JP2020190702A - Fixing device and image forming apparatus - Google Patents

Abstract

To prevent the occurrence of a slip of a fixing member and uneven conveyance caused by a lubricant accumulated at a contact part of a heating member and the fixing member, and thereby prevent the occurrence of an abnormal image, such as a jitter image.SOLUTION: A fixing device 105 comprises: a rotatable fixing member 126 that is wound over a heating member 122 and a nip forming member 125; and a rotatable pressure member 121 that is in pressure contact with the nip forming member with the fixing member therebetween, and the fixing device fixes a toner image on a recording medium P conveyed in the vertical direction at a fixing nip formed by the fixing member 126 and the pressure member 121. A lubricant is applied on an inner surface of the fixing member 126. The nip forming member 125 has a slide member 123 on an opposing surface to the inner surface of the fixing member 126. The slide member 123 is a sheet metal member in which coating is performed on at least a slide surface with the inner surface of the fixing member 126. A lowest end of the heating member 122 is located at a position higher than a lowest end of the nip forming member 125.SELECTED DRAWING: Figure 2

Description

The present invention relates to a fixing device and an image forming device.

In the fixing device used in the electrophotographic image forming device, the fixing film method having a short heating time is widely used. In this method, a pressure roller is brought into contact with a nip forming member via a thin film fixing film to form a fixing nip, and a lubricant is interposed between the nip forming member and the inner surface of the fixing film sliding on the nip forming member. ing. The nip forming member is composed of a sliding member formed by applying a coating to a sheet metal member.

In such a fixing device, the fixing belt is bridged between a nip forming member composed of a sliding member coated on a sheet metal member and a heating roller, and the nip forming member is rotationally driven via the fixing belt. The pressure roller is brought into pressure contact, and the toner image is fixed to the recording medium at the nip portion.

For example, in Patent Document 1, as shown in FIG. 6, a fixing belt 33 is wound so as to bridge the heating roller 31 and the nip forming member 32, and the nip forming member is rotationally driven via the fixing belt. A fixing device 30 that press-contacts the roller 34 to fix the toner image t to the recording medium S at the nip portion between the fixing belt and the pressure roller, and guides the fixing belt between the nip forming member and the heating roller. A configuration is disclosed in which the member 35 is provided separately from the nip forming member, and the sliding member 36 is provided at least between the portions where the nip forming member and the fixing belt come into contact with each other.

In the fixing device described in Patent Document 1, a sliding member 36 provided with a fluororesin 36b so as to cover the sheet material 36a made of glass fiber is used in the nip forming portion (Patent Document 1). Figure 3). Further, unevenness is formed on the surface of the sliding member 36 on the fixing belt 33 side, and the uneven portion holds, for example, a lubricant g using fluorine-based grease having high viscosity and excellent heat resistance. There is.

However, when a layout in which the recording medium is conveyed in the vertical direction is used as in the fixing device described in Patent Document 1, the lubricant applied to the inner peripheral surface of the fixing belt tends to accumulate downward due to gravity. In the fixing device configuration described in Patent Document 1, since the heating roller is located at the lowermost position in the vertical direction, it is possible to prevent slippage and uneven transfer due to the lubricant between the heating roller and the inner circumference of the fixing belt. There is a risk that abnormal images such as jitter images will occur.

Therefore, it is an object of the present invention to prevent the occurrence of an abnormal image such as a jitter image by suppressing the occurrence of slip and transfer unevenness of the fixing member due to the lubricant staying at the contact portion between the heating member and the fixing member. ..

This task includes a rotatable fixing member wound around a heating member and a nip forming member, and a rotatable pressurizing member that is pressed against the nip forming member via the fixing member, and is conveyed in the vertical direction. In a fixing device for fixing a toner image on a recording medium with a fixing nip formed by the fixing member and the pressure member, a lubricant is applied to the inner surface of the fixing member, and the nip forming member is A sheet metal member having a sliding member on a surface facing the inner surface of the fixing member, and the sliding member having at least a coating on the sliding surface with the inner surface of the fixing member, and the heating member. The problem is solved by a fixing device characterized in that the lowermost end portion is located at a position higher than the lowermost lowermost portion of the nip forming member.

