Image forming apparatus

Abstract

The present invention provides a fixing device that can uniformly supply lubricant to the fixing belt and suppress lubricant loss, and an image forming apparatus equipped with the fixing device. [Solution] A fixing device comprising: an endless fixing belt that is rotationally driven; a heating member for heating the fixing belt; a nip forming section that supports the fixing belt from the inner circumference; a pressurizing rotating member that forms a nip section by pressing against the nip forming section via the fixing belt; and a lubricant supply section provided on the nip forming section and supplying a lubricant to the inner circumference of the fixing belt upstream of the nip section in the rotational direction of the fixing belt; and an image forming apparatus equipped with the fixing device.

Description

Technical Field

[0001] The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile apparatus, or a multifunction machine having a plurality of these functions, and a fixing device used in the image forming apparatus.

Background Art

[0002] Some image forming apparatuses such as printers are provided with a fixing device of a pad fixing method in which a fixing pad, which is a non-rotating body disposed on the inner peripheral side of an endless belt that is heated and travels in a loop, is pressed by a pressure roller disposed on the outer peripheral side of the belt via the belt, a nip portion is formed between the belt and the pressure roller, and a recording material is passed through the nip portion to fix an unfixed image on the recording material.

[0003] In such a pad fixing method, since the pressing force generated between the pressure roller and the fixing pad via the belt is large, the frictional resistance between the belt and the fixing pad also increases, and the wear of the inner peripheral surface of the belt tends to progress. Therefore, conventionally, a lubricant has been applied to the inner peripheral surface of the belt to reduce the frictional resistance between the belt and the fixing pad.

[0004] However, since the pressure in the nip portion is high, when the lubricant applied to the inner peripheral surface of the belt tries to pass through the nip portion, it is likely to be divided into the lubricant that can enter between the belt and the fixing pad and the lubricant that flows to the end side in the width direction of the belt (corresponding to the axial direction of the pressure roller) without entering.

[0005] The lubricant that flows to the ends will eventually leak out of the belt from the widthwise edge. The lubricant that leaks to the ends will wrap around the outer surface of the belt and adhere to the recording material, or the lubricant that flows to the outside of the belt will drip into the fuser, resulting in a loss of lubricant and an increase in frictional resistance between the belt and the fixing pad. This increase in frictional resistance may accelerate belt wear, or the torque driving the belt may increase, causing the belt and pressure rollers to not rotate smoothly, potentially leading to poor transport of the recording material.

[0006] Therefore, in the fixing device described in Patent Document 1, a convex portion is provided on the inner circumferential surface of the belt at a position immediately upstream of the nip portion in the belt circumferential direction, which gradually decreases from the end side in the belt width direction toward the center, thereby facilitating the lubricant at the end in the belt width direction toward the center and preventing the lubricant from leaking out from the end of the belt. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2022-187288 [Overview of the project] [Problems that the invention aims to solve]

[0008] The pad convex shape configuration in Patent Document 1 does work to move the lubricant on the inner surface of the belt toward the center relative to the lubricant that has gathered at the belt end, but it is difficult to recover the lubricant that has overflowed onto the belt end. Therefore, it cannot prevent the frictional resistance between the belt and the fixed pad from increasing due to the loss of lubricant.

[0009] Furthermore, the convex shape of the pad makes it easier for lubricant to concentrate in the center of the belt, resulting in less lubricant in the area between the belt edge and the convex surface in the belt width direction compared to the center, causing an uneven distribution of lubricant in the width direction of the nip section.

[0010] Furthermore, in the configuration of Patent Document 1, since the lubricant supply member is located immediately after the exit of the nip section, lubricant will leak out from the belt end into the fuser from the time of lubricant supply until it reaches the nip section, resulting in a loss of lubricant.

[0011] As a result of the above, problems arise such as increased frictional resistance of the belt, leading to faster belt wear, and increased torque driving the belt, which can hinder the smooth rotation of the belt and pressure rollers, causing poor transport of the recording material.

