JPH04182686A - Fixing device - Google Patents

Abstract

PURPOSE:To allow sure cleaning without increasing the rotational driving force of a fixing roller and without using a web roller by disposing a web take-up shaft and a web supply shaft in such positions where the web comes into pressurized contact with the fixing roller at a prescribed width. CONSTITUTION:One end of a detecting arm 14 is pressed by its own weight to the surface of the web 5 and a brush 16 is provided at the other end and is brought into contact with the surface of a resistor 15. The outside diameter of the web 5 is largest and, therefore, the resistance value between a lead wire 18 and a lead wire 19 is large in the initial period when the web is mounted to the fixing device by turning the arm 14 around a shaft 17. On the other hand, the arm 14 descends downward and the resistance value between the wires 18 and 19 falls gradually as the web 5 is gradually taken up. Namely, the detection of the outside diameter of the web 5 is possible and the detected signal is inputted to a controller which is a control means. The speed of a motor 12 is increased in the initial and end periods of the taking up of the web than in the middle period, by which the feed rate to the web is increased and the cleaning performance is improved. Always the specified performance is thus maintained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a fixing device used in an image forming apparatus such as a copying machine, and particularly relates to a cleaning mechanism for a fixing roller.

[Prior Art] Conventionally, in an image forming apparatus such as a copying machine, an unfixed developer image formed on a recording material (hereinafter referred to as transfer paper) by a developing process such as electrostatic photography is transferred to the recording material (hereinafter referred to as transfer paper). A fixing device for fixing to paper is usually provided, and FIG. 6 shows an example of such a fixing device.

In the example shown in FIG. 6, the transfer paper enters the nip formed by a pair of pressure rollers 3 and fixing roller 2 from six directions in the figure, and without passing through the nip, pressure and fixing are applied. Heat is applied by a heater 4 built into the roller, and the developer is melted and fixed to the transfer paper.

In the fixing device having the above configuration and operation, the fixing roller 2
The pressure roller 3 is usually formed as a roller with a hard surface such as metal, while the pressure roller 3 is formed as a roller with a soft surface such as silicone rubber.

In the above-mentioned fixing operation, it is known that some of the developer carried on the transfer paper and conveyed to the nip part adheres to the fixing roller in an offset manner, and if this is left unattended, subsequent During the fixing operation, the offset developer adheres to the transfer paper, resulting in smearing the image.

Therefore, in conventional fixing devices, a cleaning mechanism for the fixing roller is provided along with the fixing roller (in the example shown in FIG. 6, above the fixing roller). The cleaning mechanism in this example is.

A thin sheet of non-woven paper called a web impregnated with a release promoter such as silicone oil is rolled up and driven from the unwinding shaft 8 to the winding shaft 7 in conjunction with the passage of the transfer paper, while the rubber The fixing roller is pressed by a web roller 6 made of an elastic material such as, etc., thereby wiping off the dirt caused by the offset on the fixing roller 2, and uniformly applying the silicone oil impregnated into the web onto the surface of the fixing roller 2. It is configured as follows.

In addition, in this cleaning mechanism, as shown in the example of FIG. Usually, the web is pressed against the web on the unwinding shaft 8 with a predetermined pressure to apply tension to the web to provide continuous unwinding resistance and to prevent the web from sagging or wrinkling.

Further, the web roller 6 is usually made of an elastic member such as a spring.
It is pressed against the fixing roller with a certain predetermined pressure to form a nip. If this nip is small, the ability to clean the offset developer on the fixing roller may be degraded, or the silicone oil impregnated into the web may cause problems such as not being applied uniformly on the surface of the fixing roller. Are known. Therefore, in the past, settings were made to form a sufficient nip portion.

[Problem to be solved by the invention] However, in the above conventional example, (1) In order to form a sufficient nip width between the fixing roller and the web roller, the web roller must be pressed against the fixing roller with a predetermined pressure. Therefore, it is necessary to increase the rotational driving force for rotating the fixing roller. Therefore, there are problems in that it is difficult to rotate the fixing roller when handling jammed paper, and that the drive source for the fixing roller needs to have a high output, which increases costs.

