JP2018155803A - Fixing device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device that prevents an increase in cost and consumed energy, prevents an increase in size of the device, and is designed for various types of recording media, and an image forming apparatus using the same.SOLUTION: A fixing device 20 comprises: a fixing member 21 that has a heat source therein and a movable surface; a pressure rotating body 22 that is arranged opposite to the fixing member 21; urging means 29 that brings the fixing member 21 and pressure rotating body 22 into pressure contact at a predetermined pressure to form a fixing nip part that sandwiches a recording medium P; a pair of adjustment members 32 that can adjust an urging force generated by the urging means 29 in multi-steps, and are respectively disposed movably corresponding to both ends in the longitudinal direction of the fixing member 21; and an interlocking mechanism 33 that interlocks the adjustment members 32 with each other.SELECTED DRAWING: Figure 5

Description

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

  As a fixing device that is used in an image forming apparatus and fixes a toner image to a recording medium, a pressure heating type fixing device is known. In this fixing device, a recording medium is passed through a fixing nip formed by a fixing member heated by a heating unit and a pressure member pressed against the fixing member, and a toner image carried on the recording medium is subjected to heat and pressure. It is fixed by heat welding.

  In this fixing device, a fixing nip portion is formed by applying a load to the pressure member and deforming the pressure member and / or the elastic layer of the fixing member. As an example of this configuration, a configuration is known in which a fixing member or a pressure member is held rotatably and movably, and a load is applied to the held member by a biasing means such as a spring.

However, the fixing device having a single urging unit as described above cannot cope with various types of recording media, and the recording medium is wrinkled, curved, bent, or the like. There was a problem.
In view of this, there has been disclosed a technique for adjusting the nip pressure in the fixing nip portion by using a motor-driven cam and rotating the cam to an arbitrary angle even with a single urging means (for example, “Patent Document”). 1 ”).

However, the above-described technique has a problem that it is necessary to newly provide a cam mechanism, a driving unit, and the like, which increases cost and energy consumption, and requires a mounting space, resulting in an increase in size of the apparatus.
The present invention solves the above-described problems, and uses a fixing device that can handle various types of recording media without increasing cost and energy consumption and without increasing the size of the device. An object of the present invention is to provide an image forming apparatus.

  According to a first aspect of the present invention, a fixing member having a heat source therein and having a movable surface, a pressure rotator disposed opposite to the fixing member, the fixing member and the pressure rotator are predetermined. And a biasing means for forming a fixing nip portion for clamping the recording medium by pressure, and a biasing force by the biasing means can be adjusted in multiple stages, corresponding to both longitudinal ends of the fixing member. It is characterized by having a pair of adjustment members arranged movably, and an interlocking mechanism for interlocking the adjustment members.

  According to the present invention, when one adjusting member is moved by the action of the interlocking mechanism, the other adjusting member is also moved in conjunction therewith, so that the load balance at both ends of the shaft of the fixing member and the pressure rotating body is lost. Therefore, the urging force can be adjusted by the urging means without being able to cope with various types of paper, and a fixing device that has a longer life and is easy to use can be provided.

1 is a schematic front view of an image forming apparatus to which an embodiment of the present invention can be applied. 1 is a schematic perspective view of a fixing device to which an embodiment of the present invention can be applied. 1 is a front view of a main part of a fixing device for explaining an embodiment of the present invention; It is a schematic perspective view of the adjustment apparatus used for one Embodiment of this invention. It is a schematic plan view of the interlocking mechanism used for one embodiment of the present invention. It is a schematic perspective view explaining the attachment state of the interlocking mechanism used for one Embodiment of this invention. It is a principal part perspective view explaining the adjustment member used for other embodiment of this invention.

  FIG. 1 shows an image forming apparatus to which an embodiment of the present invention can be applied. In the figure, a color copying apparatus 30 as an image forming apparatus has four process units 1Y, 1C, 1M, and 1K as image forming units that are configured to be detachable from the apparatus main body 30a. Each process unit 1 has the same configuration except that it contains toners of different colors of yellow, cyan, magenta, and black corresponding to the color separation components of the color image.

