JP2000214707A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent ingression of powder due to contact abrasion into a heating element inside the roller member of a fixing device without a cost increase and hindrance of compaction. SOLUTION: A contact face between an electrode unit 25 and a power feeder for feeding power to a heating element disposed on the internal face of a fixing roller 10 via the electrode unit 25 is positioned further inside the roller than the end face of the fixing roller 10. Also, a holder for holding the brush 26 of the power feeder is provided with a receiving part, which is situated below the contact face.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device in an image forming apparatus such as an electrophotographic printer, a facsimile, and a copying machine.

[0002]

2. Description of the Related Art An example of an engine process in a conventionally known image forming apparatus is as follows. In FIG.
The recording paper P conveyed from the paper feeding device 5 is conveyed to the latent image carrier as the photoconductor 4 at a timing by the registration roller 6. The photoreceptor 4 is driven to rotate in a counterclockwise direction as viewed in the figure. At this time, the surface of the photoreceptor is charged by the charging charger 2 and is irradiated with laser light from the laser optical system 1 to form an electrostatic latent image on the surface I do. When passing through the developing device 3, the latent image is visualized by toner, and is transferred to the recording paper by the transfer roller 7. After the transfer, the recording paper once in contact with the photoconductor 4 is separated by the curvature of the photoconductor. Then, the recording paper separated from the photoreceptor is conveyed to a fixing device 8, where the image transferred to the recording paper is fixed, and the recording paper carrying the fixed image is discharged to a paper discharge unit 9.

The fixing device 8 fixes the image by applying at least the action of heat and pressure to the toner on the recording paper, and includes a fixing roller 10 and a pressure roller 11 which is pressed and driven by the roller.
And the basic elements. A resistance heating element is provided in the roller for heating the fixing roller or the pressure roller, and a power receiving unit (electrode unit) is provided at an end of the roller for supplying electricity to the resistance heating element. The electrode unit rotates with the roller. A power feeder contacts the electrode unit from the outside in the roller axis direction.

[0004]

When the electrode unit rotates together with the roller, the mutual contact surface between the electrode unit and the power supply may shift. Not only may there be a failure in energization due to displacement of the contact surface, but also, in some cases, a leak between the power supply and the core member forming the roller, particularly an outer short surface of the power supply and the core member in the direction of the rotation center axis. Can occur. Therefore, Japanese Patent Laid-Open No. 10-1869
In Japanese Patent Publication No. 18, the mutual contact surface between the electrode unit and the power feeder that comes into contact with the electrode unit is located more than the outer end surface in the rotation center axis direction of the core member adjacent to the mutual contact surface in the rotation center axis direction of the core member. To the outside by a certain distance. With such a configuration, there is an advantage that abrasion powder of the brush constituting the power supply body does not enter the resistance heating element layer inside the roller.

However, since the contact position between the electrode serving as the electrode unit and the brush serving as the power feeder is set outside the roller, the roller end protrudes by that much, which limits the scale down of the fixing device and the image forming apparatus using the same. There is a problem that exerts. If a separate member is used to prevent the abrasion powder from entering the inside of the roller, the cost increases. Further, in the above publication, the insulating layer is provided in substantially the same region as the cored bar, but a U-groove edge portion for driving the gears and a retaining ring for attaching a retaining ring for preventing the roller from moving in the axial direction and coming off are provided. It is difficult to ensure insulation at the edge of the long hole. If an insulating member is inserted between the electrode and the power supply brush and the roller core in order to ensure insulation, the cost increases.

In order to stably maintain the contact state between the electrode and the power supply brush even when the power supply brush abutting on the electrode serving as the electrode unit is slightly rotated by the rotation of the electrode, Japanese Patent Application Laid-Open No. Hei 10-186921 discloses the following. It has been proposed that the twist direction of a stranded wire constituting a lead wire drawn out from the power supply brush in the roller rotation center axis direction is set to be a further twisted direction when the power supply brush is lifted and rotated. This prevents buckling of the lead wires, but such a setting reverses the twist direction of each lead wire at both ends of the roller, one of which is custom-made and extremely expensive. Further, depending on the case, it is conceivable that the lead wire is twisted too much with the rotation and causes disconnection.