It is possible to suppress the occurrence of slip and transfer unevenness between the heating member and the fixing member due to the retained lubricant, and prevent the occurrence of an abnormal image such as a jitter image.

It is a schematic block diagram of the image forming apparatus which concerns on embodiment of this invention. It is a figure which shows the cross-sectional view of the fixing device which concerns on embodiment of this invention. It is a figure which shows the cross-sectional view of the fixing device which concerns on another embodiment of this invention. It is a figure which shows the cross-sectional view of the fixing device which concerns on another embodiment of this invention. It is a figure which shows the cross-sectional view of the fixing device which concerns on another embodiment of this invention. It is a figure which shows the sectional view of the conventional fixing device. It is a figure which shows the sectional view of the conventional fixing device.

FIG. 1 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention. First, the overall configuration and operation of the image forming apparatus will be described with reference to FIG.

The image forming apparatus 101 shown in FIG. 1 is an electrophotographic monochrome laser printer. In addition to the printer, the image forming apparatus according to the embodiment of the present invention may be a copying machine, a facsimile, or a multifunction device having any two or three functions thereof. Further, the device is not limited to the monochrome image forming apparatus, and may be a color image forming apparatus.

As shown in FIG. 1, the image forming apparatus 101 transfers an image to an image forming unit 102 that forms an image, a recording medium supply unit 103 that supplies paper P as a recording medium, and the supplied paper P. A transfer unit 104, a fixing device 105 for fixing the image transferred to the paper P, and a discharge unit 106 for discharging the paper P on which the image is fixed to the outside of the device are provided.

The image forming unit 102 includes a drum-shaped photoconductor 107, a charging roller 108 as a charging means for charging the surface of the photoconductor 107, and a latent image forming means for exposing the surface of the photoconductor 107 to form a latent image. Exposure device 109, a developing roller 110 as a developing means for supplying a toner (developer) to the surface of the photoconductor 107 to visualize a latent image, and cleaning as a cleaning means for cleaning the surface of the photoconductor 107. It includes a blade 111 and.

When instructed to start the printing operation, the photoconductor 107 starts rotating in the image forming unit 102, and the surface of the photoconductor 107 is charged to a uniform high potential by the charging roller 108. Next, the exposure device 109 exposes the surface of the photoconductor 107 based on the image information of the document read by the document reader or the print information instructed to print from the terminal, so that the potential of the exposed portion is lowered. Then, an electrostatic latent image is formed. Then, toner is supplied from the developing roller 110 to the electrostatic latent image, and a toner image is formed on the photoconductor 102.

The toner image formed on the photoconductor 107 is transferred to the paper P at the transfer nip between the transfer roller 115 arranged on the transfer unit 104 and the photoconductor 107. This paper P is supplied from the recording medium supply unit 103. In the recording medium supply unit 103, the paper P housed in the paper feed cassette 112 is fed out one by one by the paper feed roller 113. The fed paper P is conveyed to the transfer nip by the timing roller pair 114 in time with the toner image on the photoconductor 107. Then, at the transfer nip, the toner image on the photoconductor 107 is transferred to the paper P. Further, after the toner image is transferred, the toner remaining on the photoconductor 107 is removed by the cleaning blade 111.

The paper P on which the toner image is transferred is conveyed to the fixing device 105. Then, in the fixing device 105, the toner image is fixed to the paper P by being heated and pressed when the paper P passes through the fixing nip between the heating side member 120 and the pressure roller 121. After that, the paper P is conveyed to the ejection unit 106 and ejected to the outside of the apparatus by the output roller pair 116 to complete a series of printing operations.

