Fixing apparatus 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 that heats and fixes an unfixed toner image on a recording material and is used in an image forming apparatus that employs an electrophotographic method, an electrostatic recording method, or the like, such as a copying machine, a printer, or a facsimile machine, and an image forming apparatus equipped with the same.

Background Art

[0002] Conventionally, as a fixing device mounted on an electrophotographic copying machine or printer, a film heating method is known. The fixing device of the film heating method includes a cylindrical film, a heater that contacts the inner surface of the film, and a pressure roller that forms a nip portion with the heater through the film. The heater includes a surface heating heater provided with a surface heating element on a ceramic substrate and is held by a resin guide member. The guide member is reinforced by a metal reinforcing member. A through hole is provided in a part of the longitudinal direction of the guide member, and a temperature detection element provided in the space between the guide member and the reinforcing member detects the temperature of the heater through the through hole of the guide member. The heater is controlled according to the detected temperature of the temperature detection element. Similarly, a protection element such as a thermostat or a temperature fuse is provided in the space between the guide member and the reinforcing member, and the protection element also senses the heat of the heater through another through hole provided in the guide member. The protection element has a role of cutting off the power supply to the heater when the heater reaches an excessive temperature. Such a heating unit is brought into contact with a pressure member called a pressure roller at a desired pressure to form a nip portion. The sheet carrying the unfixed toner image passes through the heated nip portion by the driving force of the pressure roller, thereby fixing the unfixed toner image on the sheet. Generally, these heating unit materials and the pressure roller are held by a metal frame so that the frame of the fixing device does not deform significantly due to thermal expansion, thermal deformation, and the pressing force, and are configured as a fixing device.

[0003] On the other hand, the heater generates heat by passing an alternating current through a heating element formed on the heater's substrate. Therefore, safety standards stipulate that the film in contact with the heater, and the pressure roller in contact via the film, must be configured to maintain a desired distance from the safety ground. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2012-013780 [Overview of the project] [Problems that the invention aims to solve]

[0005] However, recent fixing devices are required to be high-speed, compact, and low-cost. Therefore, it is necessary to increase the diameter of the pressure roller to achieve higher speeds, and to reduce the size of the device frame to achieve lower speeds. In this case, simply reducing the distance between the device frame and the pressure roller would bring them closer than the insulation distance required by safety standards. Therefore, to ensure the insulation distance between the pressure roller and the device frame, it is necessary to ensure creepage distance, which requires insulating resin or sheet materials between the pressure roller and the device frame. However, this method has the drawback of increasing costs.

[0006] This invention was made under these circumstances, and aims to provide an inexpensive and space-saving fixing device that meets safety standards. [Means for solving the problem]

[0007] 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 member that contacts the inner circumferential surface of the rotating body; a pressure roller that contacts the outer circumferential surface of the rotating body and has a core metal and a rubber layer covering the core metal, and together with the heating member, sandwiches the rotating body and forms a nip portion with the rotating body; and a metal frame that holds the pressure roller and has an inlet portion with an opening for the recording material to be transported to the nip portion and an outlet portion with an opening for the recording material to be transported from the nip portion to the outside, wherein the frame has regions other than the inlet portion and the outlet portion and the surface of the region facing the pressure roller The fixing device is characterized in that an opening is provided in which the length of the pressure roller in the rotation axis direction is longer than the length of the rubber layer in the rotation axis direction.

[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) for fixing the toner image formed by the image forming means to the recording material. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide an inexpensive and space-saving fixing device that meets safety standards. [Brief explanation of the drawing]

[0011] [Figure 1] Schematic cross-sectional view of the fixing device of Example 1 [Figure 2] Schematic diagrams of the fixing devices for Examples 1-3 [Figure 3] Schematic diagrams of heaters in Examples 1-3 [Figure 4] Schematic cross-sectional view of the fixing device of the comparative example. [Figure 5] Schematic diagram of the fixing device of the comparative example. [Figure 6] Schematic perspective view of the fixing device of Example 1 [Figure 7] Schematic cross-sectional view of the fixing device of Example 2 [Figure 8] Schematic perspective view of the fixing device of Example 2 [Figure 9] Schematic cross-sectional view of the image forming apparatus of Example 3 [Figure 10] Schematic cross-sectional view of the fixing device of Example 3 [Figure 11] Schematic perspective view of the fixing device of Example 3

Best Mode for Carrying Out the Invention

[0012] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the following embodiments do not limit the invention according to the claims, and not all combinations of features described in the embodiments are essential for the solution means of the invention.

