JP3850609B2 - Heating device and fixing device using the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a heating device and a fixing device using the same, and more particularly to temperature management control of a heat source.
[0002]
[Prior art]
2. Description of the Related Art Image forming apparatuses such as copying machines, printers, and facsimile machines are equipped with a fixing device for fixing a visible image transferred from a latent image carrier such as a photoconductor to a recording sheet.
The fixing device includes a heating member that sets a temperature at which toner can be fused when the visible image is a toner image, and a pressure member that abuts the toner image against the heating member. In general, a heating member and a pressure member are constituted by rollers, and a position where both rollers abut each other is known as a nip portion capable of nipping and conveying a recording sheet.
[0003]
2. Description of the Related Art Conventionally, there is a type in which a heating member used in a fixing device has a built-in heater and heat generation control of the heater is performed based on detection of the surface temperature of the heating roller.
The heating roller is set to a temperature at which the toner can be fused in a state where the toner does not transfer to the surface of the heating roller. For this reason, the heater responds to changes in the surface temperature of the heating roller. It is turned on and off repeatedly. The heater is turned on and off using a control method in which the heater is turned on when the temperature falls below the predetermined temperature based on the predetermined temperature that satisfies the above-described conditions for the toner, and is turned off when the temperature reaches the predetermined temperature or higher. Yes.
[0004]
The temperature control of the heating roller is executed not only at the time of fixing but also at the standby time corresponding to the non-fixing time when the image forming apparatus is in operation. The temperature management during standby is, for example, that the heater is repeatedly turned on and off at intervals of 10 to 120 seconds to be maintained at a predetermined temperature during standby, thereby improving the rise in temperature when shifting to fixing. ing.
[0005]
[Problems to be solved by the invention]
The temperature of the heating roller changes within the specified temperature range in which the heater turn-on start temperature and the turn-off temperature are set. However, the heat deprivation is stable only by heat radiation to the air, and the required power to the heater Easy to set (power consumption). In addition, since the heat capacity and heat transfer amount in the components of the fixing device are known in advance and do not change, the number of heaters to be lit to obtain the required power by calculating the required power during standby by calculation or experiment, There is no difficulty in setting the amount of power.
[0006]
However, when the fixing process is executed during the operation of the image forming apparatus, it is not possible to obtain the power necessary for fixing in general, unlike the standby time.
That is, the amount of heat required for image fixing differs depending on the size of the recording paper used in the fixing process and the size of the image forming area on the recording paper, and the power may vary greatly. For this reason, it is practically difficult to set the number of heaters and the amount of electric power according to individual fixing conditions.
[0007]
Conventionally, in order to be able to cope with each fixing condition, the maximum power amount is the maximum number of heaters that can obtain the power amount when the image forming area is the maximum and the maximum size is used for fixing. In addition, the amount of electric power of each heater is set in advance, and the number of heaters and the amount of electric power are selected and set in accordance with individual fixing conditions. As a result, when the temperature of the heating roller is lowered during fixing, the heater is turned on , and when the temperature is sufficiently increased , the heating temperature corresponding to the fixing condition can be obtained simply by turning off the heater.
[0008]
However, at the time of fixing, the above-described maximum power amount is not always used. For this reason, as shown in FIG. 4, during normal use, the heater is turned on when the temperature of the heating roller is lowered, and the heater is turned off when the temperature of the heating roller reaches a set temperature.
When the heater is turned on and off, the current between the electrodes of the heater is disconnected, and particularly when the heater is turned on, a large inrush current is generated between the electrodes, and the image forming apparatus equipped with the fixing device Power supply line changes, resulting in a shortage of power in other appliances installed in the room where the image forming device is installed. For example, in the case of fluorescent lamps, instantaneous illuminance Decrease or flicker may occur.
[0009]
An object of the present invention is to prevent power shortage to other electrical appliances due to an increase in inrush current generated when a heater used in the heating device is turned on in view of the problems in the conventional heating device and the fixing device using the same. It is providing the heating apparatus provided with the structure.
[0010]
Another object of the present invention is to provide a configuration capable of preventing adverse effects on other electrical appliances caused by turning on and off the heater when using a fixing device having a heating device equipped with a heater. It is to provide a fixing device.
[0011]
[Means for Solving the Problems]
The invention described in claim 1
A heating roller incorporating a plurality of heaters ;
A pressure roller capable of contacting and interlocking with a part of the peripheral surface of the heating roller;
In the fixing device having a temperature detecting means for detecting the temperature of the surface of the heating roller,
When fixing,
When a predetermined temperature is reached within the temperature range necessary for heat-fusing the developer on the recording material,
Turn off the heater located on the side close to the temperature detection means among the heaters that are lit,
When reaching the upper limit temperature of the temperature range, turn off all the heaters,
When the lower limit temperature of the temperature range is reached, all of the plurality of heaters are turned on .
