JP7508871B2 - Fixing device and image forming apparatus - Google Patents

Description

This disclosure relates to a fixing device that fixes an unfixed image on a sheet, and in particular to a technology that improves the efficiency of using heat used in fixing.

Some fixing devices have a heater inserted into a cylindrical heating roller, and the heating roller is heated by the radiant heat of the heater to heat the sheet. In this configuration, the internal space of the heating roller communicates with the outside of the heating roller through openings at both ends of the heating roller, so the heat of the heater can escape from the openings at the ends of the heating roller.

As a configuration for sealing this opening, Patent Document 1 discloses a configuration in which a shielding member is provided at the end of the heating roller. Figure 12 is a simplified diagram showing one end of the heating roller 935 in the rotation axis direction on which this shielding member is provided. As shown in the figure, a doughnut-shaped shielding member 950 having a circular hole 951 in the center is supported by a support member 952 so that it can be inserted into the opening 935a of the heating roller 935.

JP 2011-47995 A

However, the shielding member 950 is not in contact with either the heating roller 935 or the heater 936, and gaps 950a and 950b are formed between the shielding member 950 and the heating roller 935 and the heater 936, respectively, and the heat of the heater 936 escapes through these gaps 950a and 950b.

This disclosure was made in consideration of the above problems, and aims to provide a fixing device that can prevent heat generated by a heat-generating member from escaping through an opening in a rotating cylinder, and an image forming apparatus equipped with the fixing device.

In order to achieve the above-mentioned object, the present disclosure provides a fixing device that fixes a toner image on a sheet by passing the sheet through a fixing nip formed by a heating member and a pressure member, the heating member comprising: a heat-generating member that is long in the width direction of the sheet; a cylindrical rotating cylinder with openings at both ends into which the heat-generating member is inserted and heated by the heat-generating member; and a shielding member that includes an elastic body and is pressed into the opening so that the elastic body elastically contacts at least one of the rotating cylinder and the heat-generating member by its elastic restoring force , the elastic body being disc-shaped and having a tongue with a free end on the center side of the disc by making a plurality of cuts radially from the center of the disc in the circumferential direction, the heat-generating member being pressed in from the center side of the disc in a state in which the tongue is bent and deformed, and the elastic restoring force of the tongue brings the peripheral surface of the heat-generating member and the tongue into close contact with each other .

The elastic body may also be in elastic contact with the rotating cylinder and the heat-generating member.

Furthermore, the multiple cuts may extend from the center of the disk to the periphery of the elastic body.

The elastic body may also have a two-layer laminate structure, with one layer having a thermal expansion coefficient different from the other layer.

The heat generating member may be a heater in which a heat generating portion is sandwiched between a non-heat generating portion in the longitudinal direction, and the elastic body may be in elastic contact with the non-heat generating portion of the heater.

Furthermore, a blowing means may be provided for blowing air from the outside of the rotating cylinder to the elastic body so that the tongue of the elastic body bends in the thickness direction of the disc and toward the internal space of the rotating cylinder.

In addition, a fixing device according to another aspect of the present disclosure is a fixing device that fixes a toner image on a sheet by passing the sheet through a fixing nip formed by a heating member and a pressure member, the heating member comprising: a heat-generating member that is long in the width direction of the sheet; a rotating cylinder that is cylindrical with openings at both ends and into which the heat-generating member is inserted and heated by the heat-generating member; and a shielding member that includes an elastic body and is pressed into the opening so that the elastic body elastically contacts at least one of the rotating cylinder and the heat-generating member by its elastic restoring force, the heat reflectivity of the side of the elastic body facing the internal space of the rotating cylinder being higher than the heat reflectivity of the opposite side in the pressing direction of the shielding member.

The shielding members may also be inserted into the openings at both ends of the rotating cylinder.

The present disclosure also relates to a fixing device for fixing a toner image on a sheet by passing the sheet through a fixing nip formed by an endless belt and a pressure member, the fixing device including a housing for accommodating the belt therein, a heat generating member fixed to the housing and elongated in the width direction of the sheet, a heating roller around which the belt is wound, the heating roller being tubular with open ends and into which the heat generating member is inserted and which is heated by the heat generating member, a bearing for supporting the heating roller movably in a direction in which tension is applied to the belt relative to the housing, and a fixing member for fixing a toner image on the sheet by passing the sheet through a fixing nip formed by an endless belt and a pressure member, the fixing device including: a housing for accommodating the belt therein; The device comprises a biasing member that biases the bearing, a shielding member made of an elastic material and inserted into the opening, and a support member that fixes and supports the shielding member to the housing so that the shielding member is in close proximity to the inner surface of the heated roller with a gap when the belt is stopped and the heated roller is not heated and the device is not in use, and the size of the gap is such that when the heated roller moves in a direction in which tension is applied to the belt due to thermal expansion of the belt while the device is in use, the shielding member comes into elastic contact with the inner surface of the heated roller .

A fixing device according to yet another aspect of the present disclosure is a fixing device that fixes a toner image on a sheet by passing the sheet through a fixing nip formed by an endless belt and a pressure member, the fixing device including a housing that houses the belt therein, a heat-generating member that is fixed to the housing and is long in the width direction of the sheet, a heating roller that is tubular with both ends opened and around which the belt is wound, the heat-generating member is inserted through the openings and is heated by the heat-generating member, a bearing that supports the heating roller movably in a direction in which tension is applied to the belt relative to the housing, a biasing member that biases the bearing in a direction in which the heating roller applies tension to the belt, and a shielding portion that includes an elastic body and is inserted into the opening. the elastic body is disc-shaped with a central hole in the center, its periphery is fixed to the inner circumferential surface of the heating roller, and a tongue is formed by making a plurality of cuts radially from the central hole in the circumferential direction, with the central hole side being a free end, the long heat-generating member is inserted into the central hole of the shielding member, and when the belt is stopped and the heating roller is not heated and the device is not in use, the tongue and the heat-generating member are in close proximity with a gap therebetween, and the size of the gap is such that when the heating roller moves in the direction in which tension is applied to the belt due to thermal expansion of the belt while the device is in use, the tongue comes into elastic contact with the heat-generating member.
An image forming apparatus according to the present disclosure is characterized by including the fixing device described above.

