JP2008001483A - Image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce fluctuation of a sheet conveying speed due to swelling of a sheet conveying member. <P>SOLUTION: The image forming device (U) is provided with a fixing device (F) for heating/fixing an unfixed toner image on a surface of recording sheet (S); the sheet conveying member (Ra1), i.e., a sheet conveying member (Ra1) arranged on a downstream side in a sheet conveying direction of the fixing device (F) and conveying the recording sheet (S), deposited with a liquid-like component contained in the toner and becoming liquid-like by being heated/melted by the fixing device (F); and an absorption member (4) abutted/arranged on the sheet conveying member (Ra1) and absorbing the liquid-like component deposited on the surface of the sheet conveying member (Ra1). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a printer, a FAX, a copying machine, or a multi-function machine having all or a plurality of functions, and more particularly, an image forming apparatus having a fixing device on which an unfixed toner image on a recording sheet surface is heated and fixed. About.

In a conventional electrophotographic image forming apparatus, a toner image is transferred to the surface of a recording sheet, and the toner is heated and melted by a fixing device to be fixed on the recording sheet. The toner to be heat-fixed is made of a material such as a resin that is melted by heating. Some recently used emulsion polymerization toners contain a low melting point wax (paraffin).
When the toner containing the low melting point wax is transported by a rubber roll (sheet transport member) on the downstream side of the fixing device before being sufficiently cooled after passing through the fixing region, the liquid wax comes into contact with the rubber roll. , May penetrate into the rubber. When the wax penetrates, the rubber roll swells, the roll diameter increases, and the peripheral speed of the rubber roll fluctuates. As a result, there is a problem that the peripheral speed, that is, the sheet conveying speed fluctuates due to swelling of the rubber roll, and trouble such as paper jam occurs.

Although different from the swelling of the rubber roll by the melted toner, in the technical field of the image forming apparatus, the following conventional techniques (J01) and (J02) are provided as techniques for preventing the liquid from penetrating and swelling the member. It is known.
(J01) Technology described in Patent Document 1 (Japanese Patent Laid-Open No. 11-219051) Patent Document 1 describes a fixing device having an oil application unit that applies silicon oil as a release agent to the surface of a fixing belt. In order to prevent swelling by silicon oil, a technique is described in which an elastic layer of a belt is formed by laminating a first elastic layer, a release agent barrier layer (fluororubber), and a third elastic layer.
(J02) Technology described in Patent Document 2 (Japanese Patent Laid-Open No. 2004-138743) Patent Document 2 describes a liquid developer (dimethylpolysiloxane oil or the like) in a developing device that uses a liquid developer in a developer storage tank. An intermediate roller is provided between the application roller and the developing roller, and the intermediate roller has a three-layer structure of a metal core, an elastic layer, and a conductive layer (a coating layer of PTFE dispersion), and the material of the elastic layer is the solubility index of the developer. A technique for preventing the elastic layer from being swollen or dissolved by a liquid developer by being two or more away from (SP value) (urethane rubber or the like) is described.

Japanese Patent Application Laid-Open No. 11-219051 (“0035” to “0036”, “0047” to “0048”) JP 2004-138743 A ("0006", "0010" to "0011")

(Problems of conventional technology)
In the prior arts (J01) and (J02), since the belt and roll are composed of a plurality of layers, the structure is complicated, and the thickness of the layer can be controlled with high accuracy in manufacturing, and materials with different characteristics can be used. There is a problem that it is very difficult to mold. In addition, since parts are composed of a combination of materials with different characteristics, peeling between layers may occur due to differences in the degree of deterioration of each layer during deterioration over time, thermal deterioration, or deterioration due to paper feeding. There was a problem that the shape was distorted and the parts were broken. Furthermore, the fluororubber and PTFE coating used for the barrier layer for preventing the permeation of oils are expensive, and these materials have a low affinity with other materials. In the case of the belt shape, there is a problem that it is difficult to maintain the adhesive strength with other materials.

