JPH01118174A - Image forming device - Google Patents

Abstract

PURPOSE:To reduce power consumption and also to make the rising of temperature of the inside and outside of a device minimum by alternating the set temperature of a heating body of a heat fixing device according to a power source voltage. CONSTITUTION:The 2nd set temperature of the heating body 20 of the heat fixing device 19, that is, the temperature of the heating body 20 which is in a state different from usual image formation is altered according to the power source voltage. When a power source is turned on, the power source voltage of the power source 28 is detected by a voltage detection circuit 29. And a voltage detection signal is inputted in a central processing unit 30 (CPU) and a temperature detection signal detected by the thermistor 24 of the heating roller 20 is inputted in the CPU 30. By controlling on/off in terms of the action of a heater control circuit 27, the temperature of the heating roller 20 is kept within a prescribed temperature range of a constant range where the temperature is proper as a fixing temperature in the longitudinal direction even if impressed power source voltage is altered. Thus, the quantity of the power consumption can be reduced and the rising of the temperature of the inside and outside of the device can be made minimum.

Description

Detailed Description of the Invention Production--1 The present invention provides a method for fixing an image transferred to a transfer material through a series of predetermined image forming processes such as various latent image forming processes, development processes, and transfer processes. used,
The present invention relates to an image forming apparatus equipped with a heat fixing device having an electric heating element, and particularly relates to an image forming apparatus that operates with a wide range power supply having a wide allowable range of power supply voltage, with the maximum allowable voltage being twice or more the minimum allowable voltage.

' - and its □ ton Conventionally, it is used to fix images transferred to a transfer material through a series of predetermined image forming processes such as various latent image forming processes, development processes, and transfer processes as described above. 2. Description of the Related Art Image forming apparatuses equipped with a heat fixing device generally include a heat fixing device that uses an electric heating element to fix an image transferred to a transfer material.

When an electric heating element is used in such a heating fixing device, the amount of heat generated by the electric heating element varies significantly depending on the power supply voltage, so the thermal characteristics of the heating fixing device using the electric heating element greatly depend on the power supply voltage. That will happen.

Therefore, since there are various power supply voltages currently used commercially in various countries from 100V to 240V, until now, image forming apparatuses with heat fixing devices such as those described above have been used with voltages of approximately 100V and 200V. There were at least two types of power supplies and they were manufactured for different pressures.

In this case, manufacturing an image forming apparatus with two or more types of power supply voltages not only increases the number of parts, but also complicates the manufacturing process and increases costs. It was desirable to manufacture an image forming apparatus having a heat fixing device using an electric heating element that can be used with a single power supply installed in a wide range of power supply voltages.

For this reason, it has a heat fixing device using an electric heating element.
In conventional image forming apparatuses of this type, the allowable range of power supply voltage must be made small in order to stabilize the thermal characteristics of the heat fixing device, and the ratio of the maximum allowable voltage to the minimum allowable voltage is usually set at 1.3. (e.g. 85V~l)
10V), and the maximum voltage is about 1.5 (for example, 8
The limit was to set it to 5V to 127V). However, in recent years, there has been a demand for image forming apparatuses with a wider permissible voltage range of the frL source voltage.
There is a growing demand for an image forming apparatus that can be used in a power supply voltage range of V to 264V.

This power supply voltage range is 3 or more in terms of the above-mentioned allowable voltage ratio, and as mentioned above, it significantly affects the thermal characteristics of the heat fixing device. In particular, the difference in power output of one heating element greatly affects the heating characteristics of the heating element, so the rise time from room temperature,
The rise time from standby (standby) temperature varies greatly depending on the power supply voltage.

However, in recent years, image forming apparatuses have been designed to reduce power consumption and suppress temperature increases inside and outside the image forming apparatus.
Furthermore, by raising the ambient temperature of the heat fixing device even in the early stages of startup from room temperature, the temperature during normal image formation (hereinafter referred to as the first temperature) is In many cases, the temperature of the heating element is maintained at a different temperature (hereinafter referred to as the second temperature).