[0012] The present invention has been made in view of the above circumstances, and aims to provide a fixing device that can uniformly supply lubricant to the fixing belt and suppress the loss of lubricant, and an image forming apparatus equipped with the fixing device. [Means for solving the problem]

[0013] To achieve the above objective, the present invention provides a fixing device comprising: an endless fixing belt that is rotationally driven; a heating member for heating the fixing belt; a nip forming section that supports the fixing belt from the inner circumference; a pressurizing rotating member that forms a nip section by pressing against the nip forming section via the fixing belt; and a lubricant supply section provided in the nip forming section and supplying a lubricant to the inner circumference of the fixing belt upstream of the nip section in the rotational direction of the fixing belt; and an image forming apparatus equipped with the fixing device. [Effects of the Invention]

[0014] According to the present invention, it is possible to provide a fixing device that can uniformly supply lubricant to the fixing belt and suppress the loss of lubricant, and an image forming apparatus equipped with the fixing device. [Brief explanation of the drawing]

[0015] [Figure 1] This is a front cross-sectional view of an image forming apparatus according to the first embodiment of the present invention. [Figure 2]This is an enlarged cross-sectional view of a fixing device according to the first embodiment of the present invention. [Figure 3] This is a schematic diagram of the lubricant supply member surrounding the first embodiment of the present invention. [Figure 4] This is a schematic diagram of the lubricant supply member and nip pad according to the first embodiment of the present invention. [Figure 5] This is an enlarged cross-sectional view of a fixing device according to a second embodiment of the present invention. [Modes for carrying out the invention]

[0016] Preferred embodiments of the present invention will be described in detail below with reference to the drawings. Note that the components described in the following embodiments are merely illustrative, and the configuration, function, dimensions, materials, shape, relative arrangement, and other conditions of the apparatus to which the present invention is applied can be modified or changed as appropriate without departing from the spirit of the invention, and the invention is not limited to the following embodiments.

[0017] [First Embodiment] Figure 1 is a front cross-sectional view of an image forming apparatus according to a first embodiment of the present invention.

[0018] In Figure 1, the printer 500, which functions as an image forming apparatus, has four cartridges 7Y, 7M, 7C, and 7K arranged diagonally in an up-and-down direction, which serve as image forming units that sequentially form toner images of four colors: yellow (Y), magenta (M), cyan (C), and black (K). The four cartridges 7Y, 7M, 7C, and 7K are equipped with photoreceptor drum units 26Y, 26M, 26C, and 26K, each containing a photoreceptor drum 1Y, 1M, 1C, and 1K as an electrophotographic photoreceptor, and developing units 4Y, 4M, 4C, and 4K.

[0019] The photoreceptor drums 1Y, 1M, 1C, and 1K are each driven to rotate in the clockwise direction (Q direction) in Figure 1 by a drive member (not shown). Around the photoreceptor drums 1Y, 1M, 1C, and 1K, in order of their rotational direction, are the cleaning members 6Y, 6M, 6C, and 6K, the charging rollers 2Y, 2M, 2C, and 2K, and the developing units 4Y, 4M, 4C, and 4K, respectively.

[0020] The cleaning members 6Y, 6M, 6C, and 6K remove the toner agents remaining on the photosensitive drums 1Y, 1M, 1C, and 1K after transferring the toner images formed on the photosensitive drums 1Y, 1M, 1C, and 1K onto the intermediate transfer film 5. The toner agents removed by the cleaning members 6Y, 6M, 6C, and 6K are recovered in the removed toner chambers within the photosensitive drum units 26Y, 26M, 26C, and 26K.

[0021] Also, the charging rollers 2Y, 2M, 2C, and 2K uniformly charge the surfaces of the photosensitive drums 1Y, 1M, 1C, and 1K, respectively. After the surfaces of the photosensitive drums 1Y, 1M, 1C, and 1K are charged by the charging rollers 2Y, 2M, 2C, and 2K, the surfaces of the photosensitive drums 1Y, 1M, 1C, and 1K are exposed by laser light through the unit openings 32Y, 32M, 32C, and 32K from the scanner unit (exposure means) 3. Thereby, electrostatic latent images are formed on the surfaces of the photosensitive drums 1Y, 1M, 1C, and 1K. In this embodiment, the scanner unit 3 is disposed below the cartridges 7Y, 7M, 7C, and 7K.

