JPS5975271A - Heat roll temperature controller of electrophotographic printer - Google Patents

Abstract

PURPOSE:To prevent the surface temperature of a heat roll from rising abnormally and to prevent deterioration in printing efficiency by selecting a proper heater duty according to form width. CONSTITUTION:When the form width is small, the outputs of NAND gates 14 and 15 and an AND gate 16 go up to a High and the output HON-P3 of a controller 6 and an AND gate 12 turn on and off an S heater 2 at the same 100% duty. When the form width is intermediate, the output of the NAND gate 14 goes up to the High and the NAND gate 15 and the AND gate 16 output the signal at the 75% duty and the output signal of the AND gate 12 turns on and off an M heater 3 at the 75% duty. When the form width is large, the NAND gate 14, NAND gate 15, and AND gate 16 output the signals at the 50%, the 75%, and the 50% duty and the output signal of the AND gate 12 turns on and off an L heater 4 at the 50% duty.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for controlling the heat roll temperature of an electrophotographic printing apparatus having a fixing heat roll.

The temperature of the heat roll is generally controlled by a non-contact temperature sensor. FIG. 1 is a diagram showing an example of the principle. In the figure, 1 is a heat roll, 2 is an S heater, 3 is an M heater, 4 is an L heater, 5 is a temperature sensor, and 6
7 is a control device for turning on/off the heater according to a signal from a temperature sensor, and 7 is an electronic changeover switch for selecting an S heater 2, an M heater 3, or an L heater 4 depending on the paper width.

When the paper width is narrow, the 5HDRV-N signal becomes LOW and the S heater 2 is selected. If the paper width is medium, select M
The HDRV-N signal becomes Low, and the M heater 3 is selected. If the paper width is wide, the LHDRV-N signal is LO.
W, potash, and L heater 4 are selected.

If the surface temperature of the heat roll 1 has not reached the set temperature, the output HON-Pl signal of the control device 6 is HL.
g JL and turn on the heater.

When the surface temperature of the heat roll l reaches the set temperature, the output HON-PI signal of the control device 6 becomes LOW,
Turn off the heater.

When the power is turned on while the heat roll is cold, the heat roll is rapidly heated by the heater, and the temperature of the central part of the heat roll rises faster than the part whose temperature is detected by the temperature sensor 5. As a result, when the temperature of the temperature sensor reaches the set temperature and the heater is turned off, the temperature at the center of the heat roll oversheets and becomes 15 to 20°C higher than the temperature of the temperature sensor. Put it away.

Figure 4 shows the change in the heat roll surface temperature after the power is turned on. The maximum temperature of the heat roll surface after the power is turned on is defined as the oversheet temperature, and the time from when the power is turned on until the oversheet temperature is reached is defined as the rise time.

If printing is started with the heat roll surface temperature overheating, fixing offset may occur.

Furthermore, if the overshoot temperature is high, the silicone rubber on the surface of the heat roll will deteriorate, and the life of the heat roll will be shortened.

Therefore, in order to prevent the heat roll surface temperature from overshooting, after the power is turned on, the heater is controlled to be turned on and off at a certain rate (D payment iy) until the temperature of the temperature sensor reaches the set temperature. It will be done.

As an example, turn on the heater at D 1L2 y of 50 inches.
FIG. 5 shows the change in heat roll surface temperature after the power is turned on when the power is turned off. An embodiment of turning the heater on and off with 50 units of D u, iy is shown in FIG. Further, FIG. 3 shows a time chart of the circuit of FIG. 2.

Below, FIGS. 2 and 3 will be explained.

When the power is turned on, the HDRV-P signal changes from LOW to HL g
It becomes J. At the same time, the heat roll l starts rotating, and the temperature sensor 5 detects the heat roll surface temperature. Since the heat roll surface temperature has not reached the set temperature, the output of the control device 6 remains at HLtJ. Therefore, the flip-flop 8 remains reset and the 0 side output maintains the HLtJI- level.