Normally, this second temperature is set so that it reaches the first temperature in a shorter time than the time from the start of the image forming process until the regular process is performed, so the minimum calorific value is usually set. is set according to the However, if the allowable voltage ratio is more than doubled, depending on the maximum capacity of the power supply,
Since the maximum power at high voltage is limited, the minimum power at low voltage becomes considerably small, so the temperature increase rate of the heating element at minimum power becomes small, and therefore the second set temperature and the first set temperature In order to reduce the power consumption mentioned above and to suppress the temperature rise inside and outside the image forming apparatus, it is necessary to reduce the temperature difference between the If the temperature is increased, there is a drawback that the effect is not sufficient for the purpose of reducing temperature unevenness due to heat radiation.

An object of the present invention is to set the second set temperature of the heating element of the heat fixing device according to the power supply voltage even if the maximum allowable power supply voltage is twice the minimum allowable voltage. By changing the temperature of the heating element, which is in a different state from normal image formation, the second set temperature can be made more effective than the first set temperature, which is the temperature of the heating element during normal image formation. An object of the present invention is to provide an image forming apparatus having a heat fixing device that can be selectively selected.

Another object of the present invention is to adjust the second set temperature of the heating element of the heat fixing device according to the power supply voltage even if the maximum allowable voltage of the TL source voltage is more than twice the minimum allowable voltage, that is, the normal image temperature. By changing the temperature of the heating element, which is in a state different from that of image forming, it efficiently reduces power consumption and minimizes temperature rise inside and outside the image forming apparatus. An object of the present invention is to provide an image forming apparatus.

Another object of the present invention is to adjust the second set temperature of the heating element of the heat fixing device according to the power supply voltage even if the maximum allowable voltage of the power supply voltage is more than twice the minimum allowable voltage, that is, the second set temperature of the heating body of the heat fixing device, that is, the normal image forming temperature. It is an object of the present invention to provide an image forming apparatus that can improve image quality by reducing temperature unevenness at low voltage by changing the temperature of a heating body that is in a different state.

The above object is achieved by an image forming apparatus according to the present invention. To summarize, the present invention provides an image forming apparatus having a heat fixing device in which the maximum allowable power supply voltage is twice or more the minimum allowable voltage, and which uses an electric heating element. This is an image forming apparatus characterized by changing the set temperature of the image forming apparatus.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described based on embodiments thereof and with reference to the accompanying drawings.

FIG. 1 shows a schematic cross-sectional view of an image forming apparatus according to the present invention.

Referring to FIG. 1, an image forming apparatus 10 of the present invention includes a photoreceptor drum 11, and this photoreceptor drum 11 is uniformly charged by a band device 12 disposed adjacent to the photoreceptor tram 11. Then, the laser beam emitted from the laser light source 13 based on the image signal is transmitted to the laser beam scanning device 14.
A static latent image is formed on a developing device 15 disposed adjacent to the photoreceptor drum 11, and is visualized in the developing device 15 with toner made of resin or the like. The converted toner image is transferred to the photosensitive drum 1 at the appropriate timing.
A transfer device 17 disposed adjacent to the photoconductor drum 11 transfers the image onto a transfer paper conveyed by a conveyance roller 16 disposed upstream of the photoconductor drum 1 .
The photoreceptor drum 1 is cleaned by a cleaning device 18 disposed adjacent to the photoreceptor drum 11 and subjected to the image forming process again.

After the toner image has been transferred, the transfer paper to which the toner image has been transferred advances to a heat fixing device gl19 disposed downstream of the photosensitive drum 11 as an object to be heated, and is heated to a predetermined temperature that constitutes this heat fixing device 19. The image forming apparatus 2t10 is heated and fixed by a heating roller 20 as a heating body maintained at
is discharged to the outside.

