JPS6041353B2 - heating device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heating device that provides good temperature control.

The following will explain the fixing device in an electrophotographic recording device as an example.

Generally, a fixing device is equipped with a temperature detection element, and when the temperature of the detection element reaches a set temperature, the power supply is stopped. However, after the power is turned on and heating starts, the temperature of the heating section temporarily changes. The temperature rises above the set temperature (this transient state is referred to as overshoot), and then stabilizes at a temperature near the set temperature. The reason for this is that a temperature difference occurs between the temperature of the temperature detection element and the surface temperature of the heating section. The present invention suppresses the overshoot amount of this rise within an appropriate range to always perform good fixing. Conventionally, as shown in curve 1 in Figure 3, the temperature of the temperature detection element after the wire is inserted is lower than the actual temperature of the heating part due to the thermal resistance between the heating part and the temperature detection element and the heat capacity of the temperature detection element. An overshoot phenomenon occurs in which the heating part temperature once rises above the set temperature Tst, and then the temperature decreases and stabilizes at a temperature near the set temperature.

In particular, when a heat-resistant elastic material such as silicone rubber is used on the surface of the heating section for fixing, the low-molecular components of the heating section may evaporate and thermally oxidize during the above-mentioned overshoot, and the recording material coated on the rubber surface may peel off. Solvents such as silicone oil to facilitate evaporation or thermal oxidation occur. For this reason, there are drawbacks such as smoke and bad odor, and high-temperature offset tends to occur. According to the present invention, proper and good fixing can always be performed by preventing the excessive overshoot mentioned above.

That is, the present invention prevents excessive overshoot by providing a heating means for heating the temperature detecting element in contact with or in the vicinity of the temperature detecting element that detects the temperature of the heating section. That is, the present invention provides: "a heat generating member that generates heat when energized; a heating section that is heated by the heat generating member; a detection element that detects the temperature of the heating section; In a heating device that heats a heating material by the heating part, the heating device has a means for controlling the temperature of the heating part to a set temperature, and a heating device that is in contact with the temperature detection element that detects the temperature of the heating part or in the vicinity of the temperature detection element. A heating device comprising an element heating means for heating the provided temperature detection element, and reducing overshoot when starting heating of a heating section.

'' as the first invention, ``a heat-generating part that generates heat when energized, a heating part that is heated by the heat-generating member, a detection element that detects the temperature of the heating part, and the above-mentioned according to the detected temperature of the detection element. In a heating device which has a means for controlling a heating part to a set temperature and heats a material to be heated by the heating part, the temperature sensing element that detects the temperature of the heating part is contacted or the temperature sensing element is heated. It is characterized by having an element heating means for heating the temperature detection element provided nearby, and an energization control means for controlling the temperature of the temperature detection element by controlling energization to the element heating means. heating device.

” is the second invention. Hereinafter, the present invention will be explained in detail with reference to Examples.

Figure 1 shows Hakama Kosho 42-2 to which the heating device of the present invention can be applied.
An example of an electrophotographic apparatus based on the invention disclosed in Japanese Patent No. 391 is shown. The photosensitive drum 28 has a photosensitive layer provided on a metal cylinder.
It is uniformly positively charged by a primary charger 27, and then removed by an AC corona discharger 30' to which alternating current is applied, and at the same time, the original image is irradiated with a lamp 29. As a result, a static exposure latent image is formed on the surface insulating layer of the photosensitive drum 28 due to the difference in surface charge density, and then the entire surface of the photosensitive layer is uniformly exposed by the full-surface exposure lamp 31, thereby forming the original image. Creates a difference in surface potential depending on brightness and darkness, forms a high-contrast electrostatic latent image, develops it with a developer 32, and transfers the toner image onto a recording material supplied from a cassette 33 with a transfer charger 34, The transferred toner image is thermally fixed by rollers 1 and 4. The drum is broken
It is cleaned by the board 35 and reused. FIG. 2 shows an example of a roller fixing device to which the present invention is applicable.

1 is fixed as a heating part in which a woven material 3 such as silicone rubber or Teflon (tetrafluoroethylene resin) is thinly coated on a core metal 2 made of a material with good thermal conductivity such as aluminum or copper. 4 is a pressure roller having a core metal 5 coated with relatively thick silicone rubber 6.