Example

[0013] Hereinafter, Example 1 of the present invention will be described.

[0014] <Fixing device> The schematic configuration of the 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 flexible rotatable cylindrical rotating body as a film 3 that encloses a heater 5 having a heating element, and a pressure roller 4 that presses the heating unit 2 by a pressing means (not shown) to form a nip portion N. The pressure roller 4 is in contact with the outer peripheral surface of the film 3. By sandwiching and conveying the 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 enclosed in the device frame 100.

[0015] Figure 2 is a schematic diagram of the heating unit 2 and the pressure roller 4 of the fixing device 1. Here, the direction orthogonal to the conveyance direction Dt of the recording material P, in other words, the rotation axis direction or the longitudinal direction of the film 3 and the pressure roller 4 is defined as Dr. The heating unit 2 and the pressure roller 4 are supported at both ends by the device frame 100 (see Figure 1) of the fixing device 1, and the pressure roller 4 is configured to be rotationally driven in the rotation direction Drt by the driving force being transmitted from a driving source (not shown) to the driving gear 28. The pressure roller 4 has a core metal 4a formed of iron or the like and a rubber layer 4b covering around the core metal 4a.

[0016] The film 3 that is in pressure contact with the pressure roller 4 is configured to rotate in a driven manner with respect to the pressure roller 4. Inside the film 3, a heater 5 as a heating member is provided, and the inner peripheral surface of the film 3 and the heater <ヒータ>5 are in slidable contact with each other, and both ends are held by the flange 29. Note that the heating member may have a heater 5 and a sliding contact member (such as a metal plate), and the sliding contact member may be in contact with the inner surface of the film 3.

[0017] Grease is applied between the heater 5 and the film 3 to improve slidability. The heater 5 is configured to generate heat by being supplied with power from a power supply means (not shown) through a connector 30 which is an electrical contact part. Inside the film 3, the heater 5 is held by a heater holder 7 (Figure 1). Also, the nip portion N formed by the film 3 and the pressure roller 4 is preferably of a uniform width in the rotation axis direction (Dr) of the film 3. Therefore, a metal reinforcing member 8 (Figure 1) is attached to the heater holder 7 at the position shown in Figure 1 to improve the strength against the pressure contact force. The reinforcing member 8 receives the pressing force F of a pressing means (not shown) through the flanges 29 provided at both ends in its longitudinal direction. The heating unit 2 is attached to the device frame 100 by inserting the flange 29 into the device frame 100.

[0018] <Heater> Next, the configuration of the heater 5 will be explained 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 arranged on a ceramic heater substrate 5Ce, and the heating element 5H is covered with a glass layer 5G. The end of the heater 5 has a heater contact portion 5C, which is a contact portion with the connector 30, and by supplying alternating current to the heating element 5H via the connector 30, the heating element 5H is heated. Note that the heater contact portion 5C is not covered with the glass layer 5G.

[0019] The heating unit 2 has a temperature detection means (not shown) for detecting the temperature of the heater 5, and when transporting the recording material P, it controls the supply of AC current by detecting the temperature to control the heater 5 to a desired temperature. As 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 the basic insulation potential. For this reason, the metal device frame 100 (frame), which also serves as a safety ground, needs to ensure the necessary space distance and creepage distance to ensure additional insulation from the film 3 and pressure roller 4, which are at the basic insulation potential according to safety standards. In Example 1, the space distance between the pressure roller 4 and the device frame 100 is 2.3 mm, and the creepage distance is 2.5 mm, which are the additional insulation distances specified by the safety standard IEC62368.

