JPH0836318A - Fixing device having power supply unit inside roller - Google Patents

Abstract

(57) [Summary] (Corrected) [Purpose] Improving the thermal response of the nip portion where the fixing roller and pressure roller contact each other to speed up and ensure the fixing operation of the sheet, and control the temperature of the nip portion. To provide a fixing device having a power supply unit inside the roller that can reliably perform the above. A fixing roller 2 having a three-layer structure of a heat-resistant resin layer 19, a heat generating layer 20 composed of a group of elongated heat generating pieces 22 and an insulating layer 21 and a pressure roller 3 forming a nip portion 30 in pressure contact with the fixing roller 2. The holder 2 is provided in the fixing roller 2 of the fixing device 1.
6 and a power feeding portion 25 having a power feeding brush slidably supported by the spring 6 and a spring member 28 for pressing the power feeding brush, and the power feeding brush 27 is fitted into a circumferential groove formed by cutting the insulating layer 21. Prevent lateral displacement. The power supply brush 27 is disposed at a position facing the nip portion 30, and the heat generating piece 22 is disposed.
To contact with.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device used in, for example, an electrophotographic copying machine, a laser printer, etc., and more particularly, to a roller provided with a power feeding portion for a heating element of the fixing device. The present invention relates to a fixing device provided inside.

[0002]

2. Description of the Related Art There are various fixing devices used in electrophotographic devices, laser printers and the like. The fixing device is composed of a fixing roller and a pressure roller that presses and engages with the fixing roller.
A nip portion is formed at the pressure contact portion of both. A heating element is arranged on the fixing roller, but most of them have a power feeding portion of the heating element outside the roller.

As a known technique thereof, Japanese Patent Laid-Open No. 62-185.
81, JP-A-62-200380, JP-A-4-51071, and JP-A-5-17664.
Japanese Utility Model Laid-Open No. 4-129166, Japanese Patent Laid-Open No. 5-19730.
5, JP-A-4-204981, JP-A-61
-90180 and Japanese Patent Application Laid-Open No. 5-142962 are mentioned.

Known techniques in which a temperature fuse and a temperature detecting element are provided in the fixing roller in order to prevent overheating of the fixing roller are disclosed in JP-A-62-18581 and JP-A-5-281867. There is a "heating device".

The above-mentioned known techniques relating to the heating means for the fixing roller have their respective characteristics. For example, the "direct heating type fixing device" of Japanese Patent Laid-Open No. 62-18581 discloses a heating roll (corresponding to the fixing roller). An electric resistance layer is provided on the outer circumference of the heating roll, and a power supply section is provided on the outer circumferential surface side of the heating roll.A temperature detection sensor and a fuse are also described. It is not arranged.

The "heat roll fixing device" of Japanese Patent Laid-Open No. 62-200380 also has a heater film on the outer periphery, and the sliding electrode of the power feeding portion is arranged on the outer peripheral side surface. JP-A-4-51
The "heat fixing device" of Japanese Patent No. 071 has a heating roller provided on the outer circumference of the roller body and covered with a surface coating layer, but the power feeding portion is arranged on the outer circumferential side surface.

The "heat roller in the fixing device" of Japanese Utility Model Laid-Open No. 5-17664 discloses the structure of the power feeding portion of the heat roller. The power feeding portion is a power feeding brush that holds the outer circumference of the heat roller. Actual Kaihei 4-1291
In the endless thin-walled cylindrical body corresponding to the fixing roller of the "heat fixing device" of Japanese Patent No. 66, a heat radiator is provided at a position corresponding to the nip portion of the inner surface, and a heat generating element and a temperature sensor are arranged behind it. However, the power feeding unit is not provided inside the roller.

In the "fixing device" of Japanese Patent Laid-Open No. 5-197305, a holding means for holding a heating element is arranged inside the fixing roller along the axial direction thereof, but a power feeding portion for the heating element is arranged outside the roller. To be done. JP-A-4-204981
The "heating device" of the publication uses a fixing film instead of the fixing roller, and a heating body is provided in the nip portion inside the fixing film, and the support body of the heating body is also arranged inside the roller, but the feeding electrode portion is on the side. It is located at the edge.

