JPS6111776A - Fixing device - Google Patents

Abstract

PURPOSE:To control the surface temp. of a fixing roller to an adequate fixing temp. by providing a temp. sensor of a non-contact type having the capability to monitor the range across the part where small-sized recording paper passes and the part where said paper does not pass in the stage of feeding the small- sized paper and controlling the temp. of the fixing roller by said sensor. CONSTITUTION:The temp. sensor 5 is disposed in the position spaced by about 10mm. from the fixing roller 2 in a manner as to monitor the range across the part where the small-sized recording paper A5 passes and the part where said paper does not pass in the stage of feeding said paper, as shown by dotted lines. The IR sensor absorbs the IR rays radiated from the temp. measuring object in the temp. monitoring range according to temp. and generates the electric signal corresponding to the heat energy of the IR rays. The intermediate temp. in the part where the paper A5 passes and the part where said paper does not pass in thus measured and since the temp. control width by a control circuit is decreased, the control in a manner as to prevent the abnormal temp. decrease and increase is made possible.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is designed to prevent the surface temperature of the fixing roller during feeding of small-sized recording paper from being too high at the non-passing part and too low at the passing part of the small-sized recording paper. The present invention relates to a fixing device that is capable of controlling the temperature of a fixing roller to a temperature that would otherwise occur.

[Prior art]

FIG. 1 shows a typical example of a conventional fixing device used in copying machines, etc., which is a heat roller consisting of a fixing roller 2 in which a heater 1 is installed and a pressure roller 23 that is pressed against the fixing roller 2 with a constant pressure. This figure shows a fixing device of this type. In FIG. 1, the fixing roller 2 is heated to a predetermined temperature according to the heat generated by the heater placed inside the roller, and is heated by the thermal energy transmitted from the fixing roller 2 and the pressure applied from the pressure roller 3. Toner images transferred onto recording sheets A and A of different sizes, for example, A3 and A, which are fed between the fixing roller 2 and the pressure roller 3 in the manner shown in the figure, respectively. This makes it possible for the company to take root.

In this type of fixing device, temperature control of the fixing roller 2 is particularly important from the viewpoint of maintaining fixing quality or preventing paper burning.In this regard, conventionally, the above-mentioned small size recording paper A@ on the fixing roller 22 has been used. A contact type temperature sensor 4 is provided at a passing portion or a non-passing portion of the fixing roller 2, and the surface temperature of the fixing roller 2 is controlled by turning on/off the power supply to the heater 1 based on the temperature detected by the temperature sensor 4. was. FIGS. 2 and 3 show the case where the temperature monitoring position of the temperature sensor 4 is set to the passing portion and non-passing portion of the small size recording paper A, respectively, when feeding the dog size recording paper A3 and the small size recording paper A6. It shows the surface temperature characteristics a and b of the fixing roller 2 during document feeding, with the horizontal axis representing the position of the fixing roller 2 and the vertical axis representing the temperature.

As is clear from FIGS. 2 and 3, when the fixing device is performing fixing, the entire width of the fixing roller 2 becomes the recording paper passing portion when feeding a large-sized recording paper A3. The surface temperature (see Figures 2a and 3a) of the small-sized recording paper A is maintained almost uniformly in each part, but there are a mixture of passing and non-passing parts. There is a tendency for the non-passing portion of A to rise more than the passing portion (see Figures 2 and 3). At this time, if the temperature sensor 4 is provided in the passing portion where the temperature is lower than that of the non-passing portion to control the temperature, the surface temperature i of the fixing roller 2 has a temperature distribution characteristic as shown in FIG. Since the temperature of the non-passing portion increases abnormally, there is a problem in that the surrounding mechanisms such as the fixing roller 2 itself, the peeling claw, the bearing, and other members are likely to be thermally damaged. In addition, if a temperature sensor 4 is provided in the non-passing part, which tends to be more dense than the passing part, to control the temperature, the surface temperature distribution of the fixing roller 2 will have the characteristics shown in FIG. There has been a problem in that fixing quality deteriorates because the temperature of the area where the image passes through becomes low. This was also the case when a non-contact type temperature sensor having the same temperature monitoring range as described above was used.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned circumstances. When small-sized recording paper is transported, the temperature of the part of the fixing roller 2 that does not pass through the surface of the fixing roller 2 is lower than that of the fixing roller and the surrounding area. Equipped with a temperature control function that can control the surface temperature of the fixing roller to an appropriate fixing temperature that does not rise to the extent of causing thermal damage to the mechanism and does not reduce the temperature of the passing portion to the point of causing fixing failure. The purpose of the present invention is to provide a fixing device.

[Structure of the invention]

Therefore, in the present invention, a non-contact type temperature sensor is provided that can monitor the range spanning the passing portion and non-passing portion of the small size recording paper when the small size recording paper is sent, and the high temperature portion detected by this temperature sensor is provided. The above-mentioned object is achieved by controlling the temperature of the fixing roller based on the average temperature between the (non-passing part) and the low temperature part (passing part).