The heat fixing device 19 of the image forming apparatus 10 described above will be described in more detail with reference to FIG. Width 212mm, fixing speed 50mm
/5 (approximately 8 A4 size sheets per minute), a fixing processing temperature (first set temperature) of 180°C, and a minimum fixing temperature of 170°C. The heating roller 20 as a heating body in the heating fixing device 19 has an outer diameter of 25 mm and a wall thickness of 1, for example.
．． A cylinder made of 4 mm aluminum 11 is used as a base material, the inner peripheral surface is coated with heat-resistant black paint, and the outer peripheral surface is provided with a fluororesin layer such as PFA or PTFE as a molded layer.For example, the total length is 250 mm. belongs to.

Inside the heating roller 20 of the heat fixing device 19, a halogen lamp heater 23 with a heat generation length of 226 mm, for example, which exhibits a core force of 400 W when turned on at 115 V, is provided as an electric heating element, that is, a heat generation source. . The pressure roller 21, which is placed in pressure contact with the heating roller 20, is provided with an elastic layer made of silicone rubber or the like, and when both rollers rotate together, the toner image on the transfer paper becomes a permanent image. A fixing process is performed.

A thermistor 24 is disposed on the heating roller 20 of the heat fixing device 19 as a temperature detection base for detecting its temperature.

The heater 23 of the heating roller 20 including the thermistor 24 is connected in series to a heater control circuit 27 which is an electric heating element control circuit, and this heater control circuit 27 is connected to a power source 28.

The source 28 for this '11 can take a voltage from 85V to 264V, for example.

Further, a voltage detection circuit 29 for detecting the power supply voltage of the power supply 28 is connected in parallel to the heater 23.
The voltage detection signal detected by the pressure detection circuit 29 is
Central processing bag'j! 130 (CPU). Note that the output of the thermistor 24, that is, the temperature detection signal from the thermistor, is also input to the central processing unit 30 (CPU), and the temperature detection signal from the thermistor 24 and the voltage detection signal described above are used to control the central processing. The device 30 (CPU) outputs a signal to the heater control circuit 27 to ON10FF control the power supply from the power source to the heater 23, thereby maintaining the temperature of the heating roller 20 within a predetermined temperature range.

In the image forming apparatus of the present invention having such a configuration, when the power is turned on, the voltage detection circuit 29 detects the power supply voltage of the power supply 28 applied to the heater 23 of the heating roller 20.
The voltage detection signal detected by the voltage detection circuit 29 is input to the central processing unit ff130 (CPU), and the power supply voltage of the power supply 28 is also applied to the heater 23 of the heating roller 20.

In this way, the power supply 2 is connected to the heater 23 of the heating roller 20.
When the power supply voltage 8 is applied, the thermistor 24 of the heating roller 20 is activated, and the temperature detection signal detected by the thermistor 24 is input to the central processing unit (CPU) 30, and these voltage detection signals and temperature detection signals are input to the central processing unit (CPU) 30. Based on the signal, the central processing unit 30 determines whether the temperature of the heating roller 20 is within a certain range appropriate for the fixing temperature, and if it is not within an appropriate certain range, outputs a signal to the heater control circuit 27. turns ON10 the operation of the heater control circuit 27.
FF control, and then turn ON10 FF the application of electric voltage to the heater 23 to maintain the temperature of the heating roller 20 in its longitudinal direction as the fixing temperature within an appropriate predetermined temperature range. .

Here, even if the applied power supply voltage changes, the abrasion of the heating roller 20 of the present invention is maintained within a predetermined temperature range suitable for the fixing temperature in the direction of its handle, as described above. This will be discussed with reference to Table 1 and Figure 3.

That is, Table 1 shown below shows the heater effective power and the thermal characteristics of the heating roller 20 when the heater 23 used in this embodiment is used at a power supply voltage of 85V to 264V.