The "heat roller fixing device" of Japanese Patent Application Laid-Open No. 61-90180 is characterized in that a heater is arranged along the axial direction at an intermediate portion inside the heat roller, and is characterized by a structure for driving the heat roller. Although the structure of the power feeding portion is not disclosed, it is arranged outside the roller as viewed from the structure of the illustrated heating roller.

The "heat fixing device" of Japanese Patent Laid-Open No. 5-142962 has a thin hollow cylindrical heat roller made of a conductive resin, and an elastic roller made of a conductive elastic material is provided inside the heat roller, and the elastic roller and the heat roller are slidably contacted to each other. Although it is connected with electrodes,
This sliding contact electrode is arranged outside the roller.

[0011] Further, Japanese Patent Laid-Open No. 5-281867 discloses a "heating device" such as a temperature fuse and a temperature detecting element for safety measures, which are all provided at a nip portion on the inner surface of a heating film corresponding to a fixing roller. It is not placed in contact with each other. Further, as described above, JP-A-62-1
Although the temperature detection sensor and fuse of the 8581 publication are arranged inside the heating roller, they are not arranged at the nip portion.

[0012]

In the case of the above-mentioned known technique, the power feeding portion and the portion corresponding thereto are all arranged on the outer side or outer side surface of the roller. for that reason,
The overall width in the longitudinal direction becomes longer, which is contrary to space saving.
In addition, it is necessary to maintain the insulation distance from the pressure roller,
Unreasonableness occurs in the arrangement structure. Also, as explained later,
The power supply unit of the present invention has a function of preventing lateral displacement of the fixing roller, and is also characterized by its holding structure, but no known technique similar to this is found. Further, the prior art does not disclose any means for preventing deformation of a thin fixing roller.
Further, the temperature sensor and the like also do not have good thermal responsiveness.

The present invention was devised in view of the above circumstances and has a rapid heating rise speed and thermal responsiveness of the fixing roller, which can reduce power consumption and prevent lateral deviation and deformation of the fixing roller. An object of the present invention is to provide a fixing device having a power supply unit inside the roller that can accurately detect the temperature in the nip portion of the fixing roller and reliably prevent excessive temperature rise.

[0014]

In order to achieve the above object, the present invention sandwiches a sheet carrying unfixed toner conveyed from an image forming section between a fixing roller and a pressure roller, A fixing device that heat-melts toner by a fixing roller and fixes it on the sheet, comprising the fixing roller, a pressure roller, and a power supply unit disposed in the fixing roller, and the fixing roller is a surface layer of the fixing roller. A thin heat-resistant resin layer is formed, and a heat-generating layer is formed between the innermost insulating layer and the heat-resistant resin layer, and the power feeding unit holds the tip side of an electric wire connected to the power source side. A holder arranged substantially immovably near both side surfaces of the fixing roller;
The holder and / or the power supply unit is composed of a power supply brush slidably supported by the holder and having a tip end surface thereof abuttingly engaged with the heat generation layer, and a spring member for urging the power supply brush to press the heat generation layer. The brush is characterized by a fixing device having a power supply unit formed inside the roller so as to be fitted into a circumferential groove formed in the insulating layer in order to restrain the axial movement of the fixing roller.

In the heat generating layer, heat generating pieces each having a length substantially the same as the axial length of the fixing roller and having a relatively narrow width are arranged along the circumferential direction of the roller at appropriate circumferential intervals to generate heat. One piece is fixed to the heat-resistant resin layer and / or the insulating layer, and the holder is pivotally supported by a plurality of rotating members abutting against the inner circumference of the insulating layer for centripetal support of the holder. A connecting member disposed in the roller along the roller axial direction so as to connect the pair of holders disposed in the vicinity of both ends of the fixing roller to the inner surface of the insulating layer at a position corresponding to the nip portion. A backing member having an appropriate axial length in contact with the roller axial direction is elastically supported. Further, a temperature detecting means and / or an overheat preventing means is disposed in contact with the inner surface of the fixing roller at a position corresponding to the nip portion on the inner surface of the insulating layer.

