Fixing apparatus and image forming apparatus

Abstract

To provide a fixing device that can adjust the amount of lubricant supplied. [Solution] The fixing device 1 includes an endless fixing belt 31, a pressure roller 32 that applies pressure from the outside of the fixing belt 31, a pressure adjustment unit 50 that adjusts the pressure applied by the pressure roller 32 to the fixing belt 31, a fixing pad 34 provided on the inside of the fixing belt 31 and forming a nip portion N together with the pressure roller 32, and a lubricant holding unit 41 impregnated with lubricant and attached to the fixing pad 34. The lubricant holding unit 41 performs a supply operation to supply lubricant to the inner surface of the fixing belt 31 and a recovery operation to recover lubricant from the inner surface of the fixing belt 31 in accordance with the pressure applied by the pressure roller 32.

Description

Technical Field

[0005]

[0001] The present disclosure relates to a fixing device and an image forming apparatus for fixing an image on a sheet.

Background Art

[0002] Conventionally, in a fixing device used in an electrophotographic image forming apparatus such as a copying machine or a printer, a toner image that has not been fixed is formed on a sheet, and the toner image is fixed by applying pressure and heat. In recent years, a fixing device using an endless fixing belt has been proposed. In such a fixing device, a nip forming member is disposed inside the endless fixing belt, and a pressure roller is pressed against the nip forming member via the fixing belt to form a nip portion.

[0003] In the nip portion, a sliding sheet impregnated with a lubricant is provided to reduce the frictional resistance between the inner peripheral surface of the fixing belt and the nip forming member. However, since there is a concern about leakage of the lubricant, a method for suppressing this has been proposed (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Conventional fixing devices include a rotatable, endless fixing belt, a nip-forming member positioned on the inner circumference of the fixing belt, a pressing member positioned opposite the nip-forming member with the fixing belt in between, which pressurizes the fixing belt toward the nip-forming member so that a nip portion is formed by sandwiching the nip-forming member and the fixing belt, and a lubricant-impregnating member that impregnates a lubricant between the fixing belt and the nip-forming member. Between the lubricant-impregnating member and the nip-forming member, a lubricant-holding member is provided, which has a higher lubricant-holding capacity than the lubricant-impregnating member.

[0006] Conventional fixing devices required impregnating a lubricant-impregnated member with a large amount of lubricant to achieve a lubricating effect. However, a lubricant-impregnated member containing a large amount of lubricant cannot retain the lubricant when pressure is applied by the pressure roller, and the lubricant that is no longer retained seeps out around the nip. The seeped lubricant moves to the end of the fixing belt, and when the fixing belt is driven, even more lubricant is sent to the end of the belt, and the lubricant that reaches the end of the belt leaks out of the fixing belt mounting area. If use continues under these conditions, the amount of lubricant will gradually decrease, the lubricating effect with the fixing belt will decline, and there is a concern that malfunctions such as belt damage may occur due to an increase in the fixing belt drive load.

[0007] This disclosure is made to solve the above-mentioned problems and aims to provide a fixing device and an image forming device that can adjust the amount of lubricant supplied by supplying and recovering the lubricant. [Means for solving the problem]

[0008] The fixing device according to the present disclosure comprises an endless fixing belt, a pressing member that applies pressure from the outside of the fixing belt, a pressing pressure adjustment unit that adjusts the pressure applied by the pressing member to the fixing belt, a fixing pad provided on the inside of the fixing belt and forming a nip together with the pressing member, and a lubricant holding unit impregnated with a lubricant and attached to the fixing pad, wherein the lubricant holding unit performs a supply operation to supply lubricant to the inner surface of the fixing belt and a recovery operation to recover lubricant from the inner surface of the fixing belt in accordance with the pressure applied by the pressing member.

[0009] The fixing device according to this disclosure may be configured to rotate the fixing belt while applying pressure with the pressurizing member during the supply operation.

[0010] The fixing device according to this disclosure may be configured to perform the supply operation before the fixing belt performs the fixing operation.

[0011] The fixing device according to this disclosure may be configured to rotate the fixing belt while reducing the pressure of the pressurizing member during the recovery operation.

[0012] The fixing device according to this disclosure may be configured to perform the retrieval operation after the fixing belt has performed the fixing operation.

[0013] The fixing device according to this disclosure may be configured to include a torque detection unit for detecting the driving torque of the fixing belt, and to perform the supply operation when the driving torque exceeds a threshold.

[0014] The fixing device according to this disclosure may be configured to include a temperature detection unit for detecting the temperature of the fixing belt, and to perform the supply operation when the temperature of the fixing belt exceeds a threshold.