The effective power P1 of the halogen lamp heater 23 used in this embodiment is the rated voltage Vo, the rated power PO1, and the power supply voltage v.
Regarding No. 1, it can be seen that the power consumption varies greatly depending on the power supply voltage, as shown in Figure 2, 85V-C'251W, and 1438W at 264V.

Further, as the thermal characteristics of the heating roller 20, the temperature rise per unit time (heating rate; deg ('C), /S) and 20
℃ room temperature to the above-mentioned first set temperature If (180℃;
The time required to reach TO) is 1j31 (heating time: S
) is shown, and this Table 1 also shows: As shown,
It can be seen that the thermal characteristics of the heating roller vary greatly depending on the power supply voltage.

Table 1 also shows the first time delay when the time delay from the start of image formation to the start of fixing processing is, for example, 5 seconds.
The maximum value of the difference between the set temperature and the second set temperature, which is the temperature of the heating roller during standby, which will be described later, is shown.

It should be noted that each heater power showed the maximum value that could raise the temperature within 5 seconds.

In this embodiment, as shown in Table 2 below, the second set temperature, which is the temperature of the heating roller during standby, is set in stages according to the power supply voltage (T
+~Ts). The image forming apparatus of this embodiment is in standby state 8 (a state in which image formation can be started immediately; the heating roller is
The temperature is maintained at the second set temperature. ), as mentioned above, Table 2 shows that it takes 5 seconds from the start of image formation to the start of fixing process, and as can be understood from Tables 1 and 2, in this embodiment, the power supply voltage is Accordingly, the second set temperature is changed, and the fixing processing temperature is reached in the aforementioned 5 seconds.In this embodiment, the power supply voltage detection circuit 29 shown in FIG. The voltage is detected and the temperature is set to standby at a predetermined second temperature according to Table 2. Here, by further increasing the positive portion of the power supply voltage, it is possible to determine the second set temperatures that are more efficient in the -layer. Furthermore, without using the power supply voltage detection circuit 29, the user can judge and manually send a signal according to the power supply voltage to the central processing bag 21 (CPU) using a voltage changeover switch or the like.
30, the central processing unit outputs a signal corresponding to the power supply voltage at this time, and the heater may be operated, thereby implementing the present invention.

A specific example of the above is shown in FIG. FIG. 3 shows the temperature of the heating roller 20 over time when the second set temperatures are T, , T3, and T5.

In Fig. 3, the curve (■) shows the temperature rise characteristics from room temperature (20°C) when the second set temperature is T1 (172°C) in the area (■) where the voltage is in the range of 85 to 100V, and during standby and It shows the temperature change during printing, and the curve ■
is the region ■ where the voltage is in the range of 115 to 187V, and the second
Curve 1 shows the temperature rise characteristics from room temperature (20℃) when the set temperature is T3 (162℃), the temperature change at STUN/ζ4 and during printing.
In the region ■ which is the range of 4V, the second set temperature is T+(1
35° C.), the temperature rise characteristics from room temperature (20° C.), and temperature changes during standby and printing are shown, respectively.

In this embodiment, the effects of the present invention appear particularly when used at a high voltage, but it is also effective even at voltages around toov by making the positive component of the voltage fine. As described above, in this embodiment, the temperature of the heating roller 20 during standby, that is, the second set temperature, is set according to the power supply voltage, so that the power consumption of the image forming apparatus can be efficiently reduced. It is also possible to minimize the temperature rise inside and outside the image forming apparatus.

FIG. 4 shows the temperature distribution of the heating roller 20 in this embodiment, and when the power supply voltage is 85V, it is 190°C, 'i[
The fixing process is performed at 185°C when the voltage is 115V, and at 180°C when the power supply voltage is 240V. As shown in Fig. 4, by changing the fixing temperature according to the power supply voltage, it is possible to exceed the minimum fixing temperature over the effective fixing width even at low voltages, and even at high voltages. can effectively reduce power consumption.

