JPH04288579A - Heat roller fixation device - Google Patents

Abstract

PURPOSE:To provide the heat roller fixation device equipped with a protecting means which detects abnormal temperature by two temperature sensors previously and maintains safety at all times so that respective parts are not broken owing to the abnormal high temperature while the temperature sensor for temperature control does not function. CONSTITUTION:The 1st temperature sensor 3A is installed in a paper passage area on the peripheral surface of a heat roller 1 and the 2nd temperature sensor 3B is installed outside the paper passage area; and the settings of the temperature detection levels of the respective temperature sensors are varied corresponding to the temperature distribution of the heat roller which varies in a warm-up or with the size of used paper, and control is performed by detecting the abnormal temperature, thereby obtaining the heat roller fixation device equipped with the protecting function.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat roller fixing device used in an electrophotographic image recording apparatus for melting and fixing a toner image on a transfer material.

0002

2. Description of the Related Art A heat roller fixing device for an image recording apparatus such as a copying machine is known, for example, from Japanese Patent Application Laid-Open No. 55-81378.

[0003] The heat roller for fixing has a surface thickness of 20 μm to 60 μm.
Wall thickness 4mm to 5m coated with μm Teflon, etc.
It consists of a roller made of aluminum and has a heating element such as an infrared lamp (halogen heater) installed inside. Further, the circumferential surface of the heat roller is in contact with, or in a state close to, the recording paper insertion and ejection guide, separation claw, toner cleaning web, its pressing roller, and the like. A pressure roller is provided between the heat roller and the pressure roller for sandwiching and passing the recording paper, and is usually made of silicone rubber or coated with silicone rubber. Further, a temperature sensor is installed on the circumferential surface of the heat roller to detect the surface temperature, such as a thermocouple or a thermistor.

The recording paper on which the toner image has been formed is continuously inserted between a heat roller and a pressure roller, and is held and held while receiving heat.
Pressurized. As a result, the toner is fused to the recording paper surface and fixed. The toner is fixed in this way, but in order to keep the surface temperature of the heat roller constant and to detect abnormal temperature conditions, the surface temperature of the heat roller is detected by a temperature sensor and controlled by an electrical signal. There is.

However, if the temperature does not rise even after a predetermined period of time has passed, or if the temperature suddenly rises because the control does not work, an abnormal situation may occur, and thermal fuses and thermostats are always on hand to prevent danger. If this happens, there is a method that shuts off the power. In addition, the ready state may not be reached within the specified time, the temperature may not change even when the infrared lamp is energized, or the sensor signal may not be output correctly even though the control command is to turn on the infrared lamp. In order to deal with abnormal conditions, there is also a method of cutting off the power depending on the detection level of the temperature sensor. Furthermore, there is a method in which two temperature sensors are provided so that even if the first temperature sensor fails, the second temperature sensor detects abnormal temperature and safely takes measures.

[0006]

[Problems to be Solved by the Invention] Countermeasures against abnormalities in thermal fixing devices have been taken as described above, but thermal fuses and thermostats have poor thermal response, and if the thermal roller goes out of control from a cold state, it can cause a fire. Although the worst situation can be avoided, cleaning rollers, separation claws, etc. that are in contact with the heat roller become unusable due to the abnormally high temperature (290° C.). Furthermore, in the case of the detection level of the temperature sensor or the method using two temperature sensors, if the temperature sensor itself malfunctions due to poor contact, etc., the abnormal temperature detection function will not work. All of these methods have problems such as the abnormal temperature detection function not working if recording paper, cleaning web, etc. get wrapped around the roller, or if these parts get stuck between the temperature sensor and the roller. .

[0007]

[Means for Solving the Problems] It is an object of the present invention to eliminate these problems, to ensure that toner images are always stably fixed by a heat roller, and to provide a protective function for safely functioning a heat fixing device. An object of the present invention is to provide a fixing device with the following features.

The present invention achieves the above object by providing a first temperature sensor that comes into contact with the paper passing area of the heat roller to control temperature and detect abnormal temperature, and also includes a first temperature sensor that comes into contact with the outside of the paper passing area to detect abnormal temperature. The heat roller fixing device is provided with a second temperature sensor that performs detection, and during warm-up and idling, the abnormal temperature detection level of the first temperature sensor is set higher than the abnormal temperature detection level of the second temperature sensor. , when passing paper, the abnormal temperature detection level of the first temperature sensor is set lower than the abnormal temperature detection level of the second temperature sensor, and when fixing the maximum width size of paper passing, the abnormal temperature of the first temperature sensor is set to be lower than the abnormal temperature detection level of the second temperature sensor. When setting the detection level to a temperature higher than or equal to the abnormal temperature detection level of the second temperature sensor, and fixing a size smaller than the maximum paper passing width,
This is achieved by a heat roller fixing device characterized in that the abnormal temperature detection level of the first temperature sensor is set to a lower temperature than the abnormal temperature detection level of the second temperature sensor.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the heat roller fixing device of the present invention will be described below with reference to FIG.