Specifically, each process unit 1 includes a photosensitive drum 2 that is a latent image carrier, a charging device 3 that is a charging unit that uniformly charges the surface of the photosensitive drum 2, and a developer on the surface of the photosensitive drum 2. A developing device 4 as a developing means for supplying the toner, and a cleaning blade 5 as a cleaning means for cleaning the surface of the photosensitive drum 2.
In FIG. 1, only the members constituting the yellow process unit 1Y are denoted by reference numerals, and the other process units 1C, 1M, and 1K are not denoted by the reference numerals.

  An exposure device 6 as an electrostatic latent image forming unit that exposes the surface of the photosensitive drum 2 is disposed above each process unit 1, and a transfer device 7 is disposed below each process unit 1. ing. The transfer device 7 includes an intermediate transfer belt 8 that is a transfer target composed of an endless belt. The intermediate transfer belt 8 is stretched by a driving roller 9 and a driven roller 10, and is driven to run in a direction indicated by an arrow in FIG. 1 when the driving roller 9 is rotationally driven by a driving force of a driving means (not shown).

  Four primary transfer rollers 11 serving as primary transfer units are disposed at positions facing the respective photosensitive drums 2 via the intermediate transfer belt 8. Each primary transfer roller 11 presses the inner peripheral surface of the intermediate transfer belt 8 at each position, and each primary transfer roller 11 is in contact with the outer peripheral surface of the photosensitive drum 2 via the intermediate transfer belt 8. In step 1, a primary transfer nip portion is formed.

A secondary transfer roller 12 that is a secondary transfer unit and functions as a transfer unit is disposed at a position facing the driving roller 9 with the intermediate transfer belt 8 interposed therebetween. The secondary transfer belt 8 also presses the outer peripheral surface of the intermediate transfer belt 8, and a secondary transfer nip portion is formed at the contact portion between the intermediate transfer belt 8 and the secondary transfer roller 12.
In FIG. 1, a belt cleaning device 13 for cleaning the surface of the intermediate transfer belt 8 is disposed in the vicinity of the outer peripheral surface on the right end side of the intermediate transfer belt 8. A waste toner transfer hose (not shown) is attached to the belt cleaning device 13, and this waste toner transfer hose is connected to an inlet portion of a waste toner container 14 disposed below the transfer device 7.

Below the apparatus main body 30a, a paper tray 15 containing paper P as a recording medium, and a paper feed unit 31 having a paper feed roller for feeding the paper P from the paper tray 15 are disposed. Further, a registration roller pair 19 is provided on the downstream side of the paper tray 15 in the paper conveyance direction, and the fed paper P is temporarily stopped and then fed to the secondary transfer nip portion at a predetermined timing. .
At the upper part of the apparatus main body 30a, a paper discharge roller pair 17 for discharging the paper P after image formation to the outside of the main body 30a and a paper discharge tray 18 for stacking the discharged paper P are disposed. With the above-described configuration, a paper transport path R for feeding the paper P from the paper tray 15 to the paper discharge tray 18 is formed in the apparatus main body 30a.

A fixing device 20 as a fixing unit that fixes the toner image transferred onto the paper P by the secondary transfer roller 12 is disposed on the paper conveyance path R from the secondary transfer roller 12 to the paper discharge roller pair 17. ing. The fixing device 20 includes a fixing roller 21 as a fixing member that is heated by a heat source provided therein, a pressure roller 22 as a pressure rotator that contacts the fixing roller 21 to form a fixing nip portion, and fixing. A separating member 23 for separating the paper P from the peripheral surface of the roller 21 is provided.
In the configuration shown in the present embodiment, the fixing roller 21 and the pressure roller 22 are pressed against each other by the urging means, so that a fixing nip portion is formed at both pressing locations. However, the configuration of the fixing device is limited to this. It will never be done. For example, at least one of the fixing member and the pressure rotator may be an endless belt, and the belt may be pressed against the other side by a roller or a pad.
The configuration of the fixing device 20 will be described later.