On the other hand, FIG. 5 shows the temperature distribution when the fixing process was performed immediately after the heating roller was raised from room temperature, as a comparative example of the present embodiment.

In Fig. 5, a thermistor is placed as a temperature detector in the center of the heating roller, and the power supply voltage is 85V, 115V, 240V.
3 shows the temperature distribution in the fixing effective width at each voltage of V.

Note that the controlled temperature indicated by TN in FIG. 5 is the set temperature of the heating roller, and the minimum fixable temperature is the minimum temperature of the heating roller necessary for good fixing.

As shown in FIG. 5, the reason why the temperature distribution in the longitudinal direction of the heating roller varies greatly depending on the power supply voltage applied to the heater 23 can be considered as follows.

In other words, the temperature of the heating roller is determined by the amount of heat generated by the halogen heater as a heating element, the amount of natural heat dissipated by the heating roller itself, and
It is determined by the balance with the amount of heat radiation due to heat transfer to the transfer material. If we consider the case where the amount of heat generated by one heating element is small, the amount of heat emitted by the heating roller per unit time does not change, so the temperature will substantially increase at the end of the heating roller where the amount of natural heat radiated from the heating roller itself is large. This will result in a decline. especially,
This becomes noticeable because the heater lighting time becomes longer when the temperature around the heat fixing device is low. Therefore, as in the comparative example, a thermistor is installed in the central part of the heating roller to adjust the temperature, so the temperature is maintained at a constant level, and the voltage of the power supply 'is 240V in Fig. 5.
When in use, the temperature exceeds the minimum fixing temperature over the entire effective fixing width of the heating roller, showing good fixing performance, but when the power supply voltage is 115V or 85V, , is lower than this, and there is a possibility that fixing failure may occur.

Next, another embodiment will be described.

In the above embodiment, the outer diameter of the heating roller 20 is, for example, 20 mm and the wall thickness is 1 mm, and the power supply voltage is 85 V using a heater whose power is 350 W when turned on at 115 V.
The temperature distribution in the longitudinal direction of the heating roller 20 in this case is shown in FIG. In FIG. 6, curve a is the second
If the set temperature is 170℃ (-To), song 11
b. When the second set temperature is 180°C (=T7=To), curve C shows that the second set temperature is 190°C (=T
In the case of a), when the temperature is raised from room temperature (20°C), the temperature is controlled for 1 minute at the second set temperature, and then the fixing process is performed at the first set temperature (To = 180°C). 2 shows the temperature distribution of the heating roller 20 in FIG. 7th
The figure shows an example in which the power supply voltage is 220V in the other embodiment described in connection with FIG. 6.

As shown in FIG. 6, at 85 V, the temperature at the end of the heating roller 20 tends to be low, and if the second set temperature is low, poor fixing may occur at the end of the image. However, according to the present invention, the second set temperature is set to Ts=190.
It can be seen that if the temperature is set as high as .degree. C., it is possible to exceed the minimum fixable temperature for effective fixing. On the other hand, as shown in FIG. 7, it can be seen that when the power supply voltage is 220 cm, even if the second set temperature is low, it exceeds the minimum usable fixing temperature.

Therefore, when the voltage is low, by setting the second set temperature higher than the first set temperature, it is possible to prevent the temperature from decreasing due to heat radiation from the roller itself, and to stabilize the image quality immediately after the heating roller temperature rises. On the other hand, when the voltage is high, power consumption can be reduced by lowering the second set temperature. Also, only when the voltage is low, the processing temperature is set at a second set temperature higher than the first set temperature for a certain period of time immediately after the temperature rises, so that the predetermined temperature is maintained throughout the effective fixing period. It is also possible to FIG. 8 shows this example. In Fig. 8, when the power supply voltage is 85V, the second set temperature T (+=190°C) is operated immediately after the power is turned on, and after 10 minutes, the operation is performed at T1o = 185°C for 20 minutes. This figure shows the temperature distribution in the longitudinal direction of the heating roller 20 when the fixing process is performed at the first set temperature. By varying the second set temperature in this way, it is possible to At times, the image quality can be stabilized by making the temperature exceed the minimum fixable temperature, and conversely, when the voltage is high, power consumption can be reduced by lowering the second set temperature.

