JPH09197894A - Fixing heater controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device where a rush current is reduced and stablized fixing performance without failure in temperature control is achieved. SOLUTION: This fixing device is provided with a heating roller with a built-in heating element and a pressing roller being in press-contact with the heating roller, and recording paper where toner is stuck passes between rollers so that toner is fixed on the recording paper. A heating element at the inside of the heating roller 1 is composed of a nichrome wire heater H1 where the rush current is low and a halogen lamp heater H2 where the rush current other than that is large and the rising of temperature is quick. A CPU 4 controls to firstly turn on the heater H1 where the rush current is low and to nextly turn on the heater H2 where the rush current is large.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing heater control device, and more particularly to a fixing heater control device in a thermal pressure type fixing device in a copying machine or the like.

[0002]

2. Description of the Related Art A halogen lamp heater has been conventionally used as a heating element of a fixing device in a copying machine or the like. However, due to its characteristics, the halogen lamp heater has a current that is nearly 10 times that in a steady state. Is known,
This phenomenon becomes remarkable when the temperature of the heater is low. Therefore, in a large-capacity heater, a large current flowing at the time of lighting causes a failure in which the voltage of the power supply line is lowered, and the voltage of other electric devices connected to the line is momentarily lowered. Phenomena such as flicker of fluorescent lights occur. Further, in the recent information society, serious damage such as computer resetting and destruction of important information has been reported.

[0003]

Therefore, when the heater is changed to a heating element using a nichrome wire, the above-mentioned phenomenon can be avoided because the change in the resistance value is small and the above-mentioned phenomenon is avoided. Due to problems such as slow fall and poor responsiveness (large temperature overshoot and undershoot), it is difficult to use in a high-speed large-scale copying machine that uses a large capacity.

[0004]

According to a first aspect of the present invention, there is provided a heat and pressure type fixing device including a heating roller containing a heating element and a pressure roller pressed against the heating roller. It consists of a first heater with a low current and a second heater with a high inrush current and a rapid temperature rise, and the first heater with a low inrush current is turned on first, and then the inrush current is high. The present invention provides a fixing device which has a control means for turning on the second heater, and thereby provides a stable fixing performance with a small inrush current and no trouble in temperature control.

According to a second aspect of the present invention, in the fixing heater control device according to the first aspect, a detection for detecting which heater has broken due to a difference in temperature rising rate between the first heater and the second heater. The present invention is characterized in that it is possible to automatically determine which of the heaters is broken, the time for replacing the heater can be shortened, and the downtime of the machine can be reduced.

According to a third aspect of the present invention, in the fixing heater control device according to the first aspect, the electric power of the two heaters is distributed to the first heater having a smaller inrush current as much as possible, and at the time of copying. It is characterized in that the lighting of the heater is controlled within an appropriate temperature range, whereby a slow rising portion of the nichrome wire heater (first heater) is supplemented with a halogen lamp heater (second heater). This enables the optimum temperature control and at the same time reduces the inrush current.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a view for explaining the outline of a fixing device to which the present invention is applied. In FIG. 1, 1 is a heating roller and 2 is a pressure roller, as is well known. The recording paper on which the toner is attached is the heating roller 1 and the pressure roller 2.
And the toner is heated during that time to be pressure-bonded (fixed) to the recording paper.

Thus, in the present invention, the heater 1 is provided with two heaters H1 and H2 inside,
One is a nichrome wire heater H1 with a low inrush current.
The book is a halogen lamp heater H2 that has a large inrush current and a rapid rise in temperature. A thermistor 3 is provided outside the heating roller 1 for measuring the surface temperature.

FIG. 2 is a block diagram of a fixing heater control device according to the present invention. The two heaters H1 and H2 shown in FIG.
Are connected to solid state relays SSR ₁ and SSR ₂ , respectively, and can be turned on / off by a signal from the CPU 4. The output signal of the thermistor 3 is also CPU
4 and is converted into a digital value by A / D conversion, and the surface temperature of the heating roller 1 can be measured.

Table 1 is a summary of the differences between the nichrome wire heater H1 and the halogen lamp heater H2, and there are significant differences between the two as shown in Table 1. That is, the nichrome wire heater has a smaller rush current and a slower temperature rise than the halogen lamp heater.

[0011]

[Table 1]

FIG. 3 is a waveform diagram for explaining the operation of the present invention. FIG. 3 (A) is a standby waveform diagram, FIG. 3 (B) is a waveform diagram during copying, and FIG. 4 is a waveform diagram of the present invention. 4A and 4B are flowcharts for explaining the operation, wherein FIG. 4A shows a waiting state and FIG. 4B shows a copying state.

