JP3451460B2 - Toner image fixing device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a toner image fixing device.
Regarding the table

[0002]

2. Description of the Related Art An electrostatic latent image is formed on a latent image bearing member by charging and exposing a photoconductive latent image bearing member or by position-selective charging of a dielectric latent image bearing member. The recording method of transferring and fixing a toner image obtained by developing an electrostatic latent image on a recording paper to obtain a recorded image is widely known as an analog or digital copying apparatus, an optical printer, a recording apparatus of a facsimile, or the like.

As a method of fixing the toner image on the recording paper, the recording paper having the toner image is held between a heating roller and a pressure roller, and heat and pressure are applied to record the "toner forming the toner image". A method of fusing on paper is common.

The heating roller and the pressure roller are longer than the width of the maximum width of the recording paper through which they are passed, and therefore,
When the toner image is fixed on the recording paper, both ends of these rollers have portions that do not contact the recording paper (hereinafter referred to as non-contact portions).

The surface of the heating roller is temperature-controlled to a temperature suitable for fixing the toner image. When the toner image is fixed, the heat of the heating roller is applied to the recording paper and the toner image at the portion in contact with the recording paper. Therefore, the surface temperature of the heating roller decreases in this portion. This temperature decrease is called "temperature decrease due to sheet passing".

The temperature decrease due to the passage of paper causes a temperature difference (hereinafter referred to as a temperature difference in the longitudinal direction) in the longitudinal direction of the heating roller between the "non-contact portion" and the above.

When the temperature is lowered by passing the paper, the temperature control means of the heating roller functions to return the temperature of the lowered portion to the set temperature, but the non-contact portion at the end of the heating roller in the longitudinal direction passes the paper. If the temperature control means functions as described above, the surface temperature of the heating roller becomes higher than the original set temperature in the non-contact portion because the temperature does not decrease. This phenomenon is known as "edge temperature rise". The edge temperature rise easily occurs when the fixing operation is continuously performed.

The rise in the end temperature causes the following problems. For example, if the fixing operation is continuously performed on the recording paper with a small width and the fixing operation is performed on the recording paper with a large width while the edge temperature rises, the recording paper with a large width is performed. The toner image portion at the end portion in the width direction is heated at a temperature exceeding the appropriate temperature due to the temperature rise at the end portion, so that the "hot offset phenomenon" in which the toner at this portion adheres to the heating roller is likely to occur.

If the "temperature gradient" in the longitudinal direction of the heating roller increases with the rise in the end temperature, the heating roller itself is damaged and the life of the heating roller is shortened.

Since the above "edge temperature rise" is caused by the heat of the heating roller being taken to the recording paper at the time of fixing,
The above-mentioned problems caused by the rise in the edge temperature can be effectively reduced or prevented by reducing the amount of heat taken by the recording paper from the heating roller during fixing.

In order to "reduce the amount of heat taken from the heating roller by the recording paper at the time of fixing", prior to fixing the toner image,
It is effective to preheat the recording paper, and a method of preheating with infrared rays (Japanese Patent Laid-Open No. 3-211577) or a method of preheating while conveying the recording paper to a fixing unit by an endless heating film (Japanese Patent Laid-Open No. 5-011652). No. publication) is known.

However, these methods require "dedicated preheating means", and energy consumption for preheating is not foolish.

[0013]

SUMMARY OF THE INVENTION An object of the present invention is to effectively reduce the temperature rise in the end portion of a toner image fixing device. Another object of the present invention is to effectively reduce the rise in the end temperature in the toner image fixing method. Another object of the present invention is to effectively reduce the temperature rise in the end portion of the fixing roller.

[0014]

A toner image fixing device according to the present invention is a device for fixing a toner image transferred from a latent image carrier onto a recording sheet onto a recording sheet, which comprises a heating roller and a pressure roller. And a housing and a preheating chamber (claim 1).

The "heating roller and the pressure roller" hold the recording paper on which the toner image is transferred at the fixing portion, convey the recording paper while applying pressure and heat, and fix the toner image on the recording paper.

