JPS5857115B2 - Heat fixing device in copying machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heat fixing device, and more specifically, but not exclusively, to a heat fixing device used in an electrostatic copying machine.

The present invention is concerned with controlling the temperature of the fuser roller surface.

In conventional heat fixing devices, particularly in fixing devices using a heating roller that comes into direct contact with copy paper, the following temperature control has been considered.

That is, first, heating means for heating the center and end portions are provided inside a fixing roller having an anti-offset surface on the side that comes into contact with the toner powder image on the copy paper, and a pressure roller is pressed against this fixing roller. There is a type of roller constant fixing device that detects the surface temperature of the center and end portions of the fixing roller and independently controls both heating means to flatten the temperature distribution on the surface of the fixing roller. , secondly, a heating means is provided in the fixing roller and the pressure roller;
There is a type that detects the surface temperature of both fixing rollers and controls both heating means independently, and a third type includes a fixing roller, a pressure roller that presses against the fixing roller to fix the toner image, and this fixing roller. In a fixing device consisting of a heating roller that heats the fixing roller by contacting the fixing roller, a type of fixing device that detects the surface temperature of the fixing roller and simultaneously controls the heating means provided on the fixing roller and the heating roller is considered. There is.

The first type is intended to prevent the temperature from rising at one end of the roller when narrow sheets such as A size sheets are passed between the rollers in succession. In order to efficiently and effectively fix a toner image using a pair of heating rollers, the fixing roller and the pressure roller must each be maintained at appropriate temperatures.

However, even if only the temperature of the fixing roller is uniformly controlled as in this type, the temperature of the pressure roller is not controlled, so there is a sheet between the rollers, which prevents the conduction of heat to the fixing roller and the pressure roller. I ended up cutting it off,
The temperature at the center of the pressure roller may drop, making it impossible to perform good fixing.

However, the pressure roller has the same heating means as the fixing roller,
Providing a temperature detection element would make it extremely expensive.

Next, in the case of the second type, since the temperature of the upper and lower rollers is simply controlled, the temperature rises at one end of the roller, causing phenomena such as hot offset at the end, which is undesirable. .

The third type is that a fusing roller having a heat-resistant elastic material such as silicone rubber on its surface has a poor response to thermal changes, and therefore heat is supplied to this surface from the outside. , as with the second type, it is impossible to prevent the temperature from rising at one end of the roller, and the temperature at the center of the pressure roller decreases, resulting in defective fixing.

SUMMARY OF THE INVENTION An object of the present invention is to provide an inexpensive fixing device that eliminates the drawbacks of the conventional method and employs a relatively simple temperature control method to perform good fixing.

Hereinafter, the present invention will be explained with reference to the drawings.

As shown in FIG. 1, a pair of fixing rollers 1.2 are juxtaposed vertically in pressure contact with each other and are driven to rotate in the direction of the arrow in the figure.

The fixing roller 1 has a metal cylinder 3 having a thin coating 4 formed on the outer surface thereof to prevent offset, such as Teflon, and two heaters 5 and 6 arranged inside.

One heater 5 heats the center of the fixing roller 1, and the other heater 6 heats the ends thereof.

The fixing roller 2 has a heat insulating elastic layer 8 such as silicone rubber formed on the surface of a metal cylinder 7, and heaters 9 and 10 for heating the heat insulating elastic layer 8 are provided outside the roller. There is.

The heater 9 heats the center portion of the fixing roller 2, and the heater 10 heats the end portions thereof.

When the heat insulating elastic layer 8 is thin, it is more efficient to provide the heaters 9 and 10 inside the roller.

The fixing roller 1, which has better thermal conductivity among the l pair of fixing rollers 1 and 2, has a temperature sensing element, for example, a thermistor 1.
1 and 12 are in contact with the surface, and the surface temperature is detected.

Thermistors 11 and 12 are heaters 5 inside fixing roller 1.
, 6.

That is, the thermistor 11 is in contact with the center of the fixing roller 1, and the thermistor 12 is in contact with the end of the fixing roller 1, respectively.

