JPH0414797B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to an improvement in a sheet peeling device attached to a heating roll type fixing device among fixing devices such as copying machines using an electrophotographic process. [Prior Art] Generally, a copying machine using an electrophotographic process is equipped with a fixing device that fixes an unfixed toner image on a sheet of copy paper, and one example of this fixing device is a so-called heated roll type fixing device. have been widely adopted. Conventionally, this type of fixing device includes, for example, as shown in FIG. 1, a heated heat-fixing roll 1 and a pressure roll 2 that is in pressure contact with the heat-fixing roll 1 and rotates together with the heat-fixing roll 1. By passing the paper 4 on which the unfixed toner image 3 is held between the pair of rolls 1 and 2, the heat from the heat fixing roll 1 and the pressure from the pressure roll 2 are applied to the toner and the paper 4. The unfixed toner image 3 is fixed on the paper 4 by applying the toner image. In this type, the heat fixing roll 1 includes, for example, a cylindrical core 5 made of metal or the like that is fitted onto a shaft (not shown) and has mechanical strength that can withstand pressure.
A heater 6 disposed inside the cylindrical core 5;
Materials that satisfy heat resistance and mold release properties (toner offset prevention), such as HTV silicone rubber (High Temperrature Vulcanization Silicone)
A heat-resistant release layer 7 is formed by coating the surface of the cylindrical core 5 with polytetrafluoroethylene (PTFE) or the like. On the other hand, the pressure roll 2 has, for example, a cylindrical shape that is fitted onto the shaft 8, forms a predetermined fixing nip when it comes into contact with the heat fixing roll 1, and satisfies heat resistance, etc. Materials, specifically HTV silicone rubber, fluorocarbon rubber, EPDA rubber (Ethylene Propylene Diene Acryl Rubber)
It is molded from heat-resistant elastic material such as By the way, in such a fixing device, since the toner surface of the paper 4 comes into direct contact with the surface of the heating and fixing roll 1, there is a situation where the paper 4 gets wrapped around the surface of the heating and fixing roll 1 due to the sticky nature of the softened toner. will occur. To prevent such a situation, a device for peeling off the paper 4 wrapped around the surface of the heat fixing roll 1 is usually required. Conventionally, as shown in FIG. 1, this type of paper peeling device has a peeling claw 10 formed of metal or heat-resistant plastic and having a sharp edge portion 11 formed on the tip side. The base 12 of the peeling claw 10 is pivotally supported on a support part (not shown) near the roll 1, and the tip 11a of the edge part 11 is attached to the surface of the heat-fixing roll 1 by a biasing spring 13 or the like. They were pressed together with a load of 10 g. In order to improve the peeling performance of the paper 4 in this type, the tip angle ψ of the edge portion 11 of the peeling claw 10 is set small, as shown in FIG.
It is desirable to increase the sharpness of the edge portion 11, but since the tip 11a of the edge portion 11 is in pressure contact with the surface of the heat fixing roll 1, considering mechanical strength and thermal fatigue strength, the tip angle of the edge portion 11 is ψ
Therefore, it is necessary to set the angle to a relatively large angle, for example, about 30 to 45 degrees. Therefore, conventionally, the edge portion 11 is normally arranged at a predetermined relief angle θ with respect to the tangent s at the contact portion between the edge portion 11 and the heat-fixing roll 1, and The edge portion 11 is made to stand up slightly to ensure the peeling performance of the paper 4. In this case, as the clearance angle θ is set larger, the peeling performance of the paper 4 improves; however, if the clearance angle θ is set too large, the edge portion 11
Since the surface of the heating fixing roll 1 is damaged by the leading edge 11a of the fixing roll 1, the clearance angle θ is set to approximately 10° or less. According to such a conventional paper peeling device, the tip 11a of the edge portion 11 is in pressure contact with the surface of the heat fixing roll 1, but since the pressure contact force is set to a relatively small value, the heat fixing roll 1
And wear of the peeling claw 10 is suppressed as much as possible,
In addition to effectively preventing peeling of the heat-resistant release layer 7 and deformation of the edge portion 11 tip 11a due to the tip 11a of the edge portion 11 biting into the surface of the heat fixing roll 1, rotational vibration of the heat fixing roll 1 and the edge portion 11
For the paper 4 hitting the leading edge 11a, etc.