In view of the above circumstances, the present invention has the following contents (O01) and (O02) as technical problems.
(O01) To reduce fluctuations in the sheet conveying speed due to swelling of the sheet conveying member.
(O02) To suppress fluctuations in the sheet conveyance speed with a low-cost and simple configuration that is resistant to failure over time.

Next, the present invention that solves the above problems will be described. In order to facilitate correspondence with the constituent elements of the embodiments described later, the constituent elements of the present invention are enclosed in parentheses. I will add that.
The reason why the present invention is described in correspondence with the reference numerals of the embodiments described later is to facilitate the understanding of the present invention, and not to limit the scope of the present invention to the embodiments.

(First invention)
In order to solve the technical problem, the image forming apparatus (U) of the first invention is:
A fixing device (F) for heating and fixing an unfixed toner image on the surface of the recording sheet (S);
A sheet conveying member (Ra1) that is disposed downstream of the fixing device (F) in the sheet conveying direction and conveys the recording sheet (S), and is included in the toner and heated and melted by the fixing device (F) A sheet conveying member (Ra1) to which the liquid component that has been liquefied is attached;
An absorbing member (4) disposed in contact with the sheet conveying member (Ra1) and absorbing a liquid component adhering to the surface of the sheet conveying member (Ra1);
It is provided with.

(Operation of the first invention)
In the image forming apparatus (U) of the first invention having the above-described configuration requirements, the sheet conveying member (Ra1) disposed on the downstream side in the sheet conveying direction of the fixing device (F) conveys the recording sheet (S). . A liquid component that is contained in the toner and is heated and melted by the fixing device (F) is attached to the sheet conveying member (Ra1). The absorbing member (4) is disposed in contact with the sheet conveying member (Ra1) and absorbs the liquid component adhering to the surface of the sheet conveying member (Ra1).
For this reason, in the image forming apparatus (U) according to the first aspect of the present invention, the swelling of the sheet conveying member (Ra1) caused by the liquid component permeating into the sheet conveying member (Ra1) can be reduced. Therefore, since the change in the outer diameter of the sheet conveying member (Ra1) can be reduced, fluctuations in the sheet conveying speed can be reduced.

(First Embodiment 1)
An image forming apparatus (U) according to a first aspect of the present invention is the first invention and the first aspect of the first aspect of the present invention.
The absorbent member (4) made of a material having a difference between the SP value of the liquid component and the SP value of the absorbent member (4) within 0.5,
It is provided with.

(Operation of Form 1 of the First Invention)
In the image forming apparatus (U) according to the first aspect of the present invention having the above-described configuration, the absorbing member (4) has a difference between the SP value of the liquid component and the SP value of the absorbing member (4) of 0. Since it is comprised by the material which is less than 5, the said liquid component can be absorbed easily.

(First Embodiment 2)
The image forming apparatus (U) according to the second aspect of the present invention is the shaft (3a) rotatably supported in the second aspect of the first invention, and the SP value of the liquid component supported by the shaft (3a). A sheet conveying rubber roll (3b) composed of a material having a difference of 0.5 or more, and the sheet conveying member (Ra1),
It is provided with.

(Operation of the second aspect of the first invention)
In the image forming apparatus (U) according to the second aspect of the first invention having the above-described configuration, the sheet conveying rubber roll (3b) of the sheet conveying member (Ra1) is supported by a shaft (3a) that is rotatably supported. And since the difference with the SP value of the said liquid component is comprised with the material of 0.5 or more, the swelling of the rubber roll (3b) for sheet conveyance can be reduced.

(Embodiment 3 of the first invention)
An image forming apparatus (U) according to a first aspect of the first invention is the first invention and the first or second aspect of the first invention.
As the liquid component, a paraffin wax having an SP value of 8 is used.

(Operation of the third aspect of the first invention)
In the image forming apparatus (U) according to the third aspect of the first invention having the above-described configuration, a paraffin wax having an SP value of 8 can be used as the liquid component.