The basic operation of the image forming apparatus 30 will be described below with reference to FIG.
When the image forming operation is started, each photosensitive drum 2 of each process unit 1 receives a driving force from a driving unit (not shown) and is rotated in the clockwise direction in FIG. 1, and the surface of each photosensitive drum 2 is moved. The charging roller 3 is charged to a uniform predetermined polarity. The surface of the charged photoconductor drum 2 is irradiated with laser light from the exposure device 6 to form an electrostatic latent image corresponding to each color on the surface of each photoconductor drum 2. Each color latent image is visualized as a toner image by supplying toner of each color from each developing device 4 to the electrostatic latent image formed on the drum 2.

Further, when the driving roller 9 is rotationally driven in the counterclockwise direction in FIG. 1, the intermediate transfer belt 8 is driven to travel in the direction indicated by the arrow in FIG. In addition, a constant voltage having a polarity opposite to the charging polarity of the toner or a voltage controlled by a constant current is applied to each primary transfer roller 11, so that each primary transfer roller 11 and each photosensitive drum 2 can be connected to each other. A transfer electric field is formed at the primary transfer nip portion formed therebetween.
Then, the toner images of the respective colors formed on the respective photosensitive drums 2 are sequentially superimposed and transferred onto the intermediate transfer belt 8 by the formed transfer electric field. As a result, the intermediate transfer belt 8 carries a full-color toner image on the surface thereof.
Residual toner adhering to the surface of each photosensitive drum 2 after the toner image is transferred is removed by the cleaning blade 5, and then the surface is neutralized by a neutralizing device (not shown) to initialize the surface potential. 2 is prepared for the next image formation.

  When the image forming operation is started, the paper feed roller 16 is rotationally driven below the apparatus main body 30a, and the paper P stored in the paper tray 15 is fed to the paper transport path R. The paper P fed to the paper transport path R is timed by the registration roller pair 19 and sent to the secondary transfer nip portion formed between the secondary transfer roller 12 and the drive roller 9. At this time, a transfer voltage having a polarity opposite to the toner charging polarity in the toner image on the intermediate transfer belt 8 is applied to the secondary transfer roller 12, thereby forming a transfer electric field in the secondary transfer nip portion. The toner images on the intermediate transfer belt 8 are collectively transferred onto the paper P by this transfer electric field.

The sheet P on which the toner image is transferred is conveyed to the fixing device 20, and the sheet P is heated and pressed by the fixing roller 21 and the pressure roller 22, whereby the toner image transferred onto the sheet P is transferred to the sheet P. Fixed on top. The sheet P on which the toner image has been fixed is separated from the peripheral surface of the fixing roller 21 by the separating member 23, sent to the discharge roller pair 17, and then discharged onto the discharge tray 18.
The toner remaining on the intermediate transfer belt 8 after the image transfer is removed from the intermediate transfer belt 8 by the belt cleaning device 13, and the removed toner is conveyed to the waste toner container 14 and collected.
In the above-described embodiment, the image forming operation when a full-color image is formed on the paper P has been described. However, a monochromatic image is formed using any one of the four process units 1Y, 1C, 1M, and 1K. It is also possible to form two or three color images using two or three process units.

Next, the fixing device 20 that is a feature of the present invention will be described. As shown in FIG. 2, the fixing device 20 includes a fixing roller 21 and a pressure roller 22 and a separation member 23 (not shown).
The fixing roller 21 has a metal core, an elastic layer provided on the peripheral surface of the metal core, and a release layer provided on the peripheral surface of the elastic layer. A heat source is provided. A halogen heater or the like is used as the heat source. The fixing roller 21 has a rotation center shaft 21 a rotatably supported on both side plates 24 a of the fixing device main body 24 that functions as a fixing member support member.

