface and second surface) (third surface and fourth surface) to form the opening. Also, only one of the device frames may be divided into two members to form the opening. Furthermore, a part of the film 3 or a part of the pressure roller 4 may protrude outside the fixing device 1 from the opening formed by the two members.

[0042] As described above, according to the configuration of the second embodiment, it is possible to reduce the cross-sectional area of ​​the fixing device 1 in order to downsize the fixing device 1. Furthermore, even if the diameter of the pressure roller 4 is increased in accordance with an increase in the speed of the fixing device 1, the cross-sectional area of ​​the fixing device 1 can be reduced, making it possible to provide an inexpensive and compact fixing device. In the second embodiment, the device frames 101a and 101b are made of metal, but only one of the device frames 101a and 101b may be made of metal, and the other may be made of resin.

[0043] As described above, according to the second embodiment, it is possible to provide a fixing device that satisfies safety standards and is inexpensive and space-saving. [Example]

[0044] The configuration of Example 3 will be described. Note that in Example 3, the same components as those described in Examples 1 and 2 above are denoted by the same reference numerals. Also, descriptions of the same components and functions as those in Examples 1 and 2 will be omitted, and only the characteristic parts of Example 3 will be described.

[0045] <Image forming device> FIG. 9 is a schematic cross-sectional view of an image forming apparatus 300 using a fixing device 1. FIG. 10 is a schematic cross-sectional view of the fixing device 1 of the third embodiment, and FIG. 11 is a schematic perspective view seen from the direction of arrow C in FIG. 10. An overview of the image forming apparatus 300 equipped with the fixing device 1 will be described with reference to FIG. 9. A recording material P fed from a paper feed unit 301 has a toner image formed by an image forming unit 302 as an image forming means transferred to it in a transfer unit 303. The recording material P then passes through the fixing device 1, whereby the unfixed toner image is fixed to the recording material P, and the recording material P is discharged to a discharge unit 304. In the case of double-sided printing, the recording material P switches back at a reversing unit 306, passes through a double-sided conveying path 305, passes through the transfer unit 303 and the fixing device 1 again, and is discharged to a discharge unit 304.

[0046] 9, the recording material P transported along the double-sided transport path 305 passes below the fixing device 1 and is transported again to the transfer unit 303. More specifically, the recording material P transported along the double-sided transport path 305 passes below the device frame 101, i.e., below the opening 101H.

[0047] In this image forming apparatus 300, if the device frame 101 of the fixing device 1 has an opening 101H, there is a risk that the user may touch the hot pressure roller 4, or that the recording material P being conveyed on both sides may get caught in the opening 101H and cause a jam. Therefore, in the third embodiment, the opening 101H is covered with a resin cover member 310 shown in FIGS. 9 and 10 . The cover member 310 covers the opening 101H to protect the pressure roller 4 and also functions as a conveyance guide for the conveyed recording material P. More specifically, the cover member 310 covers the opening 101H with the surface facing the pressure roller 4, and guides the recording material P with the surface opposite to the surface facing the pressure roller 4. In this case, the creepage distance CD3 to the device frame 101 via the cover member 310 is set to 2.5 mm or more. Here, the creepage distance CD3 is the distance from the surface of the pressure roller 4 to the edge 101u via the cover member 310, and the distance from the surface of the pressure roller 4 to the edge 101d via the cover member 310. The creepage distance CD3 is shown by a dashed line in Fig. 10. The cover member 310 is also applicable to the second embodiment.

[0048] When an opening is provided in the device frame 102 on the film 3 side, the opening may be covered with a cover member. When openings are provided in both the device frame 101 and the device frame 102, both openings may be covered with a cover member. Furthermore, the cover member 310 is not limited to a shape that covers the entire area of ​​the opening 101H. Various components may be present around the area where the cover member 310 is attached. In such cases, one or more openings may be provided in the cover member 310 to avoid these components. The cover member 310 does not have to cover the entire area of ​​the opening 101H, in other words, it may cover only a portion of the opening 101H. In other words, it is sufficient that the cover member 310 covers the opening 101H to an extent that prevents a person's finger or the recording material P from entering the opening 101H.

