JPS63155168A - Fixing device - Google Patents

Abstract

PURPOSE:To recover the temperature of a fixing means before the temperature drops until a cold offset or a defect in fixation is caused by switching a set temperature by a control means according to the quantity and size of recording materials to be fixed continuously and controlling a heating means. CONSTITUTION:A desired recording quantity (n sheets) from ten keys 11 and the size of the recording materials 3 to be recorded from a cassette selection key 12 are inputted to a microcomputer 9. The computer 9 calculates roughly the heating value used for the continuous fixation from those values and estimates the drop gradient of the surface temperature of a fixing roller 5 from the relation between the in-use heating value and the heating value of the fixing roller 5 to raise the set temperature A as the turning-on point of a halogen lamp 7 by DELTAt deg. (set temperature D) so that the surface temperature of the fixing roller 5 does not drop to the lowest value B where a defect in fixation occurs at the time of continuous fixing operation, thereby storing it in a memory 13. Then a fixing device 1 performs temperature control according to the new set temperature D. Consequently, the surface temperature of the fixing roller 5 is held stably within a set temperature range.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a fixing device installed in a copying machine or the like using an electrophotographic process.

(Prior Art) Conventionally, this type of fixing device has, for example, a fixing means consisting of a pressure roller and a fixing roller equipped with a halogen lamp inside as a heating means, and a temperature sensor that detects the surface temperature of the fixing roller. A control means comprising a sensor and a microcomputer that inputs a detection signal from the temperature sensor and controls a halogen lamp so that the surface temperature of the fixing roller reaches a predetermined surface temperature set value (set temperature). something is known.

According to the above device, the minimum and maximum values of the surface temperature of the fixing roller are set at temperatures at which the toner image does not cause cold offset or hot offset on the recording material, and the predetermined set temperatures are set at these minimum and maximum values. is set between the values.

Control of the fixing roller surface temperature is performed based on a predetermined set temperature, and when the fixing roller surface temperature becomes lower than the set temperature, a certain amount of power is input to the halogen lamp by the control means, and the fixing roller surface temperature is set to the lowest temperature. Control is performed to raise the value before it drops below 1.

In the above-described temperature control, because of the heat capacity of the fixing roller itself, even if a halogen lamp is turned on to provide heat to the fixing roller, there is a time lag in the rise in the surface temperature of the fixing roller.

Therefore, when performing the fixing operation continuously,
Even if the halogen lamp is turned on because the surface temperature of the fixing roller has fallen below the set temperature, the surface temperature of the fixing roller does not rise immediately, so the heat is taken away by the recording material one after another, and the temperature eventually drops below the minimum value. A situation may arise where this happens.

In this case, reducing the heat capacity of the fixing roller to improve temperature tracking is possible, but there is a limit in securing the mechanical strength to pair with the pressure roller and press the recording material. The width of change in the surface temperature of the fixing roller becomes large and the surface temperature becomes unstable, making it difficult to maintain good fixing performance.

Therefore, in the past, in order to avoid cold offset and poor fixing of toner images, the heat capacity of the fixing roller of a fixing device that performs a large amount of continuous fixing is increased as much as possible, and the surface temperature of the fixing roller is increased. The design was designed to reduce the range of change.

(Problem to be Solved by the Invention) However, increasing the heat capacity of the fixing roller as much as possible not only increases the mass of the fixing roller, but also increases the surface temperature of the fixing roller after the device is turned on. There was a problem in that it took a long time to reach the fixing temperature.

Therefore, the present invention has been made to solve the above-mentioned problems of the conventional technology.The purpose of the present invention is to reduce the mass of the fixing roller, and to fix the fixing roller surface temperature in a short time after turning on the power. In other words, even if a large amount of recording material is continuously fixed using a fixing roller with a small heat capacity, the surface temperature of the fixing roller can be stably maintained within a set temperature range. It is an object of the present invention to provide a fixing device that can sag.