That is, the "fixing portion" is the pressure contact portion between the heating roller and the pressure roller, and the "width of the recording paper" is the paper width parallel to the longitudinal direction of both rollers in relation to this fixing portion. Say

The "housing" is made of a heat insulating material and surrounds the heating roller and the pressure roller.

The "preheating chamber" is made of a heat insulating material, and is provided integrally with the housing on the inlet side to the fixing portion of the housing.

The recording paper having the toner image to be fixed is
By advancing to the fixing unit through the preheating chamber, preheating is performed depending on the ambient temperature in the preheating chamber.

The form of "connecting the preheating chamber integrally with the housing" may be a form of "forming the preheating chamber as a part of the housing" on the inlet side of the housing or a "formation separate from the housing" on the inlet side of the housing. Fixed preheat chamber "
It may be in a form. Alternatively, the preheating chamber may be formed by "expanding the internal space of the housing itself to the entrance side".

As described above, the heating roller and the pressure roller are surrounded by the housing, and the housing is provided with the preheating chamber. Therefore, a continuous space is formed between the inside of the housing and the inside of the preheating chamber, except for the entrance and exit of the recording paper,
Thermally shielded from the outside.

In the space thus thermally shielded from the outside, the temperature of the heating roller is controlled so as to always maintain a predetermined set temperature in a state where an image can be recorded. The atmosphere in the preheating chamber is heated by the heating roller to increase the temperature.

The toner image fixing device according to claim 1 is
In order to make it easier for the warm atmosphere to accumulate in the preheating chamber,
Set the exit to a position higher than the fixing section . " In this case, the "positional relationship of the entrance of the preheating chamber with respect to the transfer portion" can be determined so that the recording paper having the toner image transferred from the latent image carrier descends from the transfer portion toward the entrance of the preheating chamber. (Claim 2 ).

In the toner image fixing device according to the first or second aspect of the present invention, at least the housing and the preheating chamber can be swung, and the entrance of the preheating chamber is a recording paper receiving position higher than the transfer portion, and the recording paper receiving device. A standby position lower than the position can be occupied (claim 3 ).
At the "standby position", the high temperature atmosphere is unlikely to leak from the entrance of the preheating chamber to the outside.

In the toner image fixing device of the third aspect, when the inlet of the preheating chamber occupies the standby position, at least one of the inlet of the preheating chamber and the outlet of the housing can be closed by a heat insulating member (claim 4 ).

Further, in the toner image fixing apparatus mounting according to claim 1 or 2 SL includes a heat insulating member for opening and closing the inlet portion of at least the preheating chamber, it is possible to have a drive mechanism for opening and closing the heat insulating member (according Item 5 ).

Further, the toner image fixing device according to any one of claims 1 to 5 is configured such that "a space for accommodating the entire recording paper is provided between the entrance of the preheating chamber and the fixing portion". also rather good, it can be provided to "auxiliary heat source" or within the preheating chamber housing (claim 6).

According to any one of claims 1 to 6 above
As the fixing roller of the toner image fixing device, "longitudinal end
The heat radiation holes are formed on the
And both ends are closed with heat insulating material. "
(Claim 7).

The toner image fixing device according to claim 8 is a latent image fixing device.
Toner image transferred from image carrier to recording paper is recorded
It is a device that fixes on paper, and a toner image is transferred.
Hold the recording paper in the fixing section and transport it while applying pressure and heat.
Then, the toner image is fixed on the recording paper,
Roller and pressure roller, and these heating roller and pressure roller
Housing with insulating material surrounding
At the entrance side of the fixing part to the fixing part,
It was connected to the body and extended along the transport path of the recording paper.
It has a preheat chamber with a heat insulating material,
The recording paper that it has may advance to the fixing section through the preheating chamber.
By the heat radiated from the fixing roller
The recording paper is preheated according to the ambient temperature in the preheating chamber.
The fixing roller is designed to be heated.
As "the end of the longitudinal direction, the part that does not contact the maximum width recording paper
Radiating holes are formed in each side, and both ends are
Is used.

