JPS6198372A - Heat fixing device - Google Patents

Abstract

PURPOSE:To reduce a number of necessary separating claws, to prevent terminal bending of each claw, and to enable almost semipermanent use of them by preparing the separating claws located on the outside of the paper passing region, of the plural claws in contact with the surface of a heat fixing roller with a ceramic sensor having a temp. detecting function. CONSTITUTION:The plural separating claws are arranged in contact with the surface of a pair of the heat fixing rollers for heat fixing a toner image transferred on a support material, usually paper, while passing it between the rollers, and the terminal part of each claw 5 located on the outside of the paper passing region alone among the plural claws is made of the ceramic sensor 4 of a temp. detection element. As the ceramic sensor material, ones composed essentially of MnO, CoO, NiO, or BaTiO3, contg. La, Y, Sb or Mn as an additive, are exemplified, thus permitting temp. change of the roller surface in contact with the sensor 4 to be detected.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention fixes the toner image on the recording sheet by passing a recording sheet having an unfixed toner image between a pair of fixing rollers that heat and pressurize the recording sheet. The present invention relates to an improvement of a heat fixing device for use in a heat fixing device.

[Background of the invention]

Conventionally, this type of heat fixing device has a heating roller 2 and a surface temperature of this roller, which is applied to an image forming device (for example, a copying machine, an information recording device, a printing machine, etc.) or a calendar processing device. A member including a temperature sensing element for contact verification, that is, a temperature sensing member is provided.

The above-mentioned heating roller generally heats and melts the material to be heated (for example, resin, powder image, powder resin, etc.) and attaches (fixes) it to a supporting material such as paper or a base material. The detection member accurately detects the surface temperature of the heating roller. In other words, in order to properly heat-treat the material to be heated, it is necessary to accurately detect the temperature on the surface of the heating roller. Therefore, the temperature detection member is brought into direct contact with a part of the surface of the heating roller to detect the temperature. ing.

Furthermore, since the temperature sensing member is pressed against the surface of the heating roller coated with a heat-resistant elastic material such as a sponge, the surface of the temperature sensing member is covered with a thin heat-resistant film to prevent damage to the heating roller surface caused by the temperature sensing member. By the way, in an image recording apparatus such as an electrophotographic copying machine that fixes an unfixed toner image to a support material (for example, transfer paper), the above-mentioned heat fixing device is used to fix the toner image on the support material. The toner image is heated, melted, and fixed by conveying the toner image in close contact with the heating roller. At this time, the supporting material tends to stick to the surface of the heating roller, so it is necessary to reliably separate the supporting material from the heating roller. Therefore, claw-shaped separation members, so-called separation claws, which come into contact with the roller surface are provided at a plurality of locations along the generatrix direction of the roller.

Furthermore, current electrophotographic copying machines are generally capable of copying on paper of various sizes, while the fixing roller is designed to prevent problems such as poor fixing even when the largest size paper is continuously passed through. The temperature is set taking various conditions into account. Therefore, when small-sized paper is passed continuously, the area on the second side of the fixing roller where the paper does not pass (hereinafter referred to as the non-paper passing area)
The surface temperature of the paper increases by an excess of 1 due to the amount of heat not removed by the paper.

□ Figure 2 shows the results of actual measurements of the above phenomenon, where the solid line a represents the temperature distribution on the two surfaces of the fixing row when the stand is in the stand position, and the dotted line represents the same temperature distribution when the largest size paper is continuously passed through. The one-dot chain line C shows the temperature distribution when small-sized paper is continuously passed through. Since the temperature detection member that comes into contact with the surface of the fixing roller is normally provided in the paper passing area of the fixing roller regardless of the size of the paper, the temperature of the fixing roller in the non-paper passing area exceeds the set temperature as shown in Figure 2. The excessive temperature rise shown by the dotted line C cannot be detected, resulting in a situation where the fixing roller enters the dangerous temperature range. Here is the dangerous temperature range.
This is a temperature range in which damage to the fixing roller itself, members in contact with or in proximity to the fixing roller, damage to the electric circuit, and malfunction of the electric circuit may occur.

