JPH0623911B2 - Heat fixing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention relates to heat fixing used in a copying machine or the like in which powder on a substrate is heated to melt and fix the powder on the substrate. Regarding the device.

<Prior Art> Electrophotographic copying machines in which a heat fixing device is most commonly used are installed in many offices and the like today. Has occurred. That is, as the speed of the copying machine increases, the power consumption increase in the heat fixing device may exceed the 15A power capacity, which is the most common power outlet standard. If you simply increase the capacity of the fixing device without taking any measures, it is likely that most high-speed machines will not be able to use ordinary power outlets, and special power supply work will be required at the same time as installing the copying machine. To be However, performing special power supply work to install the copier means that the cost of the power supply work in addition to the cost of the copier is incurred, and the actual cost to the user is the sum of both. There is an inconvenience that the cost will rise significantly. Also,
Normally, when a fixing device is installed, it is possible to sufficiently fix the toner in the worst case, that is, when the rated voltage is about 90% in consideration of the fluctuation of the power supply voltage. If the design method is simply applied, sufficient power will be supplied to the fixing device at the rated voltage, that is, more power will be supplied than was necessary, including wasted power.
The rated power consumption of the copier as a whole is increased by that amount, and there is a disadvantage that the capability (speedup) of the copier is limited when trying to be compatible with an ordinary power outlet.

<Purpose of the Invention> An object of the present invention is to maintain the high-speed copying within the rated power consumption without increasing the power consumption of the fixing device, and to obtain a constant fixing property even under adverse conditions. To provide a device.

<Constitution and Effect of the Invention> The present invention passes through the fixing device when the electric power supplied to the heater of the fixing device is reduced or the electric power supplied to the fixing device and the amount of heat emitted from the fixing device are out of balance. This is done by paying attention to the fact that the balance between the two can be maintained by reducing the number of base materials to be heated. By heating the powder on the base material, the powder is melted and fixed on the base material. In the fixing device, a fixing device that is heated by supplying electric power to a heater and melts and fixes the powder on the substrate by passing through the substrate, and a temperature sensor that detects a surface temperature of the fixing device. A temperature control circuit for controlling the power supply time to the heater based on the temperature detected by the temperature sensor to control the surface temperature of the fixing device to a predetermined temperature; and a continuous power supply time to the heater. Continuous power supply to detect When the time detection means and the continuous power supply time detected by the detection means become longer than a predetermined time, the number of the base materials passing through the fixing device within a unit time is reduced according to the length. And a heating and fixing device.

According to the configuration of the present invention, since a constant fixing property is obtained even under the worst conditions, it is not necessary to use a heater with a large power consumption as in the conventional case. In other words, if an external condition such as a decrease in the surface temperature of the fixing device is added, and the fixing device cannot be controlled to a predetermined temperature even if power is continuously supplied to the heater based on the temperature sensor, the heater is The number of base materials passing through the fixing device is reduced in a state where the continuous supply time of the supplied electric power exceeds a certain time. In other words, factors such as a decrease in voltage, a decrease in ambient temperature, and an increase in heat absorbed by the base material can be detected during the continuous supply time. It is possible to always obtain a certain fixing property without decreasing the

Therefore, unlike the conventional method, extra power is not consumed at the time of rating, and even if a large heater capacity is not used for the fixing device, it will pass through the fixing device when external conditions such as voltage drop change. By reducing the number of base materials
It is possible to always obtain a certain fixing property, and it is possible to maintain high speed without reducing the number of substrates during normal operation in which the external conditions do not change.

In addition, when reducing the number of base materials, the continuous power supply time is detected when the fixing device cannot be controlled to a predetermined temperature even if power is continuously supplied to the fixing device as described above. If the surface temperature of the paper is only temporarily reduced and the surface temperature recovers to the specified temperature, unnecessary control is performed to reduce the number of base materials that originally pass through the fixing device, and the processing speed is meaninglessly decreased. I won't let you.

