JPH10333475A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the mechanical strength of a fixing roller, for reducing the thickness and to shorten a rising time by providing a heating resistor on the outer periphery of a core metal, in the fixing roller and a reinforcing member inside a roller. SOLUTION: A first insulated layer 31 is formed on the outside surface of the core metal 11 and a heat generating layer 32 formed on the first insulated layer 31 is provided with the heating resistor made of SUS metallic foil, on the surface of a heating element base made of a heat-resistant insulator such an film-like polyimide. On the other hand, reinforcing rings 21-23 made of the same material as that of the core metal 11 are loaded. The respective reinforcing rings 21-23 are fixed on the fixing roller 1 by fixing ribs 12-14 provided projectingly on the inner peripheral side of the core metal 11. Each of the fixing ribs 12-14 is provided in pairs. Thus, the reinforcing rings 21-23 are provided inside the roller 1, so that the mechanical strength of the roller 1 can be increased, the thickness of the core metal 11 of the roller 1 is reduced to decrease heat capacity and a fixing device quick to start can be obtained.

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 a copying machine, a printer, and a facsimile.

[0002]

2. Description of the Related Art In an image forming apparatus such as a copying machine, a printer, a facsimile or the like using an electrophotographic system, a transfer paper,
A heat fixing device is widely used as a fixing device for fixing an unfixed image (toner image) transferred onto a recording material (hereinafter, referred to as a sheet) such as an OHP film on the recording material. Conventionally, as a heat fixing device, a heat roller system in which a pressure roller is pressed against a fixing roller heated by a heater, and an unfixed toner image is fixed by heat and pressure while nipping and conveying the recording material between both rollers. Things are heavily used.

In recent years, there has been a demand for a reduction in power consumption in various image forming apparatuses due to an increase in environmental regulations and environmental protection consciousness. As one of the measures, a heater of the fixing apparatus is used only when a sheet is fed to execute a fixing operation. An on-demand system has been proposed in which the power is supplied to the power supply and the power supply is not supplied at other times (preheating is not performed).

In such a power saving type image forming apparatus,
During image formation, the surface temperature of the fixing roller needs to immediately reach the fixing-possible temperature, and a high-speed (short-time) startup of the fixing device is required.

In the conventional fixing roller, a heater such as a halogen lamp is installed inside a hollow pipe-shaped metal roller, and the heater is heated to heat the entire roller. In order to enable rapid temperature rise with this type of fixing roller, the thickness of the fixing roller base (core metal) is reduced to 1 mm or less.

On the other hand, as another measure for satisfying the requirement of a high-speed start-up of the fixing device, a heating layer such as an electric resistor is provided on the outer peripheral surface or the inner peripheral surface of the roller, and a surface resistance heating method is used to generate heat. It has been proposed to use a fixing roller. This resistance heating type fixing roller has a high heating efficiency and is suitable for energy saving, but in order to raise the temperature immediately when the user uses it without performing preheating,
Achieving rapid temperature rise is achieved by a combination with a technique for thinning the fixing roller base.

[0007]

However, there has been a problem that the mechanical strength is reduced due to the reduction in the thickness of the fixing roller base, and the roller is bent or the cross section is crushed.
Such deformation of the fixing roller causes damage to the resistance heating element.

The present invention solves the above-mentioned problem in the conventional fixing device in which the thickness of the fixing roller base is reduced, and achieves a fixing device which achieves a reduction in thickness by increasing the mechanical strength of the fixing roller and has a short rise time. The task is to provide.

[0009]

According to the present invention, there is provided a fixing roller having a core metal wall thickness of 0.2 to 1.0 mm and a pressing roller pressed against the fixing roller. In a thermal fixing device for fixing an unfixed image to recording paper by passing a recording sheet carrying an unfixed image, the fixing roller has a resistance heating element on the outer periphery of a cored bar and a reinforcing member provided inside the roller. It is solved by having.

According to the present invention, in order to solve the above-mentioned problem, the resistance heating element is divided into a plurality of parts in the same heating layer according to the size of the recording material, and each of the resistance heating elements is individually energized and controlled. Propose that.

Further, according to the present invention, in order to solve the above-mentioned problem, the diameter of the fixing roller in the ring-shaped electrode mounting portion connected to the resistance heating element is made larger than the diameter of the fixing roller in the outer portion of the electrode mounting portion. It is proposed that an insulating layer provided on the periphery of the resistance heating body and on the periphery of the metal core also covers the small diameter portion of the fixing roller outside the electrode mounting portion.