The Nant gate 9 maintains the Low state, and the counter signal is counted up by CLKI. The output of the counter 10 becomes a signal of 50% D w 7→, and the output of the control device W6 remains at HLgJL, so the output HON-'P 2 signal of the AND gate Minor becomes a signal of 50% D "→. The heater is heated at 50% D sb i y. After the power is turned on, when the temperature of the temperature sensor reaches the set temperature, the output of the control device 6 changes from HL y L to Low.
become. The flip-flop 8 is set by the output signal of the control device 6, and the 0 side output becomes I'OW. When the AND gate 9 hits HLtJL, the counter m is reset and the output of the counter becomes LOW. The output of the inverter 11 remains at HA IJ, and the output HON-P2 signal of the AND gate becomes the same as the output of the control device 6. After the power is turned on, when the temperature of the temperature sensor section reaches the set temperature, the heater is turned on/off only by the output of the control device 6.

An embodiment for preventing the heat roll surface temperature from overheating has been described above. Further, FIG. 6 shows the relationship between the heater D1Liy and the oversheet temperature after the power is turned on for each paper width. Similarly, FIG. 7 shows the relationship between heater D1Lχy and rise time after power is turned on for each paper width. In FIGS. 6 and 7, the Δ mark indicates when the paper width is wide, the mark indicates when the paper width is medium, and the ○ mark indicates when the paper width is narrow.

As shown above, when the heater Dz difference y is set to 50 degrees, the overshoot temperature can be suppressed to 180°C or less. However, if the paper width is narrow, the rise time will exceed one minute.

When the rise time becomes longer, the time until printing starts becomes longer, and printing efficiency decreases.

When the heater Duiy is set to 75 inches, the rise time can be kept within 9 minutes. However, when the paper width is wide, the oversheet temperature is 180°C.
It exceeds. Heat roll offset temperature is 18
Since it is around 5°C, if the overshoot temperature exceeds 180°C, the life of the heat roll will be significantly reduced.

The purpose of the present invention is to eliminate the above-mentioned drawbacks of the prior art, prevent abnormally high temperatures on the surface of the heat roll, and prevent the printing efficiency from decreasing. Oversheet temperature and rise time are defined as follows. do.

Oversheet temperature θg0: Maximum temperature of the heat roll surface after power is turned on.

Start-up time 10: The time it takes for the trench to reach the overshoot temperature after the power is turned on.

Once the type of beer and the control temperature of the heat roll are determined, the overshoot temperature and rise time exhibit approximately constant values depending on the heater selected depending on the paper width. That is, when the paper width is wide, the rise time is short, but the oversheet temperature becomes high.

When the paper width is narrow, the overshoot temperature is lower, but the rise time is longer.

On the other hand, as the heater D is lowered after the power is turned on, the overshoot temperature becomes lower, but the rise time becomes longer.

Therefore, depending on the paper width, the appropriate heater D +7. i y
By selecting , it is possible to satisfy both the oversheet temperature and rise time for all types of paper.

Overshoot temperature of 180℃ for all paper widths
Heaters D u, i y are determined according to each sheet width so that the rise time is 8C or less and the rise time is 9 minutes or less. In this embodiment, when the paper width is wide, the heater Dw i y is set to 5.
If the paper width is medium, set the heater D w iy to 75%.
, if the paper width is narrow, set the heater D 1Li y to 100%.
shall be. In this way, the heater D u
An example in which iy is determined is shown in FIG. still,
FIG. 9 shows a time chart of the circuit of FIG. 8. A method of switching the heater Dμiy depending on the paper width will be described below with reference to FIGS. 8 and 9.

When the power is turned on, the HDRV-P signal changes from LOW to HL.
y J and force. At the same time, the heat roll 1 starts rotating, and the temperature sensor 5 detects the heat roll surface temperature. Since the heat roll surface temperature has not reached the set temperature, the output of the control device 6 remains at HLyJL. Therefore, the 7 lip-flop 8 remains reset, and the 0 side output maintains the HL y J level. Nant gate 9 maintains the low state and counter 1
0 is counted up by CLKl.

