JP5434963B2 - Fixing apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to a fixing device and an image forming apparatus, and more particularly to a technique for improving recording sheet conveyance in a fixing device in which a plurality of fixed pressure members are pressed against a fixing rotating body.

  In recent years, in order to meet the demand for low-cost image forming apparatuses, there is an increasing demand for cost reduction for fixing apparatuses. In order to reduce the cost of the fixing device, for example, a configuration in which a recording sheet is pressed against the fixing roller by a fixed pressure member (hereinafter referred to as “pressure pad”) instead of the pressure roller is adopted. It is possible to do. In this way, since the number of parts of the fixing device can be reduced, both material cost and manufacturing cost can be reduced.

Unlike the pressure roller that rotates together with the fixing roller, the fixed pressure member slides on the fixing roller to generate torque. If the force for pressing the pressure member against the fixing roller is weakened in order to reduce this torque, fixing failure occurs when a recording sheet, particularly thick paper is passed.
To solve such a problem, for example, as shown in FIG. 7, a plurality of pressure pads 703 to 705 are arranged around the fixing roller 702 heated by the electric heater 701 so as to press the fixing roller 702 and pressurize. A fixing device that forms a plurality of nip portions between each of the pads 703 to 705 has been proposed. In this fixing device, fixing defects are prevented by passing recording sheets sequentially through a plurality of nip portions and repeating fixing (see Patent Document 1).

Japanese Utility Model Publication No. 60-8966

However, the fixing device according to the related art has a problem that paper conveyance becomes unstable between a plurality of nip portions, and a jam (paper jam) of a recording sheet is likely to occur.
SUMMARY An advantage of some aspects of the invention is that it provides a fixing device and an image forming apparatus that realize stable paper conveyance using a pressure pad.

In order to achieve the above object, the fixing device and the fixing device according to the present invention include a fixing rotator that melts a toner image carried by a recording sheet, and a pressure contact member that is in contact with the peripheral surface of the fixing rotator. and a plurality of pressure member for crimping, both the plurality of pressure member, a pressure member of a rigid type having a planar portion, the planar portion is pressed against the respective fixing rotator, The planar portion exists on the extension of the discharge direction of the recording sheet discharged from the nip portion formed by the upstream pressure member and the fixing rotator in the recording sheet conveyance direction , and the fixing rotator rotates. In the plane perpendicular to the axis, the angle formed by the discharge direction and the plane portion is greater than 0 degree and equal to or less than 40 degrees , and the downstream plane portion exists on the extension of the upstream plane portion. And

  According to this configuration, the plane portion of the downstream pressure member on the extension in the discharge direction of the recording sheet discharged from the nip portion formed by the upstream pressure member and the fixing rotating body in the recording sheet conveyance direction. In the plane perpendicular to the rotation axis of the fixing rotator, the angle formed by the discharge direction and the plane portion is greater than 0 degree and less than or equal to 40 degrees. Therefore, the recording discharged from the upstream nip portion The sheet is stably guided to the flat portion, and the recording sheet that hits the flat portion also enters the upstream nip portion, that is, the nip portion formed by the downstream pressure member and the fixing rotating body. To do. Therefore, it is possible to prevent paper jamming of the recording sheet and realize high paper transportability.

In addition , since the discharge direction and the upstream plane portion coincide with each other, the angle formed by the discharge direction and the downstream plane portion can be more reliably within the above-described preferable range.

In consideration of disposing a plurality of pressure members, it is preferable that an angle formed by the discharge direction and the planar portion is 20 degrees or more in a cross section perpendicular to the rotation axis of the fixing rotating body. .
An image forming apparatus according to the present invention includes the fixing device according to the present invention. If it does in this way, the above effects can be acquired as it is.