Further, according to the present invention, in order to solve the above-mentioned problem, the thickness of the insulating layer in the small-diameter portion of the fixing roller outside the electrode mounting portion is made larger than the thickness of the insulating layer in the inside of the electrode mounting portion. It is proposed to mount a fixing roller bearing and a fixing drive gear on the small diameter portion of the fixing roller.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view showing a schematic configuration of a fixing roller in a fixing device according to an embodiment of the present invention. The fixing roller 1 shown in FIG.
It has a core metal 11, a first insulating layer 31, a heating layer 32, a second insulating layer 35, and a heat-resistant release layer 36, each having a thickness of 1 mm. The core metal 11, which is a roller base, is mainly composed of aluminum, nickel, ferrite, or the like. The first insulating layer 31 formed on the outer surface of the metal core 11 is made of a heat-resistant insulating material such as a film-like polyimide. The heating layer 32 formed on the first insulating layer 31 is a heating element base 33 made of a heat-resistant insulating material such as a film-like polyimide (see FIG. 2).
Is provided with a resistance heating element 34 (see FIG. 2) made of SUS-based metal foil. The second insulating layer 35 is formed of the same material as the first insulating layer 31. Heat release layer 36
Is made of PFA, PTFE, or the like having heat-releasing properties, and forms a roller surface.

Ring-shaped sliding electrodes 41 and 42 are fitted on both ends of the heat generating layer 32. The sliding electrodes 41, 42
Is mounted so as to be completely electrically connected to the electrode portions 34 a and 34 b of the resistance heating element 34, and rotates together with the fixing roller 1. Power supply brushes 65, 6 are provided outside the sliding electrodes 41, 42.
6 are provided, and contact with the sliding electrodes 41 and 42 to
, The resistance heating element 34 is caused to generate heat.

On the other hand, on the inner peripheral side of the fixing roller 1,
1, reinforcing rings 21, 22, 23 of the same material as those of FIG. Each reinforcing ring is fixed to the fixing roller 1 by fixing ribs 12, 13, and 14 protruding from an inner peripheral side of the metal core 11. Each fixing rib is provided as a pair. In the present embodiment, three reinforcing rings are provided, but a reinforcing ring may be provided only at a central portion of the fixing roller. Alternatively, three or more reinforcing rings may be provided.

The fixing roller 1 has rotating support portions at both ends supported by bearings 51 and 52. Fixing roller 1
A fixing drive gear 53 is fitted at one end (right side in FIG. 1). A main body drive gear (not shown) is meshed with the fixing drive gear 53 and driven to rotate.

FIG. 2 is a developed view showing the structure of the heat generating layer 32 provided on the fixing roller 1. As shown in this figure,
On the surface of the heating element base 33 of the heating layer 32, a resistance heating element 34 made of SUS-based metal foil is provided. The resistance heating elements 34 extending in the roller axis direction are refracted immediately after being refracted in the circumferential direction and extended in the axial direction, and this is repeated. Resistance heating element 3
4 are electrode portions 34a, 34b extending in the roller circumferential direction, and sliding electrodes 41, 42 are mounted.

The arrangement pattern of the resistance heating elements 34 is not limited to the example shown in FIG. FIG. 3 shows another example of the arrangement pattern of the resistance heating elements 34. In this example, the resistance heating elements 34 extending in the roller circumferential direction are arranged side by side in the roller axis direction. As in the example of FIG. 2, both end portions of the resistance heating element 34 are electrode portions 34a and 34b.

FIG. 4 is a block diagram showing the configuration of a control circuit for controlling the heat generation of the fixing roller 1. As shown in FIG. A central thermistor 81 provided in contact with the outer peripheral surface of the fixing roller 1 (see FIG. 1)
The CPU 80 controls the energization from the power supply 61 to the resistance heating element 34 based on the detected temperature of the fixing roller 1 to maintain each set temperature necessary for fixing the toner. I do. The portions related to the energization control can be provided in the image forming apparatus main body to which the fixing device is attached.

FIG. 5 is a perspective view showing the structure of the reinforcing rings 21, 22, 23 provided on the inner peripheral side of the fixing roller 1. Each reinforcing ring has the same shape, and one of them will be described as a representative. The reinforcing ring 21 is formed by bending the outer edge of a disc-shaped base 21 a having a hole
1b, and has a thin cylindrical or dish shape as a whole. Fixing ribs 12, 13, 1 of fixing roller 1
By fitting the reinforcing rings 21, 22, 23 into 4, the reinforcing ring is prevented from falling down or falling off. Such a configuration is excellent not only in preventing the fixing roller 1 from collapsing in the axial direction (radial direction) but also in preventing the roller from bending in the roller axial direction (longitudinal direction).

