JP2008083368A - Fixing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing device where electrostatic offset can be securely suppressed without generating side effects, and to provide an image forming apparatus. <P>SOLUTION: The fixing device includes: a fixing member 21 for heating and melting a toner image T; a pressurizing member 31 abutted against the fixing member 21 and forming a nip part; and a guide member 35 for guiding a recording medium P carried toward the nip part at a non-fixing face side. Then, the guide member 35 includes a destaticization member 36 for destaticizing the recording medium P by being abutted so as to be along to the non-fixing face of a carried recording medium P. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile, or a complex machine thereof, and a fixing device installed there.

Conventionally, in an image forming apparatus such as a copying machine or a printer, a fixing member such as a fixing roller or a fixing belt is brought into contact with a pressing member such as a pressure roller or a pressure belt to form a nip portion. A fixing device that conveys a recording medium to the nip portion and fixes a toner image on the recording medium is widely used.
In such a fixing device, it is known that a phenomenon in which toner electrostatically adheres to the surface of the fixing member (this phenomenon is referred to as “electrostatic offset”) occurs (for example, Patent Document 1). reference.).

The electrostatic offset is a phenomenon in which the toner (toner image) carried on the recording medium before the fixing process is electrostatically attracted to the surface of the fixing member, and is recorded at the time of the transfer process which is the previous process of the fixing process. Is unstablely charged. When electrostatic offset occurs, the toner image attached on the fixing member after the fixing member makes one rotation (or one round) is retransferred to the recording medium to become a residual image, or is fixed to the surface of the fixing member as it is. Each time one rotation (or one rotation) causes a fixing failure.
Such a problem cannot be particularly ignored in an image forming apparatus using oilless toner, for which demand has been increasing in recent years. That is, in an image forming apparatus (fixing apparatus) using oilless toner, electrostatic offset tends to occur because a release agent (for example, silicon oil) is not actively applied to the surface of the fixing member. It has become.

On the other hand, in Patent Document 2 and the like, with respect to the nip portion of the fixing device, for the purpose of preventing electrostatic offset from occurring in the second and subsequent devices when two or more image forming devices are arranged in parallel. A technique is disclosed in which a static elimination unit is provided on the upstream side in the transport direction.
Further, in Patent Document 3 and the like, a static eliminator capable of switching between grounding and insulation upstream in the transport direction with respect to the nip portion for the purpose of preventing the recording medium from wrinkling in the nip portion of the fixing device. A technique for providing the above is disclosed.
Further, in Patent Document 4 and the like, a grounded electrode plate is provided on the transfer surface side of the transfer outlet guide plate for the purpose of preventing the occurrence of an abnormal image due to the static elimination needle and suppressing the occurrence of electrostatic offset. Technology is disclosed.

JP 2003-270990 A JP 2005-331845 A JP-A-8-262887 Japanese Patent Laid-Open No. 2002-156834

  In the conventional technique described above, it has been difficult to reliably suppress electrostatic offset without causing side effects.

Specifically, the techniques of Patent Literature 2, Patent Literature 3, and the like are applied to the static elimination brush because the static elimination brush (static elimination member) abuts on the recording medium conveyed toward the nip portion substantially orthogonally. The load was great. Therefore, the static elimination brush is worn and damaged over time, and the static elimination effect cannot be stably maintained.
In addition, since the static elimination brush contacts almost perpendicularly, the contact area of the static elimination brush with respect to the recording medium is reduced, and a large static elimination effect cannot be obtained.
In addition, since the static eliminating brush abuts almost orthogonally, the force in the direction that hinders the conveyance of the recording medium is increased, and the conveyance performance of the recording medium becomes unstable.

  In addition, since the technology of Patent Document 4 and the like is to neutralize the recording medium immediately after the transfer process, when the recording medium comes into contact with the member being conveyed from the transfer process to the fixing process and is charged, A sufficient effect of suppressing electrostatic offset could not be obtained. In particular, in an apparatus in which the conveyance path from the transfer process to the fixing process is set to be short, a sufficient effect of suppressing electrostatic offset cannot be obtained.

  The above-described problem is not limited to a heat roller type (heater lamp heating type) fixing device using a heater or the like as a heat source, but is common to other types of fixing devices such as an electromagnetic induction heating method. Is.

  SUMMARY An advantage of some aspects of the invention is that it provides a fixing device and an image forming apparatus in which electrostatic offset is reliably suppressed without causing side effects.

  According to a first aspect of the present invention, there is provided a fixing device that heats and melts a toner image, a pressure member that contacts the fixing member to form a nip portion, and toward the nip portion. A guide member for guiding the recording medium to be conveyed on the non-fixing surface side, and the guide member abuts along the non-fixing surface of the recording medium to be conveyed to neutralize the recording medium. Is provided.

