Image forming apparatus

Abstract

To provide an image forming apparatus that can avoid the occurrence of an impact when a sheet is inserted into a nip part, and can provide uniform glossiness and density to a toner fixed to the sheet.SOLUTION: A fixing device 16 comprises: a heat roller 162 having a heating part 162a built therein; a fixing roller 161; an endless fixing belt 163 laid over the heat roller 162 and the fixing roller 161; and a pressure roller 164 forming a nip part with the fixing belt 163 at a position opposite to the fixing roller 161 with the fixing belt 163 therebetween. The fixing roller 161 has a base part 161a, a porous elastic layer 161b provided around the base part 161a, and a solid flat layer 161c provided around the elastic layer 161b and not including air bubbles.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to an image forming apparatus including a fixing device that fixes a toner image transferred onto paper to the paper by applying heat and pressure to the paper. [Background technology]

[0002] The image forming apparatus is configured to fix a toner image transferred onto a sheet of paper to the sheet of paper by applying heat and pressure using a fixing device.

[0003] The fixing device includes a fixing roller, a fixing roller having an internal heat source, an endless fixing belt stretched between the fixing rollers, and a pressure roller disposed opposite the fixing roller and pressing against the fixing roller via the fixing belt.

[0004] The toner transferred to the paper is melted and leveled by being heated and pressurized, which increases the glossiness. In order to obtain sufficient pressure in the nip, the surface of the fixing roller needs to have a certain degree of hardness. However, if the surface of the fixing roller is hard, the housing of the image forming device may shake due to the impact when the paper is sandwiched in the nip, and the impact may cause banding, i.e., exposure misalignment or transfer misalignment.

[0005] Patent Document 1 discloses an image forming apparatus equipped with a fixing device that includes a fixing roller having an elastic layer on its surface, a fixing roller having a heat source inside, an endless fixing belt stretched between the fixing rollers, and a pressure roller disposed opposite the fixing roller and pressing against the fixing roller via the fixing belt, and that heats and pressurizes an unfixed toner image carried on a recording material in a nip portion formed by the fixing belt and the pressure roller.

[0006] The fixing roller is provided with an elastic layer made of liquid silicon or foamed silicon, so that the surface hardness is reduced and the amount of bite of the pressure roller into the fixing roller is increased.

[0007] In this manner, since the fixing roller is provided with an elastic layer, the conveyed paper is smoothly sandwiched in the nip portion, so that the occurrence of the above-mentioned impact can be avoided.

[0008] However, since the fixing roller is provided with an elastic layer, uneven pressing of the fixing belt against the pressure roller occurs, and there is a risk that the toner fixed on the paper will not have uniform gloss and density. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] JP 2002-268436 A Summary of the Invention [Problem to be solved by the invention]

[0010] The present disclosure has been made in consideration of the above-mentioned problems, and aims to provide an image forming device that can avoid the occurrence of impact when paper is clamped in a nip portion, and can obtain uniform gloss and density in the toner fixed to the paper. [Means for solving the problem]

[0011] In order to achieve the above-mentioned object, the image forming apparatus of the present disclosure is an image forming apparatus equipped with a fixing device that fixes a toner image transferred to paper to the paper by applying heat and pressure to the paper, the fixing device comprising a heat roller with a built-in heating section, a fixing roller, an endless fixing belt stretched between the heat roller and the fixing roller, and a pressure roller that forms a nip section between the fixing roller and the fixing belt at a position facing the fixing roller and the fixing belt, the fixing roller having a base section, a porous elastic layer provided around the base section, and a solid flat layer containing no air bubbles provided around the elastic layer.

[0012] According to the above-mentioned configuration, since the fixing roller has an elastic layer, the conveyed paper is smoothly sandwiched in the nip portion, so that it is possible to prevent the occurrence of impact when the paper is sandwiched in the nip portion. This was effective even for thick paper with the thickness of two postcards (basis weight 360 g / m2).