(First aspect 4)
An image forming apparatus (U) according to a fourth aspect of the first invention is the first to third aspects of the first invention.
The absorbent member (4) made of any material of ethylene / propylene rubber, isoprene rubber, isobutylene / isoprene rubber and butadiene rubber,
It is provided with.

(Operation of the fourth aspect of the first invention)
In the image forming apparatus (U) according to the fourth aspect of the first invention having the above configuration, the absorbing member (4) is made of any material of ethylene / propylene rubber, isoprene rubber, isobutylene / isoprene rubber and butadiene rubber. Therefore, the absorbing member (4) can absorb the liquid component.

(First embodiment 5)
An image forming apparatus (U) according to a fifth aspect of the first invention is the third to fourth aspects of the first invention.
The sheet conveying member (Ra1) composed of any material of styrene / butadiene rubber, chloroprene rubber, nitrile rubber, urethane rubber and silicon rubber,
It is provided with.

(Operation of the fifth aspect of the first invention)
In the image forming apparatus (U) according to the fifth aspect of the first invention having the above-described configuration, the sheet conveying member (Ra1) is made of any material of chloroprene rubber, nitrile rubber, urethane rubber, and silicon rubber. Therefore, the swelling by the said sheet | seat conveyance member (Ra1) the said liquid component can be reduced.

The above-described present invention has the following effects (E01) and (E02).
(E01) It is possible to prevent fluctuations in the sheet conveying speed due to swelling of the sheet conveying member.
(E02) It is possible to suppress fluctuations in the sheet conveyance speed with a low-cost, simple and strong structure against failure over time.

Next, specific examples (examples) of the embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to the following examples.
In order to facilitate understanding of the following description, in the drawings, the front-rear direction is the X-axis direction, the left-right direction is the Y-axis direction, the up-down direction is the Z-axis direction, and arrows X, -X, Y, -Y, The direction indicated by Z and -Z or the indicated side is defined as front, rear, right, left, upper, lower, or front, rear, right, left, upper, and lower, respectively.
In the figure, “•” in “○” means an arrow heading from the back of the page to the front, and “×” in “○” is the front of the page. It means an arrow pointing from the back to the back.
In the following description using the drawings, illustrations other than members necessary for the description are omitted as appropriate for easy understanding.

FIG. 1 is an overall explanatory view of an image forming apparatus according to Embodiment 1 of the present invention.
In FIG. 1, in a printer U as an image forming apparatus according to a first embodiment of the present invention, a discharge tray TRh is provided on the upper surface of the printer body U1, and a recording sheet S on which an image is recorded is accommodated in the lower portion of the printer body U1. The sheet cassette TR1 to be used is accommodated. The printer main body U1 has a front cover U2 that is rotatably supported around a front rotation center U2a. When a paper jam occurs, the user rotates the front cover U2 to jam the paper. Can be eliminated. A UI (user interface) for a user to perform an input operation is provided on the upper surface of the front cover U2.

In FIG. 1, a printer main body U1 includes a controller C constituted by a microcomputer, an IPS (image processing system) whose operation is controlled by the controller C, a laser drive circuit DL, a power supply device E, and the like. The power supply device E applies a bias voltage to a charging roller CR, developing rollers GRy to GRk, a transfer roller (T1, T2b), and the like which will be described later.
The IPS (image processing system) converts print data input from an external host computer or the like into image data for forming a latent image and outputs it to the laser drive circuit DL at a predetermined timing. The laser drive circuit DL outputs a laser drive signal to the latent image forming device ROS (optical scanning device) according to the input image data. The ROS emits a laser beam (image writing light) L for image writing in accordance with a laser drive signal.

The rotationally driven image carrier (photosensitive drum) PR disposed above the ROS is uniformly charged by the charging roll CR, and then the ROS (latent image formation) at the latent image writing position Q1. An electrostatic latent image is formed by exposure scanning with the laser beam L of the apparatus. When forming a full-color image, electrostatic latent images corresponding to four color images of K (black), Y (yellow), M (magenta), and C (cyan) are sequentially formed. Only the electrostatic latent image corresponding to the (black) image is formed.
The surface of the image carrier PR on which the electrostatic latent image is formed rotates and moves sequentially through the development area Q2 and the primary transfer area Q3.