  According to a second aspect of the present invention, in the fixing device according to the first aspect, the charge eliminating member is held by the guide member via a holding member, and the holding member has conductivity. The non-adhesive coating agent is coated on the conveying surface side.

  According to a third aspect of the present invention, in the fixing device according to the second aspect, the holding member is fixed to a frame of the apparatus together with a guide member by a screw and is grounded via the screw. Is.

  A fixing device according to a fourth aspect of the present invention is the fixing device according to any one of the first to third aspects, wherein the static elimination member is disposed upstream in the transport direction of the guide member. It is.

  The fixing device according to a fifth aspect of the present invention is the fixing device according to any one of the first to fourth aspects, wherein the static elimination member is applied to the entire width direction of the recording medium having the largest width direction size. It is formed so as to touch.

  A fixing device according to a sixth aspect of the present invention is the fixing device according to any one of the first to fifth aspects, wherein the neutralizing member is a neutralizing brush.

  An image forming apparatus according to a seventh aspect of the present invention includes the fixing device according to any one of the first to sixth aspects.

  The present invention provides a neutralization member that neutralizes a recording medium by contacting a guide member that guides the recording medium conveyed toward the nip portion on the non-fixing surface side along the non-fixing surface of the conveyed recording medium. Provided. Accordingly, it is possible to provide a fixing device and an image forming apparatus in which electrostatic offset is reliably suppressed without causing side effects.

Embodiment.
Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected to the part which is the same or it corresponds, The duplication description is simplified or abbreviate | omitted suitably.

First, the configuration and operation of the entire image forming apparatus will be described with reference to FIG.
In FIG. 1, reference numeral 1 denotes an apparatus main body of a copying machine as an image forming apparatus, 2 an original reading unit that optically reads image information of an original D, and 3 an exposure light L based on image information read by the original reading unit 2. Is exposed to the photosensitive drum 5, 4 is an image forming unit for forming a toner image (image) on the photosensitive drum 5, and 7 is a toner image formed on the photosensitive drum 5 on the recording medium P. A transfer unit 10 for transferring, a document transport unit for transporting the set document D to the document reading unit 2, 12 to 14 a paper feed unit storing a recording medium P such as transfer paper, and 20 on the recording medium P A fixing device for fixing an unfixed image, 21 is a fixing roller as a fixing member installed in the fixing device 20, and 31 is a pressure roller as a pressing member installed in the fixing device 20.

With reference to FIG. 1, an operation during normal image formation in the image forming apparatus will be described.
First, the document D is conveyed from the document table in the direction of the arrow in the drawing by the conveyance roller of the document conveyance unit 10 and passes over the document reading unit 2. At this time, the document reading unit 2 optically reads the image information of the document D passing above.
Then, the optical image information read by the document reading unit 2 is converted into an electric signal and then transmitted to the exposure unit 3 (writing unit). Then, exposure light L such as laser light based on the image information of the electrical signal is emitted from the exposure unit 3 toward the photosensitive drum 5 of the image forming unit 4.

On the other hand, in the image forming unit 4, the photosensitive drum 5 is rotated in the clockwise direction in the drawing, and image information is transferred onto the photosensitive drum 5 through a predetermined image forming process (charging process, exposure process, development process). An image (toner image) corresponding to is formed.
Thereafter, the image formed on the photosensitive drum 5 is transferred by the transfer unit 7 onto the recording medium P conveyed by the registration roller.

On the other hand, the recording medium P conveyed to the transfer unit 7 operates as follows.
First, one of the plurality of paper feeding units 12, 13, and 14 of the image forming apparatus main body 1 is automatically or manually selected (for example, the uppermost paper feeding unit 12 is selected). To do.)
Then, the uppermost sheet of the recording medium P stored in the paper feeding unit 12 is transported toward the position of the transport path K.

  Thereafter, the recording medium P passes through the conveyance path K and reaches the position of the registration roller. Then, the recording medium P that has reached the position of the registration roller is conveyed toward the transfer unit 7 at the same timing in order to align with the image formed on the photosensitive drum 5.

After the transfer process, the recording medium P passes through the position of the transfer unit 7 and then reaches the fixing device 20 through the conveyance path. The recording medium P that has reached the fixing device 20 is fed between the fixing roller 21 and the pressure roller 31, and the image is fixed by the heat received from the fixing roller 21 and the pressure received from both rollers 21 and 24. The The recording medium P on which the image has been fixed is delivered from between the fixing roller 21 and the pressure roller 31 (a nip portion) and then discharged from the image forming apparatus main body 1.
Thus, a series of image forming processes is completed.