In the fixing device 105 of this embodiment, as shown in FIGS. 2 and 3, a heating roller 122 provided with a heating device such as a halogen lamp 127 inside is used as the heating side member 120, and the heating roller 122 is used. The fixing belt 126 is heated by. The heating side member 120 is not limited to such a member, and the fixing belt 126 is heated by IH, or the fixing belt 126 is stretched and heated by a resistance heating element or the like and the nip forming member 125. Can also be used.

FIG. 2 shows a cross-sectional view of the fixing device according to the embodiment of the present invention.
As shown in the figure, the fixing device 105 is wound around a heating roller 122 as a heating member provided with a heating device such as a halogen lamp 127, a nip forming member 125, and the heating roller 122 and the nip forming member 125. It has a fixing belt 126 as an endless rotatable fixing member, and a pressure roller 121 as a rotatable pressing member that is pressed against the nip forming member 125 via the fixing belt 126. The nip forming member 125 has a sliding member 123 on the surface facing the inner surface of the fixing belt 126, and the sliding member 123 is provided with a slidable coating on at least the sliding surface of the fixing belt 126 with the inner surface. It is a sheet metal member. The sliding member 123 does not have a lubricant holding function. The toner image on the paper P as a recording medium conveyed in the vertical direction is fixed by the fixing nip N formed by the fixing belt 126 and the pressure roller 121. When a fixing device having such a layout is used, it is necessary to interpose a lubricant between the nip forming member 125 and the inner circumference of the fixing belt 126. However, since the above-mentioned slidable coating does not positively retain the lubricant like glass fiber, it is difficult to obtain the desired effect with a low-viscosity lubricant such as silicone oil, and the viscosity is high and the heat resistance is excellent. Fluorine-based grease is used as a lubricant.

When a fluorine-based lubricant is used, the viscosity of the lubricant applied to the inner peripheral surface of the fixing belt 126 becomes low, and the lubricant is a liquid, especially when the fixing device 105 is heated, such as during image drawing operation. It becomes a state close to, and tends to accumulate at the lowest position inside the fixing belt 126. The same applies when the fixing device 105 is stopped after image formation.

When the lubricant accumulates at the lowest position inside the fixing belt 126, if the position of the heating roller 122 is lower than the nip forming member 125 as in the prior art, the lubricant stays in the vicinity of the heating roller 122 and the lubricant As a result, slippage occurs between the fixing belt 126 and the heating roller 122, and abnormal images such as transfer unevenness and a jitter image occur.

On the other hand, according to the present embodiment shown in FIG. 2, the center of the heating roller 122 is located above the center of the pressurizing roller 121 and the horizontal line passing substantially the center of the nip forming member 125. More specifically, the lowermost end of the heating roller 122 is located higher than the lowermost end of the nip forming member 125. Here, the "lowermost end portion" means the lowermost portion of the member in the vertical direction. Therefore, the fixing belt 126 wound around the heating roller 122 and the nip forming member 125 is inclined downward on the downstream side in the rotational direction, that is, in the portion from the heating roller 122 toward the nip forming member 125 in the rotational direction. .. As described above, since the lowermost end portion of the heating roller 122 is located higher than the lowermost end portion of the nip forming member 125, the lubricant accumulates on the lower side of the nip forming member 125 and does not stay in the vicinity of the heating roller 122. This makes it possible to suppress slippage and uneven transport of the heating roller 122 and the fixing belt 126 due to the lubricant, and prevent the occurrence of an abnormal image such as a jitter image.