With the above configuration, the elastic body is in elastic contact with at least one of the rotating cylinder and the heat-generating member, thereby reducing the gap connecting the internal space of the rotating cylinder with the space outside the rotating cylinder, thereby preventing heat generated by the heat-generating member from escaping through the opening of the rotating cylinder.

FIG. 1 is a schematic cross-sectional view illustrating the overall configuration of a printer. 4A is a schematic cross-sectional view showing the configuration of a fixing unit, and FIG. 4B is a front view of one end of a heating roller as viewed from the front. FIG. 4 is an exploded perspective view showing one axial end of the heating roller. 13A and 13B are a front view and a vertical cross-sectional view of a shielding member inserted into an opening of a heating roller. 1A is a perspective view of a shielding member according to this modified example, and FIG. 1B is a cross-sectional view taken along line EE of FIG. 13A and 13B show the state in which the shielding member is pressed into the opening of the heating roller and the halogen heater is pressed into the center of the shielding wall. 13A and 13B are a front view and a vertical cross-sectional view of a shielding member according to this modified example inserted into an opening of a heating roller. 13A is a perspective view of a shielding member according to another modified example, and FIG. 13B is a front view of the shielding member inserted into the opening of the heating roller. 13 is a vertical cross-sectional view illustrating a shielding member according to a modified example. FIG. FIG. 13 is a plan view illustrating a shielding wall according to a modified example. 1A is a cross-sectional perspective view showing the configuration of a heat-insulating shielding member, and FIG. 1B is a front view of the shielding member inserted into an opening of a heating roller. FIG. 11 is a vertical cross-sectional view showing the configuration of a conventional shielding member inserted into an opening of a heating roller.

Hereinafter, an embodiment of a fixing device and an image forming apparatus according to the present disclosure will be described with reference to the drawings, taking as an example a case where the fixing device and the image forming apparatus are applied to a tandem color printer (hereinafter simply referred to as a "printer").
[1] Overall Configuration of the Printer Fig. 1 is a schematic cross-sectional view showing the overall configuration of a printer 1. As shown in the figure, the printer 1 includes an image forming section 10, a paper feed section 20, and a fixing section 30 (fixing device).

The image forming section 10 includes imaging units 11Y, 11M, 11C, and 11K corresponding to the colors Y (yellow), M (magenta), C (cyan), and K (black), and an intermediate transfer belt 13. The imaging unit 11K includes a photoconductor drum 12, and a charging section 16, an exposure section 17, a developing section 18, and a cleaner 19 arranged circumferentially around the photoconductor drum 12.

The exposure unit 17 is equipped with a light-emitting element such as a laser diode and a lens, and modulates the laser light in response to a drive signal from a control unit (not shown) to expose and scan the photosensitive drum 12.

The photoconductor drum 12 is rotated by a drive source (not shown), and before it is exposed to the light, any remaining toner on its surface is removed by a cleaner 19, and then it is uniformly charged by a charging unit 16. When the photoconductor drum 12 is exposed to the laser light in this uniformly charged state, an electrostatic latent image is formed on the surface of the photoconductor drum 12.

The electrostatic latent image formed on the photoreceptor drum 12 is developed by the developing unit 18, thereby forming a K-color toner image on the surface of the photoreceptor drum 12. This K-color toner is primarily transferred from the photoreceptor drum 12 onto the intermediate transfer belt 13 by the primary transfer roller 14, which is arranged on the opposite side of the photoreceptor drum 12, via the circulating intermediate transfer belt 13.

Imaging units 11Y, 11M, and 11C have the same configuration as imaging unit 11K, and for each imaging unit, a toner image of the corresponding color (Y, M, or C) is formed on the photoconductor drum 12 and is then primarily transferred onto the intermediate transfer belt 13 by the primary transfer roller 14.

The image-forming operations in each of the image-forming units 11Y to 11K are performed with different timing so that the toner images are superimposed and primarily transferred to the same position on the intermediate transfer belt 13. This forms color toner images of Y to K colors on the intermediate transfer belt 13.

The paper feed section 20 includes a paper feed cassette 21 that stores recording sheets S, a feed roller 22, a transport roller 23, and a timing roller 24.

The delivery roller 22 contacts the topmost recording sheet S in the paper feed cassette 21 and delivers it to the transport path 25. The transport roller 23 transports the recording sheet S delivered by the delivery roller 22 toward the timing roller 24.

The timing roller 24 sends the recording sheet S downstream at a timing instructed by a control unit (not shown).

In the image forming unit 10, the color toner image transferred in multiple layers onto the intermediate transfer belt 13 moves to the secondary transfer position 15a, which is the contact position between the intermediate transfer belt 13 and the secondary transfer roller 15, as the intermediate transfer belt 13 rotates.

A recording sheet S is fed along a conveying path 25 from a timing roller 24 in the paper feed section 20 in accordance with the movement of the toner image on the rotating intermediate transfer belt 13, and when the recording sheet S passes through a secondary transfer position 15a, the color toner image on the intermediate transfer belt 13 is secondarily transferred onto the recording sheet S by a secondary transfer roller 15. After passing through the secondary transfer position 15a, the recording sheet S is sent to a fixing section 30.

The fixing unit 30 passes the recording sheet S, which is transported from the secondary transfer roller 15 in the direction indicated by the arrow D (sheet transport direction), through the fixing nip 3, and fixes the color toner image on the recording sheet S to the recording sheet S by applying heat and pressure.

The recording sheet S that has passed through the fixing unit 30 is discharged outside the apparatus by discharge rollers 26 and stored in a discharge tray 27 .
[2] Configuration of Fixing Unit 30 FIG. 2A is a schematic cross-sectional view showing the configuration of the fixing unit 30.