A rotary developing device G is arranged above the ROS. The rotary developing device G develops four colors of K (black), Y (yellow), M (magenta), and C (cyan) that sequentially rotate and move to the developing region Q2 as the rotation shaft Ga rotates. The units GK, GY, GM, and GC are included. Each color developing device GK, GY, GM, GC has a developing roll (developer carrier) GRk, GRy, GRm, GRc for transporting the developer to the developing area Q2, and passes through the developing area Q2. The electrostatic latent image on the image carrier PR to be developed is developed into a toner image.
During the operation of the image forming apparatus U, the developing units GK to GC are rotated from the developing position GP1 to the developing position (first stop position) GP1 facing the image carrier PR as the developing apparatus G rotates. The second stop position GP2 rotated 90 ° in the rotation direction, the third stop position GP3 rotated 180 °, and the fourth stop position GP4 rotated 270 ° are sequentially rotated and stopped.
The rotational force is transmitted to the developing rolls GRy to GRk of the developing devices GY to GK stopped at the developing position GP1, and the developing operation can be executed. Further, new developers are supplied from the toner supply cartridges TCk, TCy, TCm, and TCc to the developing devices GK, GY, GM, and GC stopped at the developing position GP1. In the developing device G of Example 1, an emulsion polymerization toner containing paraffin which is a low melting point wax is used as a developer.

In front of the image carrier PR, an intermediate transfer belt B wound around the image carrier PR, a plurality of driven rolls Rj, a wrap-in roll Rw1 disposed at a winding start position, and a primary transfer bias 1 are applied. A plurality of belt support rolls (Rj, Rw1, Rw2, T1, T2a) including a secondary bias roll (primary transfer roll) T1, a wrap-out roll Rw2 and a backup roll T2a disposed at the winding end position, and support them A belt frame (not shown).
The intermediate transfer belt B is rotatably supported by the belt support rolls (Rj, Rw1, Rw2, Rt1, T2a), and is driven by the rotation of the image carrier PR during the image forming operation, in the direction of the arrow Yb. Rotate to.

When forming a full-color image, an electrostatic latent image of the first color is formed at the latent image writing position Q1, and a toner image of the first color is formed in the development region Q2. The toner image is electrostatically primary transferred onto the intermediate transfer belt B by the primary bias roll T1 when passing through the primary transfer region Q3 between the wrap-in roll Rw1 and the wrap-out roll Rw2. Thereafter, similarly, the second, third, and fourth color toner images are sequentially superimposed and transferred onto the intermediate transfer belt B carrying the first color toner image in order, and finally, full-color multiplexing is performed. A toner image is formed on the intermediate transfer belt B.
In the case of forming a monochromatic monochromatic image, only one developing device is used, and the monochromatic toner image is primarily transferred onto the intermediate transfer belt B.
After the primary transfer, the surface of the image carrier PR is cleaned by an image carrier cleaner CL1.

At a position facing the backup roll T2a, the secondary transfer roll T2b is disposed so as to be movable between a position separated from the backup roll T2a and a position in contact with the backup roll T2a. The backup roll T2a and the secondary transfer roll T2b constitute a secondary transfer device T2. A secondary transfer region Q4 is formed by a contact region between the backup roll T2a and the secondary transfer roll T2b. The toner adhering to the secondary transfer roll T2b is cleaned by a secondary transfer roll cleaner CLt.
A secondary transfer voltage having a polarity opposite to the charging polarity of the toner used in the developing device G is supplied from the power supply circuit E to the secondary transfer roll T2b, and the power supply circuit E is controlled by the controller C.