[0049] As described above, according to the configuration of the third embodiment, it is possible to reduce the cross-sectional area of ​​the fixing device 1 in order to miniaturize the fixing device 1. Furthermore, even if the diameter of the pressure roller 4 is increased in accordance with the increase in the speed of the fixing device 1, the cross-sectional area of ​​the fixing device 1 can be reduced. Furthermore, it is possible to provide an inexpensive and compact fixing device even in a configuration in which the fixing device 1 is located in a position where the user can touch the fixing device 1 within the image forming apparatus 300 or is part of the conveyance section of the recording material P. The additional insulation distance of 2.3 mm for the spatial distance and 2.5 mm for the creepage distance conform to the values ​​of the safety standard IEC62368, and when implemented, the values ​​of the latest standard should be followed.

[0050] As described above, according to the third embodiment, it is possible to provide a fixing device that satisfies safety standards and is inexpensive and space-saving.

[0051] The disclosure of this embodiment includes the following configuration. (Configuration 1) a heating unit having a cylindrical flexible rotating body and a heating member in contact with an inner circumferential surface of the rotating body; a pressure roller having a core and a rubber layer covering the core, the pressure roller being in contact with the outer circumferential surface of the rotating body, the pressure roller sandwiching the rotating body together with the heating member to form a nip portion with the rotating body; a metal frame that holds the pressure roller and has an entrance portion provided with an opening through which the recording material is conveyed to the nip portion and an exit portion provided with an opening through which the recording material is conveyed from the nip portion to the outside; A fixing device comprising: the frame is provided with an opening in an area other than the inlet portion and the outlet portion, the opening having a length in the rotation axis direction of the pressure roller longer than a length in the rotation axis direction of the rubber layer. A fixing device characterized by: (Configuration 2) the frame has a surface facing the pressure roller, The opening is provided in the surface. 2. The fixing device according to claim 1, (Configuration 3) the frame has a first surface facing the pressure roller and a second surface facing the pressure roller and different from the first surface, The opening is formed by separating the first surface and the second surface when viewed in the rotation axis direction. 2. The fixing device according to claim 1, (Configuration 4) a part of the pressure roller protruding outward from the opening when viewed in the direction of the rotation axis; 4. The fixing device according to configuration 2 or 3. (Configuration 5) the frame has a surface facing the rotating body, The opening is provided in the surface. 2. The fixing device according to claim 1, (Configuration 6) the frame has a first surface facing the rotating body and a second surface facing the rotating body and different from the first surface, The opening is formed by separating the first surface and the second surface when viewed in the rotation axis direction. 2. The fixing device according to claim 1, (Configuration 7) a part of the rotating body protruding outward from the opening when viewed in the direction of the rotation axis; 7. The fixing device according to configuration 5 or 6. (Configuration 8) the frame has a first surface facing the pressure roller and a second surface facing the rotating body, The opening is provided in the first surface and the second surface. 2. The fixing device according to claim 1, (Configuration 9) the frame has a first surface facing the pressure roller, a second surface facing the pressure roller and different from the first surface, a third surface facing the rotating body, and a fourth surface facing the rotating body and different from the third surface; The opening is formed by separating the first surface and the second surface when viewed in the rotation axis direction; and the opening is formed by separating the third surface and the fourth surface when viewed in the rotation axis direction. 2. The fixing device according to claim 1, (Configuration 10) When viewed in the direction of the rotation axis, the pressure roller has a portion protruding outward from an opening facing the pressure roller, When viewed in the direction of the rotation axis, a portion of the rotating body protrudes to the outside from an opening facing the rotating body. 10. The fixing device according to configuration 8 or 9. (Configuration 11) When viewed in the direction of the rotation axis, an edge of the frame that forms the opening and the pressure roller are spaced apart by a predetermined distance or more. 11. The fixing device according to any one of configurations 1 to 10. (Configuration 12) The predetermined distance is an insulation distance defined by a safety standard. 12. The fixing device according to claim 11. (Configuration 13) a cover member that covers a part or all of the area of ​​the opening of the frame; 13. The fixing device according to any one of Configurations 1 to 12. (Configuration 14) the cover member has a surface opposite to the surface facing the opening that functions as a conveyance guide for the recording material; 14. The fixing device according to claim 13. (Configuration 15) an image forming means for forming a toner image on a recording material; a fixing device according to any one of configurations 1 to 14, which fixes a toner image formed by the image forming means onto a recording material; Equipped with An image forming apparatus characterized by: [Explanation of symbols]