Similarly to the fixing roller 21, the pressure roller 22 has a cored bar, an elastic layer provided on the peripheral surface of the cored bar, and a release layer provided on the peripheral surface of the elastic layer. The pressure roller 22 is rotatably supported by a roller holder 25 that functions as a pressure rotator support member.
The roller holder 25 that rotatably supports the rotation center shaft 22a between both side plates 25a is supported by the fixing device main body 24 so as to be swingable through the support shaft 26.

  Although not shown in FIG. 2, an upper portion of each side plate 24a on the side facing the roller holder 25 and an upper portion on each side plate 25a on the side facing the fixing device main body 24 are shown in FIG. Ear portions 24b and 25b each projecting outward are formed. Each ear 24b, 25b is provided with a hole through which a bolt 27 can be inserted, and a nut 28 with which the bolt 27 can be engaged is welded to the opposite side of the ear 24b opposite to the ear 25b. It is fixed by. A compression coil spring 29 that functions as an urging means is disposed between the bolt 27 and the ear portion 25b. In the present embodiment, an example in which the nut 28 that can be engaged with the bolt 27 is fixed to the ear 24b is shown. However, the configuration in which the bolt 27 can be engaged is not limited thereto, and for example, the bolt 27 can be engaged with the ear 24b. It is good also as a structure which forms a burring tap.

An adjusting member 32, which is a characteristic part of the present invention, is disposed between the ear portions 24b and 25b provided on both sides. The adjustment member 32 has a heat resistance of about 120 to 150 ° C. and is made of a resin material or a metal material having a strength capable of withstanding a load of about 100 N. When it is made of resin material, it is easy to mold the shape of the mounting and operation part, and the number of parts can be reduced. When it is made of metal material, strength can be secured, so durability can be easily secured. can do.
By providing the adjusting member 32, the load and nip width at the fixing nip portion formed by the rollers 21 and 22 change according to the tightening amount when the bolt 27 is tightened with respect to the nut 28. In the conventional configuration, the distance between the rotation center shafts 21a and 22a is fixed, so that the load and the nip width at the fixing nip portion can be made constant regardless of the tightening amount.

Next, the adjustment member 32 will be described. The adjustment member 32 is formed to have a staircase shape as shown in FIG. 4, and the portion with the width A shown in FIG. 3 is the first convex portion 32a. In addition to the first convex portion 32a, the adjusting member 32 is formed to have a width larger than the second convex portion 32b and the second convex portion 32b having a width B formed larger than the first convex portion 32a. A third protrusion 32c having a width C, a fourth protrusion 32d having a width D formed larger than the third protrusion 32c, and a width E formed wider than the fourth protrusion 32d. It has the 5th convex part 32e.
The adjustment member 32 is configured to increase in thickness from side to side with respect to the first convex portion 32a. When the adjustment member 32 is moved, the adjustment member 32 is not passed through the sheet passing area, for example, as shown in FIG. By disposing it above the paper area, it does not prevent paper jamming, paper breaks, wrinkles, and water droplet images, but it also prevents the heat-resistant area of the parts by avoiding high temperature areas. By lowering, the part cost can be reduced.
In this embodiment, the thickness difference of each convex part is 0.5 mm on both sides and 0.25 mm on one side, thereby reducing the impact during switching movement and reducing the risk of component damage.

Next, an interlocking mechanism that interlocks the respective adjustment members 32 provided on both sides will be described.
FIG. 5 shows an interlocking mechanism 33 that moves the adjusting members 32 simultaneously. The interlocking mechanism 33 is a rack-and-pinion mechanism having a drive pinion 33a disposed at the center and two racks 33b and 33c disposed so as to mesh with one end side of the drive pinion 33a. , 33c are attached with adjusting members 32 via brackets 33d, 33e, respectively.
In the present embodiment, each adjustment member 32 has its first convex portion 32a fixed to each bracket 33d, 33e, and can be moved from the state shown in FIG. 3 to the front side of the paper (the other is the back side of the paper). It is configured. That is, when the left adjustment member 32 is moved inward in FIG. 5, the right adjustment member 32 is also moved inward. The drive opinion 33a is rotationally driven by a predetermined amount by a drive means such as a stepping motor (not shown), so that each adjustment member 32 is moved step by step.