As shown in the figure, the fixing unit 30 includes a heating member 300 that forms the fixing nip 3 and a pressure roller 39 as a pressure member. The heating member 300 includes an endless belt 31 that contacts the outer peripheral surface 391 of the pressure roller 39, a pressing member 32 that contacts the inner peripheral surface 310 of the belt 31, a guide member 33 that contacts the inner peripheral surface 310 of the belt 31 and guides the belt 31, a support member 34 that fixes and supports the pressing member 32 and the guide member 33, a heating roller 35 as a rotating cylinder, a heater 36 as a heat generating member that applies heat to the heating roller 35, and a lubricant application member 38 that applies a lubricant to the inner peripheral surface 310 of the belt 31.

The belt 31 is wound around a pressing member 32, a heating roller 35, and a guide member 33, so that a certain amount of tension acts on the belt 31. The structure for applying tension to the belt 31 will be described later.

The pressure roller 39 has a rotation axis parallel to the Z axis, and the axial end of the pressure roller 39 is rotatably supported by a fixed frame 61 (FIG. 2(b)) that constitutes a housing that houses the belt 31, the pressure roller 39, etc., and the outer peripheral surface 391 of the pressure roller 39 is pressed against the belt 31 by a biasing force from an elastic member (not shown) such as a spring. The pressure roller 39 is driven to rotate at a predetermined rotational speed in the direction indicated by arrow A by the rotational driving force of the fixing and conveying motor 40. This rotation of the pressure roller 39 causes the belt 31 to rotate in the direction indicated by arrow B.

The pressing member 32 and the guide member 33 are arranged in line along the belt rotation direction, and are non-rotating bodies that do not rotate together with the rotating belt 31, and their length in the Z-axis direction is approximately the same as the length of the belt 31 in the Z-axis direction.

The pressing member 32 is a pressure pad arranged on the opposite side of the pressure roller 39 located on the outside of the belt 31, and is provided in sliding contact with the inner peripheral surface 310 of the belt, pressing the belt 31 against the pressure roller 39. As a result, the outer peripheral surface 391 of the pressure roller 39 and the outer peripheral surface 312 of the belt 31 are in pressure contact with each other, forming a fixing nip 3 between the belt 31 and the pressure roller 39.

The guide member 33 is located downstream of the pressing member 32 in the belt rotation direction and upstream of the heating roller 35 in the belt rotation direction, and is located closer to the pressing member 32 than the heating roller 35, in this case, in the vicinity of the pressing member 32, with a space 45 between them. The guide surface 335 comes into surface contact with the inner surface 310 of the belt 31 immediately after it passes through the fixing nip 3, and guides the belt 31 further downstream in the belt rotation direction.

The lubricant application member 38 is long in the Z-axis direction and has a length approximately equal to the belt width of the belt 31, and is fitted into a groove 339 along the Z-axis direction provided in the guide surface 335 of the guide member 33. The lubricant application member 38 contains a lubricant, and contacts the inner peripheral surface 310 of the belt 31 to apply the lubricant to the belt inner peripheral surface 310.

Figure 2(b) is a front view of one end of the heating roller 35. Although not shown in the figure, the other end has a similar configuration.

2(a) and (b), the heating roller 35 is a cylinder made of metal such as aluminum or SUS, whose rotation axis is parallel to the Z-axis direction, and both axial ends of the heating roller 35 are rotatably supported by bearings 63. The bearing 63 is biased in the direction indicated by arrow C by a tension spring 64 as a biasing member while being fitted into the long hole 62 of the fixed frame 61, and the belt 31 wound around the heating roller 35 is stretched with a predetermined tension via the bearing 63 and the heating roller 35 by the biasing force of the tension spring 64. Note that the biasing member that biases the bearing 63 is not limited to a tension spring, and may be any member that can bias the bearing 63 in the direction indicated by arrow C, for example, a compression spring.

The heater 36 is elongated along the axial direction of the heating roller 35, and is composed of halogen heaters 361, 362 arranged at intervals in the vertical direction. Both ends are fixed and supported while inserted into the internal space 351 of the cylindrical heating roller 35, and heat generated by the power supply from a power source (not shown) is applied to the heating roller 35.

Halogen heaters 361, 362 are configured such that a long filament (not shown) that serves as a heating element is inserted into glass tubes 361a, 362a (Fig. 3), and both longitudinal ends are sealed with sealing portions 361b, 362b. The filament is slightly longer than the maximum size sheet passing width, and is arranged in glass tubes 361a, 362a so as to heat the entire area from one end of the sheet passing width to the other evenly. As a result, the area of heater 36 where the filament is arranged becomes heating portion 36a, excluding non-heating portions 36b (Fig. 4) at both longitudinal ends.

In the above configuration, when the pressure roller 39 is driven to rotate in the direction indicated by arrow A, the belt 31 receives the rotational driving force and rotates in the direction indicated by arrow B. As the belt 31 rotates, the lubricant applied to the belt inner surface 310 by the lubricant application member 38 passes through the heating roller 35 and reaches the contact area between the belt inner surface 310 and the pressing member 32 in the fixing nip 3, reducing the sliding resistance between the belt inner surface 310 and the pressing member 32. When the heater 36 is energized while the pressure roller 39 is rotating, the heat generated by the heater 36 is transferred from the heating roller 35 to the belt 31, and reaches the fixing nip 3 as the belt 31 rotates. This supplies the heat of the heater 36 to the fixing nip 3.

Figure 3 is an exploded perspective view showing one axial end of the heating roller 35. Note that the bearing 63 is not shown. Although not shown in the figure, the other end has a similar configuration.

As shown in the figure, the end of the heating roller 35 is open, and a shielding member 50 is inserted into this opening 352. If there is nothing to shield the opening 352, such as the shielding member 50, the internal space 351 of the heating roller 35 communicates with the space outside the heating roller 35 through the opening 352, and heat from the heater 36 may escape through the opening 352.