First, an outline of the steps up to the fixing device in a copying machine is that an image is exposed on the photoconductive surface of a charged photosensitive drum (image carrier) to form an electrostatic latent image of the original image. This electrostatic latent image is developed to form a toner image,
The toner image is transferred onto transfer paper (recording paper). The recording paper onto which the toner image has been transferred is separated from the photoreceptor drum, conveyed, further thermally fixed by the heat roller fixing device according to the present invention, and discharged outside the machine.

Reference numeral 1 denotes a heat roller, and a heating element 2 such as a halogen heater is disposed inside the heat roller 1. A pressure roller 4 is provided below the heat roller 1 as an opposing roller and is pressed against the heat roller 1. By passing the recording paper P having the toner image between the pair of rollers in the direction of arrow A with the toner image directed toward the heat roller 1 side,
The toner image on the recording paper P is fixed.

The heat roller 1 is made of a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA) with a thickness of about 30 μm on the outside of a pipe-shaped metal core.
The roller is covered with a tube and has an outer diameter of about 60 mm.

The heating element 2 built into the roller 1 is
Approximately 1500W and approximately 60W located approximately in the center of heat roller 1
It is a 0W heater. As shown in FIG. 2, a first temperature sensor 3A is installed close to the circumferential surface of the central portion of the heat roller 1, and a second temperature sensor 3B is installed close to the circumferential surface of the heat roller 1 outside the paper passing area. is installed. By temperature detection by the temperature sensors 3A and 3B, the peripheral surface temperature of the heat roller 1 is controlled to be maintained at around 200° C. during copying, and abnormal temperature detection, which will be described later, is performed.

A wound cleaning web 12 is disposed above the circumferential surface of the heat roller 1, and is made of nonwoven fabric or the like. Then, the cleaning web passes through a cleaning web pressing roller 13 and is wound up by a winding roller 14. Then, the cleaning web 12 is pressed against the circumferential surface of the heat roller 1 by the elasticity of the web pressing roller 13, and the adhered toner is transferred onto the cleaning web 12, thereby performing cleaning.

The pressure roller 4 is a roller having a pipe-shaped metal core coated with a silicone resin having a thickness of 5 mm on the outside, and further provided with a perfluoroalkoxyfluorinated ethylene resin layer on top of the silicone resin. On the other hand, it is pressed from directly below and rotates counterclockwise.

A recording paper P with a toner image transferred onto its upper surface is moved toward the pressure contact portion between the heat roller 1 and the pressure roller 4.
It is carried in in the direction of arrow A under the guidance of insertion guide members 5A and 5B. The recording paper P is held between the pressure contact portions of the rollers 1 and 4 and conveyed in the direction of arrow B. At this time, recording paper P
The upper toner is heated by a heating element 2 built into the heat roller 1.
It is melted by the amount of heat generated and fixed on the recording paper P. The recording paper P with the toner image fixed thereon is transported by both the rollers 1 and 4.
It is carried out from the pressure contact part, separated from the circumferential surfaces of both rollers by separation claws 6A and 6B, and discharged in the direction of arrow B (outward) by discharge rollers 8A and 8B.

Generally, when the power is turned on to the copying machine, the heat roller 1 starts to be heated and rotates, the temperature rises, and a warm-up is performed until it reaches the fixing temperature (about 200° C.). As shown in FIG. 3, the heat roller 1 has various heat distributions depending on the state.

The temperature distribution of the heat roller 1 immediately after the warm-up is such that heat is diffused from the ends of the heat roller 1, so the temperature at the ends is lower than the temperature at the center, and the temperature distribution is as shown in C1 in FIG. distribution.

Next, when recording paper P of a relatively small size is passed continuously to fix copies, the recording paper P that passes takes away heat, so the heat roller 1 has a heat distribution in which the temperature at the center is lower than the temperature at the ends. Further, when fixing a large-sized recording paper P (passing paper), the heat distribution is such that the temperature is maintained at a substantially constant temperature as shown in C3 in FIG. It is now assumed that the temperature detection levels of the first and second temperature sensors 3A and 3B are set so that the heat roller 1 reaches a normal fixing temperature (for example, 200° C.). Assume that the first temperature sensor 3A malfunctions due to the recording paper P or the cleaning web 12 being wrapped around the roller and does not detect the temperature. Then, for example, the second temperature sensor 3B has some temperature inertia and reaches 240°C at the end of the heat roller 1.
If the abnormal temperature was detected and controlled, the temperature at the center of the heat roller 1 would be quite high (29
When the temperature reaches about 0°C, the pressure roller 4, separation claws 6A, 6B,
The cleaning web 12 etc. will be damaged.

As described above, the present invention provides the first temperature sensor 3A.
is installed at the center of the heat roller 1, and the second temperature sensor 3B is installed at the end outside the paper passing range, so that the detection level (set temperature) of each temperature sensor can be changed depending on the state.