Next, the configuration and operation of the fixing device 20 installed in the image forming apparatus main body 1 will be described in detail with reference to FIGS.
FIG. 2 is a configuration diagram showing the fixing device 20. FIG. 3 is an enlarged view showing a guide plate 35 as a guide member installed in the fixing device 20 of FIG. FIG. 4 is a view of a static elimination brush 36 as a static elimination member installed on the guide plate 35 as viewed in the width direction.

As shown in FIG. 2, the fixing device 20 includes a fixing roller 21, a pressure roller 31, guide plates 35 and 37, a separation plate 38, and the like.
Here, the fixing roller 21 as a fixing member is a thin cylindrical body that rotates in the direction of the arrow in FIG. 2, and a heater 25 (heat source) is fixed inside the cylindrical body. The fixing roller 21 is a multilayer structure in which an elastic layer 23 and a release layer 24 are sequentially laminated on a core metal 22 (core metal layer). Forming part.

The cored bar 22 of the fixing roller 21 is formed of an iron-based material such as SUS304.
The elastic layer 23 of the fixing roller 21 is made of an elastic material such as fluorine rubber, silicone rubber, or foamable silicone rubber. In particular, when silicone rubber is used as the elastic layer 23, it is preferable to coat a fluorine layer on the elastic layer 23 in order to improve the swelling resistance.
Further, as the release layer 24 of the fixing roller 21, PFA (tetrafluoroethylene bar fluoroalkyl vinyl ether copolymer resin), polyimide, polyetherimide, PES (polyether sulfide), or the like can be used. By providing the release layer 24 on the surface layer of the fixing roller 21, the releasability (peelability) for the toner T (toner image) is secured.

  The heater 25 of the fixing roller 21 is a rod-shaped heater having a heating wire inside, and both ends thereof are fixed to the side plate of the fixing device 20. The fixing roller 21 is heated by the heater 25 whose output is controlled by the power supply unit of the apparatus main body 1, and heat is applied to the toner image T on the recording medium P from the surface thereof. The output control of the heater 25 is performed based on the detection result of the roller surface temperature by a thermistor (not shown) that contacts the surface of the fixing roller 21. Further, the temperature of the fixing roller 21 (fixing temperature) can be set to a desired temperature by such output control of the heater 25.

The pressure roller 31 as a pressure member mainly includes a cored bar 32 and an elastic layer 33 formed on the outer peripheral surface of the cored bar 32 via an adhesive layer. The elastic layer 33 of the pressure roller 31 is formed of a material such as fluorine rubber, silicone rubber, or foamable silicone rubber. A thin release layer made of PFA or the like can be provided on the surface layer of the elastic layer 33.
The pressure roller 31 is brought into pressure contact with the fixing roller 21 by a pressure mechanism (not shown). In this way, a desired nip portion is formed between the pressure roller 31 and the fixing roller 21.

A guide plate 35 (entrance guide) serving as a guide member for guiding the recording medium P conveyed toward the nip portion is provided on the entrance side of the contact portion (a nip portion) between the fixing roller 21 and the pressure roller 31. Plate) is disposed. Further, a guide plate 37 (exit guide plate) for guiding the recording medium P fed from the nip portion is disposed on the outlet side of the nip portion. Both guide plates 35 and 37 are fixed to the frame (housing) of the fixing device 20, and carry the recording medium P on the non-fixing surface side (the toner image T related to the fixing process is carried). Not on the side.)
A separation plate 38 is disposed at a position facing the outer peripheral surface of the fixing roller 21 and in the vicinity of the exit side of the nip portion. The separation plate 38 prevents a problem that the recording medium P after the fixing process is wound around the fixing roller 21 along with the rotation of the fixing roller 21.

Here, in the present embodiment, a neutralizing brush 36 as a neutralizing member for neutralizing the charged charges accumulated in the recording medium P is installed on the guide plate 35 (guide member) on the entrance side.
Referring to FIGS. 3 and 4, a static elimination brush 36 as a static elimination member is composed of brush bristles 36a made of stainless steel or carbon-comprising resin fibers, and a brush holder 36b made of aluminum or the like and sandwiching the brush bristles 36a. Composed. In the present embodiment, stainless steel is used as the material of the brush bristles 36a in consideration of durability (strength) and heat resistance. Moreover, in this Embodiment, although the brush holder 36b was comprised with rigid bodies, such as aluminum, the brush holder 36b can also be comprised with tape materials, such as a double-sided adhesive tape.
As described above, by providing the neutralization brush 36 on the upstream side (upstream in the transport direction) of the nip portion in the fixing device 20, the recording medium P is efficiently neutralized and the occurrence of electrostatic offset is prevented. can do. In particular, it is an apparatus in which the transport path from the transfer process to the fixing process is set to be short, and the recording medium P is fed into the nip portion in a state where charging due to the transfer process is not sufficiently attenuated. Even if it exists, electrostatic offset can be suppressed reliably.

