Fixing device and image forming apparatus

Abstract

To provide a fixing device that can prevent leakage of lubricant.SOLUTION: A fixing device 1 comprises: an endless fixing belt 31; a pressure roller 32 that applies pressure from the outside of the fixing belt 31; a nip forming member (base 41 and heat exchanger plate 42) that is provided inside the fixing belt 31 and forms a nip part N together with the pressure roller 32; and a slide sheet 50 that is fixed to the nip forming member. The slide sheet 50 is impregnated with lubricant and slides on the inner side of the fixing belt 31. The nip forming member has a plurality of groove parts (upstream side groove part 42a and downstream side groove part 42b) formed at the ends in a conveyance direction S of a sheet P passing through the nip part N.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a fixing device that fixes an image on a sheet of paper and an image forming apparatus. [Background technology]

[0002] Conventionally, fixing devices used in electrophotographic image forming devices such as copiers and printers fix toner images by applying pressure and heat to paper on which an unfixed toner image has been formed. In recent years, fixing devices using an endless fixing belt have been proposed. In such fixing devices, 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. A sliding sheet impregnated with a lubricant is provided in the nip to reduce frictional resistance between the inner surface of the fixing belt and the nip forming member. Instead of providing a sliding sheet, a method has also been proposed in which a sliding coating is directly applied to the surface of the nip forming member (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2020-197669 Summary of the Invention [Problem to be solved by the invention]

[0004] A conventional fixing device includes a rotatable, endless first member, a heat source for heating the first member, a second member disposed outside the first member and facing the first member, a nip forming member disposed inside the first member and forming a nip between the first member and the second member, and a heat equalizing member covering the surface of the nip forming member facing the first member and transferring heat in the longitudinal direction of the first member, wherein a plurality of recesses are formed on the surface of the heat equalizing member facing the inner surface of the first member, and each of the plurality of recesses has a shape that is approximately line-symmetrical with respect to a first center line extending in the longitudinal direction of the heat equalizing member and a second center line in a cross section of the first member in the direction of travel, and a lubricant is applied between the heat equalizing member and the inner surface of the first member.

[0005] In the fixing device described above, the heat equalizing member has recesses formed on the surface facing the nip portion. Therefore, unevenness caused by the recesses can cause variations in pressure on the paper, which can result in a deterioration in image quality.

[0006] The present disclosure has been made to solve the above-mentioned problems, and has an object to provide a fixing device and an image forming apparatus that can suppress leakage of lubricant. [Means for solving the problem]

[0007] The fixing device according to the present disclosure is a fixing device comprising an endless fixing belt, a pressure member that applies pressure from the outside of the fixing belt, a nip forming member that is provided on the inside of the fixing belt and forms a nip portion together with the pressure member, and a sliding sheet fixed to the nip forming member, wherein the sliding sheet is impregnated with a lubricant and slides against the inside of the fixing belt, and the nip forming member has a plurality of grooves formed at its end in the transport direction of paper passing through the nip portion.

[0008] In the fixing device according to the present disclosure, the grooves may be formed at the upstream end and downstream end in the transport direction, outside the nip portion.

[0009] In the fixing device according to the present disclosure, the nip forming member may have a nip surface facing the inside of the fixing belt and a member side surface connected to the edge of the nip surface and extending in a direction away from the fixing belt, and the groove portion may be configured to be formed across the nip surface and the member side surface.

[0010] In the fixing device according to the present disclosure, the nip forming member may be configured to include a base and a heat transfer plate covering a surface of the base.

[0011] In the fixing device according to the present disclosure, the groove may be formed by cutting out a part of the heat transfer plate.

[0012] In the fixing device according to the present disclosure, the groove may be formed by recessing the heat transfer plate.

[0013] In the fixing device according to the present disclosure, the groove may extend along the transport direction.

[0014] In the fixing device according to the present disclosure, the groove may extend so as to be inclined with respect to the transport direction.

[0015] In the fixing device according to the present disclosure, the plurality of grooves may have the same shape.

[0016] In the fixing device according to the present disclosure, the plurality of grooves may have different shapes.