<Embodiment> FIG. 1 is a block diagram of a copying machine to which a heat fixing device according to an embodiment of the present invention is applied. In the figure, 1 is a document table on which a document 2 is placed and reciprocates, 3 is a photosensitive drum that rotates clockwise, 4 is a charger that uniformly charges the surface of the photosensitive member, 5 is a developing device, and 6 is A transfer device that transfers the image formed on the photoconductor onto the transfer paper 7, 8 is a cleaner, 9 is an exposure lamp, 10 is a plastic fiber lens that exposes the light reflected from the original 2 onto the photoconductor surface, and 11 is A cassette for accommodating the transfer paper 7,
A paper feed roller 12 conveys the transfer papers one by one from the cassette 11. Further, 13 and 14 are fixing rollers, and a heater 15 for heating the fixing rollers 13 is arranged in the fixing roller 13.

With the above configuration, when the copy button is pressed, the document table 1
Moves to the left, and at the same time, the photoconductor drum 3 rotates, the document 2 is exposed on the photoconductor, and the image visualized by the developing device 5 is transferred to the transfer paper 7. Is discharged through the fixing rollers 13 and 14. When the document table 1 completes the forward movement, a switch (not shown) detects this and causes the document table 1 to reciprocate. Then, one copy is completed when the document table 1 returns to the home position. In the case of multi-copy, the above operation is continuously repeated to send the transfer paper 7 to the fixing rollers 13 and 14 at a constant interval.

FIG. 2 is a circuit diagram of the control unit of the copying machine.

The power supply voltage supplied from the power outlet 20 is supplied to the primary side of the power detection circuit transformer 21 and the control circuit transformer 22. The winding ratio is set so that the secondary side voltage of the transformer 21 is about 8 V at the rated time, and the full-wave rectifier 23
Join in. The capacitor 24 smoothes the full-wave rectified voltage to convert the secondary voltage of 8V into a DC voltage of about 10V. The smoothed voltage is divided by the variable resistor 25 and the resistor 26,
The divided voltage is applied to the base of the transistor 27. A Zener diode 28 that forms a reference voltage is connected to the emitter of the transistor 27, and the transistor 27 is turned on by comparing the sum of the Zener voltage 5V and the base-emitter voltage of the transistor 27 with the voltage across the variable resistor 25. It is controlled to turn off. The transistor 29 receives the output of the transistor 27 and turns on / off according to the on / off state of the transistor 27 to output the power supply voltage detection signal a. With the above configuration, the circuit formed by combining the variable resistor 25, the resistor 26, the transistors 27 and 29, and the zener diode 28 constitutes the voltage detector A that detects the fluctuation of the power supply voltage.

The secondary side output of the transformer 22 is stabilized by the DC stabilizing circuit 30, and the return motor control circuit 31 and the control circuit 3 are provided.
2 is supplied. The return motor control circuit 31 receives the output of the output transistor 29 of the voltage detector and controls the speed of the return motor 33. The control circuit 32 controls the return motor control circuit 31 and a load 34 such as a solenoid, a relay, a clutch, and a motor.

The power source voltage obtained from the power outlet 20 is further supplied to the fixing device heater 15 via the relay contact 35.
It is also supplied to the exposure lamp 37 via the relay contact 36. The relay contacts 35 and 36 are included in the load 34 and are on / off controlled by the control circuit 32. for that reason,
By the control circuit 32 performing ON / OFF control of the relay contact 35 based on the temperature detection signal from the temperature sensor,
Continuous supply of electric power to the fixing device heater 15 is controlled, and the surface temperature of the fixing roller 13 is controlled to a predetermined temperature.

As the heater 15 for the fixing device, a heater having a rating of 900 W is used. Generally, in a high-speed copying machine having a copying speed of 30 sheets per minute, a certain fixing property cannot be obtained unless power of 800 W is continuously supplied to the heater for the fixing device. Therefore, it is possible to provide a margin of 100 W by using the fixing device heater 15 having a rating of 900 W.