[0016]

The holders for holding the power feeding brushes are arranged in the vicinity of both side ends inside the fixing roller. This holder is held substantially immovable by a connecting member or the like. Since the power feeding brush or the holder is arranged so as to fit in the circumferential groove of the innermost insulating layer of the fixing roller, the lateral deviation of the fixing roller is prevented.
Since the power feeding brush slidably supported by the holder is in contact with the heat generating layer in the nip portion and is pressed by the spring member, the rising speed of heating and the thermal response of the nip portion are extremely fast and reliable. Further, by providing the holder with the rotating member and the connecting member for holding the holder with the backing member, the deformation of the fixing roller can be prevented. Further, since the temperature detecting means and the overheat preventing means are arranged in contact with the inner surface of the fixing roller corresponding to the nip portion, a high thermal response can be achieved.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view showing the schematic structure of a laser printer to which the fixing device of this embodiment is applied, and FIG. 2 is a partial axial sectional view showing the structure of a fixing roller of this embodiment and a power supply unit engaging with it. 3 is a cross-sectional view taken along the line AA in FIG. 2, FIG. 4 is a partial cross-sectional view of another embodiment in which the power feeding unit and the fixing roller are engaged, and FIG. 5 is a cross-sectional view showing another embodiment of the holder of the power feeding unit. Figure, Figure 6
5 is an axial sectional view of FIG. 5, FIG. 7 is an axial sectional view showing a connecting member of a holder and a backing member supported thereby, FIG. 8 is a lateral sectional view of FIG. 7, and FIG. 9 is a connecting member of a holder and supporting members thereof. FIG. 10 is an axial sectional view showing another embodiment of the backing member shown in FIG.
11 and 12 are partial axial sectional views showing the abutting engagement state between the fixing roller and the temperature detecting means and the overheat preventing means.

First, the schematic structure of the laser printer will be described with reference to FIG. The sheet (paper) 6 in the paper feed set 5 set in the printer body 4 is fed in the direction of arrow a and conveyed to the photosensitive drum 8 at a timing by the registration roller 7. The photosensitive drum 8 rotates in the clockwise direction, the surface of the photosensitive drum 8 is uniformly charged by the charging charger 9, and an electrostatic latent image is formed on the photosensitive drum 8 by irradiation of laser light from the laser optical system 10.

The electrostatic latent image is visualized by the toner in the developing device 11. This visible image is transferred to the sheet 6 conveyed to the photosensitive drum 8 by the transfer charger 12, and the transferred visible image is conveyed to the fixing device 1 side through the conveyer 13 and heated to the fixing roller 2 of the fixing device 1. It is nipped and fixed by the roller 3. The fixed sheet 6 passes through the paper discharge path 14 and is discharged to the paper discharge unit 15 as indicated by arrow B.

A cleaning device 1 for removing the visible image formed on the photosensitive drum 8 around the photosensitive drum 8.
6 and a static eliminator 17 are arranged. Further, the air flow in the printer body 4 flows to the arrow C by the exhaust fan 18 and is exhausted to the outside of the printer body 4. The present embodiment is an invention relating to the fixing device 1 described above, and its detailed structure will be described below.

As shown in FIGS. 2 and 3, the fixing device 1
Is composed of a fixing roller 2 and a pressure roller 3. The fixing roller and the pressure roller 3 are pivotally supported on the printer body 4 side by an unillustrated supporting means, and the pressure roller 3 is pressed against the fixing roller 2 side by an unillustrated pressing means. The pressing force is variable. Further, the fixing roller 2 or the pressure roller 3 is rotated by a rotating device (not shown), and the driving force thereof is transmitted to the partner roller.

The fixing roller 2 is a hollow roller body having a three-layer structure in this embodiment. A heat resistant resin layer 19 is provided on the outermost layer, a heat generating layer 20 as an intermediate layer is formed on the inside thereof, and an insulating layer 21 is formed on the innermost layer. Note that these three layers are adhesively fixed.

The heat-resistant resin layer 19 is a thin film made of a heat-resistant resin material having a low friction coefficient, and is made of a material which does not adhere toner to the surface thereof.

