JPH02195369A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent toner from fixing firmly, to control temperature according to a recording material, and to obtain a sharp image for long time by disposing a temperature detecting element in the vicinity of the end part of a fixing roller. CONSTITUTION:The temperature detecting element 5 is disposed so as to abut on the fixing roller 1 outside a region 4 which abuts on the recording material 3 on the outer periphery of the fixing roller 1 and a means is provided with detects the width of the recording material 3. Thus, toner, etc., does not firmly fix on the temperature detecting element 5 and the surface of the fixing roller 1 is not damaged even when it is used for long time. Besides, even if the width of the recording material 3 is different, temperature is controlled so as to make the center part of the fixing roller 1 optimum temperature. In such a way, even when the width of the recording material 3 varies, fixing properties are kept and offset can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an image forming apparatus having a fixing device that heats and fixes a toner image onto a recording material.

[Prior Art] Conventionally, a fixing device generally used in an image forming apparatus has a fourth fixing device.
The configuration is as shown in the figure.

In FIG. 4, reference numeral 51 denotes a fixing roller, which has a mold release resin layer 54 made of PFA, PTFE, etc. on a core metal 53 made of aluminum, iron, etc., and is heated by a heater 50 inside. The temperature of the fixing roller 51 is detected as the surface temperature of the fixing roller 51 by a temperature detection element 58 that is brought into contact with the fixing roller, and the temperature of the fixing roller 51 is detected by intermittently operating the heater 50 by a temperature control circuit (not shown). The surface temperature is controlled to a predetermined temperature.

On the other hand, 52 is a pressure roller that rotates in pressure contact with the fixing roller 51, and is made of an elastic material such as silicone rubber or fluororubber that has heat resistance and good a-type properties on a fully bendable core metal 56 made of iron or stainless steel. A layer 57 is formed.

The recording material 61 carrying the toner image 60 is transported to an entrance guide 63.
The image is guided between the fixing roller 51 and the pressure roller 52 and fixed by being heated and pressurized.

Thereafter, the recording material 61 is separated from the fixing roller 51 by the separating claw 55.
It is peeled off by Further, a temperature detection element 58 for keeping the temperature of the surface of the fixing roller constant is installed approximately at the center in the axial direction of the fixing roller.

[Problems to be Solved by the Invention] However, in the case of such a conventional device, the temperature sensing element was brought into contact with the center of the fixing roller, and as a result of long-term use, toner and other particles may build up on the surface of the temperature sensing element. There is a problem in that the adhesion of paper dust abrades the releasable resin layer on the surface of the fixing roller, causing black streaks on the image. Therefore, the above problem has been solved by moving the temperature sensing element to the end of the fixing roller.

However, new problems have arisen even with the above solutions. Even if the surface temperature of the fixing roller is heated uniformly by a heater, it tends to exhibit a different temperature distribution depending on the size of the recording material used. When controlled to maintain the optimum temperature, the temperature at the center of the fixing roller varied as shown in FIG. 5, making it impossible to maintain the optimum temperature. Figure 5 shows three types of recording materials A and B with different widths.
, C (sizes are in the order of A>B>C). In the case of the smallest size recording material C, the temperature at the center falls and causes a fixing failure, and if the temperature is set in advance according to the recording material C, then in the case of the largest size recording material A. However, there was a problem in that the temperature at the central portion became too high, causing a high temperature offset.

The present invention solves the above problems and prevents toner etc. from sticking to the temperature sensing element even after long-term use.
It is an object of the present invention to provide an image forming apparatus that can perform appropriate temperature control even if the width of recording materials is different.

[Means for Solving the Problems] According to the present invention, the above object includes: a fixing roller that fixes a developer image on a recording material using a heater disposed inside; a means for detecting the width of the recording material; , an image forming apparatus comprising: a temperature sensing element that comes into contact with the outer circumferential surface of the fixing roller and detects the surface temperature of the fixing roller; The surface temperature at the position where the temperature sensing element is in contact with the fixing roller outside the area width of the developer image is measured at the center of the fixing roller for multiple recording materials of different widths. This is achieved by providing control means to maintain different temperatures, such as the surface temperature of the surface or the temperature required for fusing.

[Function] As described above, according to the present invention, the temperature detection element is arranged so as to come into contact with the fixing roller outside the area width of the developer image on the recording material in the longitudinal direction of the fixing roller. This prevents toner from sticking to the temperature sensing element.
The surface of the fixing roller will not be damaged even after long-term use.

Therefore, even if the width of the recording material is different, there will be no black streaks on the image, and even if the width of the recording material is different, the temperature detection element can be adjusted at the position where the temperature detection element is installed so that the temperature is optimal at the center of the fixing roller. Since the temperature is controlled, fixing performance is maintained even if the width of the recording material changes, and offset is prevented.

[Example] A first example of the present invention will be described with reference to FIGS. 1 and 2 of the accompanying drawings.

In FIG. 1, l is a fixing roller. The apparatus of this embodiment includes a heater 2 inside the fixing roller 1, and a temperature sensing element 5 that is placed in contact with the fixing roller 1 outside an area 4 on the outer periphery of the fixing roller l that comes into contact with the recording material 3. It is further provided with means (not shown) for detecting the width of the recording material 3.