Accordingly, the present invention has been made in view of the above-described problems, and has been made to prevent contact abrasion powder from entering a heating element inside a roller member of a fixing device without increasing cost and without hindering downsizing. This is the first task. The second is to ensure the insulation of the roller member of the fixing device.
Subject. It is a third object of the present invention to prevent the feeder from being twisted and rotated by the rotation of the electrode unit, and to prevent buckling or disconnection of the lead wire for energization.

[0008]

The first object of the present invention is to provide a fixing device for fixing a toner image to the recording material by nipping and conveying the recording material between a fixing roller and a pressure roller, and an inner surface of the fixing roller. A heating element, an electrode unit that is electrically connected to the heating element, and a power supply that supplies power to the heating element via the electrode unit. The contact surface of the fixing roller is located on the inner side of the roller than the end surface of the fixing roller.
A brush having a contact and an elastic member for pressing the contact against the electrode unit, and a holder for holding the brush, wherein the holder has a receiving portion located below the contact surface, Will be resolved.

A second object is to provide a heating element disposed on the inner surface of the fixing roller, an electrode unit electrically connected to the heating element, and a power supply element for supplying power to the heating element via the electrode unit. In a fixing device, wherein a contact surface between an electrode unit and a power supply is located on the inner side of a roller than an end surface of a fixing roller, the power supply includes a brush having a contact and an elastic member for pressing the contact against the electrode unit. And a holder for holding the brush, and the holder includes an insulating portion for ensuring insulation between the brush or the electrode unit and the core of the fixing roller.

In these configurations, it is even more effective if the holder has a cover for covering the end of the fixing roller.

A third object is to provide a brush, which includes a contact and a resilient member for pressing the contact against the electrode unit, wherein the power supply supplies electricity to the heating element disposed on the inner surface of the fixing roller via the electrode unit. The problem is solved by having a holder for holding the brush, and the holder having a shape or a portion for preventing the brush from rotating. In this case, it is even more effective if the contact end surface of the contact with the electrode unit is equal to or smaller than the electrode unit end surface and the material of the contact is more wear-resistant than that of the electrode unit end surface.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described based on an example shown in the drawings. The configuration and mechanism of the entire fixing device are basically the same as those of the related art. That is, a fixing roller provided with an electrode, a pressure roller driven by pressure contact with the electrode, a cleaning member for cleaning the surface of these rollers, a driving gear, a heating element disposed on the inner peripheral surface of the fixing roller, and power supply to the heating element For example, a power supply brush, a thermistor, and the like are provided, and the temperature of the surface of the fixing roller is detected by the thermistor, and a signal is sent to a power supply unit to control the temperature by a fixing control unit, thereby instructing power supply to the heating element. For the sake of simplicity, the parts described in the section of the related art will be omitted, and only the parts particularly related to the present invention will be described.

As shown in FIG. 2A, the fixing roller 10
Has a core metal 21, a fluororesin layer 22 on the outer periphery, an insulating layer 23 on the inner periphery, and a heating element 24 on the inner peripheral surface. As shown in FIG. 2B, two long holes 21 a for retaining rings for stopping the movement of the fixing roller 10 in the thrust direction are formed at each of two ends of the metal core 21 at a total of four locations. A U-groove 21b for driving a gear is also formed at one end. The core metal 21 and the insulating layer 23 extend over the entire width of the fixing roller in the longitudinal direction, and the fluororesin layer is slightly shorter than the entire width and extends over a length that completely covers the heating element 24.