When the above-mentioned dangerous temperature range occurs, the separation claw in the paper non-passing area will not come into contact with the high-temperature fixing roller 2 surface.
If this condition continues for a long time, the tip of the separating claw will suffer thermal deterioration, causing the tip to sag, resulting in the inability to separate or a significant decline in the separating function. Furthermore, even if the fixing roller itself gets stuck, the heat-resistant resin such as tetrafluoroethylene that coats the roller to prevent offset will deteriorate due to heat, and as a result, offset toner will not stick to Row 2 and the frequency of jams will increase. , a problem arises in that the performance of the copying machine is extremely degraded.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide an improved heat fixing device that solves the problems of the conventional heat fixing device described above.

[Summary of the invention]

The heat fixing device according to the present invention is a fixing device that fixes a toner image by passing a support material carrying an unfixed toner image between a pair of fixing rows 2 for heating and applying pressure. Among the plurality of separation claws arranged so as to come into contact with the fixing roller surface, the separation claw located in the non-sheet passing area is composed of a semi-sensor having a temperature detection function. Ruru. - [Examples of Practical Rights of the Invention] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows an outline of a heat fixing device to which the present invention is applied, in which a plain paper P having a toner image T formed by an image forming method is passed between a pair of heating pressure rollers 1 and 2. The film is fixed by heating.

In FIG. 1, reference numeral 1 denotes a heating roller having a heating heater 3 such as a Halodan heater therein, which rotates in the direction of the arrow shown in the drawing upon receiving a driving force from a drive motor (not shown). 2 is a pressure roller 2 with a built-in heater 3' for low heating;
It presses against and rotates in the direction of the arrow shown.

The heating row 21 is a hollow roller core made of metal such as aluminum, stainless steel, steel, etc., and a heat-resistant mold release resin layer having a thickness of 20 to 80 μm, such as tetrafluoroethylene resin, is provided on the outer peripheral surface of the core. On the other hand, the pressure roller 22 is pressed against the heating roller 1 by a known pressure means at least during fixing. A relatively thick layer of elastic material such as silicone is provided.

Reference numeral 6 denotes a cleaning member for removing foreign matter such as offset toner and paper powder adhering to the surface of the heating roller 2 from the roller surface, and a cleaning member 61 made of heat-resistant nonwoven fabric such as Nomex or Himeron is used. This cleaning web 61 is heated by a pressing row 263 having elasticity. The supply row 262 is brought into contact with the IK and driven by the take-up roller 6s.
The cleaning web 61 is moved by changing its abutting device little by little, so that a new surface of the cleaning web 61 always comes into contact with the heating row 2.

Furthermore, the web 61 moves on the rollers 64 interposed after the pressing row 263 and is guided toward the supply roller 62,
The film is wound up with the front and back sides reversed on the winder 90-, 26s. Further, if the cleaning wet f61 is impregnated with an anti-offset liquid such as trimethyl silicone oil, the cleaning effect can be further enhanced.

1η )' 7 is a curved reflection plate having heat reflection properties, which is provided close to the periphery of the heating roller and along the entire longitudinal direction of the heating roller. Further, the reflecting plate 7 has a width in the circumferential direction so as to cover the space between the position of the pressing row 26s on the circumferential surface of the heating roller 1 and the entrance opening for the paper P. Reference numeral 8 denotes a thick cover for preventing heat radiation, which is provided in close contact with the entire convex surface of the reflecting plate 7 to prevent wasteful radiation of heat from the reflecting plate 7.

16 is a casing member on the upper side of the fixing device, which includes a cleaning member 6, a reflector 7, a cover 8, and a ceramic sensor 4.
(This is provided at the tip of the separation claw 5).

On the other hand, on the pressure row 22 side, a reflection plate 9 and a cover 10 similar to the reflection plate 7 and cover 8 are provided on the pressure row 22 side, respectively.
It is set up to cover most of the aspects of 2.

