JPS62124581A - Fixing device - Google Patents

Abstract

PURPOSE:To uniform fixing performance and to simplify the structure and reduce the cost by arranging one of plural heat sources so that the heating value of heat supplied to both end parts of a roller is large, and controlling this heat source by one temperature sensor so that the heat source is turned off after other heat sources. CONSTITUTION:Two heaters as heat sources are arranged in a fixing roller 1, and a main large-capacity heater 11 which heats the fixing roller 1 nearly uniformly and a subheater 12 arranged so as to heat both end parts of the fixing roller principally are provided. Those main heater 11 and subheater 12 are turned on an off properly by a thermistor 10 provided as one temperature sensor at the outer periphery of the fixing roller 1 according to detected temperature. In a stand-by state, the subheater 12 turns off time, t2 after the main heater 11 is turned off and both end parts of the fixing roller 1 compensates a heat radiation deficiency part at the end parts, so that temperature close to that at the fitting position of the thermistor 10 is maintained.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a fixing device used in electrophotography, and in particular, a plurality of heat sources are provided on either one of a pair of rollers, and transfer between the pair of rollers is performed. The present invention relates to a fixing device that fixes a toner image on a transfer material by passing a material therethrough.

(Prior Art) Many types of fixing devices have been devised and put into practice in the past for use in the final process of electro-T-photography equipment, but the most widely used one is shown in Fig. 4. There are some things shown below. Such a conventional example is a hot roller type fixing device in which a toner image is hot-melted and pressed by a pair of rollers having one elastic body, and its basic structure is that a fixing roller l and a heating roller 2 rotate while being in pressure contact with each other. The fixing roller 1 is heated by a heat source 3 disposed within (or around) the fixing roller 1, and when the transfer material passes between the rollers 1 and 2, the toner image is heated and melted and fixed. Here, at least one of the fixing roller 1 and the heating roller 2 has an elastic surface. The fixing device also includes a temperature sensor 6 for detecting and maintaining the temperature of the fixing roller 1, a safety device 9 such as a thermoswitch, and a cleaning device 5 for removing toner offset (transferred) from the fixing roller 1. It is arranged around 1.2.

Here, the degree of toner melting and fixing (fixing performance) in the fixing device configured as shown in L is mainly influenced by the heat applied to the toner. In order to achieve this, the key is how to maintain a uniform temperature distribution in the longitudinal direction of the fixing roller l. This type of heat roller dissipates a large amount of heat not only to the transfer material but also to the surrounding area, and especially when the roller is stopped and the transfer material is not allowed to pass through, the fixing roller L has only one part open at both ends. Due to heat radiation from the roller l and conductive heat radiation from the bearings or side plates that support the roller l, the temperature at both ends of the roller is significantly lower than that at the center.

Conventionally, as a step to solve this problem, a plurality of heating sources are submerged, and at least one of the plurality of heating sources is centrally arranged at both ends to compensate for the low temperature due to heat radiation at the ends. Was.

(Problems to be Solved by the Invention) However, according to the structure of the conventional example indicated by L, at least when the heating source is turned on, the amount of heat equal to 1 is also generated at both ends! However, if multiple heating sources are turned off at the same time under the control of the temperature sensor 6, the heat dissipation at the end of the roller is large.
The temperature at both ends is significantly lower. In particular, if the main switch is turned off for a long period of time and then turned on, the area around the fuser is cooled down for 1 minute, which causes a large amount of heat to be dissipated, increasing the tendency shown in letter L, resulting in defective fixing at both ends. There was a problem. On the other hand, there is a method to control the heating sources by arranging multiple temperature sensors corresponding to multiple heating sources, but this inevitably increases the complexity and cost of the equipment including the control circuit system. There is a problem.

Therefore, the present invention has been made to solve the problems listed in L of the conventional example. However, the roller surface temperature is equalized = -
It is an object of the present invention to provide a fixing device that has a uniform temperature distribution, has a uniform fixing property, has a simple structure, and is inexpensive.

(First step for solving the problem) In order to achieve the object described in L, in the present invention, a plurality of heat sources are provided on either one of the pair of rollers, and the above-mentioned -
- A fixing device that passes a transfer material between a pair of rollers to fix a toner image on the transfer material, wherein at least one heat source among the plurality of heat sources is applied to both ends of the roller. The heating source is arranged so that the heat Y is large, and is controlled by one temperature sensor so that this heating source is turned off later than other heating sources.

(Embodiment) The present invention will now be explained based on the illustrated embodiment. In FIG. , 13
b, the pressure roller 2 is moved by bearings 14a and L4b,
Both ends of each are supported by side plates (not shown) and are rotatable, and drive force from the main body is received by a gear 15 attached to the fixing roller 1.

Two heaters as heat sources are arranged inside the fixing roller 1, and 11 is a large main heater that heats the fixing roller l almost evenly, and 12 is a main heater that heats both ends of the fixing roller 1 at t. This is a sub-heater installed to heat the area. These main heater 11 and sub-heater 12 are turned on as appropriate according to the temperature detected by a thermistor 10, which serves as one temperature sensor, provided on the outer periphery of the fixing roller 1.