Further, inside the fixing belt 126, a nip forming member 125 for forming a fixing nip N with a pressure roller 121 via the fixing belt 126 and a stay member 124 (supporting member) for supporting the nip forming member 125 are arranged. Has been done. The nip forming member 125 arranged in the width direction of the fixing belt 126 is fixedly supported by the stay member 124 to prevent the nip forming member 125 from bending due to the pressure from the pressure roller 121. A uniform nip width can be obtained over the axial direction (longitudinal direction) of the pressure roller 121. The nip forming member 125 is a heat-resistant member having high mechanical strength and a heat-resistant temperature of 200 ° C. or higher, particularly a heat-resistant resin such as a polyimide (PI) resin or a polyetheretherketone (PEEK) resin, which is reinforced with glass fiber. It is composed of the plastic. As a result, deformation of the nip forming member 125 due to heat is prevented in the toner fixing temperature range, a stable fixing nip state is ensured, and output image quality is stabilized. Further, both ends of the stay member 124 and the halogen lamp 127 in the longitudinal direction are fixedly held by a side plate of the fixing device 105 or a holder provided separately.

In the present embodiment, the sliding member 123 covers the entire surface of the nip forming member 125 facing the pressure roller 121 over the entire width of the fixing nip N.

FIG. 3 shows a cross-sectional view of a fixing device according to another embodiment of the present invention.
In the present embodiment, in addition to the fixing device configuration of the embodiment of FIG. 2, a lubricant holding portion 128 for holding the lubricant is provided on the lower end side of the nip forming member 125. Here, the "lower end side" means a portion below the central portion in the vertical direction of the member. More specifically, the nip forming member 125 has an L-shaped cross section, and a lubricant holding portion 128 is provided at the vertical bottom of the nip forming member 125 in contact with the fixing belt 126. In other words, the lubricant holding portion 128 is integrated with the nip forming member 125.

According to this configuration, the lubricant is held by the lubricant holding portion 128 on the lower end side of the nip forming member 125, which is upstream of the sliding member 123 in the rotational direction, so that the lubricant is applied to the sliding member 123. It is possible to apply a lubricant to the inner circumference of the fixing belt 126 while uniformly supplying the fixing belt 126, and the fixing belt 126 can be driven more stably.

The lubricant holding portion 128 may be a member having a lubricant holding property such as a non-woven fabric and heat resistance against high temperature, but as shown in FIG. 3, between the nip forming member 125 and the fixing belt 126. It is necessary to lay out the lubricant holding portion 128 so that a gap is not generated in the above, that is, the fixing belt 126 does not float from the nip forming member 125. In the present embodiment, the lubricant holding portion 128 is integrated with the nip forming member 125 so that the fixing belt 126 does not float from the nip forming member 125. As a result, there is no risk of unnecessary heat loss due to the lubricant holding portion 128.

On the other hand, in the fixing device described in Patent Document 2, as shown in FIG. 7, the protrusion member 35 holding the lubricant g is fixed rather than the position where the nip forming member 32 and the pressure roller 34 are in pressure contact with each other. It is provided so as to come into contact with the inner peripheral surface of the fixing belt 33 at a position on the upstream side in the moving direction of the belt 33, and prevents the fixing belt 33 heated by the heating roller 31 from coming into contact with the fixing member 32a. Further, the heating roller 31 is provided at a position on the upper side of the nip forming member 32 and on the downstream side in the moving direction of the fixing belt 33. However, in the fixing device configuration of Patent Document 2, the fixing belt 33 heated by the heating roller 31 comes into contact with the protrusion member 35 before being guided between the nip forming member 32 and the pressure roller 34, so that the fixing belt 33 is heated. The heat of the fixing belt 33 may flow to the protrusion member 35, causing unnecessary heat loss.

FIG. 4 shows a cross-sectional view of a fixing device according to another embodiment of the present invention.
In the present embodiment, the sliding member 123 covers a part of the surface of the nip forming member 125 facing the pressurizing roller 121 over the entire width of the fixing nip N, and the sliding member 123 is connected to the lubricant holding portion 128. Is also located on the upper side in the vertical direction. Other fixing device configurations are the same as those of the fixing device configuration of the second embodiment. Even in such a configuration, the above-mentioned problems can be solved by arranging the sliding member 123 vertically above the lubricant holding portion 128. That is, since the lubricant collects in the vicinity of the lubricant holding portion 128 and does not stay in the vicinity of the heating roller 122, slippage and transfer unevenness between the heating roller 122 and the inner circumference of the fixing belt 126 are less likely to occur, and the jitter image It is possible to prevent the occurrence of abnormal images such as.