In this embodiment, since the fixing rings 1, 22, and 23 are provided inside the fixing roller 1, the mechanical strength of the fixing roller can be increased.
By reducing the thickness of the metal core to reduce the heat capacity, it is possible to provide a fixing device that rises quickly. The present invention is a technique particularly effective for a fixing roller (thin fixing roller) having a core metal wall thickness of about 0.2 to 1.0 mm.

By the way, in the fixing device shown in FIG.
When small-sized paper (for example, B5 lengthwise) is continuously passed, the temperature of the central portion of the fixing roller 1 through which the paper passes is reduced because the heat of the roller surface is taken away by the paper. In this case, since the resistance heating element 34 generates heat in an attempt to increase the temperature of the roller central portion, the temperature of the roller end portion whose temperature has not decreased also increases. Then, the temperature at the end of the roller becomes much higher than that at the center, so that the temperature may be higher than the heat resistant temperature of the release layer 36 on the surface of the fixing roller 1. This may cause toner offset. In particular, this tendency becomes more remarkable as the thickness of the core metal of the fixing roller 1 is smaller.

Therefore, as another embodiment of the present invention, it is proposed to divide the resistance heating element of the fixing roller 1 into a plurality of parts corresponding to the sheet width and to control them separately. FIG. 6 is a cross-sectional view illustrating a fixing roller of the fixing device according to the embodiment. Figure 1
The following description focuses on the differences from the above-described embodiment of FIG.

Heat generation layer 7 formed on first insulating layer 31
7, a central resistance heating element 74 and an end resistance heating element 75 are provided on the surface of a heating element base 73, as shown in FIG. The central resistance heating elements 74 are provided corresponding to small-size paper, and the end resistance heating elements 75 are disposed on both sides of the central resistance heating element 74 and correspond to large-size paper. Both resistance heating elements 74 and 75 are connected to a common electrode portion 7.
6 is provided on one side of the roller, and the other end of the roller is provided with separate electrode portions 74a and 75a, respectively.

In FIG. 6, a ring-shaped sliding electrode (common electrode) 42 is fitted to one end of the heating layer 72 to supply power to the heating elements 74 and 75. Two ring-shaped sliding electrodes 41 and 43 are fitted to the opposite ends of the heat generating layer 72 so as to correspond to the individual electrodes of the heat generating elements 74 and 75. Power supply brushes 65, 66, 67 are provided so as to abut on these three sliding electrodes 41, 42, 43. A power supply 61 is provided between the power supply brushes 65 and 66, and applies a voltage to the central resistance heating element 74 to generate heat. A power supply 62 is provided between the power supply brushes 66 and 67, and applies a voltage to the end resistance heating element 75 to generate heat. Further, an end thermistor 82 is disposed on the heat-resistant release layer 36 in addition to the central thermistor 81 to detect the temperature of the fixing roller 1 at each position. Further, the fixing roller 1
Inside, three reinforcing rings 21, 22, 23 are arranged.

FIG. 8 is a block diagram showing the configuration of the control circuit according to this embodiment. The outputs of the central thermistor 81 and the end thermistor 82 are taken into the CPU 80,
U80 controls the energization from the power supplies 61 and 62 based on the detected temperature of the central portion and the temperature of the end portion of the fixing roller 1 so as to maintain each set temperature necessary for fixing the toner, thereby controlling the central resistance. The heating element 74 and the end resistance heating element 75 are controlled independently.

As described above, in the present embodiment, a plurality of resistance heating elements divided according to the sheet size are provided on the fixing roller, and each resistance heating element is individually controlled, so that small-size paper can be continuously passed. Even when paper is used, it is possible to suppress an excessive rise in temperature at the end of the fixing roller.

FIG. 9 is a developed view showing another example of the heating element pattern applicable to the present embodiment. In the example shown in this figure, the center resistance heating element 74 and the end resistance heating element 75
Both extend in the circumferential direction of the roller, and are refracted and arranged side by side in the roller axial direction. Other configurations are the same as those shown in FIG.