(2) Normally, the fixing roller is heated to about 100 to 200 degrees by a heater inside the roller, so the web roller that comes into pressure contact with the fixing roller has strong heat resistance.
Sponge-like silicone rubber with high elasticity is often used. However, such rubber is expensive and is a major factor in increasing the cost of the device itself.

The present invention solves the above problems and provides a fixing device that can reliably clean the fixing roller without increasing the rotational driving force of the fixing roller or without using a web roller made of expensive rubber. is intended to provide.

[Means for Solving the Problems] According to the present invention, the above object includes a fixing roller that heats and fixes unfixed developer on a recording material, a web supply shaft supported above the fixing roller, and a web winding shaft. A fixing device comprising a take-up shaft, a drive means for the web take-up shaft, and a web stretched over the web supply shaft and the web take-up shaft and disposed so as to be in sliding contact with the upper surface of the fixing roller. The web winding shaft and the web supply shaft are arranged at positions where the stretched web is always brought into pressure contact with the upper surface of the fixing roller by a predetermined width, and the web winding shaft and the web supply shaft are arranged at positions where the stretched web is always brought into pressure contact with the upper surface of the fixing roller at a predetermined width. means for detecting the amount of web taken up; and when it is determined that the amount of web is outside a predetermined range based on a signal from the means for detecting the amount of web, the driving speed of the driving means for the web winding shaft is adjusted so that the amount of web is The control means is set to be larger than when it is within a predetermined range.

[Function] According to the present invention, the web supply shaft and the web take-up shaft are at positions where the web is brought into pressure contact with the fixing roller at a predetermined width, so the fixing roller is cleaned by winding the web. . Further, if the web is wound around one of the shafts in a biased manner, the cleaning performance will be degraded. Therefore, by means of detecting the amount of web,
If it is detected that the web amount is outside the set range, the winding speed is increased to improve cleaning performance.

Thus, according to the present invention, sufficient leaning performance can be maintained without using a web roller or increasing the rotational drive of the fixing roller.

[Embodiment] An embodiment of the present invention will be described below with reference to the accompanying drawings. Figure 1 is a schematic diagram of the embodiment, Figure 2 (A) and (B)
, (C) is a cross-sectional view.

In FIG. 1, the web 5 is previously wound around a supply shaft 7a, and is gradually wound up by a motor 12, which is a driving means connected to the winding shaft 7.

The winding rotation direction is the direction indicated by the arrow in FIG.

The web 5 is in contact with the second part of the fixing roller 2 with a predetermined contact width d while being wound around the take-up shaft 7, and this contact part allows cleaning of the offset developer on the fixing roller. At the same time, the fixing roller is evenly coated with oil.

FIG. 2(A) shows a cross section of the web 5 in its initial state when it has just been attached to the fixing device.

Since the web 5 is sequentially wound around the winding shaft 7, the outer diameter of the web 5 and the diameter of the wound web gradually change. The state of the change is shown in FIG. 2(B) and FIG. 2(C). FIG. 2(B) shows the state when half of the web is wound up, and FIG. 2(C) shows the state before the web is completely wound up.

When the web is wound up in this manner, the contact width d between the web and the fixing roller changes as shown in FIG.

It is generally known that there is a relationship as shown in FIG. 4 between the contact width d between the web and the fixing roller and the cleaning performance of the web against offset developer. That is, the cleaning performance increases as the contact width of the web increases. Similarly, it is known that there is a relationship between the amount of web feed and cleaning performance as shown in FIG. That is, the cleaning performance increases as the web feed rate increases.

In this embodiment, means for detecting the diameter of the web 5 is provided as shown in FIG.