“Record between the entrance of the preheating chamber and the fixing unit
If there is a space for the entire paper, ”
Recording paper transporting machine with heating roller and pressure roller
Recording paper with a toner image
It is fed from the entrance of the heat chamber and the leading edge of the recording paper is dammed at the fixing section.
With the paper stopped, keep the entire recording paper in the preheating chamber inlet and fixing unit.
After the recording paper is preheated,
Then, the heating roller and pressure roller are rotated to carry out fixing conveyance.
You can also

[0031]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. In order to avoid complication, the parts which are not likely to be confused are given the same reference numerals throughout the drawings starting from FIG.

In FIG. 1 showing a reference diagram, reference numeral 1 is a recording sheet, reference numeral 2 is a heating roller, reference numeral 3 is a pressure roller, and reference numeral 5 is provided.
Is a housing, reference numeral 6 is a preheating chamber, reference numerals 31, 32, 33
Is a guide, reference numeral 34 is a separating claw, and reference numeral 35 is a discharge roller pair.

The heating roller 2 and the pressure roller 3 are pressed against each other in the longitudinal direction to form a "fixing portion". The heating roller 2 is heated from the inside by a heater 4 provided inside.

The heating roller 2 and the pressure roller 3 are surrounded by a housing 5 made of a heat insulating material. Housing 5
The entrance side to the fixing section is extended rightward in the drawing along the conveyance path of the recording paper 1 to form a preheating chamber 6. The atmosphere inside the housing 5 and the preheating chamber 6 is heated to a high temperature by the heat generated by the heating roller 2.

The recording paper 1 to which the "toner image TI to be fixed" has been transferred from a latent image carrier (not shown) is fed into the preheating chamber 6 from the entrance opening at the right end of the preheating chamber 6, and the fixing portion It is preheated while being transported to.

When the recording paper 1 passes through the preheating chamber 6, the leading end of the recording paper 1 is guided by the guide 31 to the fixing portion, and is sandwiched by the heating roller 2 and the pressure roller 3. The heating roller 2 and the pressure roller 3 rotate in the directions of the arrows respectively, and while conveying the recording paper 1 to the left, heat and pressure are applied to the recording paper 1 and the toner image TI to firmly fix the toner image TI to the recording paper 1. Settles in.

The recording paper 1 on which the toner image TI is fixed is separated from the fixing roller 2 by the separation claw 34, and the guide 32,
It is guided by 33 and discharged to the outside of the housing by a pair of discharge rollers 35.

In such a fixing operation, the recording paper 1 and the toner image TI are preheated by the high temperature atmosphere when passing through the preheating chamber 6, and the temperature of both the toner image TI and the recording paper 1 rises, and at the same time, The water content of the recording paper 1 evaporates.

Therefore, the temperature of the recording paper 1 reaching the fixing portion is increased and the water content is reduced, and fixing can be performed with relatively low energy, and a large amount of heat is applied from the heating roller 2 to the recording paper 1. It will not be robbed.

Therefore, the "temperature drop due to sheet passing" at the contact portion between the heating roller 2 and the recording paper 1 due to fixing is small, and the temperature rise at the end portion is effectively reduced.

Considering the rising characteristics of the fixing device, it is preferable that the volume of the preheating chamber 6 is small, but the preheating chamber 6 is set to an appropriate size in consideration of heat stagnation.

In this embodiment, the preheating chamber is integrally formed with the housing 5 by "forming the preheating chamber as a part of the housing", but of course, the preheating chamber is separate from the housing ( The material may be the same as or different from the housing as long as it is a heat insulating material, and the housing 5
It may be fixed on.

In FIG. 2, the entire fixing device is provided in a state in which the preheating chamber 6 occupies a position higher than the fixing portion and is inclined upward to the right as shown in FIG. The sheet is taken into the preheating chamber 6 by the pair of take-in rollers 37 provided at the entrance of the preheating chamber 6, and is guided by the guide 30 to move toward the fixing unit.