[0015] The image forming apparatus according to this disclosure is characterized by comprising a fixing device according to this disclosure. [Effects of the Invention]

[0016] According to the present disclosure, by applying a lubricant to the inner surface of the fixing belt, the sliding resistance between the fixing belt and the fixing pad can be reduced, and the fixing belt can be rotated smoothly. Further, by adjusting the pressing force of the pressing member and recovering the lubricant from the nip portion, leakage of the lubricant can be suppressed.

Brief Description of the Drawings

[0017] [Figure 1] FIG. 8 is a schematic cross-sectional view showing the configuration of an image forming apparatus according to an embodiment of the present disclosure. [Figure 2] FIG. 11 is a schematic cross-sectional view showing the configuration of a fixing apparatus according to an embodiment of the present disclosure. [Figure 3] FIG. 14 is a schematic side view showing an enlarged view of the vicinity of the nip portion of the fixing apparatus during the supply operation. [Figure 4] FIG. 17 is a schematic side view showing an enlarged view of the vicinity of the nip portion of the fixing apparatus during the recovery operation.

Embodiments for Carrying Out the Invention

[0018] Hereinafter, a fixing apparatus and an image forming apparatus according to an embodiment of the present disclosure will be described with reference to the drawings.

[0019] FIG. 1 is a schematic cross-sectional view showing the configuration of an image forming apparatus according to an embodiment of the present disclosure.

[0020] The image forming apparatus 100 is a multifunctional device having a copy function, a scanner function, a facsimile function, and a printer function, and transmits an image of a document read by the image reading device 130 to the outside, or forms an image of a document read by the image reading device 130 or an image received from the outside in color or monochrome on a recording medium such as paper.

[0021] Above the image reading device 130, a document conveying device 110 that is supported so as to be openable and closable is provided. The document conveying device 110 conveys one or a plurality of documents one by one in order. The image reading device 130 scans the scanning optical system 130b to read a document placed on the document placement table 130a, or reads a document conveyed by the document conveying device 110 to generate image data.

[0022] The image forming apparatus 100 is provided with a fixing device 1, a developing device 2, a photosensitive drum 3, a drum cleaning device 4, a charger 5, an intermediate transfer belt device 7, a secondary transfer device 11, an optical scanning device 12, a paper feeding unit 18, and the like.

[0023] In the image forming apparatus 100, image data corresponding to a color image using each color of black (K), cyan (C), magenta (M), and yellow (Y), or a monochrome image using a single color (for example, black) is handled. The image forming apparatus 100 is provided with four each of a developing device 2, a photosensitive drum 3, a drum cleaning device 4, and a charger 5 for forming four types of toner images, and each is associated with black, cyan, magenta, and yellow, respectively, to constitute four image stations Pa, Pb, Pc, and Pd.

[0024] The optical scanning device 12 exposes the surface of the photosensitive drum 3 to form an electrostatic latent image. The developing device 2 develops the electrostatic latent image on the surface of the photosensitive drum 3 to form a toner image on the surface of the photosensitive drum 3. The drum cleaning device 4 removes and recovers the residual toner on the surface of the photosensitive drum 3. The charger 5 uniformly charges the surface of the photosensitive drum 3 to a predetermined potential. By the series of operations described above, toner images of each color are formed on the surface of each photosensitive drum 3.

[0025] The intermediate transfer belt device 7 comprises intermediate transfer rollers 6, an endless intermediate transfer belt 71, an intermediate transfer drive roller 72, an intermediate transfer driven roller 73, and a cleaning device 9. Four intermediate transfer rollers 6 are provided inside the intermediate transfer belt 71 to form four different toner images corresponding to each color. The intermediate transfer rollers 6 transfer the toner images of each color formed on the surface of the photoreceptor drum 3 to the circulating intermediate transfer belt 71.

[0026] The intermediate transfer belt 71 is stretched over the intermediate transfer drive roller 72 and the intermediate transfer driven roller 73. In the image forming apparatus 100, the toner images of each color formed on the surface of each photoreceptor drum 3 are sequentially transferred and superimposed to form a color toner image on the surface of the intermediate transfer belt 71. The cleaning device 9 removes and collects waste toner that remains on the surface of the intermediate transfer belt 71 without being transferred to the paper.

[0027] The secondary transfer device 11 traps the paper that has been transported through the paper transport path 21 in the transfer nip section TN between the secondary transfer roller 11a and the intermediate transfer belt 71. As the paper passes through the transfer nip section TN, the toner image on the surface of the intermediate transfer belt 71 is transferred to the paper and it is then transported to the fuser device 1.

