JPH0219881A - Thermal fixing roll for electrophotographic device - Google Patents

Abstract

PURPOSE:To mitigate the temperature gradient on the surface of a heating roll in the peripheral direction by closely bringing an auxiliary roll into contact with the surface of the heating roll on the side opposite to the side on which the heating roll is brought into contact with a press roll as a heat flow controlling means. CONSTITUTION:A heating roll 11 is constituted of a rotating shaft 15 at the center and an elastic and heat insulating layer 16 composed of silicon foamed rubber, resistance heating layer 17 connected with an external poser source by the end section in the axial direction, and protective layer 18 composed of a fluorocarbon resin, which are successively formed on the shaft 15. An auxiliary roll 20 constituted of a metallic rotating shaft 21 and heat insulating layer 22 composed of a heat resisting resin is closely brought into contact with the roll 11 on the side 19 opposite to the side 12 on which the roll 11 is brought into contact with a press roll 10. Since the auxiliary roll 20 has a relatively large heat capacity, the excessive temperature rise in the surface of the heating roll 11 at the contacting section 19 is suppressed. Therefore, the temperature gradient on the surface of the roll 11 can be suppressed in the peripheral direction.

Description

Detailed Description of the Invention [Object of the Invention] <Industrial Field of Application> The present invention relates to a heat fixing method for an electrophotographic apparatus in which a transfer means is heated and pressurized using a pair of rolls in order to fix a mapped image. Regarding roles.

<Prior Art> Conventionally, in an electrophotographic device using an electrophotographic process such as a copying machine, a heating roll and a pressure roll are used in a heat fixing roll that transfers toner to a transfer medium such as paper and then fixes it. The toner is brought into close contact with each other, and the transfer means is passed through the nip area where both rolls touch each other, and the toner is heated and simultaneously pressed against the transfer means. Because it takes a long time, for example, the patent application filed in 1986-309 by the same applicant
No. 339 proposes a structure in which a resistance heating layer, which may be made of resin, is formed over the entire surface of a heating roll. According to this structure, the above-described fixing operation can be performed by raising the temperature of only the resistance heating layer, so that the time required to raise the temperature of the heating roll is shortened.

However, since the heating roll having the above-mentioned resistance heating layer has a small heat capacity, the flow of heat from the upper part due to convection is small, and the surface temperature becomes relatively high, and the nip part is exposed to the transfer medium. As heat is removed, the surface temperature becomes relatively low, and the temperature gradient in the circumferential direction of the roll surface becomes steep. Therefore, if the heat balance changes over time, such as when the transferred means intermittently passes through the nip, temperature ripples may occur in the nip, resulting in poor toner fixation on the transferred means. There are concerns.

<Problems to be Solved by the Invention> In view of the problems of the prior art, the main purpose of the present invention is to shorten the temperature rise time of the heating roll and to make the temperature gradient on the surface gentle in the circumferential direction. An object of the present invention is to provide a heat fixing roll for an electrophotographic device that is controlled in a controlled manner.

[Structure of the Invention] <Means for Solving the Problems> According to the present invention, the object is to pass a transfer means between a heating roll and a pressure roll that rotate in close contact with each other, and to transfer images of a subject. In a heat fixing roll of an electrophotographic apparatus for fixing an image on the transfer receiving means, a resistance heating layer is formed on the heating roll, and the roll is configured to suppress a temperature gradient in the circumferential direction on the surface of the heating roll. This is achieved by providing a heat fusing roll for an electrophotographic apparatus characterized in that it has a heat flow control means in close contact with the heat flow control means.

<Function> In this way, the temperature gradient in the circumferential direction of the heating roll surface is suppressed by the heat flow control means. By bringing the auxiliary roll into close contact with the surface of the heating roll as a heat flow control means, it is possible to suppress the surface temperature of the heating roll on the side where the auxiliary roll is in close contact with each other from rising excessively, and it is possible to provide a heat insulating layer on the pressure roll. By further heating the pressure roll using a heater means, it is possible to prevent the surface temperature of the heat roll on the side close to the pressure roll from decreasing excessively, and to reduce the surface temperature gradient in the circumferential direction of the heat roll as a whole. It becomes loose.

<Embodiments> Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows the configuration of an electrophotographic apparatus to which the present invention is applied.