In this case, the power consumption of the heater 36 must be increased by the amount of heat that escapes through the opening 352. Also, the amount of heat applied from the heater 36 to the ends of the heating roller 35 is less than the amount of heat applied to the center of the heating roller 35, which may result in insufficient fixing at the ends of the sheet width direction and cause deterioration of image quality.

In this embodiment, the shielding member having an elastic body is pressed into the opening 352 of the heating roller 35 to prevent heat from the heater 36 from escaping from the opening 352 to the outside of the heating roller 35. Note that the shielding member having an elastic body as described above also implies that the shielding member itself is an elastic body.
[3] Configuration of the shielding member 50 As shown in Fig. 3, the shielding member 50 as an elastic member has a doughnut shape with a circular central hole 53 in the center, and is made of an elastic material such as silicone rubber. In this configuration example, the shielding member 50 is configured as an elastic body. The outer diameter of the shielding member 50 is slightly larger than the inner diameter of the heating roller 35 in its natural state before being pushed into the opening 352, and the diameter of the central hole 53 of the shielding member 50 (two-dot chain line in Fig. 4(a)) is smaller than the diameter of the circle surrounding the glass tubes 361a, 362a of the halogen heaters 361, 362 in a front view (dashed line in Fig. 4(a)).

Figures 4(a) and (b) are a front view and a vertical cross-sectional view of the shielding member 50 inserted into the opening 352 of the heating roller 35.

As shown in Figures 4(a) and (b), due to the elasticity of the shielding member 50 and the above-mentioned relationship of diameters, the shielding member 50 elastically deforms so that its outer diameter shrinks to match the inner diameter of the heating roller 35, and the inner surface 52 of the central hole 53 becomes a vertically long rectangle with rounded corners along the glass tubes 361a and 362a of the halogen heaters 361 and 362. Then, due to the elastic restoring force of this elastic deformation, the outer surface 51 of the shielding member 50 elastically contacts the inner surface 353 of the heating roller 35, and the inner surface 52 elastically contacts the halogen heaters 361 and 362.

The outer and inner diameters of the shielding member 50 are fixed to the non-rotating heater 36 and do not rotate when the rotating roller 35 rotates, but are determined so that they slide against the inner circumferential surface of the heating roller 35. When the pressure roller 39 (FIG. 2(a)) is driven to rotate in the above-described elastic contact state, the belt 31 rotates, causing the heating roller 35 to rotate in the direction indicated by arrow D while rubbing the inner circumferential surface 353 against the outer circumferential surface 51 of the shielding member 50.

By pushing the shielding member 50 into the opening 352 of the heating roller 35, as shown in Figures 4(a) and (b), there is no gap between the shielding member 50 and the heating roller 35, and only a small gap 53a remains between the shielding member 50 and the halogen heaters 361 and 362.

As a result, compared to a configuration in which the shielding member is not in contact with the heating roller 35 and the halogen heaters 361, 362, the gap connecting the internal space 351 of the heating roller 35 to the space outside the heating roller 35 can be made as small as possible, and the heat generated by the heater 36 can be prevented from escaping through the opening 352.

In the above, an example of a configuration in which the shielding member 50 is in elastic contact with both the heating roller 35 and the halogen heaters 361, 362 has been described, but the present invention is not limited to this, and for example, by changing the outer diameter and inner diameter of the shielding member, a configuration in which the shielding member is in elastic contact with only one of the heating roller 35 and the halogen heaters 361, 362 can be adopted. Even in this case, the gap that communicates the internal space 351 of the heating roller 35 with the space outside the heating roller 35 can be made smaller than in a configuration in which the shielding member is not in contact with either the heating roller 35 or the halogen heaters 361, 362, so that it is possible to suppress the heat generated by the heater 36 from escaping through the opening 352 in the same manner as described above.
[4] Modified example of shielding member The above describes a configuration example in which the shielding member itself is an elastic body. However, the shielding member of this modified example is different in that it has an elastic body on which a tongue that bends and deforms is formed.

Figure 5(a) is a perspective view of the shielding member 150 according to this modified example, and Figure 5(b) is a cross-sectional view taken along line E-E in Figure 5(a).

As shown in Figs. 5(a) and (b), the shielding member 150 has a disk-shaped shielding wall 151 as an elastic body, and a cylindrical side wall 152 rising from the periphery of the shielding wall 151. A plurality of (eight in Fig. 5(a)) notches 151a are provided radially from the center 151b of the shielding wall 151 toward the periphery. These eight notches 151a form eight tongue pieces 151c with the center 151b side as the free end. The length of the eight notches 151a is longer than the combined diameter of the halogen heaters 361 and 262. The length of the eight notches is the length from the center 151b to the periphery, and the shielding wall can also be configured to be composed of eight walls divided by the notches.

The shielding wall 151 is made of, for example, a non-metal such as silicone rubber, urethane rubber, fluororubber, or polyimide, or a metal such as aluminum or stainless steel, and the thickness of the shielding wall 151 is thin enough that the tongue of the shielding wall 151 can be easily bent in the thickness direction of the shielding wall 151, for example, 0.2 mm. The cylindrical side wall 152 is made of the same material as the shielding wall 151 and is formed integrally with the shielding wall 151. Note that the side wall 152 may be made of a different material from the shielding wall 151 and may be fixed to the shielding wall 151 by adhesive or the like, or a cylindrical side wall identical to the cylindrical side wall 152 may be provided on the opposite side of the shielding wall 151 and may be formed integrally with the shielding walls 151 and 152.

Figures 6(a) and 6(b) show the shielding member 150 being pushed into the opening 352 of the heating roller 35, and the halogen heaters 361 and 362 being pressed into the central portion 151b of the shielding wall 151.

As shown in Figures 6(a) and (b), the eight tongues 151c (Figure 5(a)) are elastically deformed so as to bend due to the halogen heaters 361 and 362. The elastic restoring force of the elastically deformed tongues 151c causes the tongues 151c to elastically contact the halogen heaters 361 and 362. This brings the circumferential surfaces of the halogen heaters 361 and 362 into close contact with the tongues 151c.