A paper feed tray (manual paper feed tray) TR1 for storing the recording sheet S is disposed below the printer main body U1, and the recording sheet S in the paper feed tray TR1 is placed on the uppermost surface of the sheet by the sheet placement plate TR1a. Is held at the paper feed position in contact with the pickup roll Rp. The recording sheets S accommodated in the paper feed tray TR1 are taken out by the pickup roll Rp at a predetermined timing, separated one by one by the separating roll Rs having the feed roll Rs1 and the retard roll Rs2, and conveyed in the sheet conveyance path SH. The roll Ra is transported to the registration roll Rr. Further, the sheet S fed from the manual feed tray TR0 is conveyed to the registration roll Rr by the manual feed roll Rp0.
The recording sheet S transported to the registration roll Rr is transported to the secondary transfer area Q4 at the same timing as the multiple toner image or single color toner image that has been primarily transferred moves to the secondary transfer area Q4. .
In the secondary transfer area Q4, the secondary transfer unit T2 electrostatically secondary-transfers the toner image on the intermediate transfer belt B onto the recording sheet S. The residual toner is removed from the intermediate transfer belt B after the secondary transfer by the belt cleaner CL2.

The secondary transfer roll T2b and the belt cleaner CL2 are disposed so as to be separated from (contacted with and separated from) the intermediate transfer belt B. When a color image is formed, an unfixed toner image of the final color is formed. Is separated from the intermediate transfer belt B until it is primarily transferred to the intermediate transfer belt B.
A toner image forming apparatus that forms a toner image by transferring the toner image onto the recording sheet S by the image carrier PR, the charging roll CR, the developing device G, the primary transfer roll T1, the intermediate transfer belt B, the secondary transfer device T2, and the like. PR + CR + G + T1 + B + T2).

The recording sheet S on which the toner image is secondarily transferred is conveyed to a fixing region Q5 configured by a region (nip) where the heating roll Fh and the pressure roll Fp of the fixing device F are in pressure contact with each other. The recording sheet S passing through the fixing area Q5 is heated and fixed by the fixing device F. The recording sheet S on which the toner image has been heated and fixed is conveyed by a fixing device downstream side conveyance roll (upstream side sheet conveyance member) Ra1 disposed on the downstream side of the fixing device F in the sheet conveyance direction. The recording sheet S transported by the fixing device downstream side transport roll Ra1 is fed to the image forming apparatus by a sheet discharge roll (downstream sheet transport member) Rh disposed downstream of the fixing device downstream side transport roll Ra1 in the sheet transport direction. The sheet is discharged from the sheet discharge port Ka formed at the upper end of U1 to the discharge tray TRh.
Note that the fixing device downstream-side conveyance roll Ra1 and the sheet discharge roll Rh according to the first exemplary embodiment are configured by rubber rolls in which the outer periphery of the core material is coated with elastic rubber made of CR (chloroprene rubber). In the first exemplary embodiment, the initial roll diameters of the fixing device downstream-side transport roll Ra1 and the sheet discharge roll Rh are set to the same roll diameter, and are set to be transported at the same sheet transport speed.

When performing duplex printing, the recording sheet S on which single-sided recording has been performed is switched back by the sheet discharge roller Rh, conveyed to the sheet reversing path SH2, and retransmitted to the registration roll Rr with the front and back reversed.
The pickup roll Rp, separation roll Rs, conveyance roll Ra, fixing area downstream conveyance roll Ra1, sheet discharge roll Rh, and the like constitute the sheet conveyance apparatus of the first embodiment.

FIG. 2 is an enlarged view of a main part of the first embodiment of the present invention.
In FIG. 2, a fixing device downstream side transporting roller Ra <b> 1 disposed on the downstream side in the sheet transporting direction of the fixing device F includes a front side (X side) driven roller 2 and a rear side (−X side) driving roller 3. have. The drive roller 3 is rotated by a rotation from a drive motor (not shown). The driven roller 2 rotates following the rotation of the driving roller 3. The driven roller 2 and the driving roller 3 have shafts 2a and 3a, respectively.
Cylindrical rubber rolls 2b and 3b are supported on the outer peripheral surfaces of the shafts 2a and 3a, respectively. The rubber rolls 2b and 3b of Example 1 are composed of a single layer CR (chloroprene rubber, SP value of 8.71). A wax absorbing roll 4 (absorbing member) is in contact with a facing region 3c on the outer left peripheral surface of the rubber roll 3b of the driving roller 3. The rubber roll 4a of the wax-absorbing roll 4 of Example 1 is composed of a single-layer EPDM (ethylene propylene rubber, SP value 8.00).