The control device 13 simultaneously controls the heaters 5 and 9 according to the output of the thermistor 11, for example, compares the output of the thermistor 11 with a set value, controls the heaters 5 and 9 on and off using that output, and controls the heaters 5 and 9 at the center of the fixing rollers 1 and 2. Temperature control is performed so that the surface temperature of the part reaches the set temperature of about 180°C.

On the other hand, the control device 14 also responds to the output of the thermistor 12.
The heaters 6 and 10 are controlled simultaneously, and the fixing rollers 1 and 2 are
Temperature control is performed so that the surface temperature at the end of the tube reaches the set temperature of approximately 180°C.

The copy paper 15 on which the toner image has been formed is transferred to the fixing rollers 1 and 2.
The toner is passed through the paper 15 and heated to permanently fix the toner on the copy paper 15.

In the fixing device of such a copying machine, the fixing roller 1
, 2 are both heated by heaters 5, 9, and both end portions of fixing rollers 1, 2 are heated by heaters 6.1.
Since the fixing rollers 1 and 20 are heated at zero temperature, the surface temperature of the fixing rollers 1 and 20 decreases little during paper feeding.

Of the pair of fixing rollers 1 and 2, the fixing roller 1 having the thin layer 4 for preventing offset has good thermal conductivity, so heat is taken away by the copy paper 15 when the paper is passed through, causing an immediate drop in surface temperature.

Therefore, both the center and end portions of the fixing roller 1 are detected by thermistors 11 and 12.

As shown in FIG. 2, the heater 5 provided in the fixing roller 1 is configured so that a portion A corresponding to the narrow width of the copy paper 15 to be used, for example, A size, generates heat. The heater 6 is configured so that a portion X excluding the heat generating portion of the heater 50 generates heat.

The thermistor 11 is arranged to detect the surface temperature of the portion A, which is the center portion of the fixing roller 1, and the thermistor 12 is arranged to detect the surface temperature of the portion X, which is one end of the fixing roller.

In FIG. 1, the heaters 9 and 10 that heat the outer surface of the fixing roller 2 are the same as the heaters 5 and 6. The heater 9 heats the A portion of the fixing roller 2, and the heater 10 heats the configured to heat.

The heaters 9 and 10 may be an infrared lamp, or may be one that brings a sufficiently heated thermal roller into pressure contact with the fixing roller 2.

Further, the heaters 9 and 10 may be provided inside the fixing roller 2.

Next, the operation of the heating device will be explained. In the timing state, the heaters 5, 6, 9 and 10 are all on, and the thermistors 11 and 12 maintain the surfaces of the fixing rollers 1 and 20 at a constant temperature. Since heat escapes from the shafts of the rollers 1 and 2, the number of times the end heater 6.100 is turned on and off increases.

A narrow width copy paper such as A size is continuously transferred to the fixing roller 1.
．． When paper is passed between 2, the center heater 5.90 turns on,
The number of times off will increase.

In the case of wide-width copy paper such as B size, all the heaters must be turned on and off many times.

Even though the fixing roller 2, which has poor thermal conductivity, is heated, the surface temperature of the fixing roller 1, which has good thermal conductivity, is detected and controlled.
, 10 are independently controlled in short cycles, and the temperature control width is as small as 5 to 10°C, and the fixing rollers 1, 20
The surface temperature is made uniform and the fixing characteristics are improved.

FIG. 3 shows another embodiment of the present invention. In this embodiment, a pair of fixing rollers 16 and 17 are driven to rotate in the direction of the arrow in the figure, and the upper fixing roller 16 is mounted on a metal cylinder 18. A thermally insulating elastic layer 19 such as silicone rubber
is formed, and the lower fixing roller 17 is a metal cylinder 2.
A thin anti-offset coating 21, such as Teflon, is formed on the 0.

Note that the lower fixing roller 17 may have a metal surface.