Reference numeral 27 indicates a space provided above both end regions of the heating row 21.
Y-no! − is. The position of #-27 is such that the center of the curvature of the reflector 7 and the cover 8 is the center of the heating roller 1.
-274 Yoa□From 7. a. -2, yo. Ya 1 distance tl
hold. This distance "L1" is preferably greater than the thickness of the filter paper used and less than 10 fi from the viewpoint of improving reflection efficiency. Although the reflector 7 and the cover 8 are integrated, they are further rotatably supported about a rotation fulcrum 29, and normally their own weight causes
Stable contact with zJ-27.

Reference numeral 28 indicates a stop tJ? provided below both end regions of the pressure roller 1. − is. The position of this stop 28 is so that the center of the curvature of the reflector 9 and the cover 10 is the center of the pressure row 21. A distance t2 from the row 22 is maintained.This distance t2 is the same as the distance t1.Also, the reflector 9
The cover 10 has a rotation fulcrum 24 at one end in the direction of the circumferential surface of the pressure roller, and one end of a spring 23 latched to the fixing member 7231 is engaged at the other end. This pa costs $23! The inner surface of the reflecting plate 9 is in contact with the spherical surface of the striker 28 at a predetermined pressure (light pressure).

By providing these reflectors 7.9 and covers 8, 10, it is possible to reduce heat wasted from the surfaces of the heating roller and pressure roller.

22 is a guide plate that guides the paper P toward the heating roller 1 side, and a reflection plate 7
The heating roller IK is provided close to the heating roller IK so as to be located between one end of the reflecting plate 9 and the reflecting plate 9, respectively. The plain paper P having the unfixed toner image T passes through this guide plate 22, is conveyed while being held between the heating and pressurizing rows 21 and 2, and is heated by the surface temperature of the rows 21 and 20 to form the toner image T. is fixed, and then is ejected from the apparatus while being held between paper ejection rollers 20 and 21. In order to reliably separate the plain paper P from the heating roller, a plurality of separating claws 5 are provided along the roller axis direction and in contact with the roller surface on the discharge port side of the heating roller. Note that the separation claw 5 is held by a support plate 18 that is spaced apart from the casing member 16.

Although not shown in the drawings, a separation claw similar to the separation claw 5 described above can also be provided on the discharge port side of the pressure row 22.

The heat fixing device configured as described above can pass paper of various sizes from the largest to the smallest, and these papers are separated by a plurality of separating claws arranged at intervals in the longitudinal direction so as to come into contact with the fixing roller surface. 5, the separating claw 5 located in the non-sheet passing area (difference from the large size paper P2) when passing the small size paper P1 is particularly separated from the roller surface by the tip of the separation claw 5 according to the present invention. Accordingly, a ceramic sensor 4 is constructed of a temperature detecting element. Examples of materials for this ceramic and xensor 4 include MnO, C
oo, NiO@Ru or BaTiO3 as a main component, and additives such as LatY + Sb + Mn are used.

The separation claw composed of the above ceramic sensor is the third
The claw metal body may be made of ceramic or glue as shown in FIG. 3(a), or only the tip of the claw may be made of ceramic or glue as shown in FIG. 3(b). That is, Fig. 3(a),
In (b), 51 is the shaft support of the separation claw 5, and 52.5
3 is 'tffl located and fixed on both sides of the ceramic sensor 4, 521.531 is the electrode 52 and 53.
These wirings are respectively connected to the temperature control means 30.

With the above configuration, it is possible to detect a change in the temperature of the roller surface with which the ceramic sensor 4 is in contact.

The temperature control means 30 is also connected to the heaters 3, 3' or other temperature sensors 4', etc., and even if the start signal S1 is input, it stops the device, stops heating, etc. in response to the input of the danger signal PS. In addition, when the temperature of the roller is higher than a predetermined temperature, control is performed such as issuing a copy prohibition signal S2.

In the above configuration, the significance of the separation claw 5 itself being composed of the ceramic sensor 4 is not only to provide a separation claw that is durable against the temperature rise in the non-sheet passing area; By further developing it, we provide a safety device that prevents abnormal temperature rise at the end of the roller and prevents various types of deterioration caused by heat, and without increasing the number of parts, it also reduces roller wear and i'+*osi. 11・iE IpKi 31
W(a)Ki In one example, it is formed of a full coating of ceramic or only of ceramic, and in the example shown in FIG. 3(b), it is mainly implemented with a tip coating. Note that the separation claw in the paper passing area on the fixing a-ra surface is p.
An ordinary separation claw made of a resin such as PS coated with tetrafluoroethylene is used.