The cylindrical side wall 152 of the shielding member 150 is fixed to the inner circumferential surface 353 of the heating roller 35 with an adhesive or the like. In this state, when the pressure roller 39 (FIG. 2(a)) is driven to rotate, the shielding member 150 rotates together with the heating roller 35 as the belt 31 rotates around, with the tongue 151c of the shielding wall 151 in elastic contact with the halogen heaters 361, 362.

The shielding member 150 is pushed into the opening 352 of the heating roller 35, so that there is no gap between the shielding member 150 and the heating roller 35, as shown in Figures 6(a) and (b), and the gap between the shielding member 150 and the halogen heaters 361 and 362 is only a small gap 153a, which is almost the same as the shielding member 50 described above.

This makes it possible to minimize the gap connecting the internal space 351 of the heating roller 35 to the space outside the heating roller 35, compared to a configuration in which the shielding member is not in contact with the heating roller 35 and the halogen heaters 361, 362, and prevents the heat generated by the heater 36 from escaping through the opening 352.
[5] Modifications Although the above has been described based on the embodiment, it goes without saying that the present invention is not limited to the above-described configuration, and the following modifications are possible.
(5.1) In the above embodiment, a configuration example was described in which the shielding member is in elastic contact with the heating roller 35 and at least one of the halogen heaters 361 and 362 when pressed into the opening 352 of the heating roller 35, but this is not limited to this.

For example, the shielding member may be configured so that, when inserted into the opening 352 of the heating roller 35, it is not in elastic contact with either the heating roller 35 or the halogen heaters 361, 362.

Figures 7(a) and (b) are a front view and a vertical cross-sectional view of the shielding member 250 according to this modified example inserted into the opening 352 of the heating roller 35.

As shown in Figures 7(a) and (b), the shielding member 250 is supported by a cylindrical support member 70 fixed to a fixed frame 61 (Figure 2(b)), has a doughnut shape with a circular central hole 253 in the center, and is made of an elastic material such as silicone rubber.

The outer diameter of the shielding member 250 is slightly smaller than the inner diameter of the heating roller 35, and the diameter (inner diameter) of the central hole 253 of the shielding member 250 is slightly larger than the diameter of the circle (dashed line) surrounding the glass tubes 361a and 362a of the halogen heaters 361 and 362. Note that in the figure, the relationship between the diameters is slightly exaggerated for the sake of explanation.

Due to this relationship in diameter, when the belt 31 is stopped and the heating roller 35 is not heated (when the device is not in use), the outer peripheral surface 251 and inner peripheral surface 252 of the shielding member 250 are close to the inner peripheral surface 353 of the heating roller 35 and the halogen heaters 361 and 362 with a small gap (e.g. 0.5 mm) between them.

In a configuration in which the belt 31 is stretched by the heating roller 35 with a predetermined tension as shown in FIG. 2(b), the heating roller 35 may move in the direction indicated by the arrow C due to thermal expansion of the belt 31, and the center of the rotation axis of the heating roller 35 may become misaligned with the center 36c of the heater 36 (here, the midpoint in the X-Y plane between the halogen heater 361 and the halogen heater 362).

Specifically, since the halogen heaters 361, 362 are fixed to the fixed frame 61 (FIG. 2(b)), the heating roller 35 moves in the direction indicated by the arrow C relative to the halogen heaters 361, 362 (the amount of movement is equal to or greater than the above-mentioned gap, for example, 1.0 mm). The direction corresponding to the direction indicated by the arrow C is the direction indicated by the arrow F in FIG. 7(a).

Returning to FIG. 7(a), in a configuration in which the shielding member 250 is separated from the heating roller 35 and the halogen heaters 361, 362 with a small gap therebetween, when the heating roller 35 moves in the direction indicated by arrow F during use of the device, the inner surface of the heating roller 35 (dash-dotted line) after the movement comes into contact with the outer surface 251 of the shielding member 250 near point G, but since the shielding member 250 is made of an elastic material, it comes into elastic contact with the heating roller 35.

When the heating roller 35 then rotates, the heating roller 35 rotates in the direction indicated by the arrow D so as to slide against the portion of the outer circumferential surface 251 of the shielding member 250 near point G.

As described above, the shielding member 250 is in elastic contact with the heating roller 35, so it can reduce the impact when it comes into contact with the heating roller 35 compared to a non-elastic shielding member, and can suppress poor fixing caused by vibration of the belt 31 due to the impact.

In this way, the shielding member 250 is inserted into the opening 352 of the heating roller 35 so as to be close to the heating roller 35 with a gap smaller than the movement amount of the heating roller 35, and the gap that communicates the internal space 351 of the heating roller 35 with the space outside the heating roller 35 can be minimized while suppressing wear of the shielding member 250 and the heating roller 35. Furthermore, even if the heating roller 35 moves during use of the device, as described above, the impact caused by the collision between the shielding member 250 and the heating roller 35 can be suppressed, and even after that, since only a part of the outer circumferential surface 251 of the shielding member 250 slides against the heating roller 35, wear of the shielding member 250 and the heating roller 35 can be suppressed compared to a configuration in which the entire outer circumferential surface of the shielding member slides against the heating roller 35. The movement amount of the heating roller 35 relative to the halogen heaters 361 and 362 can be obtained in advance by experiments, etc.

In addition, the above describes an example of a configuration in which the shielding member 250 is separated from both the heating roller 35 and the halogen heaters 361, 362 with a small gap therebetween, but this is not limited to this.

For example, by changing the outer and inner diameters of the shielding member, the shielding member can be configured to be spaced apart from either the heating roller 35 or the halogen heaters 361, 362 and to be in elastic contact with the other, or the shielding member can be configured to be in elastic contact with both the heating roller 35 and the halogen heaters 361, 362.

Even in this case, the gap connecting the internal space 351 of the heating roller 35 to the space outside the heating roller 35 can be further reduced by the amount of elastic contact, so that the heat generated by the heater 36 can be prevented from escaping through the opening 352.