In the present embodiment, the heat generating layer 20 is composed of a large number of heat generating pieces 22 arranged on the same circumference at regular pitch intervals 23. The heating piece 22 is a narrow rectangular piece having an axial length substantially equal to the axial length of the fixing roller 2, and the material thereof is the same as a known heating material for the fixing roller.

The insulating layer 21 is made of an insulating material, and is formed of a hollow cylinder as shown in FIG. 3, but a part of the insulating layer 21 enters the space 23 between the adjacent heating pieces 22 to insulate the heating pieces 22 from each other. Further, a circumferential groove 24 is formed by cutting out a part of the insulating layer 21 at a position near the side end of the insulating layer 21.

The feeding portion 25 is provided in the fixing roller 2 at a position opposite to the position where the circumferential groove 24 is formed. The holder 26, the power feeding brush 27, the spring member 28, and the like are included. The power feeding brush 27 is slidably supported by the holder 26, and the tip portion 29 of the power feeding brush 27 is fitted in the circumferential groove 24 of the insulating layer 21 and is in contact with the heat generating piece 22 of the heat generating layer 20.

The spring member 28 urges the power supply brush 27 to press it against the heating piece 22. In addition, the power supply brush 27
Is disposed at a position facing a nip portion 30 formed by pressing the fixing roller 2 and the pressure roller 3. The electric wire 31 and the spring member 28 connected to the power feeding brush 27 are held by the holder 26, and the holder 26 is substantially fixed to the illustrated position via the electric wire 31 or a holding means for the electric wire 31 not shown. As described above, the power feeding brush 27 is fitted in the circumferential groove 24 and the holder 26 is held in a substantially stationary position, so that the fixing roller 2 is restrained from moving in the axial direction.

The pressure roller 3 is composed of a heat-resistant elastic roller, and its outer peripheral surface is pressed against the heat-resistant resin layer 19 of the fixing roller 2 to form the nip portion 30.

As shown in FIG. 3, when the sheet 6 is carried into the contact portion between the fixing roller 2 and the pressure roller 3, the sheet 6 is nipped by both rollers. When the power feeding unit 25 of the fixing roller 2 is energized, the power feeding brush 27 is heated to an appropriate temperature. Since the power supply brush 27 contacts only the heat generating piece 22 near the nip portion 30 where the sheet 6 is sandwiched, the heat generating piece 22 is rapidly heated to a predetermined temperature. Thereby, the fixing of the sheet 6 is performed quickly and reliably. Further, as described above, since the fixing roller 2 is restrained from moving in the axial direction (lateral displacement), the fixing operation of the sheet 6 can be performed without causing the positional deviation between the fixing roller 2 and the pressure roller 3. .
As a result, the fixing quality of the sheet 6 can be stabilized.

FIG. 4 shows a fixing roller 2 in which the layer thickness of the insulating layer 21a at both ends is made thicker than the insulating layer 21 of the other portions.
It shows a. By forming the insulating layer 21a, the holder 26 itself fits into the circumferential groove 24a formed between the insulating layers 21a and 21, and is held by the insulating layer 21a. As a result, the movement of the fixing roller 2a in the axial direction relative to the fixing roller 2 of the above-described embodiment (lateral displacement).
The effect of preventing is improved.

5 and 6 show the holder 2 of the above embodiment.
6 shows an embodiment in which the rotating member 32 is provided on both side surfaces of No. 6. Rotating member support plates 34, 34 are fixed to both side surfaces of a holder main body 33 that slidably holds the power feeding brush 27. In this embodiment, the rotary member support plate 34 is formed in a substantially semi-circular shape. The rotary member 32 is pivotally supported by the rotary member support plate 34, and in the present embodiment, the three rotary members 32 are arranged at equal intervals on one surface. The outer periphery of the rotating member 32 is brought into contact with the insulating layers 21 and 21a so that the holder body 33 is held stationary. In this embodiment, the outer diameter of the pressure roller 3a is smaller than that of the above-mentioned embodiment, but there is no particular reason for any problem, and the same one as in the above-mentioned embodiment may be used.