It will be turned off.

Next, the control state of the main heater 11 and sub-heater 12 will be explained based on m2 diagrams (A) and (B). First, when a main switch (not shown) is turned on, both the main heater ti and the sub-heater 12 are turned on.

At this time, the temperature of the fixing roller l rises from the initial temperature To, and soon the part of the fixing roller l where the thermistor 10 is attached reaches the temperature control temperature Tc. Here, fixing roller l
Since the end portion has a large amount of radiation, it is at a lower temperature than the portion where the thermistor 10 is attached. At this point, main heater 1
1 is turned off once, but in order to further raise the temperature at the end of the fixing roller 1, the sub-heater 12 is kept on for a predetermined time t1. Then, since the sub-heater 12 is arranged intensively at the end of the fixing roller 1 as described above, the amount of heat applied to the center is small, and the thermistor 1
The temperature of the central part, including the attachment part of No. 0, gradually decreases after passing through an overshoot. On the other hand, the temperature of the end portion of the fixing roller l continues to rise due to the amount of heat from the sub-heater 12 for a time t1. Then, after 1 hour tl, when the sub-heater 12 is turned off,
The temperature at the end portion undergoes a slight overshoot and then shows a gradual temperature drop similar to the temperature at the thermistor 10 attachment portion.At this point, the weight Φ is increased and the device is in a standby (start) state until it receives a copy signal. Hereinafter, the process up to this point will be referred to as temperature control A.

In the standby state, the main heater 11 and the sub-heater 12 are repeatedly turned on and off according to the temperature detected by the thermistor IO in order to control the temperature near the temperature control temperature Tc as in the conventional case. is turned off with a delay of time t2 after the main heater 11 is turned off. As a result, both ends of the fixing roller l compensate for excessive heat radiation at the ends, as in the case of temperature control A, and are maintained at a temperature close to the location where the thermistor 10 is attached, waiting for input of a copy signal. The temperature control in the standby state up to this point will be referred to as temperature control B hereinafter.

When the copy signal is input, the fixing roller l and the pressure roller 2 start rotating, and the fixing roller l rapidly radiates heat to the pressure roller 2.
temperature drops rapidly.

The thermistor IO detects this, and the main heater 11 and the sub-heater 12 turn on, and are repeatedly turned on and off so as to maintain the temperature in the vicinity of the controlled temperature Tc. In this case, as in the above case, the sub-heater 12 is controlled by the thermistor 10 to turn off with a delay of time t3 from the main heater 11, thereby compensating for heat dissipation from the end portion of the fixing roller 1 during rotation, and ensuring uniform temperature distribution. is maintained. Next, upon completion of copying, the fixed roller 1 and the pressure roller 2 are stopped, which is hereinafter referred to as temperature control C. ), the temperature control returns to standby temperature control B again. From then on, temperature control B
and temperature control C are repeated to maintain uniformity of temperature distribution.

The state of temperature change in this process is shown in FIG. 2 CB), and by controlling the thermistor 10 so that the sub-heater 12 is turned off a predetermined time later than the main heater 11 is turned off, It is possible to compensate for the inherently large amount of heat dissipated from the end of the fixing roller l, and maintain a uniform temperature distribution over the entire length of the fixing roller l as shown in FIG. 2 (B), thereby improving fixing performance. Even when the main switch is turned off for a long time and then turned on, it is uniform and satisfies F.

The joseki tools that exhibit excellent fixing properties according to the above examples are as follows.

Fixing roller; aluminum core metal wall thickness 1. E+a+s Pressure roller, SUS core metal rubber thickness 5.0+s+s 30
゜(JIS A) Main heater; 700W flat orientation sub-heater;
350W right-handed light distribution length 310mm, both ends 5oIII
Temperature control temperature (Tc): 180°C t+=10 seconds, t2=1 second, t3=3.5 gauze surface, temperature control in the above example is performed using one thermistor 10 In the above embodiment, the weight-up is performed when the sub-heater 12 is turned off, but the weight-up is not limited to this, and can be set as appropriate before or after that.

Here, the above embodiment is extremely effective when the transfer material passes over the entire length of the fixing roller l, but if the width of the transfer material is shorter than the entire length of the fixing roller l, repeating the temperature control C In some cases, the temperature at the edge where the transfer material does not pass becomes too high (so-called edge temperature rise). In such a case, the time t3 can be changed according to the paper size and the number of copies 9! Delicious. That is, according to experiments, by setting the time t3 = 3.5 seconds when passing A3 size paper, and setting the time t] = 1.5 seconds when passing small size paper such as 84 size paper, it is possible to continuously print 99 sheets. Even when copying, the y7 temperature at the edge where paper does not pass should be kept at a maximum of 2
The temperature can be kept at 30°C. Therefore, the paper size and number of copies must be adjusted accordingly. By appropriately setting , it is possible to prevent temperature rise at the end.

Next, when the circumferential speed of the fixing roller 1 is high and the number of copies per medium time is large, the amount of heat and heating of the heater may not match the one minute period. In such a case, it is desirable to increase the capacity of the main heater 11 and to increase the thickness of the fixing roller 1 as a heat storage material.