[0017] The image forming apparatus according to the present disclosure is characterized by including the fixing device according to the present disclosure. [Effects of the Invention]

[0018] According to the present disclosure, leakage of the lubricant can be suppressed by retaining the lubricant that flows out under pressure in the groove portion. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a schematic cross-sectional view showing a configuration of an image forming apparatus according to a first embodiment of the present disclosure. [Figure 2] 1 is a schematic cross-sectional view showing a configuration of a fixing device according to a first embodiment of the present disclosure. [Figure 3] FIG. 2 is a perspective view showing a nip forming member attached to a support member. [Figure 4] FIG. 4 is a front view showing a nip forming member attached to a support member. [Figure 5] FIG. 10 is a schematic side view showing the upstream side of a heat transfer plate in a second embodiment of the present disclosure. [Figure 6] FIG. 10 is a schematic side view showing the downstream side of a heat transfer plate in a second embodiment of the present disclosure. [Figure 7] FIG. 10 is a schematic bottom view showing a nip surface of a heat transfer plate in a second embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0020] (First embodiment) Hereinafter, a fixing device and an image forming apparatus according to a first embodiment of the present disclosure will be described with reference to the drawings.

[0021] FIG. 1 is a schematic cross-sectional view showing the configuration of an image forming apparatus according to a first embodiment of the present disclosure.

[0022] The image forming device 100 is a multifunction 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 an external device, and forms an image of a document read by the image reading device 130 or an image received from an external device in color or monochrome on a recording medium such as paper.

[0023] An original transport device 110 that is supported so as to be able to open and close freely is provided above the image reading device 130. The original transport device 110 transports one or more originals one by one. The image reading device 130 scans a scanning optical system 130b to read an original placed on an original placement table 130a, or reads an original transported by the original transport device 110 to generate image data.

[0024] The image forming apparatus 100 includes 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, and a paper feed section 18.

[0025] Image forming apparatus 100 handles image data corresponding to color images using black (K), cyan (C), magenta (M), and yellow (Y), or monochrome images using a single color (e.g., black). Image forming apparatus 100 is provided with four developing devices 2, four photosensitive drums 3, four drum cleaning devices 4, and four chargers 5 for forming four types of toner images, and four image stations Pa, Pb, Pc, and Pd are configured corresponding to black, cyan, magenta, and yellow, respectively.

[0026] The charger 5 uniformly charges the surface of the photosensitive drum 3 to a predetermined potential. The optical scanning device 12 exposes the surface of the photosensitive drum 3 to light 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 collects residual toner on the surface of the photosensitive drum 3. Through the series of operations described above, a toner image of each color is formed on the surface of each photosensitive drum 3.

[0027] The intermediate transfer belt device 7 includes an intermediate transfer roller 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 so as to form four types of toner images corresponding to each color. The intermediate transfer rollers 6 transfer the toner images of each color formed on the surface of the photosensitive drum 3 onto the intermediate transfer belt 71, which moves around in a circular motion.

[0028] The intermediate transfer belt 71 is stretched over an intermediate transfer drive roller 72 and an intermediate transfer driven roller 73. In the image forming apparatus 100, the toner images of each color formed on the surface of each photosensitive 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 remaining on the surface of the intermediate transfer belt 71 without being transferred to paper.

[0029] The secondary transfer device 11 sandwiches and transports a sheet of paper transported through the paper transport path 21 in the transfer nip portion TN between the secondary transfer roller 11a and the intermediate transfer belt 71. When the sheet of paper passes through the transfer nip portion TN, the toner image on the surface of the intermediate transfer belt 71 is transferred onto the sheet of paper, and the sheet of paper is transported to the fixing device 1.

[0030] 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 sandwiches a sheet of paper onto which a toner image has been transferred in a nip portion N between the fixing belt 31 and the pressure roller 32, and applies heat and pressure to fix the toner image to the sheet. Although not shown in FIG. 1, the fixing device 1 also includes components other than the fixing belt 31 and the pressure roller 32, and details of the fixing device 1 will be described later with reference to FIG. 2.

[0031] The paper feed unit 18 includes a paper feed cassette that holds recording media (paper) used for image formation, and is provided below the optical scanning device 12. The paper is pulled out of the paper feed unit 18 by a pickup roller 16 and transported to a paper transport path 21. The paper transported to the paper transport path 21 passes through the secondary transfer device 11 and the fixing device 1, and is then discharged to a paper output tray 19 by a discharge roller 17.

[0032] Conveyance rollers 13, registration rollers 14, and discharge rollers 17 are arranged on paper conveyance path 21. Conveyance rollers 13 facilitate the conveyance of paper. Registration rollers 14 convey paper at a speed equal to the process speed at which an image is formed on the paper. Registration rollers 14 are provided between paper feed unit 18 and secondary transfer device 11, and adjust the timing of paper conveyance so that the toner image is transferred to the paper by secondary transfer device 11. For example, registration rollers 14 wait (temporarily stop) while clamping paper conveyed from paper feed unit 18, and then start conveying the paper at a constant speed in synchronization with secondary transfer device 11.

