JPH04181981A - Thermal fixing device - Google Patents

Abstract

PURPOSE:To easily allow good heating control by calculating an atmosphere temp. in accordance with the temp. output from a roller temp. detecting means at the time of charging of a power source of the ratio of a change in the roller temp. output after this time and controlling a heating means. CONSTITUTION:The roller temp. detecting means 21, such as thermistors, is provided on the surface of a thermal fixing roller 17. A computing means 23 calculates the atmosphere temp. in accordance with the temp. output from the roller temp. detecting means 21 at the time of charging of the power source or the ratio of the change in the roller temp. output after this time. A heating control means 22 controls the heating of a heater 16 in accordance with the result of the computation of the computing means 23. The correct temp. control is executed in this way without using the atmosphere temp. detecting sensor, image temp. detecting sensor, paper thickness detecting sensor, etc., to be exclusively used.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a heat fixing device used in copying machines and the like.

[Prior Art] Conventionally, in a heat fixing device in a copying machine, a toner image carried on a photosensitive drum is transferred onto copy paper fed from a paper feeder by a transfer device, and the transferred image is The paper is fed between a pair of rollers of a heat fixing device and heated, thereby melting the toner on the paper and fixing it on the paper surface.

By the way, when implementing temperature control during heating, if the ambient temperature is high, not much heat is removed, so the control zone can be set low; if the ambient temperature is low, a lot of heat is removed, so the control zone can be set low. The zone needs to be high.

Therefore, when heating control is conventionally performed in consideration of the ambient temperature, a thermistor for detecting ambient temperature has been installed inside the copying machine.

[Problems to be Solved by the Invention] However, preparing the thermistor for detecting the ambient temperature in this way poses a problem in that installation is time-consuming and leads to an increase in cost.

Such a problem also exists when heating control is performed in consideration of image density and paper thickness.

The present invention takes into consideration the problems with conventional heat fixing devices, and provides a heat fixing device that can realize heating control that takes into account ambient temperature, image density, and paper thickness without using such a thermistor. The purpose is to provide equipment.

[Means for Solving the Problems] The present invention includes calculation means for calculating the ambient temperature based on the temperature output from the roller temperature detection means when the power is turned on, or based on the rate of change in the roller temperature output after that time. , and control means for controlling the heating means based on the calculation result.

Further, the present invention provides a calculating means for calculating a state of heat removal based on a rate of change in the output of a roller temperature detecting means after continuous image formation is started in an image forming apparatus provided with a heat fixing device. and a control means for controlling the heating means based on the calculation result.

[Examples] Examples of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic cross-sectional view of a copying machine using a heat fixing device according to an embodiment of the present invention.

In the figure, a document placement plate 1 is provided on the upper surface of a main body 100, and a document cover 2 for holding the document is attached thereon. Further, an optical system 3 is disposed below the document placement plate 1 for irradiating light onto the document and guiding the reflected light to the photosensitive tram 4 . Around the photosensitive tram 4, a charger 5 for charging the surface of the photosensitive drum is provided in a clockwise direction.
, an exposure section 6, a developing roller 7, and the like, a developing device 8 for performing development, a transfer separator 9 for transferring and separating, a cleaning device 10 for cleaning residual toner, and the like are arranged.

Further, on the right side wall of the apparatus main body 100, a paper feed cassette 11 for feeding paper and a manual feed/tray 12 are provided. A conveyance path 13 for conveying paper from the cassette 11 and tray 12 to the upstream side of the transfer separator 9 is provided. Further, on the downstream side of the transfer separator 9, there is a conveyance path 1 for conveying the transferred copy paper to the thermal fixing device 15.
4 is placed.

The thermal fixing device 15 internally includes a thermal fixing roller 17 having a heater 16 as an example of a heating means, a pressure roller 18 that presses against the roller 17 and feeds out the paper, and the like.

A discharge roller 19 for discharging paper and a discharge tray 20 for storing the discharged paper are provided on the downstream side of the thermal fixing device 5.

A roller temperature detection means 21 such as a thermistor is provided on the surface of the heat fixing roller 17. 23 is based on the temperature detected by the roller temperature detection means 21 when the power is turned on,
Alternatively, it is a calculation means that calculates the ambient temperature based on the rate of change in the roller temperature output after that time. 22
is a heating control means that controls the heating of the heater I6 based on the calculation result of the calculation means 23.

Next, the operation of the above embodiment of the present invention will be explained.

The surface of the photosensitive tram 40 is uniformly charged by the charger 5. Then, the optical system 3 irradiates the document with light, and the photosensitive drum 4 is exposed. The exposed photosensitive tram 4
The upper latent image is developed by the developing device 8.

On the other hand, the paper in the paper feed cassette 11 is taken out at predetermined time intervals by the paper feed roller 111 in synchronization with the operations of the optical system 3 and the photosensitive tram 4, passes through the conveyance path 13, and is transferred to the transfer separator 9. come to the place.

Then, the developed toner image on the photosensitive drum 4 is transferred onto the paper by the separation transfer device 9. The transferred paper is fed through the transport path 14 between the rollers 17 , 18 of the thermal fixing device 15 . The toner on the paper is then melted and fixed at an appropriate temperature of 185°C. The paper is sent out onto the ejection tray 20 by the ejection roller 19 from between the rollers 17 and 18 at a predetermined speed.