(Operation of Example 1)
In the image forming apparatus U of Example 1 having the above-described constituent elements, an emulsion polymerization toner containing paraffin having a low melting point (about 90 ° C.) is used, and the recording sheet S on which the unfixed toner image is transferred is used. When passing through the fixing area Q5, the toner is melted and fixed. At this time, the low melting point paraffin also melts and becomes liquid. When the recording sheet S that has passed through the fixing region Q5 (about 200 ° C.) is transported by the fixing device downstream transporting roller Ra1 on the downstream side of the fixing device before being sufficiently cooled, the liquid paraffin is downstream of the fixing device. It contacts the side transport roll Ra1 and adheres to the surface of the rubber roll 3b formed on the outer peripheral surface of the shaft 3a of the driving roller 3 of the downstream transport roll Ra1 of the fixing device. The paraffin adhering to the surface of the rubber roll 3b is conveyed to a region 3c (liquid component absorption region) facing the wax absorbing roll 4 as the rubber roll 3b rotates. In the facing region 3c, the paraffin on the surface of the rubber roll 3b adheres to and is absorbed by the wax absorbing roll 4 from the rubber roll 3b, and the paraffin is removed from the surface of the rubber roll 3b.

(Experimental example)
In this experimental example, the swelling of the outer diameter of the rubber roll that occurs when the rubber roll material that can be used in the rubber rolls 2b, 3b, and 4a of the image forming apparatus of the first embodiment having the above-described configuration is infiltrated into paraffin wax. Went to verify.
In this experimental example, a rubber roll having an SP value (polarity value, solubility parameter) shown in FIG. 3 is immersed in a paraffin liquid having a heating temperature of 100 ° C. (the melting point of paraffin wax is 90 ° C.) The change in the outer shape of the rubber roll was measured.

FIG. 3 is a diagram showing the SP value (polarity value, solubility parameter value) of the paraffin wax used in this experimental example and the rubber roll immersed in the paraffin.
In FIG. 3, the SP value of paraffin wax is 8.00. The SP value of each rubber is 7.45 for silicon rubber. IIR (isobutylene / isoprene rubber) is 7.85. EPDM (ethylene propylene rubber) is 8.00. The IR (isoprene rubber) is 8.09. BR (butadiene rubber) is 8.39. The SBR (styrene butadiene rubber) is 8.54. CR (chloroprene rubber) is 8.71. NBR (nitrile rubber) is 9.31. U (urethane rubber) is 10.00.

Next, the rubber rolls composed of the rubber shown in FIG. 3 are immersed in a paraffin liquid, and when 2, 6, 12, 18 hours have passed, the rubber rolls are exposed at three measurement positions set in advance. The result of measuring the average value of the diameter variation is shown in FIG.
FIG. 4 is a graph showing the outer diameter change amount with respect to the immersion time of the rubber roll immersed in the paraffin. The vertical axis shows the outer diameter change amount of the rubber roll, and the horizontal axis shows the rubber roll immersed in the paraffin wax. It represents immersion time.

Next, from the graph of FIG. 4, the correspondence between the average value of the outer diameter change amount of each rubber roll immersed in the paraffin liquid for 18 hours and the SP value is shown in FIG.
FIG. 5 is a graph showing the relationship between the amount of change in the outer diameter of the rubber roll 18 hours after the start of immersion in the paraffin wax shown in FIG. 4 and the SP value of each rubber roll material. Represents the outer diameter change amount of the rubber roll, and the horizontal axis represents the SP value of the rubber roll material.