1 is a diagram illustrating a main configuration of an image forming apparatus according to an embodiment of the present invention. 2 is a cross-sectional view illustrating a main configuration of a fixing device 117. FIG. 4 is a cross-sectional view showing the positional relationship between the pressure pads 202 and 205 and the fixing roller 200 in a cross section perpendicular to the rotation axis of the fixing roller 200. FIG. 10 is a table showing a relationship between an angle θ formed by flat portions 301 and 302 of the pressure pads 202 and 205 and a paper jam. FIG. 9 is a cross-sectional view illustrating a configuration of a fixing device according to a modification using a pressure roller. It is sectional drawing which shows the structure of the fixing device which concerns on the modification provided with three pressurization pads. It is a figure which shows the structure of the fixing device based on a prior art.

Hereinafter, embodiments of a fixing device and an image forming apparatus according to the present invention will be described with reference to the drawings.
[1] Configuration of Image Forming Apparatus First, the configuration of the image forming apparatus according to the present embodiment will be described.
FIG. 1 is a diagram illustrating a main configuration of the image forming apparatus according to the present embodiment. As shown in FIG. 1, the image forming apparatus 1 is a so-called multi function peripheral (MFP) having a printing function, a copying function, and a facsimile function, and includes a document reading unit 100, an image forming unit 110, and an image forming unit 110. A paper feeding unit 120 is provided. The document reading unit 100 transports a document placed on a document table tray by an automatic document feeder (ADF) and optically reads the document to generate image data. The image data is stored in the control unit 112 described later.

  The image forming unit 110 includes an image forming unit 111Y to 111K, a control unit 112, an intermediate transfer belt 113, a secondary transfer roller pair 114, a timing roller pair 115, a cleaner 116, a fixing device 117, a discharge roller pair 118, and a discharge tray 119. A reflection density sensor 102 and primary transfer rollers 103Y to 103K. Further, Y (yellow), M (magenta), C (cyan), and K (black) toner cartridges 101Y to 101K are mounted on the image forming unit 110.

  Receiving toner supply from the toner cartridges 101Y to 101K, the image forming units 111Y to 111K form toner images of YMCK colors under the control of the control unit 112, respectively. The primary transfer rollers 103Y to 103K perform electrostatic transfer (primary transfer) to the intermediate transfer belt 113 so that these toner images overlap. The intermediate transfer belt 113 is an endless rotating body, and travels in the direction of arrow A to convey the primary transferred toner image to the secondary transfer position. As the material of the intermediate transfer belt 113, polycarbonate, polytetrafluoroethylene (PTFE), or a semiconductive material in which carbon is dispersed using polyimide as a main raw material may be used.

  The paper feeding unit 120 includes a paper feeding cassette 121 that stores the recording paper P for each paper size, and supplies the recording paper P to the image forming unit 110 one by one. The supplied recording paper P is carried out in parallel with the intermediate transfer belt 113 carrying the toner image, and is carried to the secondary transfer roller pair 114 via the timing roller pair 115. The timing roller pair 115 includes a pair of rollers, and adjusts the timing at which the recording paper P reaches the secondary transfer roller pair 114.

  The secondary transfer roller pair 114 is composed of a pair of rollers to which a transfer voltage is applied, and the roller pairs are pressed against each other to form a transfer NIP portion. In the transfer NIP portion, the toner image on the intermediate transfer belt 113 is electrostatically transferred (secondary transfer) onto the recording paper P. The recording paper P to which the toner image is transferred is conveyed to the fixing device 117. Further, the residual toner remaining on the intermediate transfer belt 113 after the secondary transfer is further conveyed in the direction of arrow A, and then scraped off by the cleaner 116 and discarded.

  The fixing device 117 heats and melts the toner image carried on the recording paper P and presses the toner image on the recording paper P. The recording paper P to which the toner image is fused is discharged onto the paper discharge tray 119 by the paper discharge roller pair 118. The control unit 112 controls the operation of the image forming apparatus 1 including the above. The control unit 112 transmits / receives image data to / from other apparatuses such as a personal computer (PC) and a facsimile apparatus, and receives a print job.

In addition, the fixing device executes an image stabilization process in order to stabilize the image quality to be formed. The reflection density sensor 102 optically detects a resist pattern formed on the secondary transfer belt during image stabilization processing by illuminating the object and measuring the density based on the amount of reflected light.
In transferring the toner image, a transfer charger or a transfer belt may be used instead of the transfer roller. Further, when the residual toner on the intermediate transfer belt 113 is removed, a cleaning brush, a cleaning roller, or the like may be used instead of the cleaner 116 (cleaning blade).