A heater 22 that heats the outer surface of the upper fixing roller 16
, 23 are provided outside the roller, and the heater 22
is configured to heat the center portion of the fixing roller 16, and the heater 23 is configured to heat the end portions of the fixing roller 16, respectively.

When the heat insulating elastic layer 19 is thin, it is more efficient to provide the heaters 22 and 23 inside the roller.

On the other hand, a heater 24°25 is installed inside the fixing roller 17.
The heater 24 is configured to heat the center portion of the fixing roller 17, and the heater 25 is configured to heat the end portions of the fixing roller 17.

Temperature sensing elements, such as thermistors 26 and 27, are in contact with the surface of the fixing roller 170, which has good thermal conductivity, to detect the temperature of the surface.

The thermistor 26 measures the temperature at the center of the fixing roller 17.
The thermistor 2T detects the temperature at each end.

The control device 28 simultaneously controls the heaters 22 and 24 according to the output of the thermistor 26, and the control device 29 simultaneously controls the heaters 23 and 25 according to the output of the thermistor 27, and sets the surface temperature of the fixing rollers 16 and 170 to the set temperature. Control the temperature so that

The operation of the heating device is the same as that of the embodiment shown in FIG.

Note that the fixing roller 1° 16 on the side that contacts the toner image may be provided with a means for supplying a known offset prevention liquid, such as silicone oil, in order to prevent the toner from offsetting during fixing. In the embodiment shown in the figure, any liquid-absorbing material such as silicone rubber may be impregnated with an anti-offset liquid.

Furthermore, the configuration of the pair of fixing rollers is not limited to the above-mentioned embodiments, and may be modified as long as at least one of them has a fixing roller with good thermal conductivity. Variations are possible.

Furthermore, although we have described a copying machine with a center-based paper feeding device, suitable modifications can also be made to the fixing device of a copying machine that uses a one-sided reference system that feeds copy sheets of different sizes by aligning one side edge. Of course, it can be implemented by applying

As described above, according to the present invention, each of the pair of fixing rollers is heated by a heater, so the temperature drop of the fixing roller is small when paper is passed through, and the temperature of the fixing roller with better thermal conductivity is detected, and the upper and lower Since the heaters that heat the fixing roller are controlled at the same time, the sensitivity of the temperature control system can be increased, thus reducing the temperature control range.Furthermore, the center and end portions of the upper and lower fixing rollers are heated independently. Both heaters that heat the center section always operate at the same time, and both heaters that heat the edge section also always operate at the same time. It can maintain a uniform temperature at a constant temperature, prevent wrinkles on copy paper, non-fixing at one end of the fixing roller, or offset, and requires only two thermistors, making temperature control relatively easy. It is a method and economical.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a heat fixing device according to an embodiment of the present invention.
FIG. 2 is a sectional view of the upper fixing roller of the embodiment shown in FIG.
FIG. 3 is a sectional view of a heat fixing device according to another embodiment of the present invention. 1.2... Fixing roller 3,7...
Metal cylinder, 5.6, 9, 10... heater, 1
1, 12... Thermistor, 13, 14...
··Control device.

Claims (1)

[Claims] 1. A first fixing roller having a heated surface;
a first heating means for heating a central portion of the fixing roller;
a second heating means for heating an end of the fixing roller; a second fixing roller having a second fixing roller, a third heating means for heating a central portion of the second fixing roller, a fourth heating means for heating an end portion of the second fixing roller; and a second temperature detection means for detecting the temperature at the end of the second fixing roller.
A heat fixing device for a copying machine, characterized in that a heating means and a third heating means are simultaneously controlled, and the second heating means and the fourth heating means are simultaneously controlled by the second temperature detecting means. 2 The surface of the first fixing roller is made of a heat insulating elastic material,
2. The heat fixing device for a copying machine according to claim 1, wherein the surface of the second fixing roller is made of metal. 3. The first heating means and the second heating means are provided outside the first fixing roller, and the third heating means and the fourth heating means are provided inside the second fixing roller. A heat fixing device in a copying machine as described in Section 1.