[0022] Also, the developing units 4Y, 4M, 4C, and 4K supply toner agents to the electrostatic latent images formed on the photosensitive drums 1Y, 1M, 1C, and 1K, respectively, to develop the electrostatic latent images into toner images. The developing units 4Y, 4M, 4C, and 4K are provided with developing rollers 25Y, 25M, 25C, and 25K that contact the photosensitive drums 1Y, 1M, 1C, and 1K, respectively, to supply toner agents to the surfaces of the photosensitive drums 1Y, 1M, 1C, and 1K, and supply rollers 34Y, 34M, 34C, and 34K that contact the developing rollers 25Y, 25M, 25C, and 25K to supply toner agents to the developing rollers 25Y, 25M, 25C, and 25K.

[0023] When forming an image on the recording paper S as a recording material, the electrostatic latent image formed on the surface of the photoreceptor drums 1Y, 1M, 1C, and 1K by the scanner unit 3 is first developed as a toner image by cartridges 7Y, 7M, 7C, and 7K, and then transferred to the intermediate transfer film 5.

[0024] The intermediate transfer film 5 is stretched over the drive roller 10 and tension roller 11 and driven in the direction of arrow R in Figure 1. Furthermore, primary transfer rollers 12Y, 12M, 12C, and 12K are positioned inside the intermediate transfer film 5, opposite each photoreceptor drum 1Y, 1M, 1C, and 1K, and a transfer bias is applied by a bias application means (not shown).

[0025] For example, when using a negatively charged toner, a positive bias is applied to the primary transfer rollers 12Y, 12M, 12C, and 12K, which sequentially transfers the toner image onto the intermediate transfer film 5. The four superimposed toner images are then transported to the secondary transfer section 15.

[0026] Meanwhile, in synchronization with the image forming operation described above, the recording paper S is fed toward the secondary transfer unit 15 by a transport mechanism consisting of the feeding device 13 and the registration roller pair 17.

[0027] The feeding device 13 includes a feeding cassette 24 for storing multiple sheets of recording paper S, a feeding roller 8 for feeding the recording paper S, and a pair of transport rollers 16 for transporting the fed recording paper S.

[0028] The feed cassette 24 is configured to be detachable from the printer 500. The user removes the feed cassette 24, detaches it from the printer 500, sets the recording paper S in it, and inserts it into the printer 500 to complete the replenishment of the recording paper S. Of the recording paper S stored in the feed cassette 24, the feed roller 8 presses against the topmost sheet of recording paper S, and as the feed roller 8 rotates, the sheets of recording paper S are separated one by one by the separation pad 9 (friction-type separation method) and transported.

[0029] The recording paper S transported from the feeding device 13 is then transported to the secondary transfer unit 15 by the registration roller pair 17. In the secondary transfer unit 15, a positive bias is applied to the secondary transfer roller 18 to transfer the four-color toner images on the intermediate transfer film 5 onto the transported recording paper S. At this time, any toner remaining on the intermediate transfer film 5 after the secondary transfer to the recording paper S is removed by the transfer film cleaning device 23, and the removed toner passes through a waste toner transport path (not shown) and is collected in a waste toner collection container (not shown).

[0030] The recording paper S on which the toner image has been transferred in the secondary transfer unit 15 is transported from the secondary transfer unit 15 to the fixing unit 40, where heat and pressure are applied to the image transferred to the recording paper S to fix the image onto the recording paper S.

[0031] Subsequently, the recording paper S, on which the toner image has been fixed, is ejected into the ejection tray 20 by the ejection roller pair 19.

[0032] Figure 2 is an enlarged cross-sectional view of the fuser unit 40 in Figure 1. Here, in Figure 2, the X-axis and Y-axis directions represent the left-right and up-down directions when viewing the printer 500 from the front, and the Z-axis direction is perpendicular to both the X-axis and Y-axis, and corresponds to the depth direction of the printer 500. Figure 2 is a cross-sectional view when the fuser unit 40 is cut in the XY plane perpendicular to the Z-axis.

