JPS60150075A - Temperature controller of fixing device - Google Patents

Abstract

PURPOSE:To prevent a failure in fixation due to the temperature drop of a press-contacting roller by switching a control system and controlling the heat source of a heat roller on the basis of the detected temperature of the heat roller when copying operation is not performed and the detected temperature of the press-contacting roller when copying operation is carried out. CONSTITUTION:The detected temperature of the heat roller 1 from a temperature sensor 2 is compared with the set temperature of a temperature setter 3 to bring the heat source 1a of the roller 1 under feedback control when a switch circuit 20 selects a contact (a) by a paper discharge state detection sensor 22, i.e. in noncopying mode. The circuit 20 is switched with a copy start button 21 in copying mode and the detected temperature of the pressure-contacting roller 5 from a temperature sensor 10 is compared with the set temperature of a temperature setter 11 by a comparator 12 to control the heat source 1a. This constitution prevents a failure in fixation due to the temperature drop of the press-contacting roller.

Description

[Detailed description of the invention] [Field of industrial application] This invention detects the temperature of a heat roller and controls the heat source when not copying, and detects the temperature of the pressure roller and controls the heat source when copying. The present invention relates to a temperature control device for a fixing device.

[Conventional technology]

In order to perform stable fixing in a heat roller type fixing device generally used as a fixing device in a copying machine, the temperature of a heat roller 1 having a built-in heater 1a is detected by a temperature sensor 2, as shown in FIG. Then, a comparator 4 compares the temperature of the heat roller 1 and the temperature set by the temperature setting device 3, and if the temperature of the heat roller (2) is high, the heater 1a is turned off.

When the temperature is low, the temperature of the maturing roller 1 is kept constant by turning it on. In this case, since the pressure roller 5 receives heat conduction through the contact portion with the heat roller 1, it is at the same temperature as the heat roller 1 when no transfer paper passes through it.

When the transfer paper 6 conveyed from the developing process passes between both rollers in this state, heat is removed by the transfer paper, and the heat roller 1. The temperature of the pressure roller 5 drops rapidly.

A decrease in the temperature of the heat roller 1 is detected by the sensor 2, and the heater 1a is activated to immediately heat the heat roller 1, so that the heat roller 1 immediately returns to the set temperature.

However, the temperature of the pressure roller 5 does not immediately follow the temperature of the heat roller 1, and especially in the case of continuous copying, the time during which the heat roller and the pressure roller are in contact becomes shorter, so that the temperature of the heat roller 1 does not reach the set temperature. However, the temperature of the pressure roller 5 remains lower than the set temperature, and there is a possibility that fixing failure may occur due to the temperature drop of the pressure roller 5.

[Purpose of the invention]

This invention was made to eliminate the above drawbacks.
It is an object of the present invention to provide a temperature control device for a fixing device that prevents fixing failure due to a drop in temperature of a pressure roller.

[Structure of the invention]

This invention includes a first control system for controlling the heat source of the heat roller by detecting the temperature of the heat roller by a sensor, and a second control system for controlling the heat source of the heat roller by detecting the temperature of the pressure roller by a sensor. control system, and the heat source is controlled by the first control system during non-copying and by the second control system during copying. By providing a switching circuit for switching the second control system.

Even in the case of continuous copying, the heat source of the heat roller is kept at a temperature higher than a set temperature so that the temperature of the pressure roller does not drop, thereby achieving the above object.

〔Example〕

Next, the present invention will be explained based on embodiments shown in the drawings from FIG. 2 onwards.

FIG. 2 is a block diagram showing an example of the present invention, in which 1 is a heat roller, 2 is a temperature sensor, 3 is a temperature setting device 24 is a comparator, and 5 is a pressure roller, which are different from those shown in the conventional example. It's not different.

Since the heat roller 1 is in direct contact with the surface of the transferred image, a non-contact type sensor that does not damage the surface of the heat roller 1 and has a quick response (for example, a thermistor) is used as the temperature sensor 2.

A temperature sensor 10 detects the temperature of the pressure roller 5. As the temperature sensor 10, since the pressure roller 5 comes into contact with the back surface of the transfer paper, a contact type sensor (for example, a thermocouple) can be used satisfactorily. Of course, it is also possible to use a non-contact type sensor.

11 is a temperature setting device, and 12 is a comparator. The comparator 12 compares the temperature detected by the temperature sensor 10 and the set temperature of the temperature setter 11, and if the detected temperature is higher than the set temperature, it outputs a F signal to the heater la, and if it is lower, it outputs a F signal to the heater la. It outputs an ON signal to the comparator 4, and has the same configuration as the comparator 4 described above. The temperature set by the temperature setting device 11 is the same as or higher than the temperature set by the temperature setting device 3.

Reference numeral 20 denotes a switching circuit for switching the input terminal C of the heater 1a of the heat roller 1 to either the output terminal a of the comparator 3 or the output terminal of the comparator 11. The switching circuit 20 connects contacts A and C when the copying machine is powered on, but switches to the contact side in response to a signal from the copy start button 21 and connects contact C when the switching circuit 20 makes contact. The contact is switched to the contact a side again in response to a signal from the paper discharge state detection sensor 22. The paper discharge state detection sensor 22 detects the transfer paper after passing through the fixing device.

Next, the operation of the temperature control device configured as described above will be explained. First, when the copying machine is powered on, the switching circuit 20 connects the contact a and the contact C, so the heat roller 1
The sensor 2 detects the temperature, and the comparator 4 compares the detected temperature with a set temperature. When the detected temperature is low, the heater 1a is activated and the temperature of the heat roller 1 increases. When the temperature of the heat roller 1 reaches the set temperature, the heater 1a turns on.
The set temperature will be maintained from then on. On the other hand, the pressure roller 5
receives heat conduction from the heat roller 1 through the contact portion, and is at the same temperature as the heat roller 1.