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

[0021] As shown in Figure 4, when viewed in the direction of the rotation axis (Dr) of the film 3 and pressure roller 4, the device frame 101' has a U-shaped cross-section, with the upstream end in the transport direction Dt being designated as end 101'i and the downstream end as end 101'o. Similarly, the device frame 102' also has a U-shaped cross-section, with the upstream end in the transport direction Dt being designated as end 102'i and the downstream end as end 102'o. The ends 101'i of the device frame 101' and the end 102'i of the device frame 102' are separated by a predetermined distance, as shown in Figure 4, and form an opening (hereinafter referred to as the inlet 100'Hi) so that the leading edge of the recording material P is guided to the nip portion N of the fixing device 1. The ends 101'o of the device frame 101' and 102'o of the device frame 102' are also separated by a predetermined distance, and an opening is formed so that the leading edge of the recording material P is guided from the nip portion N of the fixing device 1 to the outside of the fixing device 1 (hereinafter referred to as the exit portion 100'Ho). Note that the device frames 101' and 102' do not have to be U-shaped in cross-section; they just need to be shaped to surround the film 3 and pressure roller 4, and have 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 Figure 5(a), the cross-section of the device frame 100' in the 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] <Spatial distance and creepage distance> In this configuration, the film 3 and pressure roller 4, which are the basic insulating potential components, are positioned at a distance of 2.3 mm in spatial distance SD and 2.5 mm or more in creepage distance CD from the device frame 100'. The ends of the film 3 and pressure roller 4 are provided with insulating resin members 3L, 3R, 4L, and 4R to ensure a creepage distance CD greater than or equal to the additional insulating distance. 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 device 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 device frame 104' via the resin member 3R. The creepage distance CD between the film 3 and the device frame 103'(104') is set so that the smaller of the two creepage distances 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 device frame 103' via the resin member 4L. At the right end of the pressure roller 4, the creepage distance CD is the distance from the core metal 4a of the pressure roller 4 through the resin member 4R to the device frame 104'. The creepage distance CD of the pressure roller 4 is set such that the smaller of the two creepage distances (left or right) satisfies the safety standards.

[0024] On the other hand, 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 an additional insulation distance. In other words, the spatial distance SD is also configured to be greater than the insulation distance specified in the safety standards (greater than the predetermined distance). Here, spatial distance SD is the distance between the surface of the film 3 and the device frame 102'. 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 miniaturization, increased speed, and lower costs in image forming apparatuses. Therefore, it is necessary to miniaturize the fixing apparatus 1 cross-section, or to increase the diameter of the pressure roller 4 while miniaturizing the apparatus frame 100'. As shown in Figure 5(b), if the spatial distance SD0 between the pressure roller 4 and the apparatus frame 101' is simply narrowed, the spatial distance SD0 will become less than 2.3 mm (SD0 < 2.3 mm). Therefore, in order to secure an additional insulation distance, it is necessary to secure a creepage distance CD0 of 2.5 mm or more, and it is necessary to secure an additional insulation distance between the pressure roller 4 and the apparatus frame 101' with an additional insulating resin member or sheet member. However, although this method allows for miniaturization, it has the problem of increasing costs. A similar problem arises when the spatial distance on the film 3 side is narrowed.

[0026] Figure 5(a) illustrates the spatial distance SD in the region of the pressure roller 4 excluding the left and right ends in the longitudinal direction Dr. As described above, the pressure roller 4 has a core metal 4a and a rubber layer 4b, and the core metal 4a is not exposed in the region excluding the 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 top of the rubber layer 4b), and the distance between the rubber layer 4b (fluororesin layer) and the device frame 101' should be considered as the spatial distance SD. However, at the left and right ends of the pressure roller 4, the core metal 4a is exposed (see Figure 2), so both the core metal 4a and the rubber layer 4b must be considered. That is, both the spatial distance between the core metal 4a and the device frame 101' and the spatial distance between the rubber layer 4b and the device frame 101' must be considered, and the smallest value among the multiple spatial distances must satisfy the safety standard. Hereafter, when referring to the spatial distance between the pressure roller 4 and the device frame 101', it shall include 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] <Opening in the device frame> In Embodiment 1 shown in Figure 1, an opening is provided in the area of ​​the device frame 100 other than the inlet portion 100Hi and the outlet portion 100Ho (other than the inlet and outlet portions). For example, in Embodiment 1, an opening 101H is provided on the opposite side of the pressure roller 4 of the device frame 101 in Figure 1. The configuration of the device frame 100 in Embodiment 1 other than the opening 101H is the same as the configuration of the device frame 100', and the reference numerals in Figures 4 and 5 are used without the "'", and the explanation is omitted.