(Means for Solving the Problems) In order to achieve the above object, the present invention includes a heating means, a fixing means for fixing an unfixed image on a recording material by being heated by the heating means, and a fixing means for fixing an unfixed image on a recording material. A fixing device comprising a temperature detection means for detecting the temperature of the means, and a control means for inputting a detection signal from the temperature detection means and controlling the heating means so that the temperature becomes a predetermined set temperature. The control means is configured to switch the predetermined temperature setting based on the number and size of the recording materials when the recording materials are continuously fixed.

(Function) In the present invention having the above configuration, when recording materials are continuously fixed, the control means switches the set temperature based on the number and size of the recording materials, and the control means switches the set temperature based on the switched set temperature. By controlling the heating means, the temperature of the fixing means can be adjusted
to recover before the temperature drops to the point where cold offset or fusing failure occurs.

(Example) The present invention will be explained below based on illustrated embodiments.

FIG. 1 shows an embodiment in which the fixing device of the present invention is applied to an electrophotographic copying machine which is an image recording device. In the figure, l is a fixing device, 2 is a fixing means provided in this fixing device 1, and a fixing roller 5 that applies heat to a recording material 3 and a toner image 4 copied on the recording material 3;
It also includes a pressure roller 6 that presses the recording material 3. Here, the heat capacity of the fixing roller 5 is set to be small, the roller mass is light, and the surface temperature rises to a fixable temperature in a short time after the power is turned on. Reference numeral 7 denotes a halogen lamp as a heating means, which is installed inside the fixing roller 5. Reference numeral 8 denotes a temperature sensor as a temperature detection means, which is disposed on the circumferential surface of the fixing roller 5 and detects the surface temperature of the fixing roller 5.

Also, 9 is a microcomputer as a control means,
Reference numeral 10 denotes an operation panel of the recording device section, which is provided in the recording device section (not shown) and controls the recording device section and the fixing device 1. Numeric keys 11 are used to input the number of sheets to be printed.
and a cassette selection device 2 for selecting a cassette containing recording material 3 of a desired size for recording. 13
is a memory in which a set temperature, which is a set value of the surface temperature of the fixing roller, is stored. 14 is a temperature signal conversion circuit which digitizes the signal from the temperature sensor 8 and sends it to the microcomputer 9.
Send to. Reference numeral 15 denotes a drive circuit which powers on the /\logen lamp 7 in response to a command signal from the microcomputer 9.

Next, the operation of the above embodiment will be explained with reference to FIG. 2, which shows changes in the surface temperature of the fixing roller 5.

In the standby state, when the power is turned on, the /\logen lamp 7 lights up and the surface temperature of the fixing roller 5 rises.

When the microcomputer 9 detects from the signal from the temperature sensor 8 that the surface temperature of the fixing roller 5 exceeds the set temperature A, the microcomputer 9 causes the halogen lamp 7 to '!' A signal to stop the force casting is output to the drive circuit 15 (part a). As a result, the halogen lamp 7 is turned off, but the surface temperature of the fixing roller 5 continues to rise for a while due to its own heat capacity, and then reaches the maximum value C. The temperature stops before the temperature reaches the temperature A, and the temperature continues to decrease. When the temperature reaches the set temperature A (section b), the /\logen lamp 7 is turned on again. In this way, the halogen lamp 7 is turned on based on the set temperature A.

After such a standby state, when fusing is performed on each sheet of recording material 3 at sufficient intervals, that is, when performing the next fusing after the surface temperature that has fallen due to the previous fusing operation has recovered, Even if the temperature is controlled based on the set temperature A, fixing can be performed without any problem.

However, when the toner image 4 is continuously transferred onto a large amount of recording material in the recording device section and then continuously fixed in the fixing device 1, the temperature is controlled at the set temperature A. As shown by the solid line E in FIG. 2, the next fixing operation is performed before the temperature has recovered from the previous fixing operation, which means that the surface temperature of the fixing roller 5 falls below the set temperature A and the halogen Although the lamp 7 is turned on, the heat is taken away by the recording material 3 that is sent next before the surface temperature of the fixing roller 5 rises due to the lighting of the halogen lamp 7.
The surface temperature of (J, K) gradually decreases and finally falls below the lowest value B (J, K).