[0013] In addition, since the fixing roller has a flat layer, the fixing belt is pressed against the pressure roller with a uniform force. This allows the toner fixed on the paper to have a uniform gloss and density. The flat layer is a layer whose surface that comes into contact with the fixing belt is flat.

[0014] In the image forming apparatus according to the present disclosure, the flat layer may be made of silicon.

[0015] As a result of extensive research, it was discovered that if the flat layer is made of silicon, the fixing belt can be pressed against the pressure roller with a uniform force.

[0016] In the image forming apparatus according to the present disclosure, the flat layer may be made of resin.

[0017] As a result of extensive research, it was discovered that if the flat layer is made of resin, the fixing belt can be pressed against the pressure roller with a uniform force.

[0018] In the image forming apparatus according to the present disclosure, the flattening layer may be made of a fluororesin.

[0019] As a result of intensive research, it was discovered that if the flat layer is made of a fluororesin, the fixing belt can be pressed against the pressure roller with a uniform force.

[0020] In the image forming apparatus according to the present disclosure, the flat layer may be characterized by having a thickness within a range of 10-100 μm.

[0021] As a result of extensive research, it was discovered that if the flat layer has a thickness within the range of 10-100 μm, the fixing belt can be pressed against the pressure roller with a uniform force.

[0022] In the image forming apparatus according to the present disclosure, the flat layer may be formed of a tube made of perfluoroalkoxy fluororesin (PFA) and having a thickness in the range of 10-100 μm.

[0023] As a result of extensive research, it was discovered that if the flat layer is made of a tube made of perfluoroalkoxy fluororesin (PFA) with a thickness in the range of 10-100 μm, the fixing belt can be pressed against the pressure roller with a uniform force.

[0024] In the image forming apparatus according to the present disclosure, the flat layer may be made of a heat-shrinkable tube made of perfluoroalkoxy fluorine resin (PFA).

[0025] As a result of extensive research, it was discovered that if the flat layer is made of a heat-shrinkable tube made of perfluoroalkoxy fluororesin (PFA), the fixing belt can be pressed against the pressure roller with a uniform force.

[0026] In the image forming apparatus according to the present disclosure, the elastic layer may be characterized by having a thickness within a range of 10-20 mm.

[0027] As a result of extensive research, it was discovered that if the elastic layer has a thickness within the range of 10-20 mm, the transported paper can be smoothly sandwiched in the nip portion.

[0028] In the image forming apparatus according to the present disclosure, the fixing belt may have a multi-layer structure, and at least a layer that comes into contact with the heat roller and the fixing roller may be made of resin.

[0029] As a result of extensive research, it was discovered that in a combination of a base portion, a fixing roller having a porous elastic layer arranged around the base portion, and a solid, flat layer containing no air bubbles arranged around the elastic layer, if the fixing belt has a multi-layer structure and at least the layers in contact with the heat roller and the fixing roller are made of resin, it is possible to avoid the occurrence of impact when the paper is sandwiched in the nip portion, and also to obtain uniform gloss and density for the toner fixed to the paper. Effect of the Invention

[0030] The image forming apparatus of the present disclosure has the advantage that it is possible to avoid the occurrence of impact when the paper is sandwiched in the nip portion, and that it is possible to obtain uniform gloss and density in the toner fixed on the paper. [Brief description of the drawings]

[0031] [Figure 1] FIG. 1 is an explanatory diagram of an image forming apparatus. [Diagram 2] FIG. [Diagram 3] 13 is a graph showing experimental results of fixing pressure. [Figure 4] 13 is a graph showing experimental results of glossiness. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0032] (Embodiment 1) Hereinafter, a first embodiment of the present disclosure will be described with reference to the accompanying drawings. Note that the same components in the respective embodiments described below are denoted by the same reference numerals, and redundant descriptions of those components will be omitted.

[0033] In the first embodiment, the image forming apparatus 1 is an electrophotographic image forming apparatus (printer) having a printing function. The image forming apparatus 1 is connected to an external device such as a personal computer (not shown) by wire or wirelessly, and forms a toner image on a medium, here a specific paper 2, in accordance with print image data sent from the external device.