In addition, the shielding member having an elastic body with a tongue piece that bends and deforms as shown in FIG. 5(a) can also be configured to be separated from the halogen heaters 361 and 362 without being in elastic contact with them.

Figure 8 (a) is a perspective view of a shielding member 450 according to another modified example.

As shown in the figure, the shielding member 450 is basically the same in configuration as the shielding member 150 in FIG. 5(a), except that a circular central hole 453 is formed at the center 451b of the shielding wall 451.

Figure 8 (b) is a front view of the shielding member 450 inserted into the opening 352 of the heating roller 35.

As shown in the figure, the diameter of the central hole 453 of the shielding wall 451 is larger than the diameter of the circle (dashed line) surrounding the glass tubes 361a, 362a of the halogen heaters 361, 362. Note that in the figure, the relationship between the sizes of the diameters is slightly exaggerated for the sake of explanation. Also, for the sake of convenience, the direction indicated by the arrow C, which is the movement direction of the heating roller 35 in FIG. 2(b), is indicated by the arrow H in FIG. 8(b).

Due to this relationship in diameter, when the device is not in use, the tongue pieces 451d to 451k of the shielding wall 451 are close to the halogen heaters 361 and 362 with a small gap. The gap between the tongue pieces 451d to 451k of the shielding wall 451 and the halogen heaters 361 and 362 and the movement amount of the heating roller 35 in the direction of the arrow H are, for example, 0.5 mm and 1.0 mm, as described above. In addition, the side wall 152 of the shielding member 450 is fixed to the inner surface 353 of the heating roller 35 by adhesion or the like, and when the heating roller 35 moves in the direction indicated by the arrow H, the shielding member 450 also moves in the direction indicated by the arrow H. Then, the tongue piece 451k of the shielding wall 451 of the shielding member 450 (two-dot chain line) after the movement and the halogen heater 361 come into elastic contact near point I.

When the heating roller 35 then rotates, the rotation of the heating roller 35 causes the shielding member 450 to rotate in the direction indicated by arrow D so that the tongues 451d to 451k slide sequentially against the halogen heater 361.

Like the shielding wall 151 of the shielding member 150, the tongue pieces 451d to 451k of the shielding wall 451 are configured to be bent in the thickness direction of the shielding wall 451 with the center 451b side as the free end, so that even if they slide against the halogen heater 361, the dynamic frictional force with the halogen heater 361 can be reduced and the rotation of the rotating roller 35 can be prevented from being hindered.

In this way, the shielding wall 451 of the shielding member 450 is inserted into the opening 352 of the heating roller 35 so that it is close to the halogen heaters 361, 362 with a gap smaller than the amount of movement of the heating roller 35. This makes it possible to minimize the gap that connects the internal space 351 of the heating roller 35 to the space outside the heating roller 35, and, as described above, prevents the rotation of the rotating roller 35 from being impeded even if the heating roller 35 moves while the device is in use.

In the above, a configuration example in which the shielding wall 451 of the shielding member 450 is close to the halogen heaters 361, 362 with a small gap therebetween has been shown, but the present invention is not limited to this. For example, the shielding wall 451 may be configured to be in elastic contact with the halogen heaters 361, 362. Even in this case, the gap that communicates between the internal space 351 of the heating roller 35 and the space outside the heating roller 35 can be further reduced by the amount of elastic contact, so that it is possible to suppress the heat generated by the heater 36 from escaping through the opening 352.
(5.2) In the above embodiment, an example configuration was described in which the entire outer circumferential surface of the cylindrical side wall 152 of the shielding member 150 was fixed to the inner circumferential surface 353 of the heating roller 35, but this is not limited to the above.

For example, as shown in the longitudinal cross-sectional view of FIG. 9, the side wall 552 can be elevated so that a portion of the outer circumferential surface of the side wall 552 is fixed to the inner circumferential surface 353 of the heating roller 35.

By adopting such a configuration, the tongue piece 551c of the shielding wall 551 can be brought into contact with the sealing parts 361b, 362b of the halogen heaters 361, 362 in the non-heating part 36b, rather than the heat-generating part 36a of the heater 36, thereby suppressing the temperature rise of the shielding wall 551.

As a result, in addition to highly heat-resistant materials, materials with low heat resistance can also be selected as materials for the shielding member 550, increasing the options for materials for the shielding member 550 and improving design freedom.

In addition, the tongue piece 551c of the shielding wall 551 can be made to contact the end 361c, 362c of the glass tube that is closer to the center in the longitudinal direction than the sealing parts 361b, 362b in the non-heat-generating parts 36b of the halogen heaters 361, 362, thereby suppressing the transfer of heat to the sealing parts 361b, 362b and suppressing thermal deterioration of the sealing parts 361b, 362b.

During printing, the halogen heaters 361, 362 generate enough heat to allow the belt 31 to supply the heat necessary for fixing to the sheets being transported sequentially through the fixing nip 3. If a paper jam occurs during printing, the transport of the sheet is halted and the supply of heat from the belt 31 to the sheet is halted, so the temperature of the belt 31 is likely to rise. This may accelerate thermal deterioration of the belt 31 and the components around the belt 31.

In this modified example, in order to suppress such thermal deterioration of the belt 31, etc., a fan 80 is further provided outside the heating roller 35, and the fan 80 blows air through a duct 81 to the shielding wall 551.

In FIG. 9, the tongue 551c bent by the air blown by the fan 80 is shown by a two-dot chain line. The strength of the air blown by the fan 80 only needs to be greater than the static friction force between the tongue 551c and the halogen heaters 361, 362 in the thickness direction of the shielding wall 551. Also, when the tongue 551c is not in contact with the halogen heaters 361, 362 and is close to them with a small gap, the strength of the air blown by the fan 80 only needs to be strong enough to bend the tongue 551c.

By bending the tongue piece 551c in this manner, the wind blown by the fan 80 is sent into the internal space 351 of the heating roller 35 through the gap 553a between the shielding wall 551 and the halogen heaters 361 and 362.