When passing thin paper through the fixing device 20, paper conveyance may not be stable due to excessive heat, and wrinkles may occur due to paper flapping or the like. In the case of excessive heat, measures such as lowering the set temperature or idling until the temperature stabilizes can be considered, but if wrinkles occur due to excessive pressure at the fixing nip, I can't respond. In this case, if the axial distance between the fixing roller 21 and the pressure roller 22 can be finely adjusted by the adjusting member 32 shown in the present invention, the pressure can be easily changed and the generation of wrinkles can be reduced. Can do.
Also, there are various types of paper, and the characteristic values such as basis weight, paper thickness, smoothness, etc. vary depending on the paper used. Fixing can be performed, and the occurrence of abnormal images can be suppressed.

  Further, when the components such as the fixing roller 21 and the pressure roller 22 gradually change with time (for example, the nip width gradually increases because the rubber hardness gradually decreases), the fixing device 20 has a wide nip width. If the hot offset occurs too much, the lifetime is reached. However, by adjusting the pressure as described above, the nip width can be reduced, the generation time of the hot offset can be postponed, and the lifetime of the fixing device 20 can be extended. Can be extended. As a result, image formation can be continued easily and at a lower cost than purchasing a new fixing device.

When the distance between the shafts of the fixing roller 21 and the pressure roller 22 is changed only at one of both end portions of the shaft, left and right deviations occur in the fixing nip portion, and uneven distribution of the nip portion load occurs, thereby causing uneven wear of the rollers. Or distortion causes paper conveyance defects such as wrinkles, skews, jams, and the like, which shortens the life of the fixing device.
In the present invention, when one adjusting member 32 is moved by the action of the interlocking mechanism 33, the other adjusting member 32 is also moved in conjunction with this, so that the load balance at both ends of the fixing roller 21 and the pressure roller 22 is fixed. It is possible to adjust the urging force by the compression coil spring 29 without damaging the sheet, and thus it is possible to cope with various types of paper, and to provide a fixing device that has a longer life and is easy to use. it can.

FIG. 6 shows a state in which the interlocking mechanism 33 is attached to the fixing device 20. The interlocking mechanism 33 is disposed on the fixing device main body 24, and the driving pinion 33a and driving means (not shown) for driving the driving pinion 33a are attached to the fixing device main body 24, respectively.
The racks 33b and 33c meshing with the drive pinion 33a are guided in movement by rail members (not shown) provided in the fixing device main body 24, and the racks 33b and 33c move at a constant speed as the drive pinion 33a rotates. It moves by equal distance, and, thereby, each adjustment member 32 is comprised so that it may move synchronizing with each other.

Further, the interlocking mechanism 33 has a disk 33f having a diameter larger than that of the drive pinion 33a on the upper surface of the drive pinion 33a, so that the engagement state between the drive pinion 33a and the racks 33b and 33c is not released. Has been.
The brackets 33d and 33e are arranged inside a cover member (not shown) provided outside the side plates 24a, and the brackets 33d and 33e come into contact with the cover member, respectively. The racks 33b and 33c are prevented from detaching from the drive pinion in the moving direction.

  With the above-described configuration, the engagement state of the drive pinion 33a and the racks 33b and 33c constituting the interlocking mechanism 33 can always be kept normal, and the engagement state of the drive pinion 33a and the racks 33b and 33c is released. Thus, it is possible to reliably prevent the occurrence of a malfunction in which the fixing device 20 does not function normally. Accordingly, it is possible to provide a fixing device that can cope with various types of paper and can continuously form an image for a long time.

FIG. 7 shows an adjustment member 34 used in a modification of one embodiment of the present invention. This adjustment member 34 is different from the adjustment member 32 described above only in that it has a dropout prevention portion 34a, and the other configuration is the same.
In the operating state of the fixing device 20, each adjustment member does not move because it is sandwiched between the respective ear portions 24b and 25b as shown in FIG. However, at the time of load adjustment, the bias by the compression coil spring 29 is temporarily released, and the adjustment member may be tilted.