[0028] The fixing device 1 includes a fixing belt 31 that rotates around an axis and a pressure roller 32 (an example of a pressure member). The fixing device 1 performs a fixing operation in which the paper on which the toner image has been transferred is sandwiched in the nip portion N between the fixing belt 31 and the pressure roller 32, and heated and pressurized to fix the toner image to the paper. Although not shown in Figure 1, the fixing device 1 also has components other than the fixing belt 31 and the pressure roller 32. Details of this fixing device 1 will be described later.

[0029] The paper feeding unit 18 is equipped with a paper feeding cassette for loading recording media (paper) used for image formation and is located below the optical scanning device 12. The paper is pulled out of the paper feeding unit 18 by the pickup roller 16 and transported to the paper transport path 21. The paper transported to the paper transport path 21 passes through the secondary transfer device 11 and the fuser device 1, and is then discharged to the output tray 19 by the discharge roller 17.

[0030] The paper transport path 21 is equipped with a transport roller 13, a registration roller 14, and an ejection roller 17. The transport roller 13 facilitates the transport of the paper. The registration roller 14 transports the paper at a speed equal to the process speed at which the image is formed on the paper. This registration roller 14 is located between the paper feed unit 18 and the secondary transfer device 11 and adjusts the timing of the paper transport so that the toner image is transferred to the paper by the secondary transfer device 11. For example, the registration roller 14 holds the paper transported from the paper feed unit 18 and waits (stops temporarily), then starts transporting the paper at a constant speed in synchronization with the secondary transfer device 11.

[0031] When image formation is to be performed on the back side of the paper as well as the front side, the paper transport direction is changed by the discharge roller 17 and the paper is transported to the inversion transport path 22. In the inversion transport path 22, the paper is guided to the registration roller 14 with its front and back sides reversed by the inversion transport roller 15. The image forming apparatus 100 forms an image on the back side of the paper guided to the registration roller 14 in the same way as the front side and discharges it to the output tray 19.

[0032] Figure 2 is a schematic cross-sectional view showing the configuration of a fixing device according to an embodiment of the present disclosure.

[0033] The fixing device 1 includes a fixing belt 31 and a pressure roller 32. As shown in Figure 2, the fixing device 1 further includes a support member 33, a fixing pad 34, a sliding sheet 35, a heating unit 36, and a reflector plate 37 inside the fixing belt 31. The fixing device 1 also includes a temperature sensing unit 38 and a release plate 39 outside the fixing belt 31.

[0034] The fixing belt 31 is an endless, flexible belt formed in a substantially annular shape. The fixing belt 31 has a structure in which a release layer is provided on the surface of a strip-shaped base material made of, for example, a synthetic resin such as polyimide or a metal such as nickel. The fixing belt 31 is rotatable about an axis that is perpendicular to the paper surface in Figure 2. The axial direction of the fixing belt 31 is substantially parallel to the width direction of the paper P being conveyed.

[0035] The fixing pad 34 is a long plate extending along the axial direction of the fixing belt 31 and is made of, for example, synthetic resin. A sliding sheet 35 is installed on the outer circumferential surface of the fixing pad 34 (the surface adjacent to the fixing belt 31). The length of the fixing pad 34 is approximately equal to the length of the fixing belt 31 in the width direction. A lubricant retaining part 41 impregnated with lubricant is attached to the fixing pad 34. Specifically, the lubricant retaining part 41 is a sponge-like elastic member impregnated with a lubricant such as silicone oil. Furthermore, since the lubricant such as silicone oil is heated together with the fixing belt, the lubricant retaining part 41 also possesses heat resistance that allows it to maintain its elasticity even when holding the lubricant at the fixing temperature. The structure of the fixing pad 34, including the lubricant retaining part 41, near the fixing belt 31 will be explained later with reference to Figure 3.

[0036] The sliding sheet 35 is provided so as to slide against the inner circumferential surface (inner surface 31a) of the fixing belt 31. The fixing pad 34 is fixed to the fixing belt 31, which performs rotational motion, and the sliding sheet 35 slides against the fixing belt 31.

[0037] The support member 33 is a member that supports the fixing pad 34 and the sliding sheet 35 while pressing them against the inner circumferential surface of the fixing belt 31. The support member 33 has a substantially L-shaped cross-section and includes a long plate-shaped fixing portion 33a to which the fixing pad 34 is fixed, and a long plate-shaped upright portion 33b that is erected from the end of the fixing portion 33a.