[0034] As shown in FIG. 1, the image forming apparatus 1 includes a charger 10, an exposure device 11, a photosensitive drum 12, a developing device 13, a cleaner device 14, a transfer device 15, a fixing device 16, a charge removal device 17, a paper feeder 18, a conveying means 19, and a paper output tray 20 in the main body of the apparatus.

[0035] When the surface of the photoconductor drum 12, which has been charged to a uniform potential by the charger 10, is irradiated with laser light from the exposure device 11, the resistance value of the exposed area decreases, lowering the surface potential, and an electrostatic latent image corresponding to the image data for printing is formed. Toner is supplied from the development device 13 to this electrostatic latent image, and a toner image is developed.

[0036] The toner image formed on the surface of the photoconductor drum 12 is transferred to an intermediate transfer belt, and the toner image transferred to the intermediate transfer belt is transferred to the paper 2 passing between the transfer device 15 and the paper 2, and is heated and pressed in the fixing device 16. In this way, the toner image is fixed to the paper 2.

[0037] Residual toner remaining on the surface of the photoconductor drum 12 is scraped off by the cleaner device 14. After the surface of the photoconductor drum 12 has been cleaned by the cleaner device 14, the electrostatic latent image remaining on the surface of the photoconductor drum 12 is removed by the charge remover 17. This returns the photoconductor drum 12 to an uncharged state.

[0038] The paper feed device 18 has a tray for loading the paper 2 to be used for image formation, and the paper 2 is transported within the main body of the image forming device 1 by a transport means 19 equipped with a transport path and transport rollers, and after the toner image is transferred, it is discharged onto a paper output tray 20.

[0039] In addition to the configuration described above, the image forming apparatus 1 includes a control unit (not shown) that controls each unit of the image forming apparatus 1.

[0040] A detailed description will now be given of the fixing device 16. As shown in FIG.

[0041] The fixing roller 161 has a rotatably supported base portion 161a, a porous elastic layer 161b provided around the base portion 161a, and a solid flat layer 161c containing no air bubbles provided around the elastic layer 161b.

[0042] The base portion 161a is made of a carbon steel pipe for mechanical construction, the elastic layer 161b is made of porous or foamed silicone rubber, and the flat layer 161c is made of a heat-shrinkable tube made of perfluoroalkoxy fluororesin (PFA). The heat-shrinkable tube can be easily arranged around the elastic layer 161b by simply placing it around the elastic layer 161b and shrinking it. However, the tube does not have to be a heat-shrinkable tube.

[0043] The elastic layer 161b is configured to have a thickness within a range of 10-20 mm, and the flat layer 161c is configured to have a thickness within a range of 10-100 μm.

[0044] By providing the flat layer 161c on the surface of the elastic layer 161b, it is possible to make uniform the temperature and surface pressure of the surface of the fixing belt 163 stretched over the fixing roller 161. This makes it possible to make the toner melt and crush uniform, thereby obtaining glossiness.

[0045] Since the fixing roller 161 has the elastic layer 161b, the conveyed paper 2 is smoothly sandwiched in the nip portion, so that it is possible to avoid the occurrence of impact when the paper 2 is sandwiched in the nip portion.

[0046] In addition, since the fixing roller 161 has the flat layer 161c, the fixing belt 163 is pressed against the pressure roller 164 with a uniform force. Therefore, uniform gloss and density can be obtained for the toner fixed on the paper 2. The flat layer 161c is a layer whose surface that comes into contact with the fixing belt 163 is flat.

[0047] The heat roller 162 has a heating portion 162a and a heat transfer layer 162b that is heated by the heating portion 162a.

[0048] Since toner melts at about 150 degrees, the heat roller 162 heats the fixing belt 163 to about 160 to 180 degrees Celsius. The heat of the fixing belt 163 is absorbed by the fixing roller 161 through thermal conduction, but since the fixing roller 161 has an elastic layer 161b made of a porous material, the heat of the fixing belt 163 is not easily absorbed, thereby saving energy.