Both rollers 1 and 4 are pressed against each other with appropriate pressure and rotate in the direction of the arrow. paper cloth holding heat-fusible toner developer T;
A recording layer C made of film or the like is conveyed in the direction of the arrow and heated and pressed between rollers 4. The fixing roller is heated by a halogen lamp 7 which is an internal heat source, and a sufficient amount of heat is applied to the contact surface with the pressure roller 4 to melt the image T. Further, the surface temperature of the fixing roller 1 is always controlled within a constant temperature range by a temperature detection element 9 such as a thermistor. 1 is an entrance guide for conveying the copy material to the loaf, and 11 and 12 are separation claws for reliably separating the recording material after fixing, and are made of heat-resistant template resin such as Teflon, or metal. The surface is coated with a template material such as Teflon coating.

Reference numeral 13 denotes an offset prevention liquid storage tank for storing an offset prevention liquid 14, and the offset prevention liquid 14 is absorbed and held in heat-resistant felts 15, 16, and 17 such as Nomex or Teflon felt by capillary action.

The heat-resistant felt 17 is supported by a support plate 18, and the support plate 18 is rotatable around a fulcrum 19. Reference numeral 22 denotes a coating roller that supplies a solvent such as silicone oil to the fixing roller to facilitate the peeling of the recording material, and rotates following the fixing roller.

23, 24, and 25 are cleaning felts for cleaning excess silicone oil and dirt on the roller surface.

Reference numeral 26 denotes a heat source for heating the thermistor, and is made of a surface heat source such as a rubber heater attached to the thermistor holder, or an infrared heater provided in a space close to the thermistor.

The above-mentioned horizontal rollers are stopped during standby to prevent noise and reduce heat radiation.

Then, it starts rotating in synchronization with the copying operation, and the crimp loaf 4
comes into pressure contact with the fixing roller and is in a pressurized state. Next, an embodiment of a temperature control circuit for achieving the object of the present invention is shown in FIG. Day 2 is a heating element 7 such as a halogen lamp, day 2 is a heating element 26 such as a rubber heater. TH is a thermistor as the temperature detection element 9, and resistors R2, R3, R4, R
6. Along with the semi-fixed resistance VR, the resistance R depends on the DC power supply Vc.
,, forms a bridge circuit to which a voltage is applied through R5, and changes its resistance value due to changes in temperature, thus causing fluctuations in the deviation of the voltage values of the resistors R2, R3, and R4 forming the bridge circuit. It works as if to force it. Q is a differential multiplier that operates as a voltage comparator, with terminals 4 and 7 for obtaining power input, terminals 2 and 3 for signal input to detect deviations in the voltage value, and terminals 2 and 3 for inputting signals; It has a terminal 1 for outputting, and the output signal is configured to be selectively applied to the bases of transistors Q2 and Q5 through diodes D5 and D6.

D8 is a full-wave rectifier circuit constituted by a diode bridge circuit, which receives AC input and outputs a full-wave rectified wave, and the output is connected to resistors R, . through transistor Q5
applied to the base of The heating element is configured to operate by receiving power from the alternating current power supply AC, and a triax Q7 is used for switching. When the power is turned on, the surface temperature of the fixing roller is in the low temperature range, the resistance value of the thermistor is high, and therefore the voltage on the input terminal 2 side of the differential multiplier Q becomes high, so the output from terminal 1 increases. becomes low, and the full-wave rectified wave output from the diode bridge D8 is applied as a base voltage to the base of the transistor Q5. Therefore,
Since the transistor Q5 is turned on when the base voltage is above the threshold level and turned off when it is below, the collector voltage of the transistor Q has a pulse waveform that occurs every half cycle of the alternating current power supply AC. . Furthermore, when the transistor Q5 is OFF, the collector voltage of the transistor Q5 is at a high level, so that the capacitor C3 is charged through the resistor 3 and the diode D9, and the voltage is applied to the anode side of the switching element Q. applied. However, the gate of the switching element Q6 has a resistor R. 4, a high level voltage approximately equal to the potential on the anode side is applied, so the switching element Q is turned off. Next, when the transistor method is ○N, a current flows through the resistor R, 3, and the collector voltage of the transistor Q becomes a low level. Therefore, a charging current flows through R, 4 to the capacitor C2, and therefore, the switching element Q6 The gate potential temporarily drops to a low level. Therefore, the switching element Q
6 is turned on, and the charge stored in the capacitor C3 is discharged through the switching element false and the winding of the pulse transformer PT, so that a pulse voltage generated every half cycle of the AC power source AC is induced in the winding. . When the surface temperature of the fixing roller is in a low temperature range due to the circuit operation as described above, the winding of the pulse transformer PT is
A pulse voltage that occurs every half cycle is induced.

