JPH0844242A - Fixing device - Google Patents

Abstract

PURPOSE:To provide a fixing device constituted so that a heater is not fed at a time other than a recording time and a waiting time is shortened and fixation is stabilized by stabilizing the temperature of a pressure roller. CONSTITUTION:The fixing device is constituted so that an image is formed by an electrophotographic process and toner on a recording material is fixed by pressure and heat. Besides, it is provided with a heating body 1, a body to be heated 2 heated by the heating body 1, the pressure roller 3 which forms a nip part 6 together with the body to be heated 2 and interposes and carries the recording material and which is not provided with the heat generation body inside, a temperature detection means 4 for controlling the temperature of the heating body 1 and a temperature detection means 9 detecting the temperature of the roller 3. Then, when a recording action is instructed to be executed or the temperature of the roller 3 becomes equal to or under the set temperature, the heating body 1 is fed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a copying machine, a printer,
The present invention relates to a fixing device which is used in an image forming apparatus such as a facsimile and heat-fixes an unfixed image on a recording material such as recording paper.

[0002]

2. Description of the Related Art Conventionally, a fixing device of this type is known as shown in FIG. In FIG. 4 showing a cross-sectional view of this fixing device, 1 is a halogen heater which is a heating body, and 2 is a fixing roller made of aluminum which is a heated body which forms a nip with the pressure roller 3 by the heat of the halogen heater. .

In this fixing device, the halogen heater 1 is not energized and the fixing roller 2 is not heated except when a print command is issued. Then, the thickness of the aluminum tube of the fixing roller 2, which is the object to be heated, is made as thin as possible so that the fixing can be carried out instantly when a print command is given, so that the heat capacity becomes low. In fact, in this conventional example, the wall thickness t is about 1 mm.

On the surface of the fixing roller 2, the thermistor 4 which is a temperature detecting means for detecting the temperature of the roller.
Are in contact.

Next, a case where a print command is actually issued will be described. As shown in FIG. 5, when a print command is issued, the halogen heater 1 as a heating body is energized to heat the fixing roller 2 as a heated body while rotating. The surface temperature of the fixing roller 2 is detected by the thermistor 4 and heated to a predetermined temperature (180 ° C.).
At that time, since the main motor is rotating at the same time as the energization, the pressure roller 3 is heated by the fixing roller 2 while rotating.

Now, the output signal of the thermistor 4 is 180 ° C.
When it is notified that the surface temperature of the fixing roller 2 has reached 18
The heater is ON / OFF controlled so as to maintain 0 ° C., and at the same time, the recording material is conveyed and undergoes a developing / transferring process (not shown), and is guided to the nip portion 6 by the inlet guide 5 where it is heated and fixed. After fixing, the paper is guided to the paper discharge roller 8 by the paper discharge guide 7 and discharged outside the apparatus.

[0007]

However, in the above-mentioned conventional example, since the heater is not energized (on demand) except when there is a recording command, fixing can be performed by cooling the fixing device. The time (time to reach 180 ° C .: weight time) was not constant. In particular, in the first part of the winter morning, the fixing device is in a very cold state, and even if the user tries to record and output, there is a problem in that it is difficult to output.

Further, as another problem, when a recording command is issued and the heater is turned on, the fixing roller 2 is usually made of a metal having a high thermal conductivity such as aluminum, so that the temperature rises relatively quickly by the halogen heater 1. However, since the pressure roller 3 is generally made of a material such as silicone rubber and has a low thermal conductivity and a large heat capacity, the temperature rises slowly. Therefore, even if the thermistor 4 outputs a signal indicating that fixing is possible at 180 ° C., the halogen heater 1 is turned on.
Depending on the temperature of the pressure roller 3 immediately before setting to N, a difference occurs in the temperature of the pressure roller when fixing is possible.

That is, at the beginning of winter morning, the pressure roller is in a cold state, the heater is turned on, and the fixing roller 2 is set at 18
Even when the temperature reaches 0 ° C., the temperature of the pressure roller 3 does not rise so much because the temperature rises slowly. On the contrary, immediately after continuous printing, the pressure roller 3 is sufficiently warm,
Also, since it cools slowly, the pressure roller remains sufficiently warm even when printed again.