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

[0029] The spatial distance SD1 shown in Figure 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 Figure 6 is the distance between one end (left end) in the longitudinal direction Dr of the pressure roller 4 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 setting the opening 101H at a position where these spatial distances SD1 and SD2 are not less than 2.3 mm, it is possible to secure an additional insulation distance. Thus, in Embodiment 1, the opening 101H is provided in the portion of the device frame 101 facing the pressure roller 4 such that SD1 ≥ 2.3 mm and SD2 ≥ 2.3 mm. As shown in Figure 6, the opening 101H is formed such 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 to account for variations in the objects.

[0030] <Example 1> In the embodiment described above, 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 meeting safety standards, but the embodiment is not limited to this.

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

[0032] <Modification 2> In Figure 1 above, 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. However, 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 enclosed 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] Furthermore, when an opening is provided in the device frame 102 on the film 3 side, a portion of the film 3 may protrude from this opening to the outside of the fixing device 1. In addition, when openings are provided in both the device frame 101 and the device frame 102, a portion of the pressure roller 4 and a portion of the film 3 may both protrude from the openings. Even in this case, when viewing a cross-section from the rotation axis direction (Dr) of the fixing device 1, the area enclosed by the device frame 100 can be made smaller.

[0034] As described above, according to the configuration of Embodiment 1, 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 as the speed of the fixing device 1 increases, 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 Example 1, it is possible to provide an inexpensive and space-saving fixing device that meets safety standards. [Examples]

[0036] The configuration of Example 2 will now be described. In Example 2, the same components as those described in Example 1 will be denoted by the same reference numerals. Furthermore, the description of the same configuration and functions as in Example 1 will be omitted, and only the distinctive features of Example 2 will be described.

[0037] <Configuration of the device frame> Figure 7 is a schematic cross-sectional view of the fixing device 1 of Embodiment 2, and Figure 8 is a schematic perspective view taken in the direction of arrow B in Figure 7. In Embodiment 1, the device frame 101 had an opening 101H, whereas in Embodiment 2, the device frame 101 is divided into two members, and the opening is formed by the two members being at a distance from each other. Here, in the device frame 101, the upstream member in the transport direction Dt of the recording material P is called the device frame 101a (first surface), and the downstream member is called the device frame 101b (second surface). Furthermore, in the device frame 101a, the end facing the device frame 101b is called edge 101ae, and in the device frame 101b, the end facing the device frame 101a is called edge 101be.

[0038] As shown in Figure 8, the apparatus frame 101 is composed of apparatus frame 101a and apparatus frame 101b, which are fastened to apparatus frame 103 and apparatus frame 104, respectively. This creates an opening 101H on the opposite side of the pressure roller 4. In other words, the apparatus frames 101a, 101b, apparatus frame 103, and apparatus frame 104 form a frame shape.

[0039] The spatial distances SD3a and SD3b shown in Figure 7 are the distances from the surface of the pressure roller 4 to the edge of the opening 101H. More specifically, spatial distance SD3a is the distance between the surface of the pressure roller 4 and the edge 101ae of the apparatus frame 101a. Spatial distance SD3b is the distance between the surface of the pressure roller 4 and the edge 101be of the apparatus frame 101b. Also, the spatial distance SD4L shown in Figure 8 is the distance between the left end of the pressure roller 4 in the longitudinal direction Dr and the apparatus frame 103. Also, spatial distance SD4R is the distance between the right end of the pressure roller 4 in the longitudinal direction Dr and the apparatus frame 104. L1 and L2 are the same as in Example 1.

[0040] By setting the opening 101H at a position where the spatial distances SD3a, SD3b, and spatial distances SD4L, SD4R are not less than 2.3 mm, it is possible to secure an additional insulation distance. Thus, in Example 2, the opening 101H is provided in the part facing the pressure roller 4 such 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 spatial distances SD4L, SD4R are set to 3.5 mm to account for variations in the material.

[0041] Furthermore, when providing an opening 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. Also, when providing openings 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 respective openings. Alternatively, only one of the device frames may be divided into two members to form the opening. In addition, a part of the film 3 or a part of the pressure roller 4 may protrude from the opening formed by the two members to the outside of the fixing device 1.

[0042] As described above, according to the configuration of Embodiment 2, 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 as the speed of the fixing device 1 increases, the cross-sectional area of ​​the fixing device 1 can be reduced, making it possible to provide an inexpensive and compact fixing device. In Example 2, the device is constructed using metal frame structures 101a and 101b. However, either frame 101a or 101b may be made of metal, while the other is made of resin.