In the above embodiment, a halogen lamp heater is used as the heating element, but this is not limited to this, and other electric heating elements such as nichrome wire heaters may be used as long as the amount of heat generated changes depending on the power supply voltage. Naturally, this applies. Furthermore, the fact that the present invention is effective regardless of the longitudinal distribution of the calorific value of the heating element means that the present invention does not simply focus on the calorific value of the heating element; This is obvious because it is based on relationships. Further, the present invention is not limited to the heated roller fixing method as in this embodiment, but can also be applied to a hot plate fixing method, etc., where the heat dissipation of the heating body is not uniform in the effective fixing area.

As described above, according to the present invention, in an image forming apparatus having a heat fixing device using an electric heating element, even if the maximum allowable power supply voltage is twice or more the minimum allowable voltage, By changing the set temperature of the heating element of the heat fixing device according to the power supply voltage, it is possible to efficiently reduce power consumption and minimize the temperature rise inside and outside the image forming apparatus, and also to reduce the temperature rise at low voltage. By reducing temperature unevenness in the image forming apparatus, stable image quality can be maintained over a wide range of voltages.

Therefore, depending on the power supply voltage used commercially in each country, from about 100V to about 240V,
At least two fittings E to correspond to these power supply voltages.
According to the image forming apparatus of the present invention, an image forming apparatus having a heat fixing device that had to be manufactured for each power supply voltage can be compatible with all the power supply voltages described in the above embodiments. Furthermore, the maximum allowable voltage can be made more than twice the minimum allowable voltage, and when fluctuations in the power supply voltage are taken into account, it can be used even in a wide range of power supply voltages from 85V to 264V.

[Brief explanation of the drawing]

FIG. 1 is a machine explanatory diagram of an image forming apparatus according to the present invention. FIG. 2 is an electrical block diagram particularly related to the heat fixing device in the image forming apparatus according to the present invention. FIG. m3 is a temperature change diagram of the heating roller of an embodiment of the image forming apparatus according to the present invention. FIG. 4 is a diagram showing the temperature distribution in the heating roller of an embodiment of the image forming apparatus according to the present invention. FIG. 5 is a diagram showing the temperature distribution in the heating roller shown in FIG. 4 and the temperature distribution in a comparative example. FIG. 6 is a diagram showing the temperature distribution at low voltage in the second embodiment of the image forming apparatus according to the present invention. FIG. 7 is a diagram showing the temperature distribution at high voltage in the second embodiment of the image forming apparatus according to the present invention. FIG. 8 is a diagram showing the temperature distribution of the third embodiment of the image forming apparatus according to the present invention. 1 (1 Image forming device 19: Heat fixing device 20: Heating body 23: Electric heating element 24: Temperature detector 27: Electric heating element control circuit 28: Power supply 29: Power supply voltage detection circuit Figure 2 Time (seconds) Figure Thermistor Figure 5 (heating roller length direction) - one meeting

Claims (1)

[Scope of Claims] 1) A heat fixing device in which the maximum allowable power supply voltage is at least twice the minimum allowable voltage, and is equipped with a heating element using an electric heating element to turn a toner image into a permanent image. What is claimed is: 1. An image forming apparatus having a heating element, wherein a set temperature of the heating element is changed according to a power supply voltage. 2) The image forming apparatus according to claim 1, wherein the set temperature is a fixing temperature for a toner image transferred to a transfer material. 3) The image forming apparatus according to claim 1, wherein the set temperature is a standby temperature at which image formation can be started immediately.