The guides 30 guide the recording paper 1 by abutting on both ends of the recording paper 1 in the width direction (direction orthogonal to the drawing) where no toner image is formed.

In this embodiment, the atmosphere heated in the housing and heated to a high temperature effectively fills the preheating chamber 6 by natural convection, so that the preheating effect can be further enhanced as compared with the embodiment of FIG.

In the embodiment shown in FIG. 2, the conveyance path of the recording paper 1 is bent before and after the entrance of the preheating chamber 6, but such bending may lead to a jam of the recording paper. This is taken into consideration in the embodiment shown in FIG.

That is, the photoconductive photoconductor as a latent image carrier indicated by the reference numeral 10 rotates in the direction of the arrow while charging the charger 5.
After being uniformly charged by 0, it is exposed by an exposing means (not shown) to form an electrostatic latent image. The formed electrostatic latent image is developed by the developing device 60, and the toner image TI formed on the photoconductor 10 is transferred by the transfer device 9 onto the recording paper 1 fed from the paper feeding means 70.

The recording paper 1 on which the toner image TI has been transferred is
The toner image is fixed by the fixing device. The photoconductor 10 after the toner image transfer is cleaned by the cleaning device 80.

In the embodiment of FIG. 3, the transfer portion (transfer device 9
The recording paper 1 to which the toner image has been transferred at the portion facing the peripheral surface of the photoconductor 10) moves downward from the transfer portion toward the entrance of the preheating chamber 6. That is, the positional relationship between the entrance of the preheating chamber 6 and the transfer portion is determined so that the recording paper 1 descends from the transfer portion toward the entrance of the preheating chamber 6 as described above.

In this way, the recording paper 1 that has left the transfer portion naturally goes to the entrance of the preheating chamber 6 without unnatural bending of the conveying path, so that there is little risk of "jam".

In the embodiment of FIG. 3, the entire fixing device is also swingable, and the entrance of the preheating chamber is at a recording paper receiving position (solid line position) 7a higher than the transfer portion and lower than this recording paper receiving position. It can occupy the standby position (the position of the chain line: approximately the same height as the fixing portion) 7b (claim 3 ).

Although a mechanism for realizing such swinging is not shown in FIG. 3, a known appropriate swinging mechanism using, for example, an eccentric cam or a four-bar link can be used.

When the entrance of the preheating chamber 6 is always at a high position as in the embodiment of FIG. 2, the heating atmosphere leaks to the outside due to natural convection and the high temperature atmosphere is wasted, but the embodiment of FIG. When the recording paper is not passed through the fixing portion, the preheating chamber 6 is set to the standby position 7b, so that the leakage of the high temperature atmosphere can be effectively reduced or prevented.

Of course, instead of swinging the entire fixing device, the housing and the preheating chamber may be made swingable, and the remaining part may not be swung.

In the embodiment of FIG. 3, the inlet of the preheating chamber 6 is closed by the heat insulating member 8 when the preheating chamber 6 is at the standby position 7b (claim 4 ). Insulation member 8
Is provided at a fixed position and contacts and separates from the entrance of the preheating chamber 6 as the fixing device swings.

By doing so, leakage of the high temperature atmosphere from the entrance of the preheating chamber during standby can be completely prevented. Of course, during standby, the outlet of the housing 5 may be closed alone or both the inlet of the preheating chamber and the heat insulating member may be closed.

In the embodiment shown in FIG. 4, the entire fixing device is provided in a state in which the preheating chamber 6 occupies a position higher than the fixing portion and is inclined upward to the right as shown in the figure. In order to prevent the leakage of heat, a heat insulating member 11 that opens and closes the inlet of the preheating chamber 6 and a drive mechanism that drives the heat insulating member 11 to open and close are provided (claim 5 ).

The heat insulating member 11 is fixed to one end of an arm 121 which can swing about the swing shaft 12, and
The elastic spring 1 is provided between the free end side of the
3 has been written. The elastic force of the spring 13 is
A clockwise torque is applied to 21 to bring the elastic member 11 into contact with the entrance of the preheating chamber 6. By this contact, the preheating chamber 6
The entrance of the building is closed.