  Further, in the present embodiment, referring to FIGS. 2 and 3, the static eliminating brush 36 is a non-fixed surface (surface on which an unfixed toner image T is not carried) of the recording medium P conveyed in the arrow Y10 direction. It is arranged along the. In other words, the static elimination brush 36 is disposed in the trading direction with respect to the conveyance direction of the recording medium P. That is, the neutralizing brush 36 contacts the non-fixing surface of the recording medium P to neutralize the recording medium P. Specifically, the neutralizing brush 36 is integrally installed on the guide plate 35 so that the angle formed by the recording medium P to be conveyed and the neutralizing brush 36 is an acute angle (generally 45 degrees or less). Yes.

With such a configuration, when the recording medium P comes into contact (sliding contact) with the static elimination brush 36, a load applied to the static elimination brush 36 is reduced. Therefore, the trouble that the static elimination brush 36 is worn and damaged with time is reduced, and the static elimination effect (effect of suppressing electrostatic offset) is stably maintained.
Further, since the static elimination brush 36 contacts the recording medium P in the trading direction, the contact area of the static elimination brush 36 with respect to the recording medium P increases. Therefore, the charge eliminating effect by the charge eliminating brush 36 is efficiently exhibited.
Further, since the static elimination brush 36 contacts the recording medium P in the trading direction, the static elimination brush 36 does not hinder the transportability of the recording medium P. That is, the static elimination brush 36 hardly generates a force in a direction that hinders the transportability of the recording medium P. Therefore, the transportability of the recording medium P is stabilized.

Referring to FIG. 3, in the present embodiment, the static elimination brush 36 is held by the guide plate 35 via a holding plate 45 as a holding member. The holding plate 45 (holding member) is made of a conductive metal material, and a neutralizing brush 36 (brush holder 36b) is attached to one end side of the holding plate 45 with a conductive double-sided tape, and the other end side together with the guide plate 35 by a screw 46. It is fixed to the frame 40 of the fixing device 20. The holding plate 45 and the charge removal brush 46 only have to be electrically connected to each other, and are not limited to the above-described configuration.
Here, the holding plate 45 is coated with a non-adhesive coating agent on the conveying surface side (the surface facing the recording medium P being conveyed). As the coating agent to be coated on the holding plate 45, a material having high non-adhesive properties such as Teflon (registered trademark) and excellent in toner releasability is suitable. As a result, the problem that the toner adheres to the holding plate 45 and the transportability of the recording medium P is deteriorated or the non-fixed surface of the recording medium P is stained is suppressed.

  Referring to FIG. 3, in the present embodiment, holding plate 45 (holding member) is grounded through screw 46. Specifically, the frame 40 (housing) of the fixing device 20 is grounded (earthed), and the holding plate 45 is electrically connected to the frame 40 through a screw 46 made of a metal material. With such a configuration, the assembly of the apparatus is simplified, the holding plate 45 can be grounded relatively easily, and the problem that electric charges are accumulated on the holding plate 45 (static charge brush 36) is suppressed. be able to. That is, the static elimination effect of the static elimination brush 36 is reliably exhibited.

  2 and 3, in the present embodiment, the static elimination brush 36 is disposed on the upstream side of the guide member 35 in the transport direction. That is, the static elimination brush 36 is not located close to the nip portion, but is disposed at a position slightly away from the nip portion. Accordingly, it is possible to reduce the static elimination brush 36 from directly receiving the heat of the fixing device while maintaining the effect of suppressing the electrostatic offset by the static elimination brush 36.

Referring to FIG. 4, in the present embodiment, the static elimination brush 36 is formed so as to contact the entire width direction Lmax of the recording medium P having the largest width direction size. That is, the width direction size of the static elimination brush 36 is larger than the width direction size Lmax of the maximum recording medium P that can be passed in the image forming apparatus according to the present embodiment, and the region is included. ing. In other words, the neutralizing brush 36 is configured to abut over the entire width direction of the recording medium P regardless of the size of the recording medium P.
With such a configuration, the charged charges accumulated in the recording medium P in the transfer process and the transport process are surely removed by the charge eliminating brush 36, and the occurrence of electrostatic offset is suppressed.