[Effects of embodiments of the invention]

In accordance with the present invention, the separation claws in the non-sheet passing area were made using NiO as the material of the separation claws in Example 1 and the same (NiO
Examples 2 and 3 were coated with PFA, and the following experiments were conducted on these examples by continuously passing 500 sheets of small-sized paper.

In experiment 1, 30,000 sheets of the largest size paper were passed through and the jam rate was observed. According to this experiment, Experimental Example 1 and Experimental Example 2
In the graph of FIG. 4, the solid line A and the opening are respectively indicated by 0.2 chi or less.

In contrast to Examples 1 and 2 above, the same experiment 1 as above was conducted using a separating pawl material coated with PFA on priimide as a separating pawl in the non-paper passing area as a comparative example. The Q jam rate shown in Figure 3 was as high as 0.8 to 1.0 chi.

Next, in Experiment 2, following Experiment 1, the separation claws in each of Example 1.2 and Comparative Example were replaced with new claws, and 300 sheets of maximum size paper were passed through to see how often they stuck to the fixing roller. The results of Experiment 2 are shown in the table below.

As described above, the embodiment in which a ceramic material is used as the material for the separation claw in the paper non-passing area according to the present invention has remarkable effects compared to the conventional separation claw.

〔Effect of the invention〕

According to the present invention, among the plurality of separation claws that come into contact with the fixing roller surface, the separation claw located in the non-sheet passing area is configured with a ceramic sensor having a temperature detection function, so that it is separate from the conventional separation claws. The number of parts can be reduced compared to a device equipped with a temperature sensing member such as a thermistor, and the ceramic material used for the separation claw has strong mechanical strength and very good heat resistance, so it is not necessary to use it as a separation claw. The tip does not sag even if it is in contact with two surfaces of the fixing row at a high temperature, and it can be used almost semi-permanently.

Furthermore, since the separating claw constituted by the ceramic sensor of the present invention also exhibits a resistance change of several percent per 1° C. as a temperature sensor, it is possible to control the temperature with high accuracy through resistance change measurement.

That is, as shown in FIG. 5, a separation claw 5 having a temperature detection function located in a non-sheet passing area is connected to a control circuit 12 via a comparator 11 to control the temperature on the surface of the fixing roller 2. For example, it is possible to detect the temperature of the area where the fixing roller does not pass through and turn off the relay switch 13t1 to prohibit copying before the temperature of the tetrafluoroethylene coating the fixing roller reaches a temperature that causes thermal deterioration. It not only improves the durability of the separation claw, but also greatly contributes to improving the durability of the fixing roller.

[Brief explanation of drawings]

FIG. 1 is a side view showing an outline of a heat fixing device to which the present invention is applied, FIG. 2 is a graph showing the aspect of temperature distribution on the surface of the fixing roller, and FIGS. 3 (,) and (b) are A diagram showing a specific example of a temperature sensing member that also serves as a separating claw, FIG. 4 is a graph diagram showing experimental results for the embodiments of the present invention and comparative examples, and FIG. 5 is an explanatory diagram of the temperature control mode in the device of the present invention. be. 1... Heating roller 2... Pressure roller 3...
・Heater 4...Ceramic, Xensor 5...Separation claw 6...Cleaning member 7.9...Reflector 8.10...Cover 11
... Comparator 12 ... Control circuit 13 ...
Relay switch 'AS 1 Figure, 2: OLO one +5 two and -1

Claims (1)

[Claims] In a fixing device that fixes a toner image by passing a supporting material carrying an unfixed toner image between a pair of fixing rollers for heating and applying pressure, a support material carrying an unfixed toner image is passed between the pair of fixing rollers for heating and applying pressure. A heat fixing device characterized in that a separation claw located in a non-paper passing area among a plurality of separation claws provided is configured with a ceramic sensor having a temperature detection function.