When the paper width is narrow, the 5HDRV-N signal becomes bOW, and the heater 2 is selected. 5HDRV-N signal is L
Because of OW, the outputs of the Nands gate 14 and Nands gates 1 and 5 become HL g J, and the output d of the AND gate 16 becomes HL g &, regardless of the output of the counter p.

Therefore, the output of the control device 6 and the output of the AND gate ν HO
The N-P3 signals are the same, +11.100% D w
The S heater 2 is turned on/off at iy.

When the paper width is medium, the MHDRV-N signal is LOW and the M heater 3 is selected. At this time, LHDRV-N
The signal and the 8HDRV-N signal become HLyJL. LH
Since the DRV-N signal is HLyI, the output of the inverter B becomes Low, and the output of the Nant gate 14 becomes tic HL y &, which is unrelated to the output of the counter signal. 5HD
Since the RV-N signal is HLyI, the output of the Nantes gate is equal to the output of the counter 10, and 75% DK,t,
It becomes a signal.

The output of AND gate 16 is also a 75% Dwiy signal, and the output HON-P3 signal of AND gate ν is 75% Dwiy.
It becomes 5 Liy. Therefore, at 75%D 1Li y,
M heater 3 is turned on/off.

When the paper width is wide, the LHDRV-N signal becomes LOW and the L heater 4 is selected. At this time, 5HDRV-N
Since the signal is HL y J, the outputs of Nantesgater and Nantesgater are both determined by the output of the counter shout. The output of Nant gate 14 is 50%Dz
fν, and the output of NAND gate 15 is 75% D
It becomes wχy. And the output of the AND gate 16 is 50
%D u, iy, and the output of the AND gate HON
-P3 signal becomes 50chi. Therefore, 5Q % D st
The L heater 4 is turned on/off based on the difference y.

After the power is turned on, when the temperature of the temperature sensor reaches the set temperature, as explained in FIG. The heater is turned on/off.

According to the present invention, the heater D can be easily adjusted depending on the paper width.
Since the siy can be switched, it is possible to prevent the heat roll surface from becoming abnormally high temperature, and at the same time, it is possible to prevent the printing efficiency from decreasing.

[Brief explanation of drawings]

FIGS. 1 and 2 are schematic diagrams showing the principle of conventional heat roll temperature control. FIG. 3 is a time chart of the control circuit of FIG. 2. FIG. 4 is a graph showing changes in heat roll surface temperature due to the circuit shown in FIG. 1, and FIG. 5 is a graph showing changes in heat roll surface temperature due to the circuit shown in FIG. FIG. 6 is a graph showing the relationship between heater D w iy and overshoot temperature in the conventional example, FIG. 7 is a graph showing the relationship between heater Dwi, y and rise time, and FIG. 8 is an example of the present invention. FIG. 9 is a schematic diagram showing the time chart. In the figure, 1 is a heat roll, 2.3.4 is a heater, 5 is a temperature sensor, 6 is a control device, 7 is an electronic changeover switch, 8 is a flip-flop, 9 is a nant gate, 10 is a counter, ■ is an inno ( -ta, hill is and gate, B is inverter, 14.15 is nant gate, and taku is and gate. Name of patent applicant Hitachi Koki Co., Ltd. Middle 30 50% σty Middle 6 figure heat 70 core ty O Δ diagram −)? Figure 5 + Figure 7 Heater tsulzty

Claims (1)

[Claims] A heat roll, a heater for heating the heat roll, an electronic changeover switch for selecting a heater of different length depending on the paper width, a temperature sensor for detecting the surface temperature of the heat roll, and a heater for heating the heat roll based on a signal from the temperature sensor. In an electrophotographic printing apparatus W, which has a control device for turning on/off the heater and an electric circuit for turning the heater on/off at a certain rate until the heat roll reaches the set temperature after power is turned on, The heat roll temperature control device is characterized in that the rate at which the heater is turned on and off is switched according to the paper width until the heat roll reaches a set temperature.