As described above, even in the same fixing possible state, there is a difference in the temperature of the pressure roller 3 between the morning and immediately after continuous printing, and as a result, the temperature of the nip portion 6 is not stable and the fixing is performed. There was a problem that defects occurred.

According to the present invention, in a fixing device in which the heater is not energized except during recording, the temperature of the pressure roller is stabilized to shorten the wait time and stabilize the fixability. The purpose of.

Further, the present invention reduces the energization time of the heater by conducting the energization of the heater except at the time of recording only when the temperature of the pressure roller is detected and the temperature falls below room temperature. The second purpose is to reduce power consumption.

Further, according to the present invention, by using a ceramic heater in a fixing device for directly heating the nip portion through a thin film, the weight time can be shortened and the fixing stability can be further improved. The purpose of.

[0014]

According to the present invention, the first object is to form an image by an electrophotographic process,
In a fixing device for fixing toner on a recording material by pressure and heat, a heating body and a heated body heated by the heating body and a nip with the heated body are formed to nip and convey the recording material, and heat is generated inside. A pressure roller having no body, a temperature detection means for controlling the temperature of the heating body, and a temperature detection means for detecting the temperature of the pressure roller are provided, and when a recording command is issued or the pressure roller is used. This is achieved by the first invention, in which the heating element is energized when the temperature becomes below the set temperature.

The second object is achieved by the second invention in which the temperature of the pressure roller for energization is 40 ° C. or lower.

A third object is to have a ceramic heater as a heating body, a holding member for holding the ceramic heater, and an endless belt-shaped film as a heated body, and press the ceramic heater and pressure. This is achieved by the third invention in which the roller forms the nip directly through the film.

[0017]

In the first aspect of the invention, the heater is normally turned off except when a recording command is issued, but when the temperature of the pressure roller falls below a certain temperature, the pressure roller is warmed up. Is preheated. In this way, the temperature of the pressure roller is maintained above a certain set temperature to prevent defective fixing,
The wait time is shortened.

In the second aspect of the invention, in the fixing device described above, the temperature of the pressure roller to be energized is set to around room temperature or lower to prevent the pressure roller from being preheated at all times, and the temperature of the morning of winter is reduced. The heating is performed only when the temperature of the number is extremely low. This reduces power consumption.

According to a third aspect of the invention, in the above fixing device, the fixing roller is different from the aluminum roller type fixing roller.
The weight time is shortened because the temperature of the heating element rises quickly and the heat transfer efficiency is good.

[0020]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

(First Embodiment) FIG. 1 shows an embodiment of the present invention. In FIG. 1, the same members as those of the conventional example shown in FIG.

In the present embodiment, a thermistor 9 is provided so as to come into pressure contact with the pressure roller 3.

As shown in the flow chart of FIG. 2, in this embodiment, when recording is not performed, the heater is turned off.
When recording, in the present invention, the temperature is detected by the thermistor 9 provided on the pressure roller 3, and when the temperature of the pressure roller 3 becomes 20 ° C. or less, the pressure roller is too cold. Judge and turn on the heater to warm the pressure roller. At this time, the main motor is rotated to prevent temperature unevenness.

Heating is continued as it is, and the pressure roller 3 is heated to 80.degree.
When it reaches, the heater is turned off, heating is stopped, and the main motor is stopped. By performing such control, the temperature of the pressure roller is stabilized, and even if a sudden recording need occurs as a recording means of a facsimile, for example, it is possible to prevent the pressure roller 3 from being too cold in the winter morning. , The fixing property is stable, and the wait time is shortened.

(Second Embodiment) In the first embodiment, the preheating temperature of the pressure roller 3 is set to 30 ° C., but it may be higher or lower.

However, if the pressure roller is set to be preheated at a temperature higher than room temperature, the preheating time (for example, at 50 ° C. or 60 ° C.) increases,
Power consumption is wasted, and the meaning of the configuration in which the heater is not turned on except when recording is diminished.

Therefore, the preheating of the pressure roller does not operate at room temperature, for example, 10 to 40 ° C., but if it is operated only in a cold place, for example, at 10 ° C. or less in the first winter morning, power consumption is reduced. There is almost no loss, and the fixability is stable.

(Third Embodiment) In the first embodiment, a thin aluminum fixing roller is used.
In the present embodiment shown in FIG.
0, the thermistor 14 as a temperature detecting means is adhered to the back surface of the heater 10, and the heater 10 is held by a heater holder 11 as a holding member. Further, 13 is a film made of PI having a thickness of about 60 μm, which forms a nip so as to be sandwiched between the pressure roller 3 and the heater 10.