[0038] The heating unit 36 ​​is a component that heats the fixing belt 31 and is installed to extend along the axial direction of the fixing belt 31. The heating unit 36 ​​is, for example, a lamp heater such as a halogen lamp. In this embodiment, the heating unit 36 ​​includes a main lamp 36a that heats the central part of the fixing belt 31 in the width direction and sub-lamps 36b that heat both ends of the fixing belt 31 in the width direction. The operation of the main lamp 36a and sub-lamps 36b is determined according to the size of the paper P, etc. The fixing belt 31 is heated to, for example, 130°C to 180°C by these main lamps 36a and sub-lamps 36b.

[0039] The reflector 37 is thin and plate-like, and is positioned to cover the side of the support member 33 facing the heating section 36. The fixing belt 31 is configured to be efficiently heated by this reflector 37.

[0040] The pressure roller 32 is positioned opposite the fixing pad 34, with the fixing belt 31 in between. The pressure roller 32 rotates around an axis of rotation parallel to the axial direction of the fixing belt 31 and is positioned to extend approximately parallel to the fixing belt 31. At the nip portion N between the pressure roller 32 and the fixing belt 31, the fixing pad 34 presses the fixing belt 31 against the pressure roller 32. The pressure roller 32 is constructed by covering the surface of a cylindrical core material, for example, made of a metal such as aluminum, with an elastic material such as rubber.

[0041] The pressure roller 32 receives a driving force from a drive source such as a motor (not shown) via gears or the like. The pressure roller 32 rotates in response to this driving force, and the fixing belt 31 rotates in the opposite direction to the rotation of the pressure roller 32 as it rotates. The paper P passes through the nip section N between the pressure roller 32 and the fixing belt 31 along the conveying direction S.

[0042] The pressure roller 32 has its rotation axis (pressure axis 32a) supported by the pressure adjustment unit 50 and is configured to move in a direction away from the nip portion N (pressure direction D). In this embodiment, the pressure applied by the pressure roller 32 to the fixing belt 31 is adjusted by moving the pressure roller 32 using the pressure adjustment unit 50.

[0043] The temperature sensing unit 38 detects the fixing temperature, which is the surface temperature of the fixing belt 31. The fixing temperature may be measured at multiple locations; for example, it may be measured at the center of the fixing belt 31 in the width direction and at the ends of the fixing belt 31 in the width direction. The release plate 39 is positioned downstream of the nip portion N in the transport direction S to prevent the paper P from wrapping around the fixing belt 31.

[0044] The fixing device 1 is equipped with a torque detection unit that detects the driving torque of the fixing belt 31. The torque detection unit is connected, for example, to the drive source of the pressure roller 32 and receives signals such as voltage related to the driving force, and estimates the driving torque from the strength of the signal.

[0045] Figure 3 is a schematic side view showing an enlarged view of the vicinity of the nip portion of the fixing device during the supply operation, and Figure 4 is a schematic side view showing an enlarged view of the vicinity of the nip portion of the fixing device during the retrieval operation.

[0046] The lubricant holding portion 41 described above is attached to the inner surface 31a side of the fixing pad 34 via a sealing member 43. The sealing member 43 is made of a material that does not allow liquids such as lubricants to penetrate, preventing the lubricant impregnated in the lubricant holding portion 41 from leaking to the fixing pad 34 side.

[0047] The surface of the lubricant holding portion 41 is covered by a sliding sheet 35 via a protective film 42. The protective film 42 is made of a porous material, and the sliding sheet 35 is mesh in shape, formed into a sheet by weaving fibers together. In other words, the lubricant moves back and forth between the lubricant holding portion 41 and the inner surface 31a of the belt through the protective film 42 and the sliding sheet 35.

[0048] Figure 3 shows the state in which the pressure roller 32 is pressed against the fixing belt 31 with a strong pressure (first pressure F1). In this state, the first pressure F1 from the pressure roller 32 deforms the lubricant holding portion 41, reducing the lubricant holding space within the lubricant holding portion 41. As a result, as indicated by arrow G1, the impregnated lubricant seeps out, and a supply operation is performed to supply lubricant to the inner surface 31a of the belt.

[0049] Figure 4 shows the state in which the pressure roller 32 is in contact with the fixing belt 31 under a second pressure F2 which is weaker than the first pressure F1. In this state, the load is such that the lubricant holding part 41 does not deform, so the lubricant holding space within the lubricant holding part 41 is restored. Then the lubricant holding part 41 functions to absorb lubricant from its surroundings. As a result, as indicated by arrow G2, a recovery operation is performed in which lubricant is recovered from the inner surface 31a of the belt through the protective film 42 and the sliding sheet 35.