4 and 5, the change in outer diameter of the rubber roll for each rubber roll material after 18 hours of immersion was as follows.
IIR (isobutylene / isoprene rubber, SP value: 7.85) was about 1.75 mm. EPDM (ethylene propylene rubber, SP value: 8.00) was about 3 mm. IR (isoprene rubber, SP value: 8.09) was about 2.5 mm. BR (butadiene rubber, SP value: 8.39) was about 1.75 mm. SBR (styrene-butadiene rubber, SP value: 8.54). CR (chloroprene rubber, SP value: 8.71), NBR (nitrile rubber, SP value: 9.31), silicon rubber (SP value: 7.45) and U (urethane rubber, SP value: 10.00) are There was little change.

  In this experimental example, from FIG. 3 to FIG. 5, EPDM (ethylene / propylene rubber) having the same SP value as paraffin wax (SP value: 8.00) has the largest amount of change in the outer diameter of the roll. The difference in the SP values of these is IR (isoprene rubber, SP value: 8.09), IIR (isobutylene / isoprene rubber, SP value 7.85), BR (butadiene rubber, SP value: 8.39). ) Also showed a certain amount of swelling of the outer diameter change of the roll. On the other hand, CR (chloroprene rubber, SP value: 8.71), NBR (nitrile rubber, SP value: 9.31), silicon rubber (SP value) where the difference in SP value from the paraffin wax is greater than 0.5. : 7.45), almost no change in the outer shape of the roll was observed. Therefore, in this experimental example, EPDM (ethylene propylene rubber) having the same value as the paraffin wax (SP value: 8.00) of the rubber roll has the largest change in the outer diameter of the rubber roll, and the rubber roll swells due to immersion. I found it big. It was also found that the change in outer diameter tends to decrease as the difference from the SP value (8.00) of paraffin wax increases.

In the image forming apparatus U of Example 1, the SP value of the liquid paraffin is different from the SP value of the CR of the rubber roll 3b of the conveyance roller Ra1 on the downstream side of the fixing device, compared with the SP value of the paraffin and the rubber roll of the wax absorbing roll 4. The difference between the SP value of the EPDM of 4a is smaller, and the solubility is higher. For this reason, in the image forming apparatus U according to the first embodiment, the paraffin that adheres to the surface of the rubber roll 3b of the fixing device downstream-side transport roll Ra1 on the downstream side of the fixing region F and the transported paraffin adheres to the outer periphery of the rubber roll 3b in the facing region 3c. It adheres to and penetrates the rubber roll 4a of the wax absorbing roll 4 in contact with the surface and is easily absorbed.
Therefore, in the image forming apparatus U according to the first exemplary embodiment, it is possible to reduce swelling of the fixing device downstream side transporting roll Ra1 caused by the penetration of the paraffin into the fixing device downstream side transporting roll Ra1. Therefore, since the change in the outer diameter of the fixing device downstream side transporting roll Ra1 can be reduced, fluctuations in the sheet transporting speed can be reduced.
Further, since the roll portion of the wax absorbing roll 4 is made of a single material, production and processing are easy. Therefore, the wax absorbing roll 4 of the first embodiment can reduce fluctuations in the sheet conveyance speed with a low-cost, simple and strong structure against failure over time.

(Example of change)
As mentioned above, although the Example of this invention was explained in full detail, this invention is not limited to the said Example, A various change is performed within the range of the summary of this invention described in the claim. It is possible. Examples of modifications of the present invention are illustrated below.
(H01) In the above-described embodiment, the printer as the image forming apparatus has been exemplified. However, the present invention is not limited to this, and a FAX, a copying machine, or a multifunction machine having all or a plurality of functions may be used. Further, the image forming apparatus is not limited to a color image forming apparatus, and may be configured by a monochrome image forming apparatus. The present invention is not limited to a so-called rotary image forming apparatus, and can be applied to an image forming apparatus such as a tandem type. is there.