Reference numeral 12 is a guide stay of a guide member for guiding the rotation of the film.

In this embodiment, the ceramic heater 10 as a heating element has a lower heat capacity than the thin roller of the first embodiment, and further heats the nip portion 6 directly through the PI film of only 60 μm. Therefore, there is an advantage that the wait time for fixing can be short. However, on the contrary, the difference between the temperature rising rate of the heating element and the temperature rising rate of the pressure roller 3 becomes larger, and as a result, the influence of the initial temperature of the pressure roller 3 becomes larger as described above.

In the case of the fixing device as shown in this embodiment, the preheating of the pressure roller becomes particularly effective, the fixing property becomes stable, and the waiting time, which is a characteristic of the original fixing device, is further reduced. Can be improved.

In the first embodiment, the thermistor is used as the temperature detecting means for the pressure roller, but the ambient temperature may be measured, for example, without directly contacting the pressure roller. When the thermistor directly contacts the pressure roller,
Although the temperature accuracy to be controlled is naturally good, there is a problem that dirt such as toner adheres. Therefore, for example, the temperature in the vicinity of the device is used as a substitute, and the heating time is appropriately set to be OFF. Good.

The temperature detecting means may of course be replaced by a heater thermistor. For example, the heater is heated at a constant wattage for a fixed period of time, the cooling degree of the pressure roller is predicted by the degree of temperature rise at that time, and the pressure roller is heated according to the result. Good. In this case, the accuracy is lowered, but the thermistor is not required, and the cost can be reduced.

Furthermore, if recording is not performed for a certain period of time, it may be determined that the pressure roller is in a cold state, and heating may be performed for a certain period of time. In this case as well, the temperature accuracy is reduced, but the pressure roller thermistor is not required,
The cost can be reduced.

That is, a means for judging the temperature of the pressure roller is provided, and the preheating may be carried out based on the judgment.

[0036]

As described above, the first aspect of the present application
According to the invention, in the fixing device in which the heater is turned off except during recording, the pressure roller is preheated when the temperature of the pressure roller becomes equal to or lower than a certain temperature.
The temperature of the nip portion is stable and the fixing property is improved, and at the same time, the wait time can be shortened.

According to the second invention of the present application,
Since it was decided to preheat the pressure roller only when the temperature was around room temperature or below, it is possible to prevent wasteful heating by not operating the heating roller normally and only when it is cold. Power consumption can be reduced.

According to the third invention of the present application,
Since the pressure roller according to the present invention is preheated to the fixing device that directly heats the nip portion through the film by using the ceramic heater as a heating body, the weight time is shortened and the fixing property is further improved. It can be done effectively.

[Brief description of drawings]

FIG. 1 is a sectional view of a first embodiment of the present invention.

FIG. 2 is a flowchart of the apparatus shown in FIG.

FIG. 3 is a cross-sectional view of a third embodiment.

FIG. 4 is a cross-sectional view of a conventional device.

5 is a flowchart in the conventional apparatus shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Heated body (halogen heater) 2 Heated body (aluminum fixing roller) 3 Pressure roller 4 Temperature detection means (thermistor) 6 Nip 9 Pressure roller temperature detection means 10 Heating body (ceramic heater) 11 Holding member (heater holder) 13 Film 14 Temperature detection means (thermistor)

Claims (3)

[Claims] 1. A fixing device for forming an image by an electrophotographic process and fixing toner on a recording material by pressure and heat, a heating body, a heated body heated by the heating body, and the heated body. A pressure roller that forms a nip to nip and convey the recording material and does not have a heating element therein; a temperature detecting means for controlling the temperature of the heating element; and a temperature detecting means for detecting the temperature of the pressure roller. A fixing device comprising: a heating member that is energized when a recording command is issued or when the temperature of the pressure roller falls below a set temperature. 2. The temperature of the pressure roller for energizing is 40 ° C.
The fixing device according to claim 1, wherein: 3. A ceramic heater as a heating body, a holding member for holding the ceramic heater, and an endless belt-shaped film as a heated body, wherein the ceramic heater and the pressure roller are provided with a film therebetween. The fixing device according to claim 1, wherein the nip is directly formed.