JPH08152923A - Heater - Google Patents

Abstract

PURPOSE: To control the power consumption of a heater to a necessary and sufficient quantity by setting the duty ratio of energizing a heating element during the time in which the temp. of the heating element is raised to a fixing temperature at the time of printing corresponding to the temperature increase rate of the heating element of the heater. CONSTITUTION: The heater is installed along the direction almost orthogonal with the moving direction of a film 1 and composed of a ceramic 6 with satisfactory heat conductivity and a resistance heating element 5 provided on the lower surface of the ceramic 6. On the upper surface of the ceramic 6, a thermistor 4 is provided as a temperature detector. The output signal of the thermistor 4 is inputted through an A/D converter to a CPU. Based on this input signal, the CPU controls the energizing power to the heating element 5 through an AC driver and adjusts the temperature so that the surface temperature of the heater can be the prescribed temperature. In this case, the heater is energized before the paper of a member to be heated is supplied and corresponding to the temperature change rate of the heater, the duty ratio of energizing to the heater from the start of paper supply to the rising up to the adjusted temperature is set.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heating device used in an image forming apparatus such as an electrophotographic apparatus or an electrostatic recording apparatus for heating an image on a recording material to fix or modify the surface property. .

[0002]

2. Description of the Related Art As a heat fixing device which is a representative of image heating devices, JP-A-63-313182 and JP-A-2-15 are known.
In Japanese Patent No. 7878, there is proposed a device using a heating body having a rapid temperature rise and a thin film.

An example of such a film heating apparatus is shown in FIG.
Shown in

Thin heat-resistant film 1 (or sheet)
A movement driving means 11 for the film 1, a heater 6 fixedly supported on one side of the film 1 for fixed temperature control, and a heater 6 on the other side for facing the heater 6. Has a pressing member 2 for closely contacting the developed image bearing surface of the recording material P to be image-fixed to the heater 6 via the film 1, and the film 1 is applied to the film 1 at least during image fixing. The recording material P to be image-fixed which is conveyed and introduced between the pressure member 2 and the recording material P is moved in the forward direction at substantially the same speed, and is held by pressing the heater 6 and the pressure member 2 with the traveling moving film 1 interposed therebetween. The surface is heated by the heater 6 through the film 1 to apply thermal energy to the visible image (unfixed toner image) to soften / melt it, and then the film 1 after passing through the fixing portion and the recording material P are separated at a separation point. It is a heating device that is basically operated.

Reference numeral 12 is a tension roller for applying tension to the film 1.

The temperature of the heater 6 is controlled by the thermistor 4
So that the temperature detected by the heater 6 is constant.
Control energization to.

Phase control, wave number control, or the like is used as a method for controlling the energization. For example, in the case of wave number control, the input power is changed depending on which of the 14 AC input voltages is a basic unit and how many of these waves are energized to the heating element. Let The ON / OFF ratio is represented by a duty ratio and can be changed between 0% and 100%.

In such a film heating system, a heating body having a very small heat capacity and a rapid temperature rise can be used, and the time required for the heater to reach a predetermined heating temperature can be greatly shortened. In addition, since the temperature can be easily raised to a high temperature even from room temperature, it is not necessary to adjust the standby temperature when the apparatus is in a standby state during non-printing, which contributes to power saving.

[0009]

Since the film heating type heating device heats a thin film with a heating body having a low heat capacity, it can be used with much lower electric power than the heating roller type heating device. However, if the input voltage to the heating element fluctuates or the resistance value of the heating element fluctuates, the power consumption of the heating element fluctuates, and if the voltage is high, it consumes more power than is necessary and It could be a constraint. Especially in recent years, printers using electrophotography,
Faxes and the like have a tendency to spread not only to offices but also to general households, and considering the power supply situation, power consumption has never been low. In the conventional case, when the temperature of the heating element is controlled to a certain temperature, for example, the fixing temperature, P
The energization duty ratio is changed by ID control or the like to control the power consumption to an optimum value for temperature control. However, when the heating body temperature is raised from the room temperature to the fixing temperature on the first print of the apparatus, if the energization duty ratio at the start of the rise is set uniquely low, the duty ratio will be increased due to restrictions when the voltage is insufficient. It takes a long time to complete the process, and the heating device may not start up before the recording material rushes in. Therefore, it is normal to perform full power / 100% energization. Therefore, at the start of start-up, there is no choice but to be strongly affected by fluctuations in the input voltage. In order to control the energization duty ratio at the start of startup to the optimum value, it is sufficient to detect the input voltage, but this will increase the cost of the device and solve the problem of variation in the resistance value of the heating element. This is not the preferred method because it cannot be done.