The metal core 21 has a diameter of 15 to 40 mm and a thickness of 0.2 if the base material is iron (STKM11, STKM12).
5 to 0.5 mm, the base material is aluminum (A5052,
A6063), the thickness is 0.6 to 2 mm, and the length is 350 to 410 mm for the A3 paper passing type. The insulating layer 23 is made of a substance having a heat resistance of 450 ° C. or higher, for example, a resin or a ceramic material mainly composed of polyimide, mica, or aluminum oxide, and has a thickness of 25 to 100 μm.
m. The fluororesin layer 22 is made of perfluoroalkoxy resin (PFA) or ethylene tetrafluoride resin (PTFE), and has a thickness of 10 to 30 μm. The heating element 24 is 1
It is a nickel-chromium alloy film, a barium titanate film, or a palladium alloy film having a thickness of 0 to 100 μm, but is not particularly limited as long as it generates heat by passing an electric current.

As an embodiment of the fixing device of the A3 paper passing type, in order to make the fixing device compact, a core metal made of a material S is used.
TKM11 iron with a length of 360 mm, an outer diameter of 30 mm, a thickness of 0.39 mm, and a heat-resistant insulating layer composed mainly of polyimide having a heat resistance of 450 ° C. or more, a length of 360 mm, a thickness of 25 μm, and a fluororesin layer made of perfluoroalkoxy resin Length 340
It is assumed that the heating element has a length of 325 mm with a nickel-chromium alloy film of 40 μm. On the other hand, as shown in FIG.
0, and is connected to both ends of the heating element 24, and its contact portion with the power supply brush is 10 to 16 mm in diameter (in a fixing device having a current of 8 A or less, so as not to be smaller than the brush described below). φ10). By making the contact surface with the brush inside the roller end surface, the entire fixing device including the brush portion can be made compact.

Next, the power supply brush unit will be described. The brush portion includes the brush 26 shown in FIG. 4 and the holders 27, 28, and 29 shown in FIGS.
And a screw 3 for fixing the brush shown in FIG. 8 to the holder.
0 (omitted in other drawings), which is not shown in any of the drawings, comprises a bracket or a screw for fixing the holder to the fixing device. The brush 26 shown as a perspective view in FIG. 4 and a sectional view in FIG.
6d (a brass plate having a wall thickness of 0.8 to 1.6 mm), and a lead wire 26b (φ0.
(Several tens of copper wires of 0.5 to 0.15 mm are bundled together and twisted in several bundles), which is one of the elastic members for positioning the lead wire inside and pressing the contact against the electrode side. It consists of a spring 26c (pressing force to the electrode is 1 to 5N).

The brush contact 26a is made of a material containing copper as a main component and 10 to 60% by weight of carbon. The contact part with the electrode has a cylindrical shape,
The diameter is 6 to 15 mm, which is not larger than the electrode side. Regarding the outer diameter, when the same current is applied, the material needs to be increased if the material has a large amount of carbon, and if the amount of carbon is the same, the diameter needs to be increased if the current flowing through the brush is large. As a specific example, the amount of carbon is 30% by weight, the current is 8A, and the diameter is φ8. Contact 26
The guide part of a is a polygon, a rectangle with a ridgeline of 0.5 to 1 m.
m is chamfered. By making the contact surface of the contact with the electrode circular, the distance from the center of rotation of the electrode can be minimized, the contact linear velocity can be suppressed to the minimum necessary, and the generation of sparks and noise is reduced. It is possible. The reason why the guide portion of the contact is formed in a polygonal shape is that when the electrode portion rotates together with the fixing roller, the contact is firmly held so that the contact rotates, the twist of the lead wire is eliminated, or the twist is performed. This is to prevent a situation in which the wire is too disconnected. For such a purpose, as shown in FIG.
A convex (not shown, but may be concave) detent portion 26e may be formed on the peripheral surface of 6a ', and the holder may be fitted to the detent portion 26e to prevent rotation.