Further, in the fixing device for fixing the paper P while moving it upward in the vertical direction, as shown in FIG. 4, the lubricant holding portion 128 is arranged in the fixing device 105 below the sliding member 123 in the vertical direction. As a result, the lubricant holding portion 128 arranged upstream and in the vicinity of the sliding member 123 in the rotation direction enables stable supply of the lubricant and prevents the lubricant from wrapping around the heating roller 122. ..

FIG. 5 shows a cross-sectional view of a fixing device according to another embodiment of the present invention.
In the present embodiment, in addition to the fixing device configuration of the embodiment shown in FIG. 4, a scraping member 129 that scrapes off the lubricant on the inner peripheral surface of the fixing belt is located upstream of the heating roller 122 in the rotation direction of the fixing belt 126. Have been placed. This makes it possible to circulate the lubricant more efficiently. That is, by scraping the lubricant between the nip forming member 125 and the heating roller 122, it is possible to prevent the lubricant from being supplied to the heating roller 122, and slip at the contact portion between the heating roller 122 and the fixing belt 126. And uneven transport can be prevented more effectively, and the occurrence of abnormal images such as jitter images can be prevented.

The scraping member 129 is, for example, a blade-shaped member that abuts on the entire inner circumference of the belt.
The lubricant scraped by the scraping member 129 falls below the scraping member 129 due to gravity and is collected by the lubricant holding portion 128, so that the lubricant can be used without waste.

Further, since the image forming apparatus according to the embodiment of the present invention has the fixing apparatus described above, an image forming apparatus capable of stable image formation without causing an abnormal image is realized.

As described above, according to the present invention, the lowermost end of the heating roller 122 is located higher than the lowermost end of the nip forming member 125, so that the lubricant applied to the inner peripheral surface of the fixing belt 126 forms a nip. It collects on the lower side of the member 125 and does not stay in the vicinity of the heating roller 122. Therefore, slippage and uneven transport of the heating roller 122 and the fixing belt 126 due to the lubricant are less likely to occur, and abnormal images such as a jitter image can be prevented from occurring.

105 Fixing device 121 Pressurizing roller (pressurizing member)
122 Heating roller (heating member)
123 Sliding member 125 Nip forming member 126 Fixing belt (fixing member)

JP-A-2018-49136 JP-A-2018-49133

Claims (6)

A rotatable fixing member wrapped around a heating member and a nip forming member,
A rotatable pressurizing member that is pressed against the nip forming member via the fixing member.
In a fixing device for fixing a toner image on a recording medium conveyed in the vertical direction with a fixing nip formed by the fixing member and the pressure member.
Lubricant is applied to the inner surface of the fixing member.
The nip forming member has a sliding member on a surface facing the inner surface of the fixing member.
The sliding member is a sheet metal member whose sliding surface with at least the inner surface of the fixing member is coated.
A fixing device characterized in that the lowermost end portion of the heating member is located at a position higher than the lowermost end portion of the nip forming member. The fixing device according to claim 1, wherein a lubricant holding portion for holding the lubricant is provided on the lower end side of the nip forming member. The fixing device according to claim 2, wherein the lubricant holding portion is integrated with the nip forming member so that the fixing member does not float from the nip forming member. The fixing device according to claim 2 or 3, wherein the sliding member is located on the upper side in the vertical direction with respect to the lubricant holding portion. Any of claims 1 to 4, wherein the scraping member that scrapes off the lubricant on the inner peripheral surface of the fixing member is arranged on the upstream side of the heating member in the rotation direction of the fixing member. The fixing device according to one item. An image forming apparatus comprising the fixing apparatus according to any one of claims 1 to 5.

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