The rotatable photosensitive drum 1 has an outer peripheral surface plated with selenium. A charging section 2, a photosensitive section 3, a developing section 4, a transfer section 5, a cleaning section 6, and a static eliminating section 7 are provided along the outer peripheral surface of the photosensitive drum 1 in this order. Further, a fixing section 8 is provided downstream in the direction in which the transfer paper 9 is carried out from the transfer section 5, that is, in the direction of arrow A.

When the photosensitive drum 1 rotates in the direction of arrow B in FIG. 1, the surface of the drum passes through a charging section 2 consisting of corona charging means, and as a result, the drum surface reaches a uniform potential of about 700 volts. charged. Next, the surface portion of the photosensitive drum 1 passes through an exposure section 3, and a latent image corresponding to the shape of the subject is formed by exposure. Then, toner conveyed to a carrier (not shown) in the developing section 4 adheres to the surface of the photosensitive drum 1 in correspondence with the latent image. Further, in the transfer section 5, the transfer paper 9, which is conveyed in the direction of arrow A from the right side in FIG.
At the same time as being charged by a, the toner adhering to the surface portion of the drum 1 is transferred onto the paper 9. The surface portion of the photosensitive drum 1 after the toner has been transferred passes through a cleaning section 6, and residual toner is cleaned off. And a static eliminator 7 consisting of an exposure lamp
At this point, the electric potential is removed to approximately - in the axial direction, and the above process is repeated again. On the other hand, the toner transferred to the paper 9 is heated and pressed onto the paper 9 at the same time in the fixing section 8, so that the image is fixed on the paper 9.

FIG. 2 is an enlarged sectional view of a main part of FIG. 1 showing a first embodiment based on the present invention. The fixing unit 8 includes a pressure roll 1-0 that is rotationally driven by a driving means (not shown) and a heating roll 11 that is driven by coming into close contact with the pressure roll at a contact portion 12.

The pressure roll 10 includes a rotation shaft 13 and a rubber roll portion 14 provided on the outer periphery of the rotation shaft 13. On the other hand, the heating roll 11 has, from its center to its outer periphery, a rotating shaft 15, an elastic/insulating layer 16 made of silicone foam rubber, and a resistance heating N17 connected to an external power source (not shown) at the axial end. A protective layer 18 made of fluororesin is laminated in this order. Moreover, an adhesive layer is formed between each layer of the first bullet/insulation layer 16, the resistance heating layer 1-7, and the protective layer 18.

This adhesive layer is a layer for preventing the resistance heating tape 17 and the protection 118 from peeling off when the resilient/insulating layer 16 is deformed when the heating roll 11 is operated.

On the other hand, on the side opposite to the contact portion 12 of the heating roll 11,
The auxiliary roll 20 comes into close contact with the contact portion 19, and the heating roll]
1. This auxiliary roll 20 has a metal rotating shaft 21 and a heat insulating layer 22 made of a heat-resistant resin having a thickness of 0.3 to 1 mm and layered around the outer periphery thereof. Since this auxiliary roll 20 has a relatively large heat capacity, it suppresses the surface temperature of the heating roll 11 at the contact portion 19 from increasing excessively. In this embodiment, since the rubber roll portion 14 fitted to the pressure roll 10 has a heat insulating effect, the surface temperature of the heating roll 11 at the contact portion 12 is prevented from decreasing excessively. ing.

For example, in a conventional heat fixing roll, when a pressure roll whose rotary shaft is fitted with a rubber roll is brought into close contact with the lower surface of the heat roll, the surface temperature of the contact part of the heat roll with the pressure roll and this contact The difference in surface temperature between the opposing side parts is approximately 40°C, and when a pressure roll made of a metal pipe is brought into close contact with this heating roll, the difference in surface temperature between the above-mentioned side parts of the heating roll is approximately 80°C. However, by configuring as in this embodiment, the difference in surface temperature between the contact portion 12 and the contact portion 19 of the heating roll 11 can be made 20° C. or less. Therefore, the heating roll 12
2, the surface temperature that has decreased due to contact with the transfer paper 9 can be easily restored to a predetermined temperature during one rotation of the roll, and temperature ripples do not occur at the contact portion 12. do not have.

FIG. 3 is a diagram similar to FIG. 2 showing a second embodiment based on the present invention. According to this embodiment, the pressure roll 23 is
It has a rotating shaft 24 made of a hollow metal pipe, and a heat insulating layer 25 made of a heat-resistant resin with a thickness of 0.1 to 1 m layered around the outer periphery of the rotating shaft 24. In fact, a protective layer made of a releasable film such as fluororesin may be laminated on the surface of the heat insulating layer 25.