In the apparatus of this embodiment, three types of recording materials A, B, and C (
The size is in the order of A>B>C), and when the paper is passed based on the center of the fixing roller 1, the temperature Tf required for fixing is maintained at the center of the fixing roller l. The temperature was controlled as described above, and the surface temperature distribution of the fixing roller l at that time was investigated. The results are shown in FIG. 2. As shown in FIG. 2, when the surface temperature of the center portion is maintained at the temperature Tf required for fixing, the end portion of the fixing roller 1 where the temperature sensing element is disposed In the vicinity, it was confirmed that different values were shown depending on the width of the recording material. In other words, the widest size recording material A has a lower temperature Ta, the medium size recording material B has a temperature Tb that is almost equivalent to the temperature Tf required for fixing, and the smallest size recording material C has a higher temperature Tb. Temperature T
It turned out to be c.

From this, if the type of recording material to be used and the surface temperature distribution state of the fixing roller l corresponding to the recording material are known in advance, the temperature near where the temperature sensing element is arranged can be determined for each recording. By controlling according to the material, the temperature Tf required for fixing can be maintained near the center of the fixing roller l.

Based on the above facts, the following experiment was conducted using the apparatus of this embodiment.

The fixing roller has a wall thickness of 3.5 am and an outer diameter of 30 Ill.
A 750 W halogen heater was disposed inside the fixing roller to heat the fixing roller.

In addition, as a pressure roller, a silicone rubber sponge (Ask
er-C hardness 3G') was used. The fixing roller and pressure roller have a total pressure of 11. Pressure was applied to Okg.

At that time, the nip width was 3.51■. In addition, in order to compensate for the outflow of heat from both ends of the roller, the amount of light emitted from a halogen heater at a position 90 mm away from the center to the end is 1/2 at the center.
．． It is set to be 6 times.

As for the recording material, the largest size recording material A is B4.
A4 was used as the medium-sized recording material B, and B5 was used as the smallest-sized recording material C. The surface temperature of the center portion of the fixing roller l is maintained at 180° C., and the surface temperature near where the temperature detection element is disposed when each recording material is used, that is, Ta, Tb, and Tc in FIG. 2 are as follows:
Recording material A was heated to 170°C, and recording material B was heated to 1
The temperature was set at 82°C, and the temperature for recording material C was set at 195°C.

Under the above conditions, when each recording material was passed with the center as a reference, the surface temperature near where the temperature detection element was arranged was controlled by each recording material, so the center of the fixing roller 1 was controlled regardless of the recording material. It was confirmed that the surface temperature Tf of the toner could be maintained at around 180° C., and neither fixing failure nor high-temperature offset occurred. In addition, even when using the largest size 84, the temperature sensing element is located outside the area where the fixing roller and recording material come into contact, so the fixing roller will not be damaged even if more than 200,000 sheets are printed. It was confirmed that no black streaks appeared on the image.

Next, a second embodiment of the present invention will be described using FIG. 3 of the accompanying drawings. Note that the same parts as in the first embodiment described above are given the same reference numerals, and the description thereof is omitted.

As shown in FIG. 3, when the largest size recording material is used, the temperature sensing element is located inside the area 4 where the fixing roller l contacts the recording material, as indicated by the dotted line in FIG. The developer image is disposed outside the area width 6 of the developer image.

In the apparatus of this embodiment as described above, since the temperature is detected at a position close to the center of the fixing roller l, it is possible to control the temperature with higher precision, and the temperature sensing element is placed outside the area width 6 of the developer image. Since toner and the like are not stuck to the fixing roller 1, the fixing roller 1 is not damaged. Furthermore, since the length of the fixing roller 1 can be made shorter than in the first embodiment described above, it is possible to downsize the apparatus.

[Effects of the Invention] As explained above, according to the present invention, since the temperature sensing element is disposed near the end of the fixing roller, toner etc. do not stick to it and do not damage the fixing roller. Therefore, it is possible to provide clear images, and furthermore, it is possible to extend the life of the fixing roller. Furthermore, since the temperature is controlled according to the recording material, poor fixing and offset at high temperatures can be prevented, and clear images can be provided for a long period of time, regardless of the type of recording material.

[Brief explanation of the drawing]

FIG. 1 is a parent view of the apparatus according to the first embodiment of the present invention, FIG. 2 is a diagram showing the surface temperature distribution of the fixing roller in the apparatus according to the first embodiment, and FIG. 3 is a perspective view of the apparatus according to the second embodiment. 4 is a vertical sectional view showing a conventional device, and FIG. 5 is a diagram showing the temperature distribution on the surface of the fixing roller when temperature control is performed in the device shown in FIG. l...Fuser roller 2...
・・・・・・Heater 3・・・・・・・・・Recording material

Claims (1)

[Scope of Claims] A fixing roller that fixes a developer image on a recording material using a heater disposed inside, means for detecting the width of the recording material, and a fixing roller that comes into contact with the outer peripheral surface of the fixing roller. In an image forming apparatus including a temperature detection element that detects a surface temperature of a roller, the temperature detection element detects the temperature of the fixing image outside the area width of the developer image on the recording material in the longitudinal direction of the fixing roller. The surface temperature at the position where the temperature sensing element is in contact with the roller is
An image forming apparatus comprising: a control means for maintaining a plurality of recording materials of different widths at different temperatures such that the surface temperature at the center of the fixing roller is the temperature required for fixing.