[2] Configuration of Fixing Device 117 Next, the configuration of the fixing device 117 will be described.
FIG. 2 is a cross-sectional view showing the main configuration of the fixing device 117. As shown in FIG. 2, the fixing device 117 includes a fixing roller 200, a halogen heater 201, pressure pads 202 and 205, support members 203 and 206, and bolts 204 and 207. The fixing roller 200 is a cylindrical body made of aluminum (may be made of iron) and having a thickness of 0.6 mm and an outer diameter of 30 mm. In the fixing roller 200, the outer peripheral surface of the aluminum cylinder is blasted and then coated with a fluororesin to form a release layer.

  Each of the pressure pads 202 and 205 is formed by bending a sheet metal made of SUS (Steel Use Stainless). Further, the pressure pads 202 and 205 are coated with fluorine on the surfaces that contact the fixing roller 200. The pressure pads 202 and 205 are fixed to the support members 203 and 206 by bolts 204 and 207, respectively, at one end, and are fixed to the housing (not shown) of the fixing device 117 via the support members 203 and 206. Further, the free end sides of the pressure pads 202 and 205 are in pressure contact with the outer peripheral surface of the fixing roller 200, and the pressing force is about 30N.

Note that the pressure pads 202 and 205 are fixed to the support members 203 and 206 so as to be in pressure contact with the outer peripheral surface of the fixing roller 200 in a state of being elastically deformed. As a result, the pressure contact force on the outer peripheral surface of the fixing roller 200 is adjusted.
The recording sheet enters the fixing device 117 in the direction of arrow B, and is first pressed against the fixing roller 200 by the pressure pad 202 to melt and press the toner image. Subsequently, the recording sheet is also pressed against the fixing roller 200 by the pressure pad 205, and the toner image is further melted and pressed. During this time, the recording sheet is conveyed as the fixing roller 200 rotates in the direction of arrow C due to the frictional force with the fixing roller 200.

Thereafter, the recording sheet is guided to the discharge roller pair 118 by the guide member 208 and discharged onto the discharge tray 119 by the discharge roller pair 118.
[3] Positional relationship between the pressure pads 202 and 205 and the fixing roller 200 Next, the positional relationship between the pressure pads 202 and 205 and the fixing roller 200 will be described from the viewpoint of whether or not the conveyance property of the recording sheet is good.

FIG. 3 is a cross-sectional view showing the positional relationship between the pressure pads 202 and 205 and the fixing roller 200 in a cross section perpendicular to the rotation axis of the fixing roller 200. As shown in FIG. 3, the pressure pads 202 and 205 have flat portions 301 and 302 that press against the fixing roller 200, respectively.
The flat portion 301 is located upstream of the flat portion 302 in the recording sheet conveyance direction. When the flat portion 301 is extended to the downstream side in the recording sheet conveyance direction, the flat portion 302 exists. For this reason, since the flat portion 302 exists on the extension in the discharge direction of the recording sheet discharged from the nip portion formed by the pressure pad 202 and the fixing roller 200, the recording sheet is added by the flat portion 301 of the pressure pad 202. Guided to the planar portion 302 of the pressure pad 205. As a result, the recording sheet is smoothly conveyed to the nip formed by the fixing roller 200 and the pressure pad 205, so that a paper jam can be prevented.

  Further, the angle θ formed by the plane portions 301 and 302 cannot be less than 0 degrees because of contact with the outer peripheral surface of the fixing roller 200, and is always larger than 0 degrees. On the other hand, when the angle θ is too large, the recording sheet guided to the pressure pad 202 hits the flat portion 302 of the pressure pad 205 at a deep angle, which may cause a paper jam. For this reason, an experiment for confirming whether or not a paper jam has occurred by changing the angle θ formed by the planar portions 301 and 302 yielded the following results.