Finally, the operation of the fixing device 20 configured as described above will be briefly described.
When the power switch of the apparatus main body 1 is turned on, electric power is supplied to the heater 25 and rotation driving of the fixing roller 21 and the pressure roller 31 in the direction of the arrow in FIG.
Thereafter, the recording medium P is fed from the paper feeding units 12 to 14, and an unfixed image is carried on the recording medium P by the image forming unit 4. The recording medium P carrying the unfixed image T (toner image) is conveyed in the direction of the arrow Y10 in FIG. 2 while being guided by the guide plate 35, and the nip portion between the fixing roller 21 and the pressure roller 31 in the pressure contact state. To be sent to. At this time, the recording medium P is neutralized by the neutralizing brush 36 installed on the guide plate 35.
Then, the toner image T is fixed on the surface of the recording medium P by the heating by the fixing roller 21 and the pressing force of the fixing roller 21 and the pressure roller 31. Thereafter, the recording medium P sent out from the nip portion by the rotating fixing roller 21 and the pressure roller 31 is conveyed in the direction of the arrow Y11.

  As described above, in the present embodiment, the recording medium P conveyed to the guide plate 35 (guide member) that guides the recording medium P conveyed toward the nip portion on the non-fixing surface side. A neutralizing brush 36 (a neutralizing member) that abuts along the non-fixing surface and neutralizes the recording medium P is provided. Accordingly, it is possible to reliably suppress the occurrence of electrostatic offset without causing side effects such as a decrease in the transportability of the recording medium P, a deterioration of the static elimination brush, and a reduction in the static elimination effect.

In the present embodiment, the present invention is applied to a heat roller type fixing device, but the present invention can naturally be applied to another type of fixing device such as an electromagnetic induction heating method. In this case, the same effect as that of the present embodiment can be obtained.
In this embodiment, the present invention is applied to a fixing device using a fixing roller as a fixing member and a pressure roller as a pressure member. However, a fixing belt is used as a fixing member or a pressure member is used as the fixing member. The present invention can also be applied to a fixing device using a pressure belt.
Furthermore, in the present embodiment, the present invention is applied to a fixing device (a horizontal transport device) in which the transport direction of the recording medium P transported to the nip portion is substantially horizontal. The application of the invention is not limited to this. For example, the present invention can naturally be applied to a fixing device (vertical conveyance device) in which the conveyance direction of the recording medium P conveyed to the nip portion is substantially vertical.

  It should be noted that the present invention is not limited to the present embodiment, and it is obvious that the present embodiment can be modified as appropriate within the scope of the technical idea of the present invention, other than suggested in the present embodiment. is there. In addition, the number, position, shape, and the like of the constituent members are not limited to the present embodiment, and the number, position, shape, and the like suitable for implementing the present invention can be achieved.

1 is an overall configuration diagram illustrating an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a configuration diagram illustrating a fixing device installed in the image forming apparatus of FIG. 1. FIG. 3 is an enlarged view showing a guide member installed in the fixing device of FIG. 2. It is the figure which looked at the static elimination brush in the width direction.

Explanation of symbols

1 image forming apparatus body (apparatus body),
20 fixing device,
21 fixing roller (fixing member),
22, 32 cored bar, 23, 33 elastic layer, 24 release layer,
25 heater,
31 Pressure roller (pressure member),
35 Guide plate (guide member),
36 Static elimination brush (static elimination member),
36a brush hair, 36b brush holder,
40 frames,
45 holding plate (holding member),
46 screw, P recording medium.

Claims (7)

A fixing member that heats and melts the toner image;
A pressure member that contacts the fixing member to form a nip portion;
A guide member that guides the recording medium conveyed toward the nip portion on the non-fixing surface side,
The fixing device according to claim 1, wherein the guide member includes a charge eliminating member that abuts along a non-fixing surface of the recording medium to be conveyed to neutralize the recording medium. The static elimination member is held by the guide member via a holding member,
The fixing device according to claim 1, wherein the holding member has conductivity and is coated with a non-adhesive coating agent on a conveyance surface side.   The fixing device according to claim 2, wherein the holding member is fixed to a frame of the apparatus together with a guide member by a screw, and is grounded through the screw.   The fixing device according to claim 1, wherein the charge eliminating member is disposed upstream of the guide member in a conveyance direction.   5. The fixing device according to claim 1, wherein the static eliminating member is formed so as to abut on an entire width direction of a recording medium having a maximum width direction size.   The fixing device according to claim 1, wherein the charge eliminating member is a charge eliminating brush.   An image forming apparatus comprising the fixing device according to claim 1.

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