Next, still another embodiment of the present invention will be described. In each of the above embodiments, the ring-shaped electrodes 41, 42, 43 for supplying power to the resistance heating element are
In order to insert the straight fixing roller 1 from the end into the roller, if the roller diameter of the ring-shaped electrode mounting portion is the same as the diameter of the roller end, or if the difference is small even when the diameter of the roller end is small, When attaching the ring-shaped electrode (inserting the ring-shaped electrode into the fixing roller), the first insulating layer 31 is used.
May be damaged, in which case current leakage may occur. Further, in order to enhance insulation between the bearings 51 and 52 for rotatably supporting the fixing roller 1 and the fixing drive gear 53, an insulating layer at a portion where the bearings 51 and 52 and the fixing drive gear 53 are mounted (roller end portion). When the thickness of the ring-shaped electrode 31 is increased after the insulating layer is formed,
42 and 43 cannot be inserted. Configurations of still another embodiment of the present invention for solving these will be described with reference to FIGS.

In FIG. 10, the core metal 111 of the fixing roller 101 is drawn so that the diameter at both ends is smaller than the diameter at the center. The first insulating layer 131 formed on the metal core 111 is applied up to the roller end. On the other hand, the heat generating layer 132 formed on the first insulating layer 131 at the center of the roller is not provided at both ends of the roller, but is provided only at the center of the roller. Heat generation layer 13
2 has the same configuration as the heat generating layer 32 shown in FIGS. 2 and 3, and has ring-shaped electrodes 141, 14 on electrode portions 134a, b provided at both ends of a resistance heating element 134 (not shown).
2 are fitted. The configuration of the second insulating layer 135 and the heat-resistant release layer 136 formed on the heat generating layer 132 is as follows.
This is the same as the second insulating layer 35 and the heat-resistant release layer 36 in the above embodiments.

The roller diameter d ₁ including the heat generating layer 132 at the central portion of the fixing roller 1 (the inner portion of the mounting portion of the ring-shaped electrode 141 in the roller axis direction) includes the first insulating layer 131 at the roller end. It is larger than the roller diameter d _2. That is, d ₁ > d ₂ . In the portion of the fixing roller 101 having the roller diameter d ₂ , that is, the region A and the region B, the bearings 151, 15
2 and a fixing drive gear 153 are mounted.

In the fixing roller 101 according to the present embodiment, since the diameter d _{1 at the} center of the roller is larger than the diameter d ₂ at the end of the roller, the ring-shaped electrodes 141 and 142 fitted on the large diameter portion are fixed. When the roller is inserted into the roller 1, the first insulating layer 131 in the small diameter portion is not damaged.
It does not cause current leakage.

As shown in FIG. 11, the first insulating layer 1
31 is not shown for the thickness direction of y ₂ is larger (A region of the insulating layer 131 of the roller ends be (A, B area) than the thickness y ₁ of the insulating layer 131 of the roller center part ).
By mounting the bearings 151 and 152 and the fixing drive gear 153 in the areas A and B where the thickness of the insulating layer 131 is increased, the insulation of the bearings 151 and 152 and the fixing drive gear 153 can be increased. Therefore, it is not necessary to use a special material for the bearing or the fixing drive gear, and the cost can be reduced.

Further, as described above, since the diameter d ₁ of the roller central portion is larger than the diameter d ₂ of the roller end portion, the insulating layer 131 in the A and B regions is provided in order to enhance the insulation between the bearing and the fixing drive gear. Even if the thickness is increased, the ring-shaped electrode 1
41 and 142 can be inserted into the fixing roller 1. If the thickness of the insulating layer at the end of the roller is increased with a straight fixing roller, the diameter of the end of the roller becomes larger than the diameter of the central part of the roller (the part where the ring electrode is fitted), and the ring electrode Insertion becomes impossible.

Incidentally, the fixing roller 101 of this embodiment is
In FIG. 10, as shown in FIG. 10, a reinforcing ring 21 is provided at one central portion in the axial direction inside the roller. Since both ends of the fixing roller 101 are drawn,
The mechanical strength of the roller core 111 is greater than that of a normal straight shape, and the same strength as that of the fixing roller 1 shown in FIGS. The thickness of the metal core can be reduced and a high-speed rise can be achieved.

Further, since the roller strength is improved by drawing both ends of the fixing roller 101, the reinforcing ring can be omitted. In this case, an example of the fixing roller is shown in FIG.
It is shown in FIG. The fixing roller 201 shown in FIG. 12 is the same as the fixing roller 101 of FIG. 10 except that the reinforcing ring is not provided inside the roller and the protrusion for fixing the reinforcing ring is not provided on the cored bar 211. .