FIG. 4 is a table showing the above experimental results. As shown in FIG. 4, no paper jam occurred when the angle θ was in the range of 30 degrees to 40 degrees, but the occurrence frequency of paper jams increased when the angle θ exceeded 45 degrees. It should be noted that in each of the cases where the recording sheet conveyance speed is 70 mm / second and 140 mm / second, the pressing force for pressing the pressure pads 202 and 205 against the outer peripheral surface of the fixing roller 200 is 30 N. In both cases, the experimental results were as shown in FIG. 4. In the experiment, plain paper having a basis weight of 80 g / m ² was used, and the fixing temperature was 180 ° C.

  Now, since both the flat portions 301 and 302 are in contact with the outer peripheral surface of the fixing roller 200, the angle θ must be less than 180 degrees. In the case where the angle θ is greater than 50 degrees and less than 180 degrees, no experiment has been performed, but the recording sheet guided to the pressure pad 202 reaches the flat surface portion 302 of the pressure pad 205 at a deeper angle. Obviously, the occurrence frequency of the paper jam is further increased.

For this reason, it is desirable to arrange the pressure pads 202 and 205 so that the angle θ is 40 degrees or less. In order to arrange the pressure pads 202 and 205 without interfering with each other, it is practical to set the angle θ to 20 degrees or more.
Therefore, if the pressure pads 202 and 205 are disposed so that the angle θ is in the range of 20 degrees or more and 40 degrees or less, the recording sheet can be smoothly placed in the nip portion formed by the pressure pad 205 and the fixing roller 200. You can rush. As a result, paper jams can be prevented and high paper transportability can be realized.

[4] Modifications Although the present invention has been described based on the embodiments, it is needless to say that the present invention is not limited to the above-described embodiments, and the following modifications can be implemented. .
(1) In the above embodiment, the case where the two pressure pads 202 and 205 are brought into pressure contact with the fixing roller 200 has been described, but the present invention is not limited to this. Anyway. FIG. 5 is a cross-sectional view illustrating a configuration of a fixing device according to this modification.

  As shown in FIG. 5, the fixing device 5 according to this modification includes a pressure roller 501 instead of the pressure pad 202. A flat portion 302 of the pressure pad 205 exists on the extension in the discharge direction of the recording sheet discharged from the nip formed by the pressure roller 501 and the fixing roller 200. Therefore, the recording sheet discharged from the nip portion formed by the pressure roller 501 and the fixing roller 200 hits the flat portion 302 of the pressure pad 205 and then enters the nip portion formed by the pressure pad 205 and the fixing roller 200. To do.

  The angle θ formed by the discharge direction of the recording sheet discharged from the nip portion formed by the pressure roller 501 and the fixing roller 200 and the flat portion 302 of the pressure pad 205 is set to 40 degrees or less to prevent paper jamming. The recording sheet can be smoothly conveyed and fixed. In order to avoid the interference between the pressure pad 205 and the pressure roller 501, it is conceivable to reduce the outer diameter of the pressure roller 501. However, if the outer diameter of the pressure roller 501 is made too small, the discharge direction of the recording sheet discharged from the nip formed by the pressure roller 501 and the fixing roller 200 may become unstable. Is preferably 20 degrees or more.

(2) In the above embodiment, the case where the two pressure pads 202 and 205 are brought into pressure contact with the fixing roller 200 has been described, but it is needless to say that the present invention is not limited to this. The above pressure pad may be pressed against the fixing roller 200. FIG. 6 is a cross-sectional view illustrating a configuration of a fixing device according to this modification.
As shown in FIG. 6, the fixing device 117 according to this modification includes three pressure pads 202, 205, and 601, and one end portion (fixed end) of the pressure pad 601 is a support member. It is fixed to the housing of the fixing device 117 by being fixed to 602 using a bolt 603. The flat portion 604 on the free end side of the pressure pad 601 is in pressure contact with the outer peripheral surface of the fixing roller 200, and the pressing force is about 30N.