[0033] In Figure 2, the fixing device 40 consists of an endless fixing belt 102, a heating roller 104 as a heating member that contacts the inner circumferential surface of the fixing belt 102 and heats the fixing belt 102, a heating heater 107 as a heating source, a nip pad 105 and a pad stay 103 that support the nip pad 105, which are sliding members that support the fixing belt 102 from the inner circumferential side and constitute the nip forming section, a pressure roller 101 as a pressure rotating member that presses the nip pad 105 from the outer circumferential side of the fixing belt 102 to form a nip section, a lubricant supply member 106 provided on the nip pad 105 in the nip forming section and supplies lubricant to the nip section of the nip pad 105 downstream of the heating roller 104 in the rotational direction of the fixing belt 102 and to the inner circumferential side of the fixing belt 102 upstream in the rotational direction of the fixing belt 102, and a restricting member (not shown) that restricts the movement of the fixing belt 102 in the rotational axis direction (Z direction).

[0034] Furthermore, the fixing device 40 conveys the recording paper S while pressurizing and heating it, as the fixing belt 102 rotates in response to the drive from the pressure roller 101.

[0035] The fixing belt 102 is wrapped around the nip pad 105, the heating roller 104, and the lubricant supply member 106, and tension is applied to the heating roller 104 in a direction away from the nip pad 105 by an elastic member such as a spring (not shown).

[0036] The fixing belt 102 is a cylindrical heat-resistant fixing belt that serves as a heating element for transferring heat to the recording paper S. It consists of a base layer made of polyimide, SUS (stainless steel), Ni (nickel) electroformed, etc., on the inside, an elastic layer made of a highly heat-resistant material such as silicone rubber or fluororubber, and a release layer with release properties such as a fluorine tube or fluorine coating, which are laminated in this order.

[0037] The pressure roller 101, which serves as a pressurizing component, is composed of a metal core and a heat-resistant and elastic material layer, such as silicone rubber, fluororubber, or fluororesin, which is molded and coated concentrically around the core in a roller shape, with a release layer provided on the surface. For example, the release layer can be made of a material with good release properties and heat resistance, such as fluororesin, silicone resin, fluorosilicone rubber, fluororubber, silicone rubber, PFA, PTFE, or FEP. The pressure roller 101 is driven by a fuser motor 108 installed inside the printer 500, causing the fuser belt 102 to rotate in a driven manner relative to the pressure roller 101.

[0038] The heating roller 104 consists of a cylindrical roller made of metal such as aluminum or stainless steel, with its axis of rotation parallel to the Z-axis direction in Figure 2, and both axial ends of the heating roller 104 are rotatably supported by a frame (not shown). The outer diameter of the heating roller 104 is arbitrary, but a heating heater 107, which serves as a heat source, is inserted into the space inside the cylindrical roller, and it is desirable to make the inner surface of the cylindrical roller black so that heat transfer from the heater to the cylindrical roller is efficient.

[0039] The heating element 107 (a halogen heater in this embodiment) is a heating means (heat source). The heating element 107 is a long halogen heater that runs along the axial direction of the heating roller 104 and is inserted into and supported within the inner space of the cylindrical heating roller 104. The heating element 107 applies heat generated by power supplied from a power source (not shown) to the heating roller 104. Note that the heating element 107 is not limited to heating by the heat of a halogen heater. For example, it can also be a heater of another type, such as an infrared heater or an electric heating wire.

[0040] The lubricant supply member 106 can be made of fibrous material such as aramid fibers or fluorine fibers, or a porous, elastically deformable elastic body such as silicone sponge. As the lubricant to be impregnated, a heat-resistant silicone-based or fluorine-based lubricant is preferable, but other materials, such as fluorine grease, may also be used. By using a grease with high viscosity and containing solid components, the grease is more likely to remain between the fixing belt 102 and the nip pad 105 in the fixing nip, thereby suppressing wear for a longer period of time.