[0012]
According to a second aspect of the present invention, in the fixing device according to the first aspect, there are a plurality of the predetermined temperatures, and the heaters are sequentially turned off each time the predetermined temperature is reached .
[0013]
According to a third aspect of the present invention, the image forming apparatus includes the fixing device according to the first or second aspect.
[0019]
[Embodiments of the Invention]
Hereinafter, embodiments of the present invention will be described with reference to the illustrated examples.
FIG. 1 is a schematic diagram for explaining a configuration of a fixing device to which a heating device according to an embodiment of the present invention is applied.
In FIG. 1, the fixing device 1 includes a heating roller 2 and a pressure roller 3 that can contact and cooperate with the heating roller 2.
The heating roller 2 and the pressure roller 3 can be partly contacted with each other and interlocked in the direction of the arrow in the drawing, and the contacting part can be conveyed while sandwiching the recording paper S. It is the nip part.
[0020]
The heating roller 2 is provided with a heater, and in this embodiment, three infrared heaters 2A, 2B and 2C are provided. Each of the infrared heaters 2A to 2C has a smaller maximum power consumption than the case of a single infrared heater, and when all of the infrared heaters are turned on, the recording is conveyed toward the nip portion via the conveyance guide 4. It is possible to obtain the highest temperature among the set fixing temperatures at which the toner T on the paper S can be fused.
[0021]
The infrared heaters 2 </ b> A to 2 </ b> C are configured such that the energization state is controlled by the control unit 5.
The main part of the control unit 5 is composed of a microcomputer, a temperature sensor 6 such as a thermistor that forms temperature detection means on the input side via an I / O interface (not shown), and infrared heaters 2A to 2C on the output side. Are connected to each other.
When the surface temperature of the heating roller 2 input from the temperature sensor 6 is higher than the preset fixing temperature, the control unit 5 reduces or cuts off the energization state of the infrared heaters 2A to 2C. When the surface temperature of the heating roller 2 is low, the heating roller 2 is heated by correcting the surface temperature of the heating roller by increasing the amount of current supplied to the infrared heaters 2A to 2C. The surface temperature of the roller 2 is kept in the fixing possible temperature range.
[0022]
The temperature control executed in the control unit 5 is as follows.
When the surface temperature of the heating roller 2 is lowered when the fixing is performed while the recording paper S is nipped and conveyed, not during standby in the fixing device 1, energization of the infrared heater is started and the temperature is increased. To recover the surface temperature. At this time, a plurality of predetermined temperatures that are equal to or lower than the upper limit temperature in the fixing temperature range, in this embodiment, at least two predetermined temperatures are set, and each time the surface temperature reaches the predetermined temperature, infrared rays are set. The energization amount to the heater is reduced.
For example, when the upper limit temperature is 185 ° within the fixing temperature range, two stages of temperatures of 175 ° and 180 ° are set as the predetermined temperature.
Accordingly, when the fixing operation is started and the surface temperature of the heating roller 2 is lowered to 165 °, the infrared heaters 2A to 2C are energized and the heaters are turned on to increase the surface temperature of the heating roller 2.
[0023]
When the surface temperature of the heating roller 2 rises and recovers to 175 ° C., the energization amount to the infrared heater is reduced by one step. When the surface temperature recovers to 180 ° C. in this state, the energization amount to the infrared heater is further increased. Decrease by one level. In this case, the energization amount to the infrared heater is reduced. As a method of reducing the energization amount to the infrared heater, the energization amount to each infrared heater at the time when a predetermined temperature is reached in the control unit is stored in advance, and in the drive unit (not shown) of the infrared heater, Take measures such as changing the voltage.
Decreasing the amount of current supplied to the infrared heater slows the temperature rise, reducing the number of times the surface temperature of the heating roller 2 deviates from the fixing set temperature range, and connecting and disconnecting the infrared heater when deviating from that range. The number of times is reduced.
[0024]
As a method of reducing the energization amount to the heater built in the heating roller, not only the setting of the energization amount in each infrared heater but also the infrared heaters 2A to 2C when the energization amount of each infrared heater is constant. It is also possible to adopt a method of setting the number of lights.