Therefore, the alternating current power supply AC is connected to the gate of triac Q7.
A trigger pulse is applied that occurs every half cycle of the heating element. Approximately full cycle power is applied from the alternating current power source AC to the . Therefore, the surface temperature of the fixing roller increases as shown by curve 2 in FIG. At the same time, since the output of the locking multiplier Q is at a low level, the transistor Q2 is turned off, and the heating element 2 is turned on, heating the thermistor 9. Therefore, the thermistor receives heat from the heating element surface (from the heating element 2) and heat from the heating element 2, and the temperature rapidly rises as shown by curve 2 in FIG. When the thermistor temperature reaches the set temperature T, (first set temperature) immediately after the power is turned on, the voltage on the input terminal 2 side of the differential multiplier Q becomes low, so that the output from terminal 1 decreases. becomes high level, transistor Q2 turns on, and relay KI/
2 turns on.

From ON' of relay KI/2, contacts kl-1, kl-
2 is closed, heating element 2 is turned off, and the set temperature is
T, the temperature changes to a higher temperature Tst (second set temperature). From time t, the heating element is ON and OFF from day 2.
Therefore, the fixing roller surface temperature and the thermistor temperature rise as shown in curves 2 and 2' in Figure 3, and when the thermistor temperature reaches the set temperature Tst (second set temperature) over time,
Again, the output of the differential multiplier Q is at a high level, so the full-wave rectified wave and the output of the differential multiplier Q are simultaneously applied to the base of the transistor Q, and the threshold of the transistor Q is applied.・A voltage higher than the level is applied.

Therefore, the transistor is always on, the collector voltage is always at a low level, and the pulse voltage that was applied to the winding of the pulse transformer PT disappears. Therefore, the heating element is in an OFF state. Thereafter, the heating element is repeatedly turned on and off according to the control circuit described above, and the fixing roller surface temperature is maintained near the set temperature Tst, as shown by curve 2 in FIG. FIG. 5 shows an example of a control circuit using two differential intensifiers. When the power is turned on at time to, heating elements 1, 2 are turned on, and at time t, When the thermistor temperature reaches T, (first set temperature), the differential multiplier Q2
The output becomes high level, a trigger signal is applied to the gate of switching element Q, and Q3 is turned on. Transistor Q4 is therefore turned off and heating element 2 is turned off. With the heating element still in the ON state, the fixing roller surface temperature and thermistor temperature rise as shown by curves 2 and 2' in Figure 2, and the thermistor temperature reaches the set temperature Tst (second set temperature) at time t2. When this happens, the output of the differential intensifier goes to a high level and the heating element turns off. Thereafter, the heating element is repeatedly turned on and off according to the control circuit, and the fixing roller surface temperature is maintained near the required set temperature Tst (second set temperature) as shown in curve 2 in FIG. The temperature change when the present invention described above is applied will be explained in more detail using FIG. 3. Curve 2 represents the temperature change on the surface of the fixing roller as a heating section when the present invention is applied.
Further, the temperature change of the thermistor is shown by curve 2'.

That is, the present invention suppresses the amount of overshoot within an appropriate range by arranging the heat source 26 that heats the temperature detection element at a position in contact with or close to the temperature detection element. That is, when the power is turned on, the temperature of the fixing roller increases as shown by curve 2 in FIG. 3 due to the heating element. In addition, the thermistor as a temperature detection element receives heat from the roller surface (due to the heating element 2) and heat from the heating element 2 for heating the temperature detection element, and as a result the thermistor receives heat from the heating element 2 for heating the temperature detection element, resulting in the curve 2 in Figure 3.
′ shows a rapid rise. Then, after a certain period of time, the thermistor temperature changes to the set temperature T immediately after the power is turned on (first set temperature).
Once reached, the heating element 2 is de-energized and the set temperature is switched to T, the higher required set temperature Tst (second set temperature). Time t. After that, heating element 2 is turned ON and heating element 2 is OFF, so the fixing roller temperature and thermistor temperature rise as shown by curves 2 and 2' in Figure 3, and when the thermistor temperature reaches the set temperature Tst over time, the heating element Day, is in the OFF state. Thereafter, the heating element is repeatedly turned on and off according to the control circuit to maintain the temperature of the fixing roller near the required set temperature Tst, as shown by curve 2 in FIG. In addition, during the above reading process, the heating element will be turned off for a moment when the set temperature is switched from T to the required set temperature Tst, but no problem will occur because the current will immediately start flowing again. . As described above, the present invention provides a heating means for heating a temperature detecting element such as a thermistor, thereby reducing the temperature difference between the temperature detecting element and the heating section, thereby reducing the overshoot phenomenon that conventionally occurs due to the temperature difference to within an appropriate range. It is something to hold down. Therefore, good fixing can always be performed without producing smoke or bad odor, and without causing high temperature offset. In the case of the two embodiments described above, the thickness of the silicone rubber on the diameter 35 to 45 side of the fixing roller is 0.
1 to 0.5 fence, pressure roller diameter 35 to 45 side, silicone rubber wall thickness 5 to IQ rib, heating element temperature IKW, required set temperature Tst to 190oo, heating element day 2. A power of about 1 to 20 watts is sufficient.