[0043] As described above, according to Example 2, it is possible to provide an inexpensive and space-saving fixing device that meets safety standards. [Examples]

[0044] The configuration of Example 3 will now be described. In Example 3, the same reference numerals are used for components that are the same as those described in Examples 1 and 2. Furthermore, the descriptions of components and functions similar to those in Examples 1 and 2 will be omitted, and only the distinctive features of Example 3 will be described.

[0045] <Image forming apparatus> Figure 9 is a schematic cross-sectional view of the image forming apparatus 300 using the fixing device 1. Figure 10 is a schematic cross-sectional view of the fixing device 1 of Example 3, and Figure 11 is a schematic perspective view taken from the direction of arrow C in Figure 10. The outline of the image forming apparatus 300 equipped with the fixing device 1 will be explained using Figure 9. The recording material P fed from the paper feeding section 301 has the toner image formed by the image forming section 302 as an image forming means transferred to it by the transfer section 303. After that, the unfixed toner image is fixed to the recording material P by passing through the fixing device 1, and the recording material P is discharged to the discharge section 304. In the case of double-sided printing, the recording material P switches back in the reversal section 306, passes through the double-sided transport path 305, passes through the transfer section 303 and the fixing device 1 again, and is discharged to the discharge section 304.

[0046] Here, as shown in Figure 9, the recording material P being 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 being transported along the double-sided transport path 305 passes below the device frame 101, that is, below the opening 101H.

[0047] In such an image forming apparatus 300, if there is an opening 101H in the apparatus frame 101 of the fixing device 1, there is a risk that the user may come into contact with the high-temperature pressure roller 4, or that the recording material P being transported on both sides may get caught in the opening 101H and cause a jam. Therefore, in Example 3, the opening 101H is covered with a resin cover member 310 as shown in Figures 9 and 10. The cover member 310 covers the opening 101H and protects the pressure roller 4, and also functions as a transport guide for the transported recording material P. More specifically, the cover member 310 covers the opening 101H with the side facing the pressure roller 4, and guides the recording material P with the side opposite to the side facing the pressure roller 4. At this time, the creepage distance CD3 to the apparatus frame 101 via the cover member 310 is configured to be 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 Figure 10. Note that the cover member 310 is also applicable to Example 2.

[0048] Furthermore, if an opening is provided in the device frame 102 on the film 3 side, this opening may be covered with a cover member. Also, if openings are provided in both the device frame 101 and the device frame 102, both openings may be covered with a cover member. Moreover, the cover member 310 is not limited to a shape that covers the entire area of ​​the opening 101H. Various parts may be present around 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 parts, and the cover member 310 does not have to cover the entire area of ​​the opening 101H; in other words, it may cover only a part of the opening 101H. That is, it is sufficient for the opening 101H to be covered by the cover member 310 to the extent that it is possible to prevent a person's finger or recording material P from entering the opening 101H.

[0049] As described above, the configuration of Embodiment 3 makes it 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 as the fixing device 1 speed increases, the cross-sectional area of ​​the fixing device 1 can still be reduced. In addition, it is possible to provide an inexpensive and compact fixing device even in configurations where the user touches the fixing device 1 within the image forming apparatus 300, or where it is part of the transport section for the recording material P. The additional insulation distances of 2.3 mm (space distance) and 2.5 mm (creepage distance) are based on the values ​​specified in safety standard IEC62368, and the latest standard values ​​should be followed during implementation.

[0050] As described above, according to Example 3, it is possible to provide an inexpensive and space-saving fixing device that meets safety standards.