  The recording sheet carrying the unfixed toner image is guided by the guide member 610 toward the nip portion formed by the pressure pad 202 and the fixing roller 200 in the direction of arrow B. As the fixing roller 200 rotates in the direction of arrow C, the recording sheet is passed through a nip portion between the fixing roller 200 and the pressure pads 205 and 601, and the toner image is thermally fixed. Thereafter, the recording sheet advances in the direction of arrow D and is guided by a guide member 208 to a pair of discharge rollers (not shown).

  The angle θ formed by the plane portions 301 and 302 of the pressure pads 202 and 205 is larger than 0 degree and within a range of 40 degrees or less, and the angle θ ′ formed by the plane portions 302 and 604 of the pressure pads 205 and 601. Is also in the range of greater than 0 degrees and less than 40 degrees. Since it is necessary to sequentially arrange the three pressure pads 202, 205, and 601 around the fixing roller 200, the angles θ and θ ′ are each preferably 20 degrees or more.

By doing so, it is possible to prevent paper jamming of the recording sheet that is passed through the fixing device 117 and realize high transportability. At the same time, since three or more fixing nips can be passed through the recording sheet, high fixability can be realized.
(3) In the above embodiment, the case where the fixing roller 200 is heated using the halogen heater 201 has been described. However, the present invention is not limited to this, and an alternating magnetic field is applied to the electromagnetic induction heating element. The fixing roller 200 may be heated using a heat source other than the halogen heater 201, such as an electromagnetic induction heating method in which Joule heat is generated by eddy current or a resistance heating method in which a resistance heating element is energized to generate heat. Even when the halogen heater 201 is used, for example, a plurality of halogen heaters 201 may be provided, and the halogen heaters 201 having different sizes may be switched depending on the size of the recording sheet to be passed. .

Even if a fixing belt is used instead of the fixing roller 200, the effect of the present invention is the same. When using the fixing belt, it is only necessary to provide a pressure contact member that presses against the pressure pad via the fixing belt. The smaller the contact area between the fixing belt and the pressure contact member, the more the thermal efficiency of the fixing device can be improved. .
(4) In the above embodiment, a so-called multi-function device has been described as an example. However, it goes without saying that the present invention is not limited to this, and a single function device such as a printer device, a copying device, or a facsimile machine can be used instead. Even if the present invention is applied to an apparatus or the like, the same effect can be obtained. Even when applied to a multi-function device, if the fixing device according to the present invention is provided, the effects of the present invention can be obtained regardless of the combination of functions provided.

  The fixing device and the image forming apparatus according to the present invention are useful as a technique for improving the transportability of a recording sheet in a fixing device in which a plurality of fixed pressure members are pressed against a fixing rotating body.

1 …………………………………………………… Image forming device 117 ……………………………………………… Fixing device 200, 702 ………… …………………… Fixing roller 201 ………………………………………… Halogen heaters 202, 205, 601, 703 to 705... Pressure pads 203, 206, 602. …………………… Support members 204, 207, 603 ……………………… Bolts 208, 610 …………………………………… Guide members 301, 302, 604 …… ………………… Flat surface portion 501 ………………………………………… Pressure roller

Claims (3)

A fixing rotator for melting a toner image carried by the recording sheet;
A plurality of pressure members that are pressed against the circumferential surface of the fixing rotator and press the molten toner to the recording sheet,
Among the plurality of pressure members, the upstream pressure member and the downstream pressure member in the recording sheet conveyance direction are fixed pressure members having a planar portion,
The plane portion is pressed against the fixing rotator,
On the extension of the discharge direction of the recording sheet discharged from the nip formed by the upstream pressure member and the fixing rotator, the planar portion exists,
In the plane perpendicular to the rotation axis of the fixing rotator, the angle formed by the discharge direction and the plane portion is greater than 0 degree and equal to or less than 40 degrees , and the downstream plane portion is on the extension of the upstream plane portion. A fixing device characterized in that it exists . The fixing device according to claim 1 , wherein an angle formed by the discharge direction and the planar portion is 20 degrees or more in a cross section perpendicular to the rotation axis of the fixing rotator. An image forming apparatus comprising: a fixing device according to claim 1 or 2.

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