[0052] 1 Fixing device 2 Fixing device 3 Film 4 Pressure roller 5 Heater 100 fixing frame, 101 device frame 101H opening

Claims

1. a heating unit having a cylindrical flexible rotating body and a heating member in contact with an inner circumferential surface of the rotating body; a pressure roller having a core and a rubber layer covering the core, the pressure roller being in contact with the outer circumferential surface of the rotating body, the pressure roller sandwiching the rotating body together with the heating member to form a nip portion with the rotating body; a metal frame that holds the pressure roller and has an entrance portion provided with an opening through which the recording material is conveyed to the nip portion and an exit portion provided with an opening through which the recording material is conveyed from the nip portion to the outside; A fixing device comprising: the frame is provided with an opening in an area other than the inlet portion and the outlet portion, the opening having a length in the rotation axis direction of the pressure roller longer than a length in the rotation axis direction of the rubber layer. A fixing device characterized by:

2. the frame has a surface facing the pressure roller, The opening is provided in the surface.

2. The fixing device according to claim 1, wherein the fixing device is a fixing device for fixing a toner image onto a recording medium.

3. the frame has a first surface facing the pressure roller and a second surface facing the pressure roller and different from the first surface, the opening is formed by separating the first surface and the second surface when viewed in the rotation axis direction.

2. The fixing device according to claim 1, wherein the fixing device is a fixing device for fixing a toner image onto a recording medium.

4. a part of the pressure roller protruding outward from the opening when viewed in the direction of the rotation axis; 4. The fixing device according to claim 2 or 3.

5. the frame has a surface facing the rotating body, The opening is provided in the surface.

2. The fixing device according to claim 1, wherein the fixing device is a fixing device for fixing a toner image onto a recording medium.

6. the frame has a first surface facing the rotating body and a second surface facing the rotating body and different from the first surface, the opening is formed by separating the first surface and the second surface when viewed in the rotation axis direction.

2. The fixing device according to claim 1, wherein the fixing device is a fixing device for fixing a toner image onto a recording medium.

7. a part of the rotating body protruding outward from the opening when viewed in the direction of the rotation axis; 7. The fixing device according to claim 5 or 6.

8. the frame has a first surface facing the pressure roller and a second surface facing the rotating body, The opening is provided in the first surface and the second surface.

2. The fixing device according to claim 1, wherein the fixing device is a fixing device for fixing a toner image onto a recording medium.

9. the frame has a first surface facing the pressure roller, a second surface facing the pressure roller and different from the first surface, a third surface facing the rotating body, and a fourth surface facing the rotating body and different from the third surface; the opening is formed by separating the first surface and the second surface when viewed in the rotation axis direction; and the opening is formed by separating the third surface and the fourth surface when viewed in the rotation axis direction.

2. The fixing device according to claim 1, wherein the fixing device is a fixing device for fixing a toner image onto a recording medium.

10. When viewed in the direction of the rotation axis, the pressure roller has a portion protruding outward from an opening facing the pressure roller, When viewed in the direction of the rotation axis, a portion of the rotating body protrudes to the outside from an opening facing the rotating body.

10. The fixing device according to claim 8 or claim 9.

11. When viewed in the direction of the rotation axis, an edge of the frame that forms the opening and the pressure roller are spaced apart by a predetermined distance or more.

2. The fixing device according to claim 1, wherein the fixing device is a fixing device for fixing a toner image onto a recording medium.

12. The predetermined distance is an insulation distance defined by a safety standard. The fixing device according to claim 11 .

13. a cover member that covers a part or all of the area of ​​the opening of the frame; 2. The fixing device according to claim 1, wherein the fixing device is a fixing device for fixing a toner image onto a recording medium.

14. the cover member has a surface opposite to the surface facing the opening that functions as a conveyance guide for the recording material; 14. The fixing device according to claim 13.

15. an image forming means for forming a toner image on a recording material; a fixing device according to claim 1, which fixes the toner image formed by the image forming means onto a recording material; Equipped with An image forming apparatus characterized by:

Images