During warm-up or idling, the set temperature of the first temperature sensor 3A is set higher than the set temperature of the second temperature sensor in order to detect abnormal temperatures. For example, the set temperature of the first temperature sensor 3A is set to 240°C, and the set temperature of the second temperature sensor 3B is set to 200°C. This way,
Even if the first temperature sensor 3A fails, the second temperature sensor 3B detects and controls the temperature at the end of the heat roller 1 (200°C), so the temperature at the center will not rise to a significantly high temperature, at most 240°C. The temperature is about 250°C, and safety is maintained without damaging any parts. Furthermore, even if the second temperature sensor 3B fails, the first temperature sensor detects and controls the temperature at the center (240° C.), so it is safe.

Further, during copying, that is, when fixing the recording paper P, the set temperature of the first temperature sensor 3A is set lower than the set temperature of the second sensor 3B. For example, the set temperature of the first temperature sensor 3A is 240°C, and the set temperature of the second temperature sensor 3B is 260°C.
Set to 0℃. In this way, even if one of the temperature sensors 3A, 3B breaks down, abnormal temperature will be detected at a maximum of about 260° C., making it safe. This will prevent damage to various parts due to abnormal temperatures.

Another method, as shown in FIG. 3, is that the heat distribution of the heat roller 1 changes depending on the size of the recording paper, so the set temperatures of the temperature sensors 3A and 3B are changed in accordance with this heat distribution to prevent abnormal temperatures. It is a method of detection and control.

That is, as shown in FIG. 3, when using the recording paper P whose size (width) is the largest, the set temperature of the first temperature sensor 3A is higher than the set temperature of the second temperature sensor 3B. or equal to. For example, in the case of A3 size (maximum size), set temperature of first temperature sensor 3A to 2.
40℃, the setting temperature of the second temperature sensor 3B is 250℃~2
The temperature shall be 40°C. Then, corresponding to the substantially uniform temperature distribution shown in C3 of FIG. 3, even if either temperature sensor 3A or 3B fails, abnormal temperature will be detected before the temperature reaches a high temperature. Also, if the size is smaller than the maximum usable size (width), C2
As shown in the figure, the heat at both ends of the heat roller 1 is high and the heat at the center is low. For this reason, the set temperature of the first temperature sensor 3A is set lower than the set temperature of the second temperature sensor 3B. For example, the set temperature of the first temperature sensor 3A is set to 240°C, and the set temperature of the second sensor 3B is set to 260°C. In this way, an abnormal temperature is detected by either the first or second temperature sensor 3A or 3B before the temperature reaches a high temperature (290° C.) that would damage each part. In this way, abnormal temperatures can be detected in any situation, and not only can dangers such as fire be prevented, but damage to various parts can also be completely prevented. Control based on these set temperatures, including driving of the heat roller, detection of the temperature sensor, and operation of the heating element, as well as control of the entire fixing device, are all performed by the CPU. A flowchart of control regarding this set temperature is shown in FIG. Electrical signals from the first and second temperature sensors 3A and 3B are A/D converted and input to the CPU. C.P.
In U, it is determined whether it is warm-up/idling, then each condition is set, and processing proceeds according to the program.

[0025]

Effects of the Invention As mentioned above, although the heat roller fixing device of the present invention can avoid the conventional dangerous situations such as fire, it can prevent the temperature sensor itself from malfunctioning and damage various parts of the fixing device. I am now able to solve problems. In other words, even when warming up or idling after turning on the power, or when copying using recording paper of various sizes and fusing with the heat roller, it is of course possible to detect abnormal temperatures that pose a risk of fire. The temperature sensor detects the abnormal temperature before it reaches an abnormally high temperature that would damage each part of the fixing device, making it possible to provide a heat roller fixing device that always has a safe protection function.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the configuration of a heat roller fixing device according to the present invention.

FIG. 2 is a perspective view showing a roller portion of a heat roller fixing device.

FIG. 3 is a diagram showing the state of temperature distribution of a heat roller.

FIG. 4 is a diagram showing the heat distribution when the heat roller is in an abnormal temperature state.

FIG. 5 is a flowchart of the control system.

[Explanation of symbols]

Claims (2)

[Claims] Claim 1: A first temperature sensor is provided which contacts the paper passing area of the heat roller to control temperature and detect abnormal temperature, and a second temperature sensor which contacts outside the paper passing area to detect abnormal temperature. A heat roller fixing device equipped with a sensor,
During warm-up and idling, the abnormal temperature detection level of the first temperature sensor is set higher than the abnormal temperature detection level of the second temperature sensor, and during paper feeding, the abnormal temperature detection level of the first temperature sensor is set higher than the abnormal temperature detection level of the second temperature sensor. A heat roller fixing device characterized in that the temperature is set lower than the abnormal temperature detection level of a temperature sensor. 2. A first temperature sensor is provided that contacts the paper passing area of the heat roller to control temperature and detect abnormal temperature, and a second temperature sensor that contacts outside the paper passing area to detect abnormal temperature. A heat roller fixing device equipped with a sensor,
When fixing the maximum paper width size, set the abnormal temperature detection level of the first temperature sensor to a temperature higher than or equal to the abnormal temperature detection level of the second temperature sensor, and fix the size smaller than the maximum paper width. A heat roller fixing device characterized in that the abnormal temperature detection level of the first temperature sensor is sometimes set to a lower temperature than the abnormal temperature detection level of the second temperature sensor.