[0051] This embodiment includes the following configuration. (Composition 1) A heating unit comprising a cylindrical, flexible rotating body and a heating member that contacts the inner circumferential surface of the rotating body, A pressure roller having a core metal and a rubber layer covering the core metal, which contacts the outer circumferential surface of the rotating body, and which, together with the heating member, sandwiches the rotating body and forms a nip portion with the rotating body, A metal frame holding the pressure roller has an inlet with an opening for transporting the recording material to the nip section, and an outlet with an opening for transporting the recording material from the nip section to the outside, A fixing device comprising, The frame is provided with an opening in a region other than the inlet and outlet portions, the length of which in the direction of rotation of the pressure roller is longer than the length of which in the direction of rotation of the rubber layer. A fixing device characterized by the following features. (Configuration 2) The frame has a surface facing the pressure roller, The aforementioned opening is provided on the surface, The fixing device according to configuration 1, characterized by the above. (Composition 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 the first surface and the second surface being separated when viewed in the direction of the rotation axis. The fixing device according to configuration 1, characterized by the above. (Composition 4) The pressure roller, when viewed in the direction of the rotation axis, has a portion that protrudes outward from the opening. A fixing device according to configuration 2 or configuration 3, characterized by the above. (Composition 5) The frame has a surface facing the rotating body, The aforementioned opening is provided on the surface, The fixing device according to configuration 1, characterized by the above. (Composition 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 the first surface and the second surface being separated when viewed in the direction of the rotation axis. The fixing device according to configuration 1, characterized by the above. (Composition 7) The rotating body, when viewed in the direction of the rotation axis, has a portion that protrudes outward from the opening. A fixing device according to configuration 5 or configuration 6, characterized by the above. (Composition 8) The frame has a first surface facing the pressure roller and a second surface facing the rotating body. The openings are provided on the first surface and the second surface. The fixing device according to configuration 1, characterized by the above. (Composition 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 the first surface and the second surface being separated when viewed in the direction of the rotation axis, and The opening is formed by the third surface and the fourth surface being separated when viewed in the direction of the rotation axis. The fixing device according to configuration 1, characterized by the above. (Composition 10) When viewed in the direction of the rotation axis, the pressure roller has a portion that protrudes outward from the opening opposite to the pressure roller. When viewed in the direction of the rotation axis, the rotating body has a portion that protrudes outward from an opening opposite to the rotating body. A fixing device according to configuration 8 or configuration 9, characterized by the above. (Composition 11) When viewed in the direction of the rotation axis, the edge of the frame forming the opening and the pressure roller are separated by a predetermined distance or more. A fixing device according to any one of configurations 1 to 10, characterized by the above. (Composition 12) The aforementioned predetermined distance is the insulation distance specified in the safety standards. A fixing device according to configuration 11, characterized by the features described above. (Composition 13) The frame comprises a cover member that covers part or all of the area of ​​the opening, A fixing device according to any one of configurations 1 to 12, characterized by the above. (Composition 14) The cover member has a surface opposite to the surface facing the opening that functions as a transport guide for the recording material. The fixing device according to configuration 13, characterized by the above. (Composition 15) Image forming means for forming a toner image on a recording material, A fixing device according to any one of configurations 1 to 14 for fixing the toner image formed by the image forming means onto a recording material, Equipped with, An image forming apparatus characterized by the following features. [Explanation of symbols]

[0052] 1. Fixing device 2. Fixing device 3 Films 4 Pressure roller 5 Heater 100 Fixing frame, 101 Device frame 101H opening

Claims

1. A heating unit comprising a cylindrical, flexible rotating body and a heating member that contacts the inner circumferential surface of the rotating body, A pressure roller having a core metal and a rubber layer covering the core metal, which contacts the outer circumferential surface of the rotating body, and which, together with the heating member, sandwiches the rotating body and forms a nip portion with the rotating body, A metal frame holding the pressure roller has an inlet with an opening for transporting the recording material to the nip section, and an outlet with an opening for transporting the recording material from the nip section to the outside, A fixing device comprising, The frame is provided with an opening on the surface of a region other than the inlet and outlet portions that faces the pressure roller, the length of which in the direction of rotation of the pressure roller is longer than the length of the rubber layer in the direction of rotation. A fixing device characterized by the following features.

2. The aforementioned surface 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 the first surface and the second surface being separated when viewed in the direction of the rotation axis. The fixing device according to feature 1.

3. The pressure roller, when viewed in the direction of the rotation axis, has a portion that protrudes outward from the opening. The fixing device according to feature 1.

4. The frame holds the rotating body, The frame is provided with openings different from the openings in areas other than the inlet and outlet portions, and in areas facing the rotating body. The fixing device according to feature 1.

5. The frame is provided with a resin cover member that covers part or all of the area of ​​the opening. The fixing device according to feature 1.

6. The cover member has a surface opposite to the surface facing the opening that functions as a transport guide for the recording material. The fixing device according to feature 5.

7. Image forming means for forming a toner image on a recording material, A fixing device according to claim 1, which fixes a toner image formed by the image forming means onto a recording material, Equipped with, An image forming apparatus characterized by the following features.

Images