Therefore, the roller temperature detection means 21 detects the temperature of the heat fixing roller 17.
Since the surface temperature of the copying machine is constantly detected, the temperature when the copying machine is turned on, the temperature at startup after that, and the temperature after that are detected.

FIG. 2 is a graph showing the detected temperature. The horizontal axis is time, the vertical axis is detected temperature, and the solid line indicates the ambient temperature of 25°C.
In this case, the broken line is for 10°C, and the dashed-dotted line is for 35°C. If a sufficient amount of time has passed since the power was turned off, for example when the power was turned on in the morning, the detected temperature at the time of power-on is naturally the respective ambient temperature. Therefore, the calculation means 23 can directly detect the ambient temperature from the temperature. Note that the power-on timing information can be known from a signal from a microcomputer or the like that controls the entire copying machine.

Alternatively, as is clear from the figure, the manner in which the temperature rises after the power is turned on differs depending on the ambient temperature. That is, the higher the ambient temperature is, the more quickly it approaches the proper temperature of 185°C, and the lower the ambient temperature is, the slower it approaches the proper temperature of 185°C. Therefore, the calculation means 23 calculates the ambient temperature from this temperature increase rate. Data for this purpose is collected in advance through experiments.

In this way, the ambient temperature data obtained by the calculation means 23 is input to the control means 22, and
controls the heater 16 as shown in FIG.

That is, as shown in Table 1, the temperature is controlled to an appropriate temperature (185° C.).

Table 1 Both the upper and lower limits are changed.

Alternatively, control is performed as shown in FIG. That is, as shown in Table 2, the proper temperature (185°C) is controlled.

Table 2 Only one of the upper limit or lower limit is changed.

Since the heating is controlled according to the ambient temperature, proper heat fixing can be achieved.

Next, another embodiment of the present invention will be described.

Since only the calculation means 23 and the control means 22 differ from the above-described embodiment, explanations of the other means will be omitted.

That is, the calculation means 23' in this embodiment calculates the amount of heat removed based on Kariya of the output change of the roller temperature detection means 2I after the copying machine equipped with the heat fixing device starts continuous copying. 9 (including being taken away by other things in the atmosphere, in addition to being taken away by paper).

FIG. 5 shows the detected temperature change.

After the continuous copying starts, φ, (tl),
This is caused by the rate of temperature drop, differences in ambient temperature, differences in paper thickness, differences in copy density, etc. There are cases where the rate of temperature drop is small (see the solid line), cases where the rate of temperature fall is large (see the broken line), and so on. Therefore, 5. Calculate the school's deprivation status from that child's data. The reason for the difference in the rate of drop is the ambient temperature, the thickness of the paper, or the difference in copy density. The fact that continuous copying has started can be determined using a signal from a computer that controls the entire copying machine. Alternatively, it can be recognized from the fact that the temperature has begun to drop significantly.

The control means 22' performs heating control corresponding to the difference in the way heat is removed. How to deal with it should be determined in advance through experiments.

Incidentally, the apparatus that uses the heat fixing apparatus of the present invention is not limited to a copying machine, and may of course be other apparatuses.

Further, the expanding temperature detecting means of the present invention may of course include not only a thermistor but also other temperature detecting sensors.

Further, the calculation means and the control means may be implemented in software using a computer, or a dedicated heart circuit having the functions thereof may be used.

[Effects of the Invention] As is clear from the above explanation, the heat fixing device according to the present invention can be used without using a dedicated atmospheric temperature detection sensor, image density detection sensor, paper thickness detection sensor, etc. Since the temperature can be controlled appropriately, it is a heat fixing device that does not take much time to assemble and is excellent in terms of cost.

[Brief explanation of drawings]

FIG. 1 is a schematic sectional view of a copying machine incorporating an embodiment of the thermal fixing device of the present invention, FIG. 2 is a graph of the fixing roller surface temperature change when the power is turned on, and FIG. Figure and 4th
The figure is a temperature control graph of the fixing roller of the same embodiment, and FIG. 5 is a graph of the change in the fixing roller surface temperature during continuous copying of the same embodiment. 15... Heat fixing device, 16... Heating means, 17...
- Heat fixing roller, 18... Pressure roller, 21... Roller temperature detection means, 22... Heating control means, 23...
・Calculation means.

Claims (2)

[Claims] (1) A heat fixing roller having a heating means and heat fixing the toner image while sequentially passing the transferred paper;
In a heat fixing device equipped with a roller temperature detection means for detecting the surface temperature of the heat fixing roller, based on the temperature output from the roller temperature detection means when the power is turned on, or based on the temperature output from the roller temperature detection means after that time, A thermal fixing device comprising: a calculation means for calculating an ambient temperature based on the ratio; and a control means for controlling the heating means based on the calculation result. (2) a heat fixing roller having a heating means and heat fixing the toner image while sequentially passing the transferred paper;
In a heat fixing device including a roller temperature detection means for detecting a surface temperature of the heat fixing roller, the roller temperature is detected after continuous image formation of an image forming apparatus provided with the heat fixing device is started. A thermal fixing device comprising: a calculation means for calculating a state of heat removal based on a rate of change in the output of the means; and a control means for controlling the heating means based on the calculation result.