[0049] The fixing belt 163 has a multi-layer structure, and includes a surface layer, an intermediate layer laminated inside the surface layer, and an inner layer laminated inside the intermediate layer.

[0050] The surface layer is made of an electroformed base material, the middle layer is made of silicone rubber, and the inner layer is made of a tube made of perfluoroalkoxy fluororesin (PFA).

[0051] The surface layer is 50 μm±10 μm, the intermediate layer is 300 μm±40 μm thick, and the inner layer is 30 μm±10 μm thick, giving a fixing belt thickness of 380 μm±60 μm.

[0052] The pressure roller 164 has a base portion 164a that is rotatably supported, an elastic layer 164b provided around the base portion 164a, and a flat layer 164c provided around the elastic layer 164b.

[0053] The base portion 164a is made of an Al-Mg alloy, the elastic layer 164b is made of solid silicone rubber, and the flat layer 164c is made of a tube made of perfluoroalkoxy fluorine resin (PFA).

[0054] In order to confirm that the above-mentioned configuration of the fixing roller 161 can provide a predetermined operational effect, an experiment was conducted in which a fixing roller according to Comparative Example 1, a fixing roller according to Comparative Example 2, and a fixing roller according to the embodiment were used to print on paper 2, and the fixing pressure in the nip portion was measured, and the glossiness of the paper 2 after printing was measured. Note that the fixing pressure in the nip portion was measured at the center of the nip portion in the width direction.

[0055] A fixing roller composed of a base and a solid flat layer containing no air bubbles provided around the base was prepared as Comparative Example 1. In this fixing roller, the base was made of a carbon steel pipe for mechanical construction, and the flat layer was made of solid silicone rubber containing no air bubbles.

[0056] In Comparative Example 1, the base portion is φ29 mm, the flat layer is 10.5 mm thick, and the fixing roller is φ50 mm. The surface hardness of the fixing roller is 40°.

[0057] As shown in FIG. 3, the fixing roller according to Comparative Example 1 had a poor banding level in both monochrome and color modes, and the shock caused by the paper being sandwiched in the nip caused large exposure and transfer misalignments. In FIG. 3, the vertical axis banding level is 1: completely pass, 2: pass, 3: marginally fail, 4: fail, and 5: completely fail. As shown in FIG. 4, the results showed that even with thin glossy paper, sufficient glossiness was obtained. The glossiness was measured using a HANDY GLOSSMETER PG-1 according to a measurement method conforming to the JIS standard. The same applies to Comparative Example 2 and the examples described below.

[0058] However, when the fixing pressure in the nip portion is high, an impact is likely to occur when the paper is sandwiched in the nip portion, which may cause exposure deviation or transfer deviation.

[0059] A fixing roller composed of a base and an elastic layer provided around the base was prepared as Comparative Example 2. In Comparative Example 2, the fixing roller was not provided with a flat layer. In this fixing roller, the base was made of a carbon steel pipe for mechanical construction, and the elastic layer was made of porous foamed silicone rubber.

[0060] In Comparative Example 2, the base portion is φ20 mm, the flat layer is 15 mm thick, and the fixing roller is φ50 mm. The surface hardness of the fixing roller is 40°.

[0061] The fixing roller according to Comparative Example 2 had a low fixing pressure in the nip formed at the pressure contact portion between the fixing belt and the pressure roller in both monochrome and color modes, as shown in Fig. 3. The low fixing pressure in the nip means that shock is unlikely to occur when the paper is sandwiched in the nip, and thus the risk of exposure misalignment or transfer misalignment is avoided.

[0062] However, as shown in FIG. 4, the gloss level was lower than that in Comparative Example 1.

[0063] As an example, a fixing roller was prepared that was composed of a base part, an elastic layer of porous foamed silicone rubber provided around the base part, and a solid flat layer that does not contain air bubbles provided around the elastic layer, as shown in Figure 2. In this fixing roller, the base part was composed of a carbon steel pipe for mechanical construction, the elastic layer was composed of porous foamed silicone rubber, and the flat layer was composed of a tube made of perfluoroalkoxy fluororesin (PFA).