FIG. 2 is a timing chart for explaining this case. When the predetermined temperature is reached below the upper limit temperature of the set temperature, the infrared heater 2A is turned off, and the temperature is increased by the remaining infrared heaters to reach another predetermined temperature. Then, one more infrared heater 2B is turned off. As a result, the tendency of the surface temperature of the heating roller 2 to change is slower than in the case shown in FIG. 4, and the time until the temperature deviates from the set temperature range becomes longer. The number of times is reduced. As a result, it is possible to reduce the generation time of the input current to the infrared heater that causes power shortage of other electrical appliances installed in the room in which the image forming apparatus equipped with the fixing device is installed.
[0025]
It is also possible to adopt the following method as a method of reducing the energization amount of the infrared heater.
That is, the infrared heaters close to the temperature detection sensor 6 among the infrared heaters 2A to 2C arranged in the heating roller 2 are turned off. In FIG. 1, the infrared heaters 2A, 2B, and 2C are turned off in this order.
FIG. 3 is a timing chart for explaining this case. In FIG. 3, when the predetermined temperature set in advance is reached, the infrared sensor 2A closest to the temperature sensor 6 and the temperature sensor 6 are the most. The infrared heaters 2C at the distant positions are turned off in order.
[0026]
According to such a method, since the infrared heater 2A that most affects the temperature sensor 6 is turned off, the heat transfer time to the temperature sensor 6 is delayed and the response time by the temperature sensor 6 is delayed. As in the turn-off sequence shown in FIG. 2, the change in surface temperature can be made slower than when the infrared heaters 2B other than the infrared heater 2A closest to the temperature sensor 6 are turned off first. As a result, the number of times of lighting can be further reduced as well as the timing of turning off the infrared heater, so the frequency of occurrence of power shortage to other electrical appliances due to the input current at the time of lighting can be reduced. A similar result can be obtained even when the power of the infrared heater that has been lit to the end is smaller than that of the other infrared heaters.
[0027]
【The invention's effect】
According to the first and second aspects of the invention, when performing temperature control at the time of fixing in which the recording paper is nipped and conveyed, it is within a temperature range necessary for heat-fusing the developer on the recording material. When the temperature reaches a predetermined temperature, the heaters located on the side closer to the temperature detection means among the lit heaters are turned off, and when the upper limit temperature of the temperature range is reached, all the plurality of heaters are turned off, and the temperature range When the lower limit temperature is reached, the plurality of heaters are turned on to reduce the number of inrush currents when a large amount of power is required to sharply control the amount of heat for fixing unlike atmospheric heat dissipation. It is possible to prevent power shortage to electrical products other than the image forming apparatus. Moreover, it is a premise that by turning off the light from the side close to the temperature detecting means for detecting the change in the surface temperature of the heating roller, the detection time of the rising temperature by the temperature detecting means is delayed and the lighting operation by the heater is performed. As a result, the turn-off timing is delayed, and as a result, the number of turn-on times corresponding to the turn-off number is reduced, and the number of occurrences of inrush current during turn-on is reduced to reduce the number of times power shortages occur in other electrical appliances. It becomes possible .
[0028]
According to the third aspect of the present invention, the number of occurrences of inrush current due to the increase in the number of times of lighting in the fixing device used in the image forming apparatus is reduced, and the temperature management necessary for fixing is performed to reduce the power shortage in other electrical appliances. It can be done without inviting .
[Brief description of the drawings]
FIG. 1 is a schematic diagram for explaining a configuration of a fixing device using a heating device according to an embodiment of the present invention.
FIG. 2 is a timing chart for explaining an operating state of a heater used in the heating apparatus shown in FIG.
FIG. 3 is a timing chart for explaining another operation state of the heater used in the heating apparatus shown in FIG. 1;
FIG. 4 is a timing chart for explaining an operating state of a heater used in a conventional heating device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Fixing device in which heating device is used 2 Heating rollers 2A to 2C that are one member constituting the heating device Infrared heater 3 Pressure roller 5 that is another member constituting the heating device 5 Control unit 6 Temperature sensor that is temperature detecting means

Claims (3)

A heating roller incorporating a plurality of heaters ;
A pressure roller capable of contacting and interlocking with a part of the peripheral surface of the heating roller;
In the fixing device having a temperature detecting means for detecting the temperature of the surface of the heating roller,
When fixing,
When a predetermined temperature is reached within the temperature range necessary for heat-fusing the developer on the recording material,
Turn off the heater located on the side close to the temperature detection means among the heaters that are lit,
When reaching the upper limit temperature of the temperature range, turn off all the heaters,
When the lower limit temperature of the temperature range is reached, turn on all the heaters.
A fixing device characterized . The fixing device according to claim 1,
There are a plurality of the predetermined temperatures, and the heater is turned off in turn each time the predetermined temperature is reached .   An image forming apparatus comprising the fixing device according to claim 1.

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