The detection arm 14 has one end brought into contact with the surface of the web 5 under its own weight. At the other end of arm 14 is a flange]
6 are provided, and are in contact with the surface of the resistor 15 wound in a coil shape. Arm 14 rotates around axis 17. With this configuration, in the initial stage when the web 5 is attached to the fixing device, since the outer diameter of the web 5 is the largest, the lead wire 18 coming out from the resistor 15 and the coming out from the flange 16 attached to the arm are connected. The resistance value between the lead wire 19 and the lead wire 19 shown in FIG. on the other hand,
As the web 5 is gradually wound up on the winding roller ruff, the web diameter becomes smaller, so the arm 14 moves downward, and accordingly, the brush rotates upward, resulting in a gap between the wires 18 and 19. The resistance value will gradually decrease. That is, by measuring this resistance value, the outer diameter of the web 5 can be detected.

As described above, at the beginning and end of winding of the web 5, the contact width of one web with the fixing roller becomes small, and as a result, the cleaning performance is inferior to that at the middle stage of winding. Therefore, a signal that detects the outer diameter of the web 5, that is, a resistance value between the Riet wires 18 and 19, is input to a controller (not shown) as a control means, and the signal is used to determine the initial stage of web winding and the final stage of web winding. The speed of the motor 12 is controlled to increase the amount of web feed. In other words, at the beginning and end of web winding, the speed of motor I2 is increased compared to the middle stage of web winding, increasing the web feed amount, improving cleaning performance, and always -"RO)')') - It becomes possible to maintain the cleaning performance.

In this way, cleaning performance is maintained by changing the web feed amount without using a web roller, so cleaning can be performed reliably without increasing the rotational driving force of the fixing roller. In addition, since no web roller is used, there is no need to use expensive rubber, which does not increase costs.

Note that a solenoid may be used as the web winding means, and it is also possible to control the web winding speed by controlling the stroke of the solenoid. Furthermore, as for the four stages for detecting the outer diameter of the web, it is of course possible to use means such as measuring the outer diameter using an optical sensor.

[Effects of the Invention] As explained above, the present invention has a web winding shaft;
The web supply shaft is placed in a position where it comes into pressure contact with the web or the fixing roller at a predetermined width, and cleaning performance is maintained by controlling the web winding speed. There is no need to force the fixing roller into contact, and there is no need to increase the rotational driving force of the fixing roller.

Furthermore, since no web roller is used, there is no need to use expensive rubber, and costs can be reduced.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing a schematic configuration of a device according to an embodiment of the present invention, FIG. 2(A) is a cross-sectional view showing the initial state of the web attachment of the device shown in FIG. 1, and FIG. 2(B) is a Fig. 1 is a cross-sectional view showing the state in which the web of the device is half wound up;
Figure 3 is a cross-sectional view showing the device in which the web has been wound up; Figure 3 is a diagram showing the relationship between the length of the fed web and the contact width of the web in the device shown in Figure 1; Figure 4 is the device shown in Figure 1. Figure 5 is a diagram showing the relationship between the cleaning performance of the apparatus shown in Figure 1 and the web feed amount; Figure 6 is a cross-section showing the schematic configuration of the conventional apparatus Fig. 2...Fixing roller 5...Web 7...Web winding shaft 7a...
... Web supply shaft 12 ... Drive means (motor) 14 ...
・・・・・・Means (arm) for detecting web amount Patent applicant Canon Co., Ltd. Representative Patent attorney Toru Fujioka Cleaning performance Cleaning performance

Claims (1)

[Scope of Claims] A fixing roller that heats and fixes unfixed developer on a recording material, a web supply shaft and a web winding shaft supported above the fixing roller, and a driving means for the web winding shaft. , a fixing device comprising the web supply shaft and a web stretched around the web take-up shaft and disposed so as to be in sliding contact with the upper surface of the fixing roller, the web take-up shaft and the web supply shaft being stretched; means for detecting the amount of web wound on the web winding shaft or the web supply shaft, the means being disposed at a position where the suspended web is always brought into pressure contact with the upper surface of the fixing roller at a predetermined width; When it is determined that the web amount is outside a predetermined range based on a signal from the means for controlling the web, the driving speed of the drive means for the web winding shaft is set to be higher than when the web amount is within the predetermined range. A fixing device comprising: a control means.