Further, as for each material of the contact and the electrode, a material which is easy to be cut by the contact is used. This is to extend the life by cutting off the contact having a high degree of freedom in length. As for the contact portion, the contact is not larger than the electrode, and when worn, the entire contact is worn. If the contact is wider than the electrode in terms of area, a portion that is worn and a portion that is not worn appear at the end face of the contact, and eventually a step occurs. It is difficult to ensure that the rotating electrode does not have eccentricity at all in terms of assembly accuracy.If a step occurs in the contact, the contact and the electrode float over the step and the contact area decreases, in other words, the contact area decreases. The resistance increases, there is a problem of abnormal heating, and a problem such as leakage between floating minute gaps can also occur. In order to avoid these inconveniences, it is related that the contact is not larger than the electrode at the contact portion. FIG. 13 schematically shows the contact state between the electrode 25 and the contact of the brush 26 when the brush portion is assembled to the fixing roller 10, and the brush-electrode contact position is indicated by reference numeral 31.

Next, the brush holder will be described.
The brush is fixed, the electrode rotates, and the brush contacts are made of a material that is easy to scrape, so that abrasion powder is generated. Since the contact portion is located inside the end of the fixing roller, if the abrasion powder enters a heating element whose surface is not insulated inside the roller, there is a danger that leakage or abnormal heating may occur. In order to avoid such danger, the shape of the holder made of an insulating material is characterized. One example is shown as a perspective view in FIG. 7 and a sectional view in FIG. The holder 27 includes a portion 27a that entirely covers and holds the guide portion of the brush contact, a receiving portion 27b extending from the lower side to the side of the contact area with the electrode, and a connection with the brush fixing plate using the screw 30. And a plate-like portion 27c. The tray 27b has a U-shaped cross section that cuts its longitudinal direction perpendicularly.

FIG. 9 is a perspective view and FIG. 10 is a sectional view of a holder 28 having another structure. The holder 28 covers the contact area between the contact of the brush 26 and the electrode portion in the circumferential direction. In the fixing roller, an insulating layer is provided on the inner side of the core metal. However, since the U-groove and the elongated hole for the retaining ring cannot secure the insulating property of the edge portion, the insulating property between the portion and the electrode or the power supply brush is determined by using this holder. It is realized by the circumferential covering.
The circumferential cover also serves as a sink for wear powder.

A holder 29 according to still another configuration is shown in FIG.
10 is a perspective view, and FIG. 10 is a sectional view. In the holder 29, the cover portion 2 further covers the cylinder portion 29a that circumferentially covers the contact region between the contact of the brush 26 and the electrode portion.
9b is provided. The positional relationship between the cylinder part 29a and the cover part 29b is adjusted so that the end of the core of the fixing roller or the like is located between the cover part 29b and the cylinder part 29a. Such a positional relationship can prevent powder flowing in the image forming apparatus, that is, iron powder and paper powder used for the toner and the developer, from entering the fixing roller, resulting in leakage and abnormal overheating. In addition, generation of off-flavor can be suppressed. The holder can be made by integral molding, and the cost can be reduced.

As the material of the holders 27, 28, 29 described above, a resin mixed with inexpensive PET graphite which has heat resistance and insulation properties can be used, but when higher heat resistance is required. , PPS or PA (nylon) may be used.

[0023]

According to the present invention, the fixing device can be made compact because the contact surface between the electrode unit and the power supply is located inside the roller than the end surface of the fixing roller, and the holder of the power supply is a brush. And a receiving portion located below the contact surface of the electrode unit, so that no separate member is provided, in other words, cost is prevented, and abrasion powder falling from the contact surface portion is generated on the heating element on the inner surface of the fixing roller. It is possible to avoid a problem in which a leak or the like is caused by entering.

In a fixing device in which the contact surface between the electrode unit and the power supply is located inside the roller from the end surface of the fixing roller, the holder of the power supply ensures the insulation between the brush or the electrode unit and the core of the fixing roller. Is provided in the fixing roller, the insulating portion enters the fixing roller, and the insulating property can be ensured even in the range of the U-shaped groove or the long hole in the fixing roller.