Further, since the electric power required for starting the heating element and the electric power for maintaining the control temperature are different, it is necessary to switch the starting duty and the energization duty ratio immediately after reaching the control temperature of the heating element. However, if only PID control is used for this, since the duty ratio is switched in stages, it takes time until the temperature control of the heating element becomes stable, and undershoot or overshoot may increase.

Therefore, there is a method in which the energization duty ratio immediately after the control temperature is reached is set to an appropriate value in advance and is switched to this value at the same time when the heating body starts up.
If the duty ratio is uniquely determined, it will be affected by the input voltage fluctuation, and the optimum duty ratio will change depending on the thermal condition of the device. It was difficult.

Further, the film heating method has an advantage that the standby temperature control is not required. Therefore, when the apparatus starts printing in the same condition as room temperature (cold st)
art) and printing is performed to some extent and printing is performed again while the pressure roller is warm (reprinting after passing the paper), the difference in fixing ability is large. Therefore colds
By changing the temperature control temperature of the heating element between start and reprint after paper feed and setting the temperature control temperature of cold start higher than that after reprint after paper feed, the fixability is made equal as much as possible, and fixing failure or excessive fixing is caused. It is general to prevent the offset due to. To change the temperature control as described above,
Conventionally, a method is known in which the temperature of the heating element immediately before printing is detected and the temperature control temperature is set accordingly.

However, this method cannot know the print history of the apparatus until printing is performed.
After printing one sheet from the old start, continue 1
Even after printing two sheets, if the temperature of the heating element is the same just before printing, the temperature of the first printed sheet will be adjusted to the same temperature, and the heating element should always be adjusted to an appropriate temperature. Was insufficient.

[0014]

In order to achieve the above-mentioned object, the first invention according to the present application has a heating body and a temperature detecting member for detecting the heating body, and detects the temperature detected by the temperature detecting member. In the image heating device that energizes the heating element so that the temperature is kept constant at a predetermined temperature, the heating element is energized before feeding the material to be heated, and the sheet feeding is performed according to the temperature change rate of the heating element It is characterized in that the duty ratio of energization to the heating body is set from the start to the time when the heating body is raised to the controlled temperature. By detecting the temperature rise rate in the above configuration, the input voltage to the device and the thermal state of the device can be estimated. This makes it possible to start up the heating element with an appropriate amount of electricity and to control the power consumption as necessary and sufficient.

The second invention, like the first invention, detects the rate of temperature rise at the time of energization of the heating element before feeding, and the temperature of the heating element is adjusted on the first sheet of paper in accordance with the detection rate. It is characterized in that the duty ratio of electricity to the heating body immediately after reaching the temperature is set. With the above configuration, overshoot or undershoot of the heating element can be reduced and stable temperature control can be performed.

Further, according to a third aspect of the present invention, the heating element is energized before the sheet is fed to detect the temperature rise rate, and the heating element temperature before the energization is referred to. The temperature control temperature of the heating element can be optimized.

[0017]

【Example】

(First Embodiment) An electrophotographic printer and a fixing device therefor used in this embodiment will be described.

The printer has a process speed of 25 mm /
sec, and OPC with a diameter of 30 mm as shown in FIG.
The photoconductor 13 is uniformly charged to −650 V by the primary charging roller 14, and the laser diode 15 modulated by the image signal is supplied.
Image exposure is performed with a laser beam from the above to form an electrostatic latent image.

The electrostatic latent image is visualized as a toner image by jumping development with magnetic one-component toner.

The toner image is transferred onto the recording material by the transfer roller 18 to which a bias is applied, and the untransferred residual toner is removed by the cleaning blade 19 made of urethane rubber which is in contact with the photosensitive member, and the next image is transferred. Prepared for formation.

The recording material on which the toner image has been transferred is conveyed to the fixing device, where it is fixed by heat and discharged to the outside of the device. The basic configuration of this heat fixing device is the same as that of FIG. 4, and detailed description thereof will be omitted.

The heater 6 is provided along a direction substantially orthogonal to the moving direction of the film, has a thickness of 1 mm, and has a good thermal conductivity, and a resistance value 3 provided on the lower surface of the ceramic.
It consists of a resistance heating element 5 of 4Ω. A thermistor 4, which is a temperature detecting element, is provided on the upper surface of the ceramic. The output signal of the thermistor 4 is sent to the CPU via the A / D converter.
8 is input. Based on this input signal, the CPU 8
Control the electric power supplied to the heating element 5 via the C driver 9,
The surface temperature of the heater is adjusted to a predetermined temperature. The so-called wave number control is used to control the electric power supplied to the heater 6, in which 14 waves of the AC input voltage are used as a basic unit and the input electric power is changed depending on how many of these waves are applied to the heating element. Therefore, the ON / OFF ratio is represented by a duty ratio, and 0 to 100% can be changed in 15 steps in steps of about 7.14%. Of course, the wave number unit is not limited to 14 waves, and may be 20 waves, for example, so that the power can be switched in steps of 5%.