[0041] The nip pad 105 is a heat-resistant and heat-insulating component whose longitudinal side is perpendicular to the transport direction of the recording paper S. It is made of insulating and heat-resistant materials such as phenolic resin, polyimide resin, polyamide resin, polyamide-imide resin, PEEK resin, PES resin, PPS resin, PFA resin, PTFE resin, and LCP resin. It serves to back up the fixing belt 102, pressurize the fixing nip section formed by pressure contact between the pressure roller 101 and the fixing belt 102, and ensure transport stability when the fixing belt 102 rotates.

[0042] Furthermore, on the sliding surface side of the nip portion of the nip pad 105 that is upstream of the fixing belt 102 in the rotational direction of the fixing belt 102, a groove 105a, as shown in Figure 3(B), is formed along the longitudinal direction of the nip pad 105 (the width direction of the fixing belt 102 which is perpendicular to the rotational direction of the fixing belt 102) to hold the lubricant supply member 106, and the lubricant supply member 106 is held in this groove 105a. The lubricant supply member 106 is held in the groove 105a of the nip pad 105 so as not to shift or fall off due to fitting or attachment with adhesive, etc.

[0043] Figure 3 is a schematic diagram of the lubricant supply member 106, showing the positional relationship between the lubricant supply member 106, the nip pad 105, and the fixing belt 102 in a direction perpendicular to the recording paper transport direction (Z direction). Figure 3(A) is a front view of the lubricant supply member 106, and Figure 3(B) is a cross-sectional view AA of Figure 3(A).

[0044] Here, a tilt-restricting member (not shown) is provided at both ends of the fixing belt 102 on the rotational trajectory of the fixing belt 102, restricting the tilt of the fixing belt 102 in the Z direction.

[0045] In Figure 3(A), in order for the lubricant supply member 106 to collect the lubricant that has leaked out to the end of the anchoring belt 102, the distance L2 from the center in the width direction of the anchoring belt 102 to the end of the width direction on the lubricant supply member 106 is configured to be longer than the distance L1 from the center in the width direction perpendicular to the rotation direction of the anchoring belt 102 to the end of the width direction.

[0046] Furthermore, when the opposite ends are designated as L1' and L2', the structure is similarly configured so that L2' is longer than L1'.

[0047] Furthermore, as shown in Figure 3(B), the lubricant supply member 106 is always in contact with the inner circumferential surface of the anchoring belt 102 in the region including the width direction perpendicular to the rotation direction of the anchoring belt 102. Therefore, even if the lubricant is biased in the longitudinal direction within the suspension range of the anchoring belt 102, it is smoothed out after passing through the lubricant supply member 106, and a stable and even supply of lubricant is provided to the anchoring nip.

[0048] Figure 4 is a schematic diagram of the lubricant supply member 106 and nip pad 105 when the anchoring belt 102 is not suspended. Figure 4(A) is a front view of the lubricant supply member 106, and Figure 4(B) is a cross-section of Figure 4(A) in the direction (Y direction) when the lubricant supply member 106 is in contact with the anchoring belt 102.

[0049] As shown in Figure 4(B), by making the height H2 in the Y direction of the lubricant supply member 106 higher than the height H1 in the Y direction of the groove of the nip pad 105, when the fixing belt 102 is suspended, the belt contact area of ​​the elastic lubricant supply member 106 is compressed and contacts the inner surface of the fixing belt 102 in a press position, and the lubricant accumulated in the fibrous or porous elastic material is supplied to the downstream side in the rotational direction of the fixing belt 102 from the sliding part between the fixing belt 102 and the lubricant supply member 106.

[0050] At the outer edges of the widthwise ends of the fixing belt 102 (outside L1 and L1' in Figure 3(A)), the lubricant supply member 106 is exposed to the outer circumference of the fixing belt 102 by elastic force, thereby recovering the lubricant that has leaked out from the widthwise ends of the fixing belt 102. This prevents the lubricant that has leaked out to the outer edges of the widthwise ends of the fixing belt 102 from leaking into the fixing device, thereby minimizing lubricant loss.