First, waiting (FIG. 3 (A), FIG. 4)
Explaining the operation of (A), the fixing roller must be warmed within a certain temperature range so that copying can be started at any time during standby other than during copying. C
The PU 4 sequentially reads the temperature from the thermistor 3, and when the temperature becomes lower than the lower limit temperature, first, the SSR ₁ is turned on and the nichrome wire heater H1 is turned on. The nichrome wire heater H1 has a small inrush current and has an effect of warming the halogen lamp heater H2. Next, after a certain period of time, SSR ₂ is turned on and the halogen lamp heater H2 is turned on to cover the rising delay of the nichrome wire heater H1. At this time, since the halogen lamp heater H2 itself has already been warmed by the nichrome wire heater H1, the inrush current is small. When the target temperature is reached, SSR ₁ and SSR ₂ are sequentially turned off and turned off.

Next, during copying (FIG. 3 (B), FIG. 4)
Explaining the operation of (B), since a large amount of heat is taken off by the transfer paper during copying, the SSR is started at the same time when the copying is started.
₁ turns on the ON and nichrome wire heaters H1 and temperature control during the copy has been adjusted by the SSR ₂ i.e. the halogen heater H2. The CPU 4 monitors the rate of temperature increase and measures it when the SSR ₁ and SSR ₂ are turned on. If the temperature does not increase at a constant rate of increase, the copy operation is stopped and an abnormality occurs in the operation unit. Display that. The rate of change in temperature is different for SSR ₁ and SSR ₂ , so it can be determined, and which heater has failed is displayed on the display screen exclusively for service personnel.

[0015] Figure 5 is a diagram showing the relationship between the SSR _1, ON operation and the temperature rise of the SSR _2, as shown, SSR ₁ is O
N, the fixing roller 1 rises in temperature at a rate of change of Δ ₁ ,
When SSR ₂ is turned on, the temperature rises at a rate of change of Δ ₂ .
Therefore, it is possible to know which heater has operated from this difference in the rate of change in temperature rise, and it is possible to know which heater has failed by monitoring this rate of temperature change by the CPU 4.

[0016]

According to a first aspect of the present invention, there is provided a heat and pressure type fixing device comprising a heating roller containing a heating element and a pressure roller pressed against the heating roller, wherein the heating element has a low inrush current. No. 1 heater and a second heater with a large inrush current and a rapid rise in temperature, other than that, the first heater with a lower inrush current is lit first, and then the second heater with a larger inrush current Since the control means for turning on is provided, it is possible to provide a fixing device which has a small inrush current and exhibits stable fixing performance without any trouble in temperature control.

According to a second aspect of the present invention, in the fixing heater control device according to the first aspect, the detection of which heater is broken is detected based on the difference in temperature rise rate between the first heater and the second heater. Since the means is provided, it is possible to automatically determine which of the heaters is broken, the time for replacing the heater can be shortened, and the downtime of the machine can be reduced.

According to a third aspect of the present invention, in the fixing heater control device according to the first aspect, the power distribution of the two heaters is distributed to the first heater having the smaller inrush current as much as possible, and the power is distributed to the first heater at the time of copying. Since the lighting of the heater is controlled within an appropriate temperature range, the halogen lamp heater (second heater) compensates for the slow rising portion of the nichrome wire heater (first heater) to achieve optimum temperature control. Enable and
At the same time, the inrush current can be reduced.

[Brief description of drawings]

FIG. 1 is a diagram showing an outline of a fixing device to which the present invention is applied.

FIG. 2 is an electrical block diagram for explaining an embodiment of a fixing heater control device according to the present invention.

FIG. 3 is a waveform diagram (time chart) for explaining the operation of the present invention.

FIG. 4 is a flowchart for explaining the operation of the present invention.

FIG. 5 is a diagram showing a difference in change in temperature rise rate when a nichrome wire heater is turned on and when a halogen lamp heater is turned on.

[Explanation of symbols]

1 ... heating (fixing) roller, 2 ... pressure roller, 3 ... thermistor, 4 ... CPU, H1 ... nichrome wire heater, H2 ... halogen lamp heater, SSR _1, SSR ₂ ... solid-state relay.

Claims (3)

[Claims] 1. A heat-pressure type fixing device comprising a heating roller containing a heating element and a pressure roller pressed against the heating roller, wherein the heating element is a first heater having a low inrush current, and other than that. The second heater has a large inrush current and a quick rise in temperature, and the first heater having a low inrush current is used first.
The fixing heater control device is provided with a control means for turning on the second heater having the next largest inrush current after turning on the first heater. 2. The fixing heater control device according to claim 1, further comprising a detection unit that detects which heater has broken due to a difference in temperature rising rate between the first heater and the second heater. A fixing heater control device characterized by the above. 3. The fixing heater control device according to claim 1, wherein the power distribution of the two heaters is distributed as much as possible to a heater having a smaller rush current, and the heaters are turned on during copying in an appropriate temperature range. A fixing heater control device characterized by being controlled inside.