The tip 11a of the edge portion 11 is the heat fixing roll 1
The peeling claw 10 is stably arranged with respect to the heat fixing roll 1 without being unnecessarily lifted from the surface. Therefore, the paper 4 that is being conveyed wrapped around the surface of the heat fixing roll 1 is
1 and is effectively peeled off by the tip 11a of 1 and guided to the discharge roll 15 side through the guide member 14. ``Problem to be Solved by the Invention'' However, in the case of such a conventional paper peeling device, it is difficult to peel off the paper 4 with a large amount of toner near the leading edge, or when peeling off the paper 4 with a large amount of toner near the leading edge, or when separating the heat fixing roll 1 and the ejection roll 15. If a paper jam occurs between the heating and fixing roll 1, a large load may be applied in the direction of pressing the peeling claw 10 against the heat fixing roll 1. In this state, since the peeling claw 10 is rigid, the peeling claw 10 rotates about the pivot point toward the heating and fixing roll 1, and the tip 11a of the edge portion 11 There is a risk that it will dig into the heat-resistant release layer 7 of the heat fixing roll 1. As a result, the heat-resistant mold release layer 7 may peel off, or the tip 11a of the edge portion 11 may be deformed, resulting in the inconvenience that both must be replaced each time. Such a problem is particularly noticeable when a flexible elastic material such as HTV silicone rubber is used as the heat-resistant mold release layer 7. By the way, the inventor of the present application has developed the above-mentioned peeling claw 10.
In order to analyze the biting phenomenon of When the load P value when the edge portion 11 bites was investigated, the results shown in Table 1 below were obtained.

[Means to solve the problem]

That is, the present invention provides a fixing device that is attached to a fixing device equipped with a heat fixing roll that rotates in contact with a recording sheet on which an unfixed toner image is held, and a peeling claw with a sharp tip is attached to a support near the heat fixing roll. A sheet peeling device of a fixing device is provided, in which a base is pivotally supported, and the tip of the peeling claw is pressed into contact with the surface of the heat fixing roll to peel off the recording sheet wound around the heat fixing roll, A flexible part that is elastically deformed is formed in the middle part of the peeling claw, and when an abnormal load is applied to the peeling claw toward the heat-fixing roll, the edge of the peeling claw is attached to the heat-fixing roll. The bending rigidity of the flexible portion is set so that the relief angle with respect to the tangent to the contact portion with respect to the tangent to the flexible portion is reduced from a normal positive setting value to zero or a negative value. [Operation] According to the above-mentioned technical means, it is possible to peel off a recording sheet that has a large amount of toner near its leading edge, or when a recording sheet jams accident occurs on the sheet ejection side of the heat-fixing roll. In this case, if an abnormal load is applied to the peeling claw toward the heat-fixing roll, the peeling claw will flex and deform at the flexible part, but the tip edge of the peeling claw will escape from the tangent of the contact with the heat-fixing roll. As the angle decreases from its normal positive set value to zero or negative value,
The tip of the edge portion of the peeling claw is always kept floating above the heat-fixing roll. [Example] Hereinafter, the present invention will be described in detail based on an example shown in the accompanying drawings. In the embodiment shown in FIGS. 3 and 4, the peeling claw 10 constituting the paper peeling device is molded from metal or heat-resistant plastic, as in the past, and has a tip angle ψ of 30 degrees on the tip side. It has a certain sharp edge 11. Then, the above peeling claw 1
The base portion 12 of the heat fixing roll 1 is pivotally supported by a support portion (not shown) near the heat fixing roll 1, and the tip 11a of the edge portion 11 is attached to the surface of the heat fixing roll 1 so that the clearance angle θ is 2°, for example. several grams to several tens of grams
It is pressed with a load of . In this embodiment, the base 1 of the peeling claw 10 is
2 and the edge portion 11 has a notch 20 on the side surface of the heat fixing roll 1. Due to the existence of this notch 20, a flexible portion is formed into a thin plate shape and is elastically deformed. It is configured as 21. The bending rigidity of the flexible portion 21 is set such that, for example, when a load of 1000 g is applied to the peeling claw 10 toward the heat-fixing roll 1 side, the bending rigidity changes by about 3° in the direction of decreasing the relief angle θ. There is. Therefore, according to this embodiment, in the normal state, the edge portion 11 of the peeling claw 10 has a relief angle θ.