〔Example〕

Embodiments of the present invention will be described in detail below based on the accompanying drawings. FIG. 4 is a conceptual diagram showing an embodiment of the fixing device of the present invention. As a novel structure, a non-contact type temperature sensor 5 is provided at a position a predetermined distance away from the fixing roller 2. FIG. For example, an infrared sensor is used as the non-contact temperature sensor 5, and a predetermined temperature monitoring range is defined by the fixed viewing angle of the infrared sensor and the distance from the fixing row 22 described above. In this embodiment, the temperature monitoring range of the pigeon temperature sensor 5 is the boiling range shown by the dotted line in FIG. The temperature sensor 5 is disposed at a position about 10 meters away from the fixing row 22 so as to span the area opposite to the non-passing portion. As is well known, an infrared sensor used as a temperature detection element absorbs infrared rays (heat rays) emitted according to the temperature from an object to be measured within the temperature monitoring range, and generates an electrical signal according to the thermal energy of the infrared ray. do. The electric signal line corresponding to the detected temperature thus output is inputted to a control circuit (not shown) and compared with the electric quantity corresponding to the reference temperature. The control circuit then controls the temperature of the fixing roller 2 by controlling the supply of electricity to the heater 1 based on this comparison result. In the conventional apparatus shown in FIG. 1, when the temperature monitoring area by the temperature sensor 4 is the small size recording paper A on the fixing roller 22, the detected temperature of the passing part is low, and in order to correct this. As a result of the control circuit trying to raise the overall temperature of the fixing roller 2, there is a problem that the temperature of the valve exit section becomes abnormally high. There is a problem in that the detected temperature of the non-passing portion is high, and as a result of the opposite temperature control to that described above being performed in order to correct this, the temperature of the passing portion remains low.

In this respect, in the present invention, as described above, the non-contact type temperature sensor (infrared sensor) 5 detects the temperature according to the amount of thermal energy within its temperature monitoring range, so that the small size recording paper A6 passes This means that the intermediate temperature between the part and the non-passing part can be measured. As a result, the temperature control period by the control circuit is narrowed, so that the fixing roller 22 must be controlled so as not to cause an abnormal temperature drop or excessive temperature rise in the portion where the small-sized recording paper A6 passes and the portion where it does not pass, respectively. becomes possible.

The temperature monitoring range of the temperature sensor 5, which determines the magnitude of the electrical signal corresponding to the temperature detected by the temperature sensor 5 input to the control circuit, is determined by its viewing angle and the distance from the fixing roller 2, as described above. At this time, the temperature of the fixing roller 2 whose temperature is controlled by the control circuit is determined by the separation distance between the large-size recording paper A3 and the small-size recording paper A6, respectively, for example in FIGS. 5a and b.
Experiments were carried out to ensure that the temperature distribution characteristics as shown in Fig. 1 were not so high that the non-passing portion of the small size recording paper A6 would not rise so high as to cause thermal damage, and that the passing portion would not become too low as to cause fixing failure. It is desirable that the

〔Effect of the invention〕

As explained above, according to the fixing device of the present invention, a non-contact type temperature sensor is used to detect the temperature, with the monitoring range extending over the area where the small-sized recording paper passes and the area where the small-sized recording paper does not pass on the fixing roller. Since the temperature of the fixing roller is controlled, the temperature of the fixing roller can be controlled to a temperature that is not too high in the non-passing portion and not too low in the passing portion, thereby preventing thermal damage to the fixing roller and surrounding mechanisms. Moreover, it has the excellent effect of maintaining good fixing quality.

[Brief explanation of the drawing]

Fig. 1 is a conceptual diagram showing an example of the configuration of a conventional fixing device, and Figs. 2 and 3 show the feeding of large-sized recording paper and small-sized recording paper when the temperature monitoring position of the temperature sensor is different in the conventional device. FIG. 4 is a conceptual diagram showing an embodiment of the present invention,
FIG. 5 is a diagram showing an example of the temperature distribution characteristics of the fixing roller when feeding dog-sized and small-sized recording sheets in the apparatus of the present invention. DESCRIPTION OF SYMBOLS 1... Heater, 2... Fixing roller, 3... Pressure roller, 4... Contact type temperature sensor, 5... Non-contact type temperature sensor.

Claims (2)

[Claims] (1) In a fixing device equipped with a fixing roller that fixes at least two types of recording paper of different sizes, large and small, the monitoring range is a surface area of the fixing roller that spans the portion through which the small-sized recording paper passes and the portion through which the small-sized recording paper does not pass. A fixing device comprising a non-contact type temperature sensor for controlling temperature of a fixing roller. (2) The fixing device according to claim (1), wherein the temperature sensor is an infrared sensor.