Since the heater must rise to the fixing temperature before the recording material enters the fixing device, the electric power supplied to the heater during the rise from the normal temperature to the fixing temperature maintains the heater at the fixing temperature. Will be greater than the power required to Therefore, the maximum power consumption of the heater is determined when the heater is started up. Considering the fluctuation of the input voltage, the power consumption at the maximum input voltage becomes very large in the conventional device, and an unnecessarily large current is supplied. Further, if the electric power supplied to the heater at the time of start-up is large, the heater rises too quickly, and the overshoot becomes large.
Therefore, in this embodiment, when a print signal is input to the printer, the heater is energized for a predetermined time before the start of paper feeding, the temperature increase rate at this time is detected, and the heater is started up from now on. Set the necessary and sufficient energization ratio. By thus energizing the heater for a predetermined time before starting the actual printing operation, it is possible to determine the thermal state of the device and the input voltage to some extent. For example, if the temperature of the heater is room temperature, the input The higher the voltage, the higher the temperature rise rate. Here, the purpose of this embodiment is to make the power consumption at the time of starting the heater constant irrespective of the input voltage. Therefore, if a voltage of 130 V is input, the power consumption will be 497 W at full power. Things,
Energization duty ratio is 40% to suppress to about 200W
It should just be set to about. Here, 200 W is the electric power necessary to raise the heater to the fixing temperature before the recording material enters the fixing device in a low temperature environment, but of course, this value can be changed depending on the configuration of the device. . Alternatively, it is not necessary to stick to this value even when the device is warm and started up at 200 W or less.

As a method of setting the energization ratio, specifically,
After receiving the print signal from the host computer, the heater 6 is energized for 0.5 seconds before paper feeding (before the recording material enters the nip between the heater and the pressure roller in this embodiment). Detects the temperature rise rate of. From this temperature rise rate and the heater temperature before energization, the energization rate at the time of starting the heater is determined according to the control table of FIG. The reason for referring to the heater temperature before energization is that the difference between the heater temperature and the target fixing temperature at that time can be used to determine the amount of power necessary and sufficient to start up the temperature difference within a certain period of time, but the device does not cool. You can also see if it is warm or warm after printing a few sheets. Although the energization time before sheet feeding is set to 0.5 seconds in the present embodiment, this may be set to any number of seconds depending on the configuration of the apparatus and the ability to detect temperature rise. In addition, immediately after the printer finishes the previous printing, if the heater temperature is still quite high, you may decide not to energize before feeding, but to uniquely set the energization rate at heater startup to be low. .

Further, it is possible to detect the temperature rise rate even at 50% without conducting the energization before the paper feed at the duty ratio of 100%, and it is naturally possible to detect the temperature rise rate from 1% to 100%. Especially when the full power consumption is large, it is effective to reduce the duty ratio.

As described above, the power consumption of the device can be controlled to a necessary and sufficient amount by adopting the configuration of this embodiment.

(Second Embodiment) In this embodiment, the first embodiment is used.
Similarly to the above, electricity is supplied for a certain time before feeding, and the rate of electricity supply to the heater immediately after the heater rises to the fixing temperature is determined from the rate of temperature rise of the heater at this time. As mentioned above, the energization duty ratio is switched before and after the heater reaches the fixing temperature in order to quickly start up the heater.However, if the duty ratio immediately after switching is not an appropriate value, overshooting occurs. Or the undershoot becomes large. Since the proper value of the duty ratio immediately after switching depends on the input voltage to the device and the thermal state, in this embodiment, by energizing the heater before startup, the input voltage to the device and the device The degree of warming is determined and the duty ratio immediately after switching is determined.

Specifically, there is a print signal input,
Before the printer starts feeding the paper, the roller and the heating device in the non-rotationally driven state of the film are energized with full power for 0.5 seconds to detect the temperature rise rate of the heater at this time. Further, the temperature of the heater before energization is also referred to, and the energization ratio immediately after the heater is started is determined from these two parameters according to the control table of FIG. In this embodiment, the 14-wave number control is used for the energization control as in the first embodiment, but other energization controls such as phase control may be used, and this is the same in the first embodiment.

When the paper feeding of the printer is started and the heater rises to the fixing temperature, the heater is energized according to the control table of FIG. 2. However, in this embodiment, this energization amount is appropriate, There is no overshoot or undershoot, or it can be extremely small. After that, the amount of electricity supplied to the heater is automatically switched at any time by PID control or the like to adjust the temperature of the heater to the fixing temperature.