[0064] In the embodiment, the base portion is φ20 mm, the elastic layer is 15 mm thick, and the flat layer is 0.05 mm thick, so that the fixing roller is φ50.1 mm. The surface hardness of the fixing roller is 40°.

[0065] As shown in Fig. 3, in both monochrome and color modes, the fixing roller according to the embodiment had a fixing pressure in the nip formed at the pressure contact portion between the fixing belt and the pressure roller that was higher than that of Comparative Example 2 but lower than that of Comparative Example 1. Also, as shown in Fig. 4, the gloss level was lower than that of Comparative Example 1 but higher than that of Comparative Example 2.

[0066] In other words, since impact is less likely to occur when the paper is sandwiched in the nip area, the risk of exposure misalignment and transfer misalignment is avoided more than in Comparative Example 1, and a sufficient gloss level is obtained more than in Comparative Example 2.

[0067] (Embodiment 2) The flat layer 161c of the fixing roller 161 may be made of a solid layer of silicon. As a result of intensive research, it has been found that if the flat layer 161c is made of a solid layer of silicon, the fixing belt 163 can be pressed against the pressure roller 164 with a uniform force.

[0068] (Embodiment 3) The flat layer 161c of the fixing roller 161 may be characterized by being made of a resin, in particular a fluororesin other than perfluoroalkoxy fluororesin (PFA). As a result of intensive research, it has been found that if the flat layer 161c is made of a resin, in particular a fluororesin, the fixing belt can be pressed against the pressure roller with a uniform force. However, the resin may be a resin other than a fluororesin.

[0069] The configurations disclosed in any of the above-described embodiments may be applied in combination with configurations disclosed in other embodiments, provided that no inconsistencies arise. Furthermore, the embodiments disclosed in this specification are merely examples, and the embodiments of the present disclosure are not limited thereto, and may be modified as appropriate within the scope of the present disclosure. [Explanation of symbols]

[0070] 1: Image forming device 2: Paper 16: Fixing device 16b: Heat transfer layer 161: Fuser roller 161a: Base part 161b: Elastic layer 161c: flat layer 162: Heat roller 162a: Heating part 162b: Heat transfer layer 163: Fixing belt 164: Pressure roller 164a: Base part 164b: Elastic layer 164c: flat layer

Claims

1. An image forming apparatus including a fixing device that fixes a toner image transferred onto a sheet of paper by applying heat and pressure to the sheet of paper, the fixing device includes a heat roller having a built-in heating unit, a fixing roller, an endless fixing belt stretched between the heat roller and the fixing roller, and a pressure roller that forms a nip portion between the fixing roller and the fixing belt at a position facing the fixing roller and the fixing belt, The fixing roller of the image forming apparatus is characterized in that it has a base portion, a porous elastic layer provided around the base portion, and a solid flat layer containing no air bubbles provided around the elastic layer.

2. 2. The image forming apparatus according to claim 1, wherein the flat layer is made of silicon.

3. 2. The image forming apparatus according to claim 1, wherein the flattening layer is made of a resin.

4. 4. The image forming apparatus according to claim 3, wherein the flattening layer is made of a fluororesin.

5. 2. The image forming apparatus according to claim 1, wherein the flattening layer has a thickness in the range of 10 to 100 [mu]m.

6. 2. The image forming apparatus according to claim 1, wherein the flat layer is made of a tube having a thickness in the range of 10 to 100 μm and made of perfluoroalkoxy fluorine resin (PFA).

7. 2. The image forming apparatus according to claim 1, wherein the flat layer is made of a heat-shrinkable tube made of perfluoroalkoxy fluorine resin (PFA).

8. 2. The image forming apparatus according to claim 1, wherein the elastic layer has a thickness within a range of 10-20 mm.

9. 2. The image forming apparatus according to claim 1, wherein the fixing belt has a multi-layer structure, and at least a layer that comes into contact with the heat roller and the fixing roller is made of resin.

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