When the paper is passed through the fixing device, an eccentric cam (not shown) that engages with the free end of the arm 121 rotates,
The arm 121 is rotated counterclockwise. Arm 121
This rotation causes the elastic member 11 to retract from the entrance of the preheating chamber 6, the entrance of the preheating chamber 6 is opened, and the recording paper can be passed.

The arm 121, the spring 13 and the eccentric cam (not shown) form a "driving mechanism".

FIG. 5 is a diagram for explaining a reference example . In this example , the preheating chamber is “continuously connected to the housing 5” by being formed by “expanding the inner space of the housing 5 itself toward the inlet side”, and the expansion of the inner space of the housing causes the preheating chamber A preheating chamber is formed on the entrance side, and there is a "space for the entire recording paper" between the entrance of the preheating chamber and the fixing section.

In this example, the toner image is as follows.
Forming is carried out. That is, at the time of fixing the toner image, the recording paper 1 having the toner image is taken in without initially rotating the heating roller 2 and the pressure roller 3, and the roller pair 1 is used.
4, the recording paper 1 is fed from the entrance of the preheating chamber, and the front end of the recording paper 1 is blocked by the fixing unit (the pressure contact portion of the heating roller 2 and the pressure roller 3). Between "and. Reference numeral 31A indicates a guide.

Preheating is performed in this state, and after the recording paper 1 is sufficiently preheated, the heating roller 2 and the pressure roller 3 are rotated to carry out fixing and conveyance. Since the preheating is sufficiently performed, the temperature decrease due to the passing of the paper is more effectively reduced.

In the example of FIG. 5, the recording paper 1 "stagnates between the preheating chamber inlet and the fixing portion" in a meandering state.
If there is enough space, it is desirable to prevent the recording paper in the stagnant state from meandering or bending in order to prevent jams.

FIG. 6 is a diagram for explaining an embodiment of the invention described in claim 6 . In this embodiment, the preheating heater 16 is provided as an auxiliary heat source in the preheating chamber 6 formed by expanding the housing toward the inlet side, and by promoting preheating by the atmosphere in the preheating chamber, the preheating effect is improved,
We are trying to shorten the preheating time. Figure 7 shows the actual fixing roller .
It is a figure for demonstrating an embodiment .

The fixing roller 2A is internally provided with a heater 4 for heating.
Is a hollow cylinder shape having a heat dissipation hole 17 formed at both end portions in the longitudinal direction that do not contact the maximum width recording paper,
Moreover, both ends are closed by the heat insulating material 18.

In such a fixing roller 2A, when the heating amount of the heater 4 is increased in order to compensate for the temperature decrease due to sheet passing, excess heat is radiated from the heat radiating hole 17 from the end portion in the roller longitudinal direction. Therefore, the temperature of the end portion is unlikely to rise, and the heat radiated from the heat radiating holes 17 effectively heats the atmosphere in the housing and the preheating chamber to raise the temperature, thereby enhancing the preheating effect.

[0068]

As described above, according to the present invention, a novel toner image fixing device can be provided .

Since the present invention has the above-mentioned structure, it is possible to effectively reduce or prevent the problem caused by the temperature rise of the end portion of the fixing roller. Further, since preheating is performed by the high temperature atmosphere heated by the heat radiated from the fixing roller, energy consumption for preheating is small.

[Brief description of drawings]

FIG. 1 is a diagram for explaining a reference example .

FIG. 2 is a diagram for explaining an embodiment of the invention according to claim 1;

FIG. 3 is a diagram for explaining an embodiment of the invention described in claims 1, 2, 3, and 4.

FIG. 4 is a diagram for explaining an embodiment of the invention according to claim 5;

FIG. 5 is a diagram for explaining a reference example .

FIG. 6 is a diagram for explaining an embodiment of the invention according to claim 6;

FIG. 7 is a diagram illustrating an embodiment of a fixing roller.