By the way, the 0.5 second energization for determining the energization duty ratio can be detected more accurately by performing the non-rotational driving of the heating apparatus, but before the recording material enters the nip. In that case, there is no problem even if the rotation is performed. The present embodiment and the first embodiment can be used in combination. That is, the heater is started up by the control table of FIG.
It is possible to perform energization immediately after rising with the control table of. Further, the switching to the fixing temperature control from the start-up of the heater may be performed at a temperature slightly lower than the fixing temperature. This is the case when a slight overshoot is expected.

As described above, after the print signal is input, the heater is energized for a certain period of time before the paper feed is started, and the energization duty ratio immediately after the heater is started is determined according to the temperature increase rate at that time, thereby overshooting or Undershoot can be reduced.

In both the first and second embodiments, the control table is composed of a matrix of the heater temperature before the heater is energized, but it goes without saying that the control can be effected only by the temperature rise rate of the heater. Absent.

(Third Embodiment) In this embodiment, as in Embodiments 1 and 2, the heater is energized for 0.5 seconds before feeding, the temperature rise rate at that time and the heater temperature before energization. From the above, the heating condition of the heating device is determined, and the fixing temperature of the first print is determined. This control table is shown in FIG. 1
The fixing temperature of the first sheet is 160 ° C, 170 ° C, 180 ° C, 19
You can select 4 types of 0 ℃. In the conventional device, since the fixing temperature of the first print is determined only by the temperature of the heater before printing, even if the difference between cold start and reprinting after paper passing is known, it is However, it was difficult to understand how warm the heating device was. In the present embodiment, in addition to the heater temperature before printing, the rate of temperature rise is also detected, so the state of the heating device can be known more accurately than before, and a more appropriate temperature adjustment temperature can be set. As a result, it is possible to obtain a good image without offset and defective fixing.

In each of the above-mentioned embodiments, the temperature change rate is measured by energizing for a predetermined time, but the temperature change rate may be measured by detecting the time required for the temperature to rise by a predetermined temperature. .

[0035]

As described above, the first aspect of the present application
According to the invention, the heating element of the heating device is energized in advance before the recording material is fed, and the heating element is energized while the heating element is raised to the fixing temperature during printing according to the temperature increase rate. By setting the duty ratio, the power consumption of the heating device can be controlled to a necessary and sufficient amount.

According to the second invention of the present application,
Overshoot or undershoot of the heating element is determined by determining the energization duty ratio to the heating element immediately after the heating element reaches the fixing temperature for the first print sheet according to the temperature increase rate due to the energization of the heating element before feeding. The shoot can be reduced, and the temperature of the heating element can be stably controlled immediately after reaching the fixing temperature.

Further, according to the third invention of the present application, the temperature control temperature of the first print is set according to the temperature of the heating body before feeding and the rate of temperature increase due to energization. It is possible to perform the fixing operation at an appropriate temperature suitable for the state, and it is possible to obtain a good image without offset and fixing failure.

[Brief description of drawings]

FIG. 1 is a diagram showing a control table according to a first embodiment.

FIG. 2 is a diagram showing a control table according to a second embodiment.

FIG. 3 is a diagram showing a control table according to the third embodiment.

FIG. 4 is a diagram showing a conventional heating device.

FIG. 5 is a diagram illustrating a configuration of an electrophotographic printer used in the first embodiment.

[Explanation of symbols]

 1 film 2 pressure roller 3 film stay 4 thermistor 5 heating element 6 ceramic substrate 7 A / D converter of thermistor voltage 8 CPU 9 AC driver for power control of heating element 11 driving roller 12 tension roller 13 photosensitive drum 14 charging roller 15 Laser exposure device 16 Developing device 17 Paper feed roller 18 Transfer roller 19 Cleaning blade

Claims (5)

[Claims] 1. A heating device having a heating body and a temperature detecting member for detecting the temperature of the heating body, and controlling energization of the heating body according to the temperature detected by the temperature detecting member, for feeding a material to be heated. A heating device, characterized in that it comprises means for previously energizing the heating body and for deciding various controls thereafter according to the temperature change rate of the heating body. 2. The heating device according to claim 1, further comprising means for controlling an amount of electricity supplied to the heating body during the heating of the heating body to a predetermined temperature among the various controls. 3. Among the various controls described above, a means for controlling the energization amount to the heating body immediately after the switching is made while switching the energization amount to the heating body at the same time when the heating body rises to a predetermined temperature. The heating device according to claim 1. 4. The heating device according to claim 1, further comprising means for determining a control temperature of the first sheet passing sheet among the various controls described above. 5. A heating device, comprising: a film that moves together with a recording material supporting a visible image; and a heating member, wherein the heating member heats the recording material carrying the visible image through the film. The heating device according to any one of claims 1 to 4, wherein the heating element is heated before the movement of the heating element.