(text), the fixability of the toner image 4 deteriorates, and after a while, the heat from the halogen lamp 7 is transmitted to the surface of the fixing roller 5, the surface temperature rises, and the fixability is restored.

This situation cannot occur completely even if the heat capacity of the fixing roller 5 is reduced (there is a limit to ensuring mechanical strength for pressurizing the recording material 3) and temperature followability is improved. It cannot be avoided.

Therefore, in the embodiment of the present invention, in order to avoid the above situation, temperature control is performed as follows. That is, when the desired number of sheets to be recorded (n sheets) from Tengyu-11 and the size of the recording material 3 desired to be recorded are inputted to the microcomputer 9 from the cassette selection key 12, the computer 9 enters the desired number of sheets to be recorded (n sheets). and the recording material you wish to record 3
, calculate the approximate amount of heat used during continuous fixing, estimate the downward slope of the surface temperature of the fixing roller 5 from the relationship between the calculated amount of heat used and the heat capacity of the fixing roller 5, In order to prevent the surface temperature of the fixing roller 5 from dropping to the lowest value B that causes fixing failure during operation, the set temperature A, which is the lighting point of the rogen lamp 7, is increased by Δ degrees (set temperature D), and this temperature is stored in the memory 1.
3. When the new set temperature is stored in the memory 13, the fixing device l performs temperature control based on the new set temperature 1fD.

In this way, if the surface temperature of the fixing roller 5 is kept high to compensate for the amount taken by the recording material 3, as shown by the broken line F in FIG. 2, even during continuous fixing operation, The surface temperature of the fixing roller 5 is maintained within a temperature range that provides good fixing.

Here, if the last recording material 3 (nth sheet) in the continuous fixing operation is kept at the set temperature until it is fixed, the surface temperature of the fixing roller 5 will rise after the last recording material 3 is ejected from the fixing device 1. Since this overshoots the maximum value C, the microcomputer 9 switches the set temperature in the memory 13 to the set temperature A for fixing one sheet from the end of the continuous fixing operation to before the fixation.

In the above embodiment, the halogen lamp 7 is used as a heating means, and the halogen lamp 7 is installed inside the fixing roller 5 to heat the fixing roller 5. The present invention is not limited to this, and various embodiments are possible.

In addition, a table is prepared in which the set temperature calculated by multiplying the number of sheets to be recorded (number of sheets to be fixed) and the size of the recording material 3 is stored corresponding to the number of sheets to be recorded (number of sheets to be fixed) for each size of recording material 3. Then, when the number of sheets to be recorded (the number of sheets to be fixed) and the size are instructed, the microcomputer 9 may select the set temperature from the table.

(Effects of the Invention) The present invention has the above-described structure and operation, and even if a fixing operation is performed continuously using a fixing means with a small heat capacity, the 5L degree of the fixing means is stable, so good fixing performance can be achieved. Therefore, it is possible to reduce the mass of the fixing means, and the temperature can be brought to the fixing rotation temperature in a short time after the power is turned on.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, and FIG. 1 shows a block [4] showing a state in which the fixing device of the present invention is applied to an electrophotographic copying machine, which is an image recording device, and FIG. 3 is a graph showing changes in surface temperature of . Explanation of symbols 1... Fixing device 2... Fixing means 3...
Recording material 4... Toner image 5... Fixing roller 7... Heating means (halogen lamp) 8... Temperature sensor 9... Control means (microcomputer) 11...
Numeric keypad 12...Cassette selection key 13 Repair pot memory

Claims (1)

[Claims] a heating means; a fixing means heated by the heating means to fix an unfixed image on a recording material; a temperature detection means for detecting the temperature of the fixing means; In a fixing device comprising a control means for controlling the heating means so that the temperature becomes a predetermined set temperature, when recording materials are continuously fixed, the above-mentioned control means is set based on the number and size of the recording materials. A fixing device characterized in that the control means is configured to switch a predetermined set temperature.