[0050] In this way, by applying lubricant to the inner surface 31a of the belt, the sliding resistance between the fixing belt 31 and the fixing pad 34 (sliding sheet 35) is reduced, allowing the fixing belt 31 to rotate smoothly. In addition, by adjusting the pressure applied by the pressure roller 32 and recovering the lubricant from the nip portion N, leakage of the lubricant can be suppressed.

[0051] During the supply operation, it is preferable to rotate the fixing belt 31 while applying pressure with the pressure roller 32. Furthermore, it is preferable to perform the supply operation before the fixing belt 31 performs the fixing operation. By supplying the lubricant while the fixing belt 31 is rotating in this way, the lubricant can be distributed throughout the entire inner surface 31a of the belt. In addition, by performing the supply operation in advance, the fixing belt 31 can be rotated smoothly during the fixing operation.

[0052] During the recovery operation, it is preferable to rotate the fixing belt 31 while reducing the pressure of the pressure roller 32. Furthermore, it is preferable to perform the recovery operation after the fixing belt 31 has performed the fixing operation. By recovering the lubricant while the fixing belt 31 is rotating in this way, leakage of lubricant can be suppressed across the entire inner surface 31a of the belt. In addition, by performing the recovery operation after the fixing operation, excess lubricant can be wiped away.

[0053] The supply and retrieval operations may be performed at times other than those described above, depending on the detection results of the temperature detection unit 38 and the torque detection unit. For example, a threshold can be set in advance for the drive torque, and the supply operation can be performed when the drive torque exceeds the threshold. In this way, by performing the supply operation when the drive torque increases due to an increase in frictional force, the fixing belt 31 can be rotated smoothly. Alternatively, a threshold can be set in advance for the temperature of the fixing belt 31, and the supply operation can be performed when the temperature of the fixing belt 31 exceeds the threshold. For the fixing belt 31, not only the local temperature but also the temperature distribution in the axial direction may be considered, and the temperature difference between the center and the end in the axial direction may be calculated and it may be determined whether the temperature difference exceeds the threshold. In this way, by performing the supply operation when the fixing belt 31 becomes hot, the temperature rise can be suppressed.

[0054] Furthermore, the embodiments disclosed herein are illustrative in all respects and do not constitute a limiting interpretation. Accordingly, the technical scope of this disclosure is not to be interpreted solely by the embodiments described above, but is defined based on the claims. This includes all modifications within the meaning and scope of equivalents to the claims. [Explanation of symbols]

[0055] 1. Fixing device 31 Fixing belt 32 Pressure roller (an example of a pressure component) 34 Fixing Pads 35 Sliding Seat 38 Temperature detection unit 41 Lubricant holding section 50 Pressure adjustment section

Claims

1. An endless fixing belt, A pressurizing member that applies pressure from the outside of the aforementioned fixing belt, The pressurizing member includes a pressure adjustment unit that adjusts the pressure applied to the fixing belt, A fixing pad provided on the inside of the fixing belt, which together with the pressurizing member forms a nip portion, A fixing device having a lubricant-impregnated lubricant-holding portion attached to the fixing pad, The lubricant holding unit performs a supply operation to supply lubricant to the inner surface of the fixing belt and a recovery operation to recover lubricant from the inner surface of the fixing belt in accordance with the pressure applied by the pressurizing member. A fixing device characterized by the following.

2. A fixing device according to claim 1, During the aforementioned supply operation, the fixing belt is rotated while applying pressure with the pressurizing member. A fixing device characterized by the following.

3. A fixing device according to claim 2, The supply operation is performed before the fixing belt performs the fixing operation. A fixing device characterized by the following.

4. A fixing device according to claim 1, During the aforementioned retrieval operation, the fixing belt is rotated while the pressure of the pressurizing member is reduced. A fixing device characterized by the following.

5. A fixing device according to claim 4, The fixing belt performs the fixing operation and then performs the retrieval operation. A fixing device characterized by the following.

6. A fixing device according to claim 1, The system includes a torque detection unit that detects the driving torque of the fixing belt, If the aforementioned drive torque exceeds the threshold, the supply operation is performed. A fixing device characterized by the following.

7. A fixing device according to claim 1, The system includes a temperature detection unit for detecting the temperature of the fixing belt, If the temperature of the fixing belt exceeds the threshold, the supply operation is performed. A fixing device characterized by the following.

8. An image forming apparatus comprising the fixing device described in claim 1.

Images