The adjustment member 34 is configured to prevent the above-described problems. Since the adjustment portion seat 34 has the drop-off prevention portion 34a that engages with the upper end and the lower end of the ear portion 24b, even if the urging force of the compression coil spring 29 is released during load adjustment, the drop-off prevention portion 34a remains in the ear portion. By being engaged with 24b, the drop-off and inclination are prevented. With this configuration, it is possible to provide a fixing device that has good operability and can withstand long-term image formation.
In addition to the configuration shown in FIG. 7, for example, a drop-off prevention member having a shape surrounding the periphery of the ear portion 24b may be adopted as the drop-off prevention member. Thereby, the stability of the adjustment member 34 can be improved.

  In each of the above-described embodiments, the paper P is shown as a recording medium on which an image is formed. The paper P is not limited to recording paper, and includes thick paper, postcards, envelopes, plain paper, thin paper, coated paper (coated paper, art paper, etc.), tracing paper, and the like. As the recording medium other than paper, any material may be used as long as it is a sheet-like material capable of forming an image, such as an OHP sheet, an OHP film, or a resin film.

  The preferred embodiments of the present invention have been described above. However, the present invention is not limited to such specific embodiments, and unless specifically limited by the above description, the present invention described in the claims is not limited. Various modifications and changes are possible within the scope of the gist. The effects described in the embodiments of the present invention are merely examples of the most preferable effects resulting from the present invention, and the effects of the present invention are limited to those described in the embodiments of the present invention. is not.

1Y, 1C, 1M, 1K Image forming unit (process unit)
12 Transfer section (secondary transfer roller)
20 Fixing Device 21 Fixing Member (Fixing Roller)
22 Pressure Rotator (Pressure Roller)
24 fixing member support member (fixing device main body)
25 Pressure rotor support member (roller holder)
29 Biasing means (compression coil spring)
30 Image forming apparatuses 32 and 34 Adjustment member 33 Interlocking mechanism 34a Drop-off prevention part P Recording medium (paper)

Japanese Patent No. 5233369

Claims (9)

A fixing member having a heat source therein and having a movable surface;
A pressure rotator disposed opposite to the fixing member;
An urging unit that forms a fixing nip portion that presses the fixing member and the pressure rotator at a predetermined pressure to sandwich the recording medium;
A pair of adjustment members that can adjust the urging force by the urging means in multiple stages, and are respectively movably disposed corresponding to both longitudinal ends of the fixing member;
A fixing device having an interlocking mechanism for interlocking the adjusting members with each other. The fixing device according to claim 1.
Each of the adjusting members adjusts an inter-axis distance between the fixing member and the pressure rotating body. The fixing device according to claim 1 or 2,
The fixing device, wherein each of the adjustment members is disposed outside a conveyance area of the recording medium. The fixing device according to any one of claims 1 to 3,
The fixing device, wherein each of the adjusting members is formed in a stepped shape. In the fixing device according to any one of claims 1 to 4,
A fixing member supporting member that movably supports the fixing member; and a pressure rotator supporting member that rotatably supports the pressure rotator. The urging unit includes the fixing member supporting member and the pressure member. It arrange | positions between rotary body support members. A fixing device. The fixing device according to claim 5.
Each of the adjustment members is sandwiched between the fixing member support member and the pressure rotator support member. The fixing device according to any one of claims 1 to 6,
The fixing device is characterized in that the interlocking mechanism has a rack and pinion mechanism. In the fixing device according to any one of claims 1 to 7,
Each of the adjusting members has a drop-off preventing unit.   An image forming unit that forms an image, a transfer unit that transfers the image formed by the image forming unit to a recording medium, and a fixing unit that fixes the image transferred onto the recording medium by the transfer unit; An image forming apparatus comprising the fixing device according to claim 1 as the fixing unit.

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