[0051] [Second Embodiment] Next, a second embodiment of the present invention will be described with reference to Figure 5. Since the basic configuration and operation of this embodiment are the same as those of the first embodiment, the same components as in the first embodiment are denoted by the same reference numerals.

[0052] Figure 5 is an enlarged cross-sectional view of the fixing device 40.

[0053] In Figure 5, the fixing device 40 consists of an endless fixing belt 102, a heating heater 107 for heating the fixing belt 102, a nip pad 105 that holds the heating heater 107 and guides the fixing belt 102 to the fixing nip portion, a pad stay 103 that forms a nip-forming portion together with the nip pad 105 and supports a restricting member that restricts the movement of the nip pad 105 and the fixing belt 102 in the rotation axis direction (Z direction), a pressure roller 101 that presses the nip pad 105 from the outer circumference side of the fixing belt 102 to form a nip portion, and a lubricant supply member 106 that is held by the nip pad 105 and supplies lubricant to the inner circumference side of the fixing belt 102 on the upstream side of the rotation direction of the fixing belt 102 relative to the nip portion of the nip pad 105.

[0054] Furthermore, the fixing device 40 conveys the recording paper S while pressurizing and heating it, as the fixing belt 102 rotates in response to the drive from the pressure roller 101.

[0055] The heating element 107 (a ceramic heater in this embodiment) is a heating means (heat source). The heating element 107 basically consists of an elongated thin ceramic substrate and an electrically conductive heat-generating resistor layer provided on this substrate. It is a low-heat-capacity heater that heats up with a steep rise characteristic overall when power is supplied to the heating element from the printer body. The heater shape used in this embodiment is a rectangle in which the end face in the short direction is perpendicular to the end face in the long direction.

[0056] According to the configuration of the fixing device in the first and second embodiments described above, lubricant that is biased towards the end of the fixing belt can be recovered and supplied into the fixing device without leaking out.

[0057] Furthermore, by configuring a lubricant supply member to supply lubricant immediately before the nip section, it becomes possible to supply lubricant almost uniformly without bias in the direction of the nip section, thereby preventing increased frictional resistance at the nip section and stabilizing sheet conveying performance. [Explanation of symbols]

[0058] 40… Fixing device 101... Compression roller 102... Fixing belt 103... Pad Stay 104...Heating roller 105...Nipple pads 106... Lubricant supply component 107... Heating heater 108...Fuser motor 500... Printer S... Record sheet

Claims

1. A rotationally driven endless fixing belt, A heating member for heating the fixing belt, A nip-forming portion that supports the fixing belt from the inner circumference, A pressurizing rotating member that forms the nip portion by pressing it against the nip-forming portion via the fixing belt, A lubricant supply unit is provided in the nip-forming portion and is located upstream of the nip portion in the rotational direction of the fixing belt, supplying lubricant to the inner circumference of the fixing belt, A fixing device characterized by having the following features.

2. The fixing device according to claim 1, characterized in that the lubricant supply unit is held in the nip forming unit so as to be in pressure contact with the inner circumferential surface of the fixing belt.

3. The nip-forming member has a groove formed along the width direction of the fixing belt, which is perpendicular to the rotation direction of the fixing belt. The fixing device according to claim 1, characterized in that the lubricant supply member is held by the nip forming member via the groove.

4. The fixing device according to claim 1, characterized in that the lubricant supply unit is composed of a fibrous or porous elastic body.

5. The fixing device according to claim 1, characterized in that the heating member contacts the inner circumferential surface of the fixing belt to heat the belt.

6. The fixing device according to claim 1, characterized in that the length of the lubricant supply section is longer than the ends of the fixing belt in the width direction perpendicular to the rotation direction of the fixing belt.

7. The fixing device according to claim 6, characterized in that the lubricant supply unit is exposed on the outer circumference of the fixing belt at both ends in the width direction of the fixing belt.

8. An image forming unit that forms an image, A fixing device according to any one of claims 1 to 7, which fixes an unfixed image formed by the image forming unit onto a recording material, An image forming apparatus characterized by having the following features.

Images