7 and 8 show an embodiment in which a connecting member 35 and a backing member 36 are provided in order to more securely hold the holder 26, the holder body 33 and the like of the above embodiment on the stationary side. The connecting member 35 is a rod-shaped member disposed inside the fixing roller 2 along the axial direction thereof, and the pair of holders 26 (same for the holder main body 33) arranged at substantially both ends of the fixing roller 2 are formed by screws or the like. It is fixed to the connecting member 35. Although not shown, the connecting member 35 itself is fixed to the printer body 4 side. As described above, as compared with the above embodiment, the holder 26 and the like are firmly held, and the movement of the fixing roller 2 in the axial direction is more reliably prevented. The connecting members 35 are arranged facing each other in the vicinity of the nip portion 30.

A backing member 36 is supported by the connecting member 35 via a spring 37. The backing member 36 is arranged at a position facing the nip portion 30, and
It is made of a member having an appropriate axial length along the axial direction.
The backing member 36 is pressed against the inner surface of the fixing roller 2 by the spring 37. The backing member 36 reinforces the thin fixing roller 2 from the inside, and particularly prevents the fixing roller 2 from being deformed in the nip portion 30.

9 and 10, a backing roller member 38 is used in place of the backing member 36 in FIG. Both ends of the backing roller member 38 are elastically supported by the connecting member 35 via springs 39, 39.
Further, the roller outer periphery of the backing roller member 38 is arranged in contact with the inner surface of the fixing roller 2 at a position facing the nip portion 30. As described above, the deformation of the fixing roller 2 can be prevented and the fixing roller 2 can be driven more smoothly as in the above-described embodiment.

FIG. 11 shows a temperature detecting means 40 provided inside the fixing roller 2, and FIG. 12 shows an embodiment in which an overheat preventing means 41 such as a thermistor or a temperature fuse is arranged inside the fixing roller 2 as well. Show. All of these are arranged in contact with the inner surface of the fixing roller 2, and the nip portion 3
It is arranged at a position facing 0. As a result, it becomes possible to detect a temperature close to the temperature actually received by the sheet 6, and it is possible to reliably prevent heating failure or overheating of the fixing roller 2.

In this embodiment, the holder 26 and the rotating member 3
2 The material of the backing member 36 and the backing roller member 38 is not specifically described, but a material having good slidability is preferable.

[0037]

According to the present invention, the following remarkable effects are obtained. 1) Since the power feeding portion is provided inside the fixing roller, the width in the axial direction (longitudinal direction) is shortened, and the space can be saved. 2) In the prior art, since the power feeding portion is located outside, it is necessary to maintain an insulation distance from the pressure roller side, and the placement of the power feeding portion is limited. Therefore, the power feeding unit can be selectively arranged at any place. 3) Since the power feeding brush of the power feeding portion is provided in the vicinity of the nip portion where the fixing roller and the pressure roller are in pressure contact with each other, only the nip portion is rapidly and effectively heated to the desired heating temperature. In addition, since the heat generating layer is composed of elongated heat generating pieces, heating with good thermal response is performed. As a result, power saving can be achieved. 4) Since the power feeding brush of the power feeding unit is held by the holder, and the power feeding brush and / or the holder is fitted in the circumferential groove in the fixing roller and is pressed by the spring member, the lateral deviation of the fixing roller is caused. To be prevented. As a result, there is no deviation of the sheet nipped by the fixing roller and the pressure roller,
The fixing quality of the sheet can be stabilized. 5) Since the holder is held at a predetermined immovable position by the rotating member and the connecting member of the holder, the lateral displacement of the fixing roller is performed more reliably. 6) Since the backing member is provided at a position facing the nip portion inside the fixing roller, the fixing roller is prevented from being deformed. Thereby, the fixing quality of the sheet can be improved. 7) Since the temperature detecting means and the overheat preventing means are arranged at positions facing the nip portion inside the fixing roller, it becomes possible to control the temperature close to the temperature actually received by the sheet, and the fixing work can be performed with high accuracy. .

[Brief description of drawings]

FIG. 1 is a sectional view showing a schematic structure of a laser printer to which a fixing device according to an embodiment of the present invention is applied.

FIG. 2 is a partial axial cross-sectional view of the fixing device according to the present exemplary embodiment.