Since the holder has a cover for covering the end of the fixing roller, it is possible to prevent iron powder and paper powder contained in the toner and developer flowing in the image forming apparatus from entering the fixing roller. It is.

By having a shape or a portion that prevents the holder of the power supply body from rotating as the electrode unit rotates, buckling or disconnection of the lead wire is avoided. If the contact end surface of the contact with the electrode unit is the same as or smaller than the electrode unit end surface, and the material of the contact is more wear-resistant than that of the electrode unit end surface, there will be no step at the contact end surface, and thus poor contact. And sparks and noise can be prevented.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an image forming apparatus.

FIGS. 2A and 2B are diagrams showing a fixing roller of the fixing device according to the present invention, wherein FIG. 2A is a sectional view and FIG.

FIGS. 3A and 3B are diagrams showing a fixing roller incorporating a heating element of the fixing device according to the present invention, wherein FIG. 3A is a cross-sectional view and FIG. 3B is a front view.

FIG. 4 is a schematic perspective view illustrating an example of a power supply brush.

FIG. 5 is a sectional view of the power supply brush of FIG. 4;

FIG. 6 is a schematic perspective view showing a different configuration of a contact of the power supply brush.

FIG. 7 is a schematic perspective view illustrating an example of a power supply holder.

FIG. 8 is a cross-sectional view of a power supply including the holder of FIG. 7;

FIG. 9 is a schematic perspective view illustrating an example of another configuration of the holder.

FIG. 10 is a cross-sectional view of the power supply including the holder of FIG. 9;

FIG. 11 is a schematic perspective view illustrating an example of still another configuration of the holder.

FIG. 12 is a sectional view of a power supply body including the holder of FIG. 11;

FIG. 13 is a partial cross-sectional view illustrating contact between a power supply body and an electrode unit.

[Explanation of symbols]

 10 Fixing roller 25 Electrode 26 Brush 31 Brush-electrode contact position

Claims (5)

[Claims] A fixing device for fixing a toner image to the recording material by nipping and conveying the recording material between a fixing roller and a pressure roller, wherein a heating element disposed on an inner surface of the fixing roller;
In a fixing device including an electrode unit electrically connected to the heating element, and a power supply for supplying power to the heating element via the electrode unit, a contact surface between the electrode unit and the power supply is closer to an end surface of the fixing roller. Is also located inside the roller, the power supply body has a brush having a contact and an elastic member for pressing the contact against the electrode unit, and a holder for holding the brush, and the holder is provided on the contact surface. A fixing device having a receiving portion located below. 2. A fixing device for fixing a toner image on a recording material by nipping and conveying a recording material between a fixing roller and a pressure roller, comprising: a heating element disposed on an inner surface of the fixing roller;
An electrode unit electrically connected to the heating element, and a power supply for supplying power to the heating element via the electrode unit, wherein a contact surface between the electrode unit and the power supply is located on the roller inner side of the fixing roller end surface. In the fixing device, the power supply body includes a brush including a contact and an elastic member for pressing the contact against the electrode unit, and a holder for holding the brush, and the holder includes a brush, an electrode unit, and a fixing roller. A fixing device provided with an insulating portion for ensuring insulation from the metal core. 3. The fixing device according to claim 1, wherein the holder has a cover that covers an end of the fixing roller. 4. A fixing device for fixing a toner image to the recording material by nipping and conveying the recording material between a fixing roller and a pressure roller, comprising: a heating element disposed on an inner surface of the fixing roller;
In a fixing device comprising: an electrode unit electrically connected to the heating element; and a power supply body for supplying power to the heating element via the electrode unit, wherein the power supply body includes a contact and the contact to the electrode unit. A fixing device, comprising: a brush having an elastic member to be pressed against, and a holder for holding the brush, wherein the holder has a shape or a part that prevents the brush from rotating. 5. The electrode according to claim 4, wherein a contact end face of the contact with the electrode unit is equal to or smaller than the electrode unit end face, and a material of the contact is more wear-resistant than that of the electrode unit end face. The fixing device as described in the above.