(θ=2°), the paper 4 that is being conveyed wrapped around the heat fixing roll 1 can be moved by the tip 11a of the edge portion 11 as in the conventional case. It is peeled off from the heat fixing roll 1 with peeling performance corresponding to the relief angle θ. In addition, in this embodiment, when peeling off the paper 4 with a large amount of toner near the leading edge, or when a paper jam occurs between the heat fixing roll 1 and the ejection roll (not shown), A large load is applied in the direction of pressing the peeling claw 10 onto the heat fixing roll 1,
For example, suppose a load p of 1000g is applied. In the case of such an abnormality, in the conventional device, the peeling claw 10 digs into the surface of the heat fixing roll 1, as can be seen from Table 1, but in this embodiment, the peeling claw 10 does not cut into the surface. The flexible portion 21 is subject to the above load P.
As a result, it is elastically deformed from the state shown by the solid line in FIG. 4 to the state shown by the imaginary line. In this state, the clearance angle θ of the peeling claw 10 changes from +2° in a decreasing direction by Δθ (Δθ=3°) and is set to -1°. Therefore, the tip 11a of the edge portion 11 is in a floating state from the surface of the heat fixing roll 1, and a situation where the tip 11a of the edge portion 11 bites into the heat-resistant release layer of the heat fixing roll 1 is avoided. Therefore, the situation in which the heat-resistant mold release layer peels off or the tip 11a of the edge portion 11 deforms is effectively eliminated. Furthermore, in this embodiment, the edge portion 1
Since the tip angle ψ is set to 30°, the mechanical strength and thermal fatigue strength of the flexible portion 1 are ensured to be sufficiently greater than those of the flexible portion 21. Therefore, even if the tip 11a of the edge portion 11 is in pressure contact with the surface of the heat fixing roll 1, there is no risk that the tip of the edge portion 11 will be deformed early due to heat or wear. In addition, in the above embodiment, a notch 20 is provided in a part of the member.
Although the flexible portion 21 is configured by providing the flexible portion 21, it is not necessarily limited to this. For example, a spring material may be used as the flexible portion 21, and the tip forming the edge portion 11 may be formed through the spring material. The design may be modified as appropriate, such as by fixing the chip. [Effect of the invention] As explained above, according to this invention,
By optimizing the bending rigidity of the flexible part formed in the middle part of the peeling claw, even if an abnormal load is applied to the peeling claw toward the heat-fixing roll, the clearance angle of the peeling claw can be changed. Since the tip of the edge of the peeling claw is always kept floating above the surface of the heat-fixing roll, it is possible to reliably prevent the peeling claw from digging into the heat-fixing roll, effectively preventing damage to both. . Further, according to the present invention, since the peeling claws are arranged with a predetermined relief angle under normal conditions, there is no concern that the peeling performance of the recording sheet corresponding to the predetermined relief angle will be impaired.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing an example of a paper peeling device of a conventional fixing device, and FIG. 2 is an explanatory diagram of its main parts.
FIG. 3 is an explanatory view showing one embodiment of the paper peeling device of the fixing device according to the present invention, and FIG. 4 is an explanatory view of main parts showing the action of the peeling claw. Symbol explanation, θ... Relief angle, ψ... Tip angle, 1...
... Heat fixing roll, 2 ... Pressure roll, 3 ... Unfixed toner image, 4 ... Paper, 10 ... Peeling claw, 1
1... Edge portion, 11a... Tip, 12... Base, 21... Flexible portion.

Claims (1)

[Scope of Claims] 1. A peeling claw attached to a fixing device equipped with a heat fixing roll that rotates into contact with a recording sheet holding an unfixed toner image, and having a sharp tip on a supporting portion near the heat fixing roll. In the sheet peeling device of the fixing device, the sheet peeling device of the fixing device is configured to peel off the recording sheet wound around the heat fixing roll by pressing the tip of the peeling claw against the surface of the heat fixing roll. A flexible part that elastically deforms is formed in the middle part of the peeling claw, and when an abnormal load is applied to the peeling claw toward the heat-fixing roll, the edge part of the peeling claw is connected to the heat-fixing roll. A sheet peeling device for a fixing device, characterized in that the bending rigidity of the flexible portion is set such that a relief angle with respect to a tangent to the contact portion is reduced from a normal positive setting value to a zero or negative value.