In the fixing roller shown in FIGS. 10 and 12, the diameters at both ends of the roller are made smaller than the center part (d ₁ > d ₂ ) by drawing. However, when the reinforcing effect by drawing is not required, Alternatively, the diameter of both ends of the roller may be made smaller than that of the center by cutting or grinding.

[0038]

As described above, according to the fixing device of the present invention, since the reinforcing member is provided inside the fixing roller, the thickness of the fixing roller can be reduced while maintaining the mechanical strength of the fixing roller. Since the resistance heating element having good thermal efficiency is provided on the roller surface, it is possible to provide a fixing device with a fast rise.

According to the second aspect of the present invention, the resistance heating element is divided into a plurality of parts corresponding to the sheet size and each heating element is controlled independently. It is possible to suppress an increase in the temperature of the section.

According to the third aspect of the present invention, since the diameter of the end portion of the fixing roller is smaller than the diameter of the central portion (ring-shaped electrode mounting portion), the ring-shaped electrode fitted to the large-diameter portion of the fixing roller is inserted. At this time, the insulating layer in the small diameter portion is not damaged, and does not cause a current leak.

According to the fourth aspect of the present invention, the thickness of the insulating layer at both ends (small diameter portion) of the fixing roller is made thicker than the other portion (roller center portion), so that the bearing and the drive mounted on the roller end are provided. Insulation of the gear can be improved. Therefore, it is not necessary to use a special material for the bearing and the drive gear, and the cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a schematic configuration of a fixing roller in a fixing device according to an embodiment of the present invention.

FIG. 2 is a development view showing a configuration of a heat generating layer provided on a surface of the fixing roller.

FIG. 3 is a development view showing another pattern of a resistance heating element provided on a heating layer.

FIG. 4 is a block diagram illustrating a configuration of a control circuit that controls heat generation of a fixing roller.

FIG. 5 is a perspective view showing a reinforcing ring provided inside the fixing roller.

FIG. 6 is a cross-sectional view illustrating a schematic configuration of a fixing roller according to another embodiment of the present invention.

FIG. 7 is a developed view showing a configuration of a heat generating layer provided on the surface of the fixing roller.

FIG. 8 is a block diagram illustrating a configuration of a control circuit that controls heat generation of a fixing roller.

FIG. 9 is a development view showing another pattern of the resistance heating element provided on the heating layer.

FIG. 10 is a cross-sectional view illustrating a schematic configuration of a fixing roller according to still another embodiment of the present invention.

FIG. 11 is a partially enlarged view showing an end portion of the fixing roller in detail.

FIG. 12 is a cross-sectional view illustrating an example of a fixing roller in which a reinforcing ring is omitted.

[Explanation of symbols]

 1, 101, 201 Fixing roller 11, 111, 211 Metal core (roller base) 21, 22, 23 Reinforcement ring 31, 131 First insulating layer 32, 72, 132 Heating layer 34, 74, 75 Resistance heating element 35, 135 Second insulating layer 36, 136 Heat-resistant release layer 41, 42, 43 Ring-shaped electrode 65, 66, 67 Power supply brush 81 Central thermistor 82 End thermistor

Claims (4)

[Claims] 1. A fixing roller having a core metal wall thickness of 0.2 to 1.0 mm and a pressure roller pressed against the fixing roller, and a recording paper carrying an unfixed image is passed between the two rollers. A fixing device for fixing an unfixed image on recording paper by using a fixing roller, wherein the fixing roller has a resistance heating element on the outer periphery of a cored bar and a reinforcing member provided inside the roller. 2. The apparatus according to claim 1, wherein the resistance heating element is divided into a plurality of parts in the same heating layer according to the size of the recording material, and each resistance heating element is individually energized. Fixing device. 3. The fixing roller diameter of the ring-shaped electrode mounting portion connected to the resistance heating element is made larger than the fixing roller diameter of an outer portion of the electrode mounting portion. The insulating layer provided also covers the fixing roller small diameter portion outside the electrode mounting portion,
The fixing device according to claim 1. 4. The fixing roller according to claim 1, wherein the thickness of the insulating layer at a small-diameter portion of the fixing roller outside the electrode mounting portion is larger than the thickness of the insulating layer at a portion inside the electrode mounting portion. The fixing device according to claim 3, wherein a bearing and a fixing drive gear are mounted.