Alternatively, the heating element 2 may be turned on after a predetermined period of time, instead of being turned on at the same time as the power is turned on.

Note that the temperature T, (first set temperature) can be appropriately selected within a temperature range below the set temperature Tst (second set temperature), and the amount of overshoot at the rise can be arbitrarily selected thereby. Is possible. In the case of this example,
If you start copying immediately after the power is turned on and the copy operation ready signal is output, the temperature of the pressure roller will be close to room temperature and the ambient temperature inside the fuser will not be warm enough, so the surface of the fixing roller will be lower than normal. Since a larger amount of heat is removed and the fixing roller surface temperature drops more significantly, it is preferable that the amount of overshoot at the rise is within a range that does not cause smoke or high-temperature offset rather than fog. It goes without saying that the above control circuit can be applied not only to roller fixing devices but also to various heat fixing methods such as hot plate fixing and chamber fixed fixing. Furthermore, if the temperature is switched to a third set temperature higher than the second set temperature when copying is started (copy button turned on), the heat absorbed by the recording material can be compensated for and the recording material can be sufficiently heated and fixed.

As described in detail above, the present invention provides an element heating means for heating the temperature detection element separately from a heat source for heating the heating part, in contact with or near the temperature detection element, and the temperature detection element is connected to the element heating means. By heating, overshoot can be removed or suppressed within an appropriate range.

Therefore, the temperature of the heating section can be quickly stabilized at the required set temperature, which not only extends the life of the device but also has great effects in terms of safety. Incidentally, the present invention can be easily applied to temperature control of all devices having a heating section.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a transfer type electrophotographic device, FIG. 2 is a diagram of an embodiment of a roller fixing device to which the present invention can be applied, FIG. 3 is a graph of temperature control characteristics, and FIGS. 4 and 5 are FIG. 2 is a circuit diagram showing an example of a temperature control mechanism. 1...Fixing roller, 3...Silicone rubber coating,
4...Crimp roller, 7...Halogen lamp, 14...Offset prevention liquid, 22...
... Application loaf, 26 ... Heat source, 28 ...
...Photosensitive drum. Tsutomyo 4 Figure 2 Figure 3 Figure 4 Figure 5

Claims (1)

[Scope of Claims] 1. A heat generating member that generates heat when energized, a heating section that is heated by the heat generating member, a detection element that detects the temperature of the heating section, and a heating section that detects the temperature of the heating section according to the temperature detected by the detection element. in a heating device that heats a material to be heated by the heating part, the heating device has a means for controlling the temperature to a set temperature, and a heating device that heats a material to be heated by the heating part, the heating device having a heating part that is in contact with the temperature detection element that detects the temperature of the heating part or in the vicinity of the temperature detection element. A heating device comprising an element heating means for heating the provided temperature detecting element, and reducing overshoot when starting heating of a heating section. 2. Claim 1, wherein the heating section is a heat fixing roller for fixing the toner image of the heat fixing device onto the recording material.
Heating device as described in section. 3. A heat generating member that generates heat when energized, a heating section that is heated by the heat generating member, a detection element that detects the temperature of the heating section, and controlling the heating section to a set temperature according to the temperature detected by the detection element. and a means for heating a material to be heated by the heating section, the temperature detection device being in contact with or near the temperature detection element that detects the temperature of the heating section. A heating device comprising: an element heating means for heating an element; and an energization control means for controlling energization to the element heating means to control the temperature of the temperature detection element. 4. The energization control means includes means for stopping energization to the element heating means when the temperature detection element is heated by the element heating means and reaches a set temperature lower than the set temperature of the heating section. A heating device according to claim 3. 5. The energization control means starts energizing the element heating means at the same time as the energization of the heat generating member starts or after a predetermined period of time has elapsed after the start of energization of the heat generating member. Heating device as described in section. 6. Claim 3, wherein the heating section is a heat fixing roller for fixing the toner image of the heat fixing device onto the recording material.
The heating device according to items 5 to 6.