3 is a sectional view taken along line AA of FIG.

FIG. 4 is a partial axial cross-sectional view showing another embodiment of the holder holding structure of the power feeding unit.

FIG. 5 is a cross-sectional view showing another embodiment of the holder holding structure of the power feeding unit.

FIG. 6 is an axial sectional view of FIG.

FIG. 7 is an axial cross-sectional view showing a connecting member that holds a holder of a power feeding unit and a backing member supported by the connecting member.

8 is a cross-sectional view taken along the line BB of FIG.

FIG. 9 is an axial cross-sectional view showing a connecting member that holds a holder of a power feeding unit and a backing roller member supported by the connecting member.

10 is a cross-sectional view taken along the line CC of FIG.

FIG. 11 is a partial axial cross-sectional view showing a temperature detecting unit arranged in the fixing roller.

FIG. 12 is a partial axial cross-sectional view showing an overheat preventing unit arranged in a fixing roller.

[Explanation of symbols]

 1 Fixing Device 2 Fixing Roller 2a Fixing Roller 3 Pressurizing Roller 4 Printer Main Body 5 Paper Feeding Set 6 Sheet 7 Registration Roller 8 Photosensitive Drum 9 Charging Charger 10 Laser Optical System 11 Developer 12 Transfer Charger 13 Conveyor 14 Paper Ejection System 15 Ejection Paper part 16 Cleaning device 17 Static eliminator 18 Exhaust fan 19 Heat resistant resin layer 20 Heat generation layer 21 Insulation layer 21a Insulation layer 22 Heat generation piece 23 Interval 24 Circular groove 24a Circular groove 25 Holder 27 Holder 27 Power brush 28 Spring Member 29 Tip part 30 Nip part 31 Electric wire 32 Rotating member 33 Holder body 34 Rotating member support plate 35 Connecting member 36 Backing member 37 Spring 38 Backing roller member 39 Spring 40 Temperature detecting means 41 Overheat prevention means

Claims (6)

[Claims] 1. A fixing device for holding a sheet carrying unfixed toner conveyed from an image forming unit between a fixing roller and a pressure roller, and thermally fixing the toner by the fixing roller to fix the sheet on the sheet. The fixing roller comprises a pressure roller, and a power feeding section disposed inside the fixing roller. The fixing roller has a thin heat-resistant resin layer formed on the surface layer thereof, and an innermost insulating layer and the insulating layer. A holder for forming a heat generating layer between heat-resistant resin layers, wherein the power feeding portion holds a tip end side of an electric wire connected to a power source side and is substantially immovably arranged near both side surfaces of the fixing roller, The holder comprises: a power supply brush slidably supported by the holder and having a tip end surface thereof abuttingly engaged with the heat generation layer; and a spring member for urging the power supply brush to press the heat generation layer.
Alternatively, the power feeding brush is fitted in a circumferential groove formed in the insulating layer to restrain the axial movement of the fixing roller, and the power feeding unit is provided inside the roller. 2. The heat-generating layer comprises heat-generating pieces of substantially the same length as the axial length of the fixing roller and having a relatively narrow width, which are arranged at appropriate circumferential intervals along the circumferential direction of the roller. The fixing device having the power supply unit according to claim 1, which is formed by fixing a piece to the heat resistant resin layer and / or the insulating layer. 3. A fixing device having a power supply unit inside a roller, wherein a plurality of rotating members which are in contact with the inner circumference of the insulating layer are pivotally supported on the holder so as to provide centripetal support for the holder. 4. The insulating layer is provided at a position corresponding to a nip portion in a connecting member arranged in the roller along the roller axial direction so as to connect the pair of holders arranged near both ends of the fixing roller. 2. The fixing device having a power supply unit according to claim 1, which is elastically supported by a backing member having an appropriate axial length in contact with the inner surface of the roller along the roller axis direction. 5. The fixing device having the power supply unit according to claim 4, wherein the backing member is a backing roller member. 6. A power supply unit according to claim 1, wherein a temperature detecting means and / or an overheat preventing means is disposed in contact with the inner surface of the fixing roller at a position corresponding to the nip portion of the inner surface of the fixing roller. Fixing device.