That is, in order to maintain the fixing performance when the main switch is turned off for a long time and then turned on at a peripheral speed of 150 tars/sec of the fixing roller 1, the thickness of the core metal of the fixing roller l is set to 3 mm or more. must,
Furthermore, out of the total city power of 1,500 W, the maximum power used for fixing is around 800 W, so this must be used as a main heater to maintain fixing performance during continuous copying.

However, if the main heater has a capacity of only 800W, it will start slowly when the main switch is turned off for a long time and then turned on, and the temperature drop at the end of the 2, 270-I cannot be compensated for, so Therefore, it is necessary to use an edge-concentrated orientation type heater with a power of about 400 W. Even in this configuration, Fig. 3 (A)
As shown in FIG. 2(A), it is possible to maintain good fixing performance by making minor changes.

That is, by first turning on the main switch, both the main heater 11 and the sub-heater 12 are turned on immediately, and the temperature of the fixing roller l rapidly rises. After that, the center part (thermistor attachment part) of the fixing roller l is set to a predetermined temperature T.
However, when a fixing roller 1 with a relatively large heat capacity is used as in this embodiment, it takes time for heat to be conducted from the main heater 11 and sub-heater 12 to the surface of the fixing roller 1, so overheating may occur. The shoot gets bigger. At this time, in the conventional example, the timing for turning off the heater is set at the temperature control temperature T.
It is customary to carry out the process at a temperature lower than c. In this embodiment as well, the main heater 11 is forcibly turned off at a temperature TS lower than the temperature control temperature Tc, and an overshoot H occurs when the main heater 11 is turned off at a temperature TS lower than the temperature control temperature Tc.
In addition, the thermistor 10 is kept in the off state for a time t4 until it is sufficiently heated.

However, as for the sub-heater 12, after the main heater 11 is forcibly turned off in order to compensate for the heat dissipation charge at the end as shown in L, the sub-heater 12 is turned off after being turned on for a period of time 1. That is, the time tn > t, main heater 1
1. Turning the sub-heater 12 on and off is controlled by a thermistor lO.

As a result, as shown in Figure 53 (B), the fixing roller l
After the main switch is turned off, the temperature f^ of the thermistor mounting part of the thermistor lO gradually decreases through an overshoot of slightly L times around the temperature control temperature Tc, and after time E4 has elapsed, the temperature control temperature Tc is reached.
Temperature control is repeated in the vicinity, while at the end, the temperature continues to rise for approximately t1 hour, and then decreases while the thermistor lO
The temperature should approach that of the installation site, and then the temperature should be controlled to be approximately the same.

After standby, the total power is limited to L sub-heater 1.
The general Tc temperature control is repeated except that No. 2 is not lit. Note that the timing of the wait up is when the sub-heater 12 is turned off, but it is not limited to this, as in the first embodiment. Further, in this embodiment, since the relatively thick fixing roller l is used, heat conduction in the axial direction of the roller is good, and after standby, there is no significant temperature drop at the end portion.

An experimental example of this example is shown below.

Main heater, soow effective light emission length 32oIII1
1. Both ends 50mm at the center x 1.2x luminous flux 7p Sub heater, 400W Effective light emitting length 320mm 2nd both ends 50mm at the center
It was found that uniform fixing performance could always be obtained under the conditions of 1 = 10 seconds and t4 = 30 seconds or more.

(Effects of the Invention) The fixing device according to the present invention has the above-described configuration and operation, and the amount of heat applied to the end of the roller by at least one heat source among the plurality of heat sources provided on the roller is large. This heating source is controlled by one temperature sensor so that it is turned off later than other heating sources.
At any time, including when the main switch is turned off for a long time and then turned on, the roller surface temperature can be uniformly distributed and the fixing performance can be maintained uniformly at all times. Furthermore, since a plurality of heating sources are controlled by one temperature sensor, the structure of the device can be simplified and the device can be provided at low cost.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a main part showing an embodiment of a fixing device according to the present invention, FIG. 2(A) is a time chart showing the operating state of each heater in the same embodiment, and FIG. 2(B) is a Figure 3 (A
) is a time chart showing the operating state of each heater in another embodiment, FIG. 3(B) is a time-temperature graph of each part of the roller in the same embodiment, and FIG. 4 shows a conventional heat roller fixing device. FIG. Explanation of symbols 1... Fixing roller 2... Pressure roller 10.
...Thermistor 11... Main heater 12...
・Sub heater

Claims (2)

[Claims] (1) A fixing device for fixing a toner image on the transfer material by providing a plurality of heat sources on either one of a pair of rollers and passing a transfer material between the pair of rollers, wherein the plurality of heat sources At least one of the heat sources is arranged so that a large amount of heat is applied to both ends of the roller, and the heat source is controlled by one temperature sensor so as to be turned off later than the other heat sources. A fixing device characterized by: (2) The temperature sensor detects that the roller reaches a predetermined temperature after the main switch is turned on, and when turning off the plurality of heat sources, the amount of heat applied to both ends of the roller increases. The fixing device according to claim (1), wherein a heat source disposed in the fixing device is controlled to be turned off later than other heat sources.