This allows the heating roller 35 to be cooled when a paper jam occurs, and makes it possible to suppress an increase in temperature of the belt 31 heated by the heating roller 35 .
(5.3) In the above embodiment, the shielding wall 151 of the shielding member 150 is a single-layered disk shape, but this is not limiting. For example, the shielding wall 151 may be a bimetallic structure having two layers with different thermal expansion coefficients.

By selecting the materials for the two layers so that they flex when the halogen heaters 361, 362 reach or exceed a predetermined temperature, the shielding wall can be in contact with the halogen heaters 361, 362 when they are at a low temperature, and can be separated from the halogen heaters 361, 362 by flexing when they reach a high temperature.

This makes it possible to prevent the temperature of the shielding wall from rising to a predetermined temperature or higher, and thus makes it possible to suppress thermal deterioration of the shielding wall.
(5.4) Of the shielding members according to the above-described embodiments, a configuration may be adopted in which aluminum or the like is vapor-deposited on the side facing the internal space 351 of the heating roller 35 (e.g., surface 54 in FIG. 4(b)) to increase the heat reflectance compared to the side facing the external space of the heating roller 35 (e.g., surface 55 in FIG. 4(b)).

This allows the radiant heat from the heater 36 to be reflected, suppressing the temperature rise of the shielding member, and preventing the heat from the heater 36 from leaking outside the heating roller 35 due to thermal conduction by the shielding member.
(5.5) In the above embodiment, the fixing nip 3 is formed by the belt 31 and the pressure roller 39, but the present invention is not limited to this.

For example, a fixing nip can be formed by a heating roller and a pressure roller 39, and the heating roller can be heated by a heater.

It is also possible to use a so-called surf fixing method in which a fixing nip is formed by the belt and pressure roller 39, and the belt is heated by a heater placed in contact with the inside of the belt.

Furthermore, in order to more quickly raise the surface temperature of the pressure roller to a temperature suitable for the fixing temperature, a heater can be placed inside the pressure roller, and the pressure roller can be heated by this heater.

Even with this configuration, by inserting a shielding member into the openings of the heating roller, belt, and pressure roller, which are the rotating cylinders heated by the heater, it is possible to prevent the heat generated by the heater from escaping through the openings of the heating roller, belt, and pressure roller, just as in the above embodiment.

In the above embodiment, a configuration example has been described in which the shielding wall as an elastic body is disk-shaped. However, this disk shape only needs to be similar to the shape of the opening of the rotating cylinder, and in addition to being a perfect circle, it also includes the meaning of, for example, being elliptical to match the shape of the opening in the belt.
(5.6) The shielding walls 151, 451 of the shielding members 150, 450 in the above-described embodiments are not limited to being formed from a single disk-shaped member. For example, as shown in FIG. 10 , the shielding walls may be formed by joining one end 6511 and the other end 6512 of a linear sheet 651 with an adhesive or the like.
(5.7) In the above embodiment, an example of a configuration in which the heater 36 as a heat generating member is composed of two halogen heaters 361, 362 has been described, but this is not limited to this. For example, the heater may be composed of one halogen heater, or may be composed of three or more halogen heaters. Furthermore, the heat generating member is not limited to one that uses an infrared lamp such as a halogen heater, and may be, for example, a heater that uses a resistance heating element.

In the above embodiment, the configuration example in which one shielding member is inserted into each of the openings at both ends of the heating roller 35 has been described, but the present invention is not limited to this. For example, a configuration in which a shielding member is inserted into only one of the openings may be adopted, or a configuration in which one or more shielding members are inserted into each of the openings at both ends may be adopted.
(5.8) In the above embodiment, the fixing unit 30 as a fixing device is applied to a tandem color printer. However, the present invention is not limited to this. The fixing unit 30 can be applied to general image forming devices such as copiers, multifunction machines, and facsimile machines.
(5.9) The configurations of the above-described embodiments and modifications may be combined to the greatest extent possible.

Although not an embodiment of the present disclosure, the following configuration may also be adopted.
[6] Configuration of the shielding member 750 As a method for preventing the heat generated by the heater 36 from escaping through the opening 352 of the heating roller 35, it is also effective to configure the shielding member inserted into the opening 352 to have heat insulating properties. In the following, in order to avoid duplication of explanation, the explanation of the same contents as in the above embodiment will be omitted, and the same reference numerals will be used for the same components.

Figure 11(a) is a cross-sectional perspective view showing the configuration of a heat-insulating shielding member 750. Note that in the figure, only half of the shielding member 750 is shown in order to show the cross section of the shielding member 750, and the half not shown has the same configuration as the half shown.

As shown in the figure, the shielding member 750 is made of resin such as silicone rubber, has a doughnut shape with a circular central hole 753 in the center, and has multiple independent air bubbles 754 inside that are not connected to each other. The air inside these multiple air bubbles 754 gives the shielding member 750 heat insulation.

Figure 11 (b) is a front view of the shielding member 750 inserted into the opening 352 of the heating roller 35. The position where the shielding member 750 is inserted in the direction of the rotation axis of the heating roller 35 is the same as the position of the shielding member 50 (Figure 4 (b)) according to the above embodiment.

As shown in the figure, the outer diameter of the shielding member 750 is approximately the same as the inner diameter of the heating roller 35, and the diameter (inner diameter) of the central hole 753 of the shielding member 750 is slightly larger than the diameter of the circle (dashed line in Figure 4(a)) surrounding the glass tubes 361a and 362a of the halogen heaters 361 and 362.

The outer peripheral surface 751 of the shielding member 750 is fixed to the inner peripheral surface 353 of the heating roller 35 by adhesion or the like. When the pressure roller 39 (FIG. 2(a)) is driven to rotate in this state, the shielding member 750 rotates together with the heating roller 35 as the belt 31 rotates.

As described above, the shielding member 750 has thermal insulation properties, so that the heat generated by the heater 36 can be prevented from escaping to the outside of the heating roller 35 through the shielding member 750.