[0033] When an image is to be formed on the back side of the paper in addition to the front side, the conveying direction of the paper is changed by discharge rollers 17, and the paper is conveyed to reversing conveying path 22. In reversing conveying path 22, the paper is guided up to registration rollers 14 in a reversed state by reversing conveying rollers 15. Image forming apparatus 100 forms an image on the back side of the paper guided to registration rollers 14 in the same manner as on the front side, and discharges the paper to discharge tray 19.

[0034] 2 is a schematic cross-sectional view showing the configuration of the fixing device according to the first embodiment of the present disclosure. Note that in FIG. 2, the portions of heat transfer plate 42 other than the grooves are hatched to emphasize the difference between the grooves and the portions other than the grooves.

[0035] The fixing device 1 includes a fixing belt 31 and a pressure roller 32. As shown in Fig. 2, the fixing device 1 further includes, inside the fixing belt 31, a support member 33, a nip forming member (a base 41 and a heat transfer plate 42), a sliding sheet 50, a heating unit 36, and a reflecting plate 37. The fixing device 1 also includes, outside the fixing belt 31, a fixing temperature sensor 38 and a peeling plate 39.

[0036] The fixing belt 31 is an endless flexible belt formed in a substantially circular shape. The fixing belt 31 has a configuration in which a release layer is provided on the surface of a band-shaped base material formed of, for example, a synthetic resin such as polyimide or a metal such as nickel. The fixing belt 31 is provided so as to be rotatable about an axis that is perpendicular to the plane of the paper in FIG. 2. The axis direction of the fixing belt 31 is substantially parallel to the width direction W (see FIG. 3, described later) of the paper P being transported.

[0037] The nip forming member is formed of a base 41 and a heat transfer plate 42 covering the surface of the base 41. The base 41 is a long plate extending along the axial direction of the fixing belt 31 and is formed of, for example, synthetic resin. The heat transfer plate 42 is formed of, for example, metal and transfers heat evenly throughout the entire heat transfer plate 42. Because the nip forming member is thus formed of multiple components, different materials can be used to obtain thermal conductivity suitable for fixing. The length of the nip forming member is approximately equal to the length of the fixing belt 31 in the width direction W. The heat transfer plate 42 has grooves (upstream groove 42a and downstream groove 42b) cut out at its upstream and downstream ends in the conveyance direction S of the paper P. The detailed structure of the nip forming member will be described later with reference to Figures 3 and 4.

[0038] Sliding sheet 50 is fixed so as to cover the surface of the nip forming member (particularly heat transfer plate 42), and is provided so as to be in sliding contact with the inner peripheral surface of fixing belt 31. The nip forming member is fixed to fixing belt 31, which rotates, and sliding sheet 50 slides against fixing belt 31. Sliding sheet 50 is impregnated with a lubricant to reduce the frictional force with fixing belt 31.

[0039] Support member 33 is a member that supports nip forming member and sliding sheet 50 while pressing them against the inner circumferential surface of fixing belt 31. Support member 33 has a substantially L-shaped cross section and has long plate-shaped fixing portion 33a to which the nip forming member is fixed, and long plate-shaped standing portion 33b that stands upright from the end of fixing portion 33a.

[0040] The heating unit 36 ​​is a member that heats the fixing belt 31, and is installed so as to extend along the axial direction of the fixing belt 31 (the width direction W described below). 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 center of the fixing belt 31 in the width direction W, and sub-lamps 36b that heat both end portions of the fixing belt 31 in the width direction W. The operation of each of the main lamp 36a and the sub-lamp 36b is determined depending on the size of the paper P, etc. The fixing belt 31 is heated by the main lamp 36a and the sub-lamp 36b to, for example, 130°C to 180°C.

[0041] The reflecting plate 37 is a thin plate and is disposed so as to cover the surface of the supporting member 33 on the heating unit 36 ​​side. The fixing belt 31 is configured to be heated efficiently by the reflecting plate 37.

[0042] The pressure roller 32 is disposed at a position facing the nip forming member with the fixing belt 31 sandwiched therebetween. The pressure roller 32 rotates about a rotation axis parallel to the axial direction of the fixing belt 31 and is disposed so as to extend substantially parallel to the fixing belt 31. At the nip N between the pressure roller 32 and the fixing belt 31, the fixing belt 31 is pressed against the pressure roller 32 by the nip forming member. The pressure roller 32 is configured, for example, by covering the surface of a cylindrical core material formed from a metal such as aluminum with an elastic material such as rubber.