According to this embodiment, since a metal pipe with a relatively large heat capacity is used for the rotating shaft 24 of the pressure roll 23, it is conceivable that the surface temperature of the heating roll 11 at the contact portion 12 decreases. By providing a heat insulating layer 25 on the pressure roll 23, this temperature drop is suppressed.

Further, as shown by the imaginary line in the center of FIG. 3, by providing a heater 26 in the center of the inner hole 23a of the pressure roll 23, the temperature of the pressure roll 23 as a whole is raised, and the contact portion 1
The decrease in the surface temperature of the heating roll 11 in step 2 can be suppressed more suitably. In addition, in reality, the heating roll 11
A resistance heating layer similar to the resistance heating layer 17 may be provided on the outer periphery of the rotating shaft 24, and this may be used as a heater for heating the pressure roll 10.

Furthermore, as shown by the imaginary line in the upper part of FIG. 3, an auxiliary roll 27 similar to that of the first embodiment is brought into close contact with the surface of the heating roll 11 on the side opposite to the contact part 12 at the contact part 28. This suppresses an increase in the surface temperature of the heating roll 11. Therefore, it becomes possible to suppress the temperature gradient along the circumferential direction of the heating roll 11 more suitably.

As described above, even if the heat capacity of the heating roll 11 is small, the surface temperature gradient of the roll becomes gentle in the circumferential direction. It is possible to further shorten the heating time. Therefore, the heating roll 11 is always
It is not necessary to maintain the toner fixation temperature at a constant temperature of 80°C, and the temperature is maintained at a low temperature of, for example, 100°C during normal standby. It is also possible to control the surface temperature of the fixing unit 11 to increase, thereby reducing power consumption when the fixing unit 8 is on standby.

[Effects of the Invention] As described above, according to the present invention, the temperature gradient in the circumferential direction on the surface of the heating roll becomes gentle by the heat flow control means. As this heat flow control means, by bringing an auxiliary roll into close contact with the surface of the heating roll on the opposite side to the side where the pressure roll is in close contact, it is possible to suppress the surface temperature of the heating roll on the side where the auxiliary roll is in close contact from increasing excessively. By providing a heat insulating layer on the pressure roll and further heating the pressure roll with a heater means, it is possible to suppress an excessive drop in the surface temperature of the heating roll on the side that is in close contact with the pressure roll. The circumferential surface temperature gradient of the heating roll as a whole becomes gentle. Therefore, temperature ripples in the error portion of the heating roll can be prevented, and the toner can be suitably fixed on the transfer medium, which is extremely effective.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an electrophotographic apparatus to which a heat fixing roll according to the present invention is applied. FIG. 2 is an enlarged sectional view of a main part of FIG. 1 showing a first embodiment based on the present invention. FIG. 3 is a diagram similar to FIG. 2 showing a second embodiment and a modified embodiment thereof based on the present invention. 1... Photosensitive drum 2... Charging section 3... Exposure section 4... Developing section 5... Transfer section
5a...Charging section 6...Cleaning section 7...Static elimination section 8...Fixing section 9...Transfer paper 10
...Crimping roll 11...Heating roll 12...
Contact part 13... Rotating shaft 14... Rubber roll part 15... Rotating shaft 16... Resilient/insulating layer 17.
... Resistance heating layer 18... Protective layer 19... Contact portion 0... Auxiliary roll 2... Heat insulating layer 3a... Inner hole 5... Heat insulating layer 7... Auxiliary roll... Rotating shaft 3...Crimping roll 4...Rotating shaft 6...Heater 8...Contact part

Claims (4)

[Claims] (1) In a heat fixing roll of an electrophotographic apparatus for fixing an image of a subject on the transfer means by passing a transfer means between a heating roll and a pressure roll that rotate closely together, a resistance heating layer layered on a heating roll;
A heat fixing roll for an electrophotographic apparatus, comprising a heat flow control means in close contact with the heating roll to suppress a circumferential temperature gradient on the surface of the heating roll. (2) The heat fixing roll for an electrophotographic apparatus according to claim 1, wherein the heat flow control means includes an auxiliary roll that is in close contact with the heating roll. (3) The heat fixing roll for an electrophotographic apparatus according to claim 1 or 2, wherein the heat flow control means has a heat insulating layer layered on the surface of the pressure roll. (4) The heat fixing roll of an electrophotographic apparatus according to any one of claims 1 to 3, wherein the heat flow control means includes a heater means for heating the pressure roll.