Also, by making the outer diameter of the shielding member 750 slightly smaller than the inner diameter of the heating roller 35 and configuring it to be supported by the support member 70 like the shielding member 250 shown in Figures 7(a) and (b) in the above embodiment, it is possible to configure the shielding member so that it does not come into contact with either the heating roller 35 or the halogen heaters 361 and 362. Even in this case, it is possible to prevent the heat generated by the heater 36 from escaping to the outside of the heating roller 35 through the shielding member, compared to a configuration in which the shielding member does not have thermal insulation properties.

In addition, while the above describes an example configuration in which the air bubbles in the shielding member 750 are closed air bubbles, this is not limiting. For example, any material that has a certain amount of space inside the shielding member and has thermal insulation properties may be used, such as an open-cell sponge, polyimide with a honeycomb structure, or a foam metal such as aluminum with closed or open air bubbles.

This disclosure can be applied to a fixing device that fixes a toner image on a sheet by passing the sheet through a fixing nip.

3 Fixing nip 30 Fixing section 35 Heating roller (rotating cylinder)
36 Heater (heat generating member)
39 Pressure roller (pressure member)
50, 150, 250, 450, 550 Shielding member 151, 451, 551 Shielding wall (elastic body)
352 Opening

Claims (11)

A fixing device that fixes a toner image on a sheet by passing the sheet through a fixing nip formed by a heating member and a pressure member,
The heating member is
A heat generating member that is elongated in the width direction of the sheet;
a rotating cylinder having a cylindrical shape with both ends open, into which the heat generating member is inserted through the openings and which is heated by the heat generating member;
a shielding member including an elastic body, the elastic body being pressed into the opening so as to be in elastic contact with at least one of the rotating cylinder and the heat-generating member by an elastic restoring force;
The elastic body is disk-shaped, and has a plurality of cuts radially from the center of the disk toward the periphery, forming a tongue having a free end on the disk center side.
The heat generating member is pressed into the disc from the center side in a state in which the tongue is bent and deformed, and the elastic restoring force of the tongue brings the peripheral surface of the heat generating member and the tongue into close contact with each other. The fixing device according to claim 1 , wherein the elastic body is in elastic contact with the rotating cylinder and the heat generating member. 3. The fixing device according to claim 1 , wherein the plurality of cuts extend from the center of the disk of the elastic body to the peripheral edge thereof. 4. The fixing device according to claim 1, wherein the elastic body has a laminated structure of two layers, one of which has a thermal expansion coefficient different from that of the other layer. The heat generating member is a heater in which a heat generating portion is sandwiched between a non-heat generating portion in a longitudinal direction,
5. The fixing device according to claim 1 , wherein the elastic body is in elastic contact with the non-heat generating portion of the heater. The fixing device according to any one of claims 1 to 5, further comprising an air blowing means for blowing air from outside the rotating cylinder to the elastic body so that the tongue of the elastic body bends in the thickness direction of the disc and toward the internal space of the rotating cylinder. A fixing device that fixes a toner image on a sheet by passing the sheet through a fixing nip formed by a heating member and a pressure member,
The heating member is
A heat generating member that is elongated in the width direction of the sheet;
a rotating cylinder having a cylindrical shape with both ends open, into which the heat generating member is inserted through the openings and which is heated by the heat generating member;
a shielding member including an elastic body, the elastic body being pressed into the opening so as to be in elastic contact with at least one of the rotating cylinder and the heat-generating member by an elastic restoring force;
a heat reflectance of the elastic body on a side facing the internal space of the rotating cylinder is higher than a heat reflectance of the opposite side in a pushing direction of the shielding member. 8. The fixing device according to claim 1, wherein the shielding members are pressed into the openings at both ends of the rotating cylinder. A fixing device that fixes a toner image on a sheet by passing the sheet through a fixing nip formed by an endless belt and a pressure member,
A housing that houses the belt therein;
a heat generating member fixed to the housing and elongated in the width direction of the sheet;
a heating roller around which the belt is wound, the heating roller being tubular with both ends open, the heating member being inserted through the openings and being heated by the heating member;
a bearing that supports the heating roller movably relative to the housing in a direction in which tension is applied to the belt;
a biasing member that biases the bearing in a direction in which the heating roller applies tension to the belt;
A shielding member made of an elastic material and inserted into the opening ;
a support member that fixes and supports the shielding member to the housing so that the shielding member is in close proximity to an inner circumferential surface of the heating roller with a gap therebetween when the belt is stopped and the heating roller is not heated and the device is not in use;
Equipped with
The size of the gap is such that when the heating roller moves in a direction in which tension is applied to the belt due to thermal expansion of the belt during use of the device, the shielding member is in elastic contact with the inner circumferential surface of the heating roller.
A fixing device comprising: A fixing device that fixes a toner image on a sheet by passing the sheet through a fixing nip formed by an endless belt and a pressure member,
A housing that houses the belt therein;
a heat generating member fixed to the housing and elongated in the width direction of the sheet;
a heating roller around which the belt is wound, the heating roller being tubular with both ends open, the heating member being inserted through the openings and being heated by the heating member;
a bearing that supports the heating roller movably relative to the housing in a direction in which tension is applied to the belt;
a biasing member that biases the bearing in a direction in which the heating roller applies tension to the belt;
a shielding member including an elastic body and inserted into the opening;
Equipped with
the elastic body is in the shape of a disk having a central hole at its center, the periphery of the elastic body is fixed to the inner circumferential surface of the heating roller, and a plurality of cuts are made radially from the central hole toward the periphery to form a tongue having a free end on the side of the central hole;
The elongated heat generating member is inserted into the central hole of the shielding member,
When the belt is stopped and the heating roller is not heated, the tongue and the heat generating member are in close proximity to each other with a gap therebetween,
The size of the gap is such that the tongue is in elastic contact with the heat generating member when the heating roller moves in a direction in which tension is applied to the belt due to thermal expansion of the belt during use of the device.
A fixing device comprising: An image forming apparatus comprising the fixing device according to any one of claims 1 to 10.

Images