(H02) In the above embodiment, the rubber roll 4b of the wax absorbing roll (absorbing member) 4 is made of EPDM (ethylene propylene rubber), but isoprene rubber, isobutylene isoprene rubber, butadiene rubber, or a mixed rubber thereof. It can be changed. Further, the rubber roll 3b of the drive roll 3 of the conveying roll Ra1 at the fixing stage is made of CR (chloroprene rubber). However, the invention is not limited to this, and styrene butadiene rubber, nitrile rubber, urethane rubber and silicone rubber or mixed It can be changed to rubber.
(H03) Paraffin is used as the liquid component in the above embodiment, but it is not limited to paraffin, and a component that is contained in the developer and becomes liquid when passing through the fixing device and an absorbing member that can absorb the component can be used. is there. For example, in addition to paraffin, low molecular weight polyolefins, silicones, fatty acid amides, vegetable waxes, animal waxes, minerals, petroleum waxes and the like can be mentioned. Note that these SP values are approximately 8-9. At this time, it is desirable that the absorbing member is made of an SP value material having a small difference from the SP value of the liquid component, and it is particularly preferable to use a material having an SP value difference of 0.5 or less. At this time, the sheet conveying member is preferably made of an SP value material having a large difference from the SP value of the liquid component, and it is desirable to use a material having an SP value difference of 0.5 or more.
(H04) In the above embodiment, the rubber roll is exemplified as the absorbing member. However, any material and configuration can be adopted as long as the material can absorb and hold the liquid component.
For example, a material enclosing the polymer absorbent body, a foamed sponge, or the like can be employed.
Further, as the absorbing member, a blade shape instead of a roll shape can be configured to abut on the conveying member.

FIG. 1 is an overall explanatory view of an image forming apparatus according to Embodiment 1 of the present invention. FIG. 2 is an enlarged view of a main part of the first embodiment of the present invention. FIG. 3 is a diagram showing the SP value (polarity value, solubility parameter) of the paraffin wax used in this experimental example and the rubber roll immersed in the paraffin. FIG. 4 is a graph showing the outer diameter change amount with respect to the immersion time of the rubber roll immersed in the paraffin. The vertical axis shows the outer diameter change amount of the rubber roll, and the horizontal axis shows the rubber roll immersed in the paraffin wax. It represents immersion time. FIG. 5 is a graph showing the relationship between the amount of change in the outer diameter of the rubber roll 18 hours after the start of immersion in the paraffin wax shown in FIG. 4 and the SP value of each rubber roll material. Represents the outer diameter change amount of the rubber roll, and the horizontal axis represents the SP value of the rubber roll material.

Explanation of symbols

3b ... rubber roll for sheet conveyance,
4 ... Absorbing member,
F: Fixing device,
Ra1 ... sheet conveying member,
S: Recording sheet,
U: Image forming apparatus.

Claims (6)

A fixing device for heating and fixing an unfixed toner image on the surface of the recording sheet;
A sheet conveying member that is disposed downstream of the fixing device in the sheet conveying direction and conveys the recording sheet, to which a liquid component that is contained in the toner and is heated and melted by the fixing device to become a liquid adheres A conveying member;
An absorbing member that is disposed in contact with the sheet conveying member and absorbs a liquid component adhering to the surface of the sheet conveying member;
An image forming apparatus comprising: The absorbent member made of a material having a difference between the SP value of the liquid component and the SP value of the absorbent member within 0.5,
The image forming apparatus according to claim 1, further comprising: A sheet conveying member comprising: a shaft rotatably supported; and a sheet conveying rubber roll supported by the shaft and having a difference between an SP value of the liquid component of 0.5 or more,
The image forming apparatus according to claim 2, further comprising:   4. The image forming apparatus according to claim 1, wherein a paraffin wax having an SP value of 8 is used as the liquid component. The absorbent member composed of any material of ethylene / propylene rubber, isoprene rubber, isobutylene / isoprene rubber and butadiene rubber,
The image forming apparatus according to claim 4, further comprising: The sheet conveying member composed of any material of styrene / butadiene rubber, chloroprene rubber, nitrile rubber, urethane rubber and silicon rubber,
The image forming apparatus according to claim 4, further comprising:

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