[0043] A driving force from a driving source such as a motor (not shown) is transmitted to the pressure roller 32 via gears, etc. The pressure roller 32 receives this driving force and is driven to rotate, and as the pressure roller 32 is driven to rotate, the fixing belt 31 is driven to rotate in the direction opposite to the rotation direction of the pressure roller 32. The paper P passes through the nip portion N between the pressure roller 32 and the fixing belt 31 along the conveying direction S.

[0044] The fixing temperature sensor 38 detects the fixing temperature, which is the surface temperature of the fixing belt 31. The peeling plate 39 is disposed downstream of the nip portion N in the conveying direction S, and prevents the paper P from wrapping around the fixing belt 31.

[0045] In this embodiment, a configuration is shown in which a heating section 36 is provided as a heat source, but this is not limited to this. For example, instead of the heating section 36, a configuration may be used in which a heat source such as a heater is housed within the base 41 of the nip forming member.

[0046] FIG. 3 is a perspective view showing the nip forming member attached to the support member, and FIG. 4 is a front view showing the nip forming member attached to the support member.

[0047] 3 and 4 show the nip forming member attached to support member 33 with sliding sheet 50 removed. The nip forming member has nip surface 42c facing the inside of fixing belt 31 and a member side surface that is connected to the edge of nip surface 42c and extends in a direction away from fixing belt 31. In other words, nip surface 42c is the surface that is pressed against the inner circumferential surface of fixing belt 31 via sliding sheet 50, and the member side surface is a side surface that extends along the longitudinal direction (width direction W) of the nip forming member. Note that with regard to the member side surfaces, one provided on the upstream side in conveyance direction S may be referred to as upstream side surface 42d, and the other provided on the downstream side in conveyance direction S may be referred to as downstream side surface 42e.

[0048] The heat transfer plate 42 has a cross section shaped like a square bracket, and its surface corresponds to the nip surface 42c and the side surface of the component. The heat transfer plate 42 is partially cut out to straddle the nip surface 42c and the side surface of the component, forming an upstream groove 42a and a downstream groove 42b. The upstream groove 42a and the downstream groove 42b extend in the conveying direction S (the vertical direction in FIG. 4 ), a direction perpendicular to the width direction W. Specifically, the upstream groove 42a originates at the upstream end of the nip surface 42c, passes through the seam between the nip surface 42c and the upstream side surface 42d, and extends to the edge of the upstream side surface 42d. Similarly, the downstream groove 42b originates at the downstream end of the nip surface 42c, passes through the seam between the nip surface 42c and the downstream side surface 42e, and extends to the edge of the downstream side surface 42e. The starting points of upstream groove 42a and downstream groove 42b are located outside nip N, and upstream groove 42a and downstream groove 42b are each formed outside nip N. In this way, the grooves are formed to avoid nip N, which applies pressure to the paper, thereby preventing image quality from deteriorating due to unevenness in the grooves.

[0049] The upstream grooves 42a and downstream grooves 42b are spaced apart in the width direction W and arranged in a row. The widths of the upstream grooves 42a and downstream grooves 42b are, for example, approximately 1 to 2 mm. In this embodiment, the multiple grooves have the same shape, and are identical in length from the edge of the nip surface 42c to the starting point, width in the width direction W, and so on. By making the shapes of the multiple grooves uniform in this way, it is possible to suppress variations between locations.

[0050] When the sliding sheet 50 is attached to the nip forming member, the upstream groove 42a and the downstream groove 42b are covered by the sliding sheet 50, forming long, narrow gaps. The sliding sheet 50 is impregnated with lubricant to reduce friction with the fixing belt 31. However, when the sliding sheet 50 is crushed by the pressure from the pressure roller 32, it is no longer able to retain the lubricant, resulting in some of the lubricant leaking out. In this case, the grooves provide gaps that can retain the lubricant leaked under pressure and prevent leakage. Because pressure is applied to the sliding sheet 50 in the conveyance direction S, providing grooves extending in the same direction can efficiently store the lubricant. Furthermore, providing as long a groove as possible can efficiently store a large amount of lubricant. Furthermore, designing the grooves with an appropriate shape can induce capillary action, efficiently capturing the leaked lubricant. Over time, the lubricant captured in the grooves is resupplied to the sliding sheet 50 that covers the surface.

[0051] (Second embodiment) Next, an image forming apparatus according to a second embodiment of the present disclosure will be described with reference to the drawings.