[Explanation of symbols]

1 recording paper 2 heating roller 3 pressure roller 5 housing 6 preheating room

─────────────────────────────────────────────────── ─── Continuation of front page (72) Shinichi Adachi 1-3-3 Nakamagome, Ota-ku, Tokyo ・ Inside Ricoh Co., Ltd. (72) Kazuto Kishi 1-3-3 Nakamagome, Ota-ku, Tokyo No. 6 in Ricoh Co., Ltd. (56) Reference JP-A-7-56455 (JP, A) JP-A-5-188805 (JP, A) Actual development Sho-56-69753 (JP, U) Actual development Flat-5 −50471 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) G03G 13/20 G03G 15/20

Claims (8)

(57) [Claims] 1. A device for fixing a toner image transferred from a latent image carrier onto a recording paper onto the recording paper, wherein the recording paper on which the toner image has been transferred is sandwiched in a fixing section, and pressure and heat are applied. A heating roller and a pressure roller for fixing the toner image on the recording sheet while being conveyed, a housing made of a heat insulating material surrounding the heating roller and the pressure roller, and an entrance side of the housing to the fixing unit. , A preheating chamber made of a heat insulating material that is integrally connected to the housing, and a recording paper having a toner image to be fixed advances to the fixing section through the preheating chamber, so that the ambient temperature in the preheating chamber is changed. So that the recording paper is preheated,
Further, the toner image fixing device is characterized in that a high temperature atmosphere is easily accumulated in the preheating chamber by setting the entrance of the preheating chamber at a position higher than the fixing section. 2. The toner image fixing device according to claim 1, wherein the recording paper on which the toner image is transferred from the latent image carrier descends from the transfer portion toward the entrance of the preheating chamber. The toner image fixing device is characterized in that the positional relationship with respect to the transfer portion is determined. 3. The toner image fixing device according to claim 1, wherein at least the housing and the preheating chamber are swingable, and the entrance of the preheating chamber is a recording paper receiving position higher than the transfer portion, and this recording. A toner image fixing device, which can occupy a standby position lower than a paper receiving position. 4. The toner image fixing device according to claim 3, wherein when the preheating chamber inlet occupies the standby position, at least one of the preheating chamber inlet and the housing outlet is closed by a heat insulating member. Toner image fixing device. 5. The toner image fixing device according to claim 1, further comprising a heat insulating member that opens and closes at least an entrance of the preheating chamber, and a drive mechanism that drives the heat insulating member to open and close. Fixing device. 6. The toner image fixing device according to claim 1, 2 or 3 or 4 or 5, wherein an auxiliary heat source is provided in the housing or in the preheating chamber. 7. A method according to claim 1, 2 or 3 or 4 or
In the toner image fixing device described in 5 or 6, the fixing roller has a maximum width recording paper at both ends in the longitudinal direction.
A heat dissipation hole is formed in the part that does not contact, and both ends are disconnected.
Toner image fixing device characterized by being blocked by a heat material
Place 8. A toner image transferred from a latent image carrier onto recording paper.
A device for fixing the toner image onto the recording paper, and holding the recording paper on which the toner image is transferred at the fixing section.
Then, the toner image is conveyed while being pressurized and heated, and the toner image is recorded as described above.
A heating roller and a pressure roller that are fixed on the recording paper, and a heat insulating material that surrounds the heating roller and the pressure roller.
Housing and the housing side of the entrance to the fixing unit.
And the recording paper are conveyed continuously along the paper feed path.
And a preheating chamber by extending thermal insulation material, a recording sheet having a toner image to be fixed is through the preheating chamber
Then, by advancing to the fixing section,
Ambient temperature in the preheating chamber heated by the radiated heat
Depending on the temperature, the recording paper may be preheated.
Is, the fixing roller, the longitudinal ends, the maximum width recording
A heat dissipation hole is formed in the part that does not contact the paper , and both ends
The toner image is characterized by being blocked by a heat insulating material.
Wearing device.