Next, when the copy start button 2 is pressed, the contact of the switching circuit 20 is switched, and the contact and the contact C are connected. Therefore,
From this point on, the heater 1a is controlled to be turned on or off depending on the temperature of the pressure roller 5.

After exposure and development are completed, the transfer paper 6 is conveyed to a fixing device.

When the transfer paper is sandwiched between the heat roller 1 and the pressure roller 5,
Heat is removed by the transfer paper 6, and the temperature of both rollers drops rapidly. The temperature drop of the pressure roller 5 is detected by the sensor 10, and the heater 1a is set to 0IIL via the comparator 12.
, the heat roller 1 is heated. Even when the temperature of the heat roller 1 reaches the set temperature, the heat roller 1 continues to be heated until the temperature of the pressure roller 5 reaches the set temperature. This can prevent the pressure roller 5 from decreasing in temperature.

When the transfer paper 6 passes through the fixing device and reaches the paper discharge state detection sensor 22, the end of copying is detected, the contacts of the switching circuit 20 are switched, contacts A and C are connected, and the heater 1a is heated again. It will be controlled by the temperature of the roller 1.

Note that when performing continuous copying, the above operation is repeated continuously, but even if the contact time between the heat roller 1 and the pressure roller 5 is short, the heat roller 1 is heated above the set temperature. The pressure roller 5 can be maintained at a set temperature.

FIG. 3 shows a modification of this invention.

The switching circuit 20 is composed of interlocking switches Sl and 32, and the temperature setting device 3 and the sensor 2. Temperature setting device 11 and 1! 10 and 10 at the same time,
(or 12) minus the number. This has the advantage of eliminating differences in control characteristics due to variations in comparator characteristics.

FIG. 4 is a specific circuit configuration diagram of the example shown in FIG. 3. In the figure, 30 indicates a thermistor for detecting the temperature of the heat roller 1, and 40 indicates a thermocouple for detecting the temperature of the pressure roller 4. 31°, 32.4.1.42 are temperature setting resistors, which correspond to temperature setting devices 3.11, respectively. Sl
, S2 indicates an interlocking switch, and an operational amplifier 50 corresponding to the switching circuit 20 constitutes a comparator.

Note that 33, 43, and 44 are bias resistors.

45 is a room temperature compensation element, and 51 is a feedback resistor.

In the above circuit, when the switch 5LS2 is located at the upper contact point, the voltage across the thermistor 30 and the voltage across the resistor 32 are compared, and if the voltage across the thermistor 30 is large (that is, the temperature of the heat roller 1 is If the value is lower than the set value), an output is generated from the amplifier 50 and the heater 1a is turned on.

When the switch S1°S2 is switched to the lower contact by the signal from the copy start button, the voltage across the thermocouple 40 and the room temperature compensation element 45 is compared with the voltage across the resistor 42,
If the former is large, an output is generated from the operational amplifier 50 and the heater 1a is turned on.

In the first embodiment, the switching of the switching circuit 20 during copying is performed by a signal from the copying start button.
There is no need to limit it to this, and the case has been described in which the switching during non-copying in the switching circuit 20 is performed by the signal of the paper discharge state detection sensor, but in the case of continuous copying, the pressure roller side is continuously switched until the end of continuous copying. The heater may be controlled by a temperature detection sensor.

〔Effect of the invention〕

As described above, the fixing device temperature control device according to the present invention includes a first control system for detecting the temperature of the heat roller using a sensor and controlling the heat source of the heat roller, and a first control system for controlling the heat source of the heat roller by detecting the temperature of the heat roller using a sensor. a second control system for detecting and controlling the heat source of the heat roller; and a first control system for controlling the heat source by the first control system during non-copying and by the second control system during copying. Since the present invention is characterized in that it includes a switching circuit for switching the second control system, even when continuous copying is performed.

The temperature of the pressure roller can be maintained at the set temperature. Therefore, the excellent effect of being able to prevent fixing failures caused by a drop in the temperature of the pressure roller is achieved.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a conventional example, FIGS. 2 to 4 show a temperature control device for a fixing device according to the present invention, FIG. 2 is a block diagram thereof, and FIG. 3 is a block diagram of a modified example. FIG. 4 is a specific circuit diagram of FIG. 3. 1°-・Heat roller 2, 10-Temperature sensor 3.11-
- Temperature setter 4, 12 - Comparator 5 - Pressure roller 6 - Transfer paper 20/all switching circuit 21 - Copy start button 22 - Paper discharge state detection sensor Fig. 1 Fig. 2 Fig. 3 Fig. 4 figure

Claims (1)

[Claims] (11B A first control system for detecting the temperature of the roller by a sensor and controlling the heat source of the heat roller; and a first control system for detecting the temperature of the pressure roller by a sensor and controlling the heat source of the heat roller. and a switching circuit that switches the first and second control systems so that the heat source is controlled by the first control system during non-copying and by the second control system during copying. A temperature control device for a fixing device, characterized in that: (2) The temperature detection sensor of the heat roller is a non-contact type, and the temperature detection sensor of the pressure roller is a contact type sensor. (3) The temperature control device for a fixing device according to claim 1 or 2, wherein switching of the control system by the switching circuit is performed by outputting a copy start button. (4) A temperature control device for a fixing device according to any one of claims 1 to 3, wherein switching of the control system by the switching circuit is performed by an output of a paper discharge state detection sensor.