[0052] In the second embodiment, the shape of the groove is different from that in the first embodiment. Note that the second embodiment has substantially the same configuration as the first embodiment shown in Figures 1 to 4, so a description thereof will be omitted and only the differences will be described.

[0053] Figure 5 is a schematic side view showing the upstream side of a heat transfer plate in the second embodiment of the present disclosure, Figure 6 is a schematic side view showing the downstream side of a heat transfer plate in the second embodiment of the present disclosure, and Figure 7 is a schematic bottom view showing the nip surface of the heat transfer plate in the second embodiment of the present disclosure.

[0054] In the second embodiment, the grooves extend at an angle relative to the conveyance direction S (the vertical direction in FIG. 7 ) and perpendicular to the width direction W. Specifically, the upstream groove 42a has an upstream end of the nip surface 42c that starts near the center in the width direction W and extends at an angle toward the outside in the width direction W at the edge of the upstream side surface 42d. The downstream groove 42b is inclined in the opposite direction to the upstream groove 42a, has an downstream end of the nip surface 42c that starts near the outside in the width direction W, and extends at an angle toward the center in the width direction W at the edge of the downstream side surface 42e. In other words, the grooves extend at an angle such that the starting point on the nip surface 42c and the ending point on the side surface of the member are offset in the width direction W. By inclining the grooves in this way, the lubricant can be directed to the intended location.

[0055] In the present embodiment, the grooves are formed by cutting out a part of the heat transfer plate 42, but the present invention is not limited to this and the grooves may be formed by recessing the surface of the heat transfer plate 42 that contacts the sliding sheet 50. Furthermore, in addition to cutting out the heat transfer plate 42, the surface of the base 41 may be recessed to form a groove that combines the heat transfer plate 42 and the base 41.

[0056] Although the multiple grooves have the same shape in the illustrated example, the present invention is not limited to this and the multiple grooves may have different shapes. The multiple grooves may have different lengths from the edges of the nip surface 42c to their starting points, different widths in the width direction W, and different depths from the surface, depending on their positions in the width direction W. In this way, by varying the shapes of the multiple grooves, it is possible to appropriately arrange portions that are easy to store lubricant.

[0057] It should be noted that the embodiments disclosed herein are illustrative in all respects and are not intended to be limiting. Naturally, both the first and second embodiments may be included. Therefore, the technical scope of the present disclosure should not be interpreted solely by the above-described embodiments, but should be defined based on the claims. Furthermore, all modifications within the scope and meaning equivalent to the claims are included. [Explanation of symbols]

[0058] 1 Fixing device 31 Fixing belt 32 Pressure roller (an example of a pressure member) 41 Base 42 Heat transfer plate 42a Upstream ditch 42b Downstream ditch 42c nip surface 42d Upstream side 42e downstream side 50 Sliding Sheet 100 Image forming device S Conveying direction W width direction

Claims

1. an endless fixing belt; a pressure member that applies pressure to the fixing belt from the outside; a nip forming member provided inside the fixing belt and forming a nip portion together with the pressure member; a sliding sheet fixed to the nip forming member, the sliding sheet is impregnated with a lubricant and slides against the inside of the fixing belt; The nip forming member has a plurality of grooves formed at an end in the conveying direction of the paper passing through the nip portion. A fixing device characterized by:

2. 2. The fixing device according to claim 1, The grooves are formed at the upstream end and downstream end in the transport direction, outside the nip portion. A fixing device characterized by:

3. 2. The fixing device according to claim 1, the nip forming member has a nip surface facing the inside of the fixing belt and a member side surface connected to an edge of the nip surface and extending in a direction away from the fixing belt, The groove is formed across the nip surface and the side surface of the member. A fixing device characterized by:

4. 2. The fixing device according to claim 1, The nip forming member is formed of a base and a heat transfer plate covering the surface of the base. A fixing device characterized by:

5. 5. The fixing device according to claim 4, The groove portion is formed by cutting out a part of the heat transfer plate. A fixing device characterized by:

6. 5. The fixing device according to claim 4, The groove portion is formed by recessing the heat transfer plate. A fixing device characterized by:

7. 2. The fixing device according to claim 1, The groove portion extends along the conveying direction. A fixing device characterized by:

8. 2. The fixing device according to claim 1, The grooves extend so as to be inclined with respect to the conveying direction. A fixing device characterized by:

9. 2. The fixing device according to claim 1, The plurality of grooves have the same shape. A fixing device characterized by:

10. 2. The fixing device according to claim 1, The plurality of grooves have different shapes. A fixing device characterized by:

11. An image forming apparatus comprising the fixing device according to claim 1.

Images