Next, the setting position of the variable resistor 25 of the voltage detector will be described. 90 as the heater 15 for the fixing device as described above
If 0 W is used, the heater output will be about 800 W when the power supply drops to 95% of the rated power. Therefore, at a voltage of 95% to the rated voltage, a sufficient fixing property can be obtained at a copying speed of 30 sheets per minute. On the other hand, if the power supply voltage drops to 90% of the rating, which is the worst state of the power supply, the heater output will be about 700W. Therefore, in this case, the copying speed may be reduced to such an extent that the surface temperature of the fixing device does not decrease during continuous copying. According to experiments, the power supply voltage is 90
When it decreases to%, a sufficient fixing property can be obtained by setting the copying speed to 25 sheets per minute. Therefore, when a heater for a fixing device rated at 900 W is used, copying can be performed at a high copying speed of 30 sheets for 1 minute until the power supply voltage drops to 95%, and when the power supply voltage drops to 95% or less. When the copying speed is reduced to 25 sheets for 1 minute, a certain fixing property can be obtained regardless of the fluctuation amount of the power supply voltage. Therefore, the variable resistor 25 of the voltage detector is set to detect when the power supply voltage reaches 95% of the rated value.

The setting position of the variable resistor 25 will be described in more detail.

As described above, the voltage across the capacitor 24 is 10 V at the rated power supply voltage. Therefore, when the power supply voltage drops to 95% of the rated value, the voltage across the capacitor 24 becomes 9.
It drops to 5V. On the other hand, the Zener diode 28 having a Zener voltage of 5 V is selected. Therefore, when the voltage across the capacitor 24 is 9.5V, the setting position of the variable resistor 25 is 5V plus the Zener voltage.
Base-emitter voltage of transistor 27 0.65 V
If the power supply voltage is equal to or lower than 95% of the rated value, the transistor 27 remains off, and if it exceeds 95%, the transistor 27 is turned on. That is, the power supply voltage detection signal a is 95% of the rated power supply voltage.
When it is below, the state becomes "H", and when it exceeds 95%, it becomes "L".

By setting the variable resistor 25 as described above, the return motor control circuit 31 can control the speed of the return motor 33 with 95% of the rated power supply voltage as a boundary. That is, when the power supply voltage detection signal a is "H", the backward movement motor control circuit 31 reduces the number of revolutions of the backward movement motor 33 to set the copying speed to 25 sheets per minute. When the power supply voltage detection signal a is "L", the number of revolutions of the backward movement motor 33 is increased to set the copying speed of 30 sheets for 1 minute.

By detecting the fluctuation of the power supply voltage applied to the heater for the fixing device by the voltage detector A, that is, the fluctuation factor of the surface temperature of the fixing roller 13 as described above, the normal condition in which the power supply voltage is 95% or more of the rated value is obtained. High-speed performance of 30 sheets can be maintained for 1 minute. In other words, within this range 900
Since it is not necessary to use the heater 15 for the fixing device having a large capacity exceeding W, the surplus power consumed does not become so large,
Since the surface temperature of the fixing roller can be sufficiently maintained at the predetermined temperature, it is possible to obtain a copying machine capable of exhibiting high speed performance.
Moreover, when the power supply voltage drops below 95% of the rated value, the number of transfer sheets passing through the fixing roller is reduced in order to prevent the surface temperature of the fixing roller from decreasing. The copier can be used while being maintained.

Next, the return motor control circuit 31 will be described with reference to FIG. This figure is a circuit diagram of the backward movement motor control circuit 31.

In the figure, a reference signal generation circuit 310 generates a constant reference pulse and inputs it to a frequency divider 311 and a frequency divider 312 having a smaller frequency division ratio. The AND gate 313 logically ANDs the power supply voltage detection signal a and the output of the frequency divider 311. The AND gate 314 logically ANDs the signal obtained by inverting the power supply voltage detection signal a by the inverter 315 and the output of the frequency divider 312. . The OR gate 316 is the AND gate 313, 31 described above.
The output of 4 is logically summed, and the AND gate 317 logically ANDs the logical sum output and the return permission signal b from the control circuit 32 and outputs the logical product to the motor drive circuit 318. The output of the motor drive circuit 318 is supplied to the return motor 33.

With the above configuration, when the power supply voltage detection signal a is "L", the output of the frequency divider 312 is guided to the motor drive circuit 318, and when the power supply voltage detection signal a is "H", the output of the frequency divider 311 is output. It is guided to the motor drive circuit 318. Since the frequency divider 311 has a larger frequency division ratio than the frequency divider 312,
After all, the frequency of the divided pulse guided to the motor drive circuit 318 is smaller when the power supply voltage detection signal a is "L" than when it is "L". That is, the reciprocating motor 33 makes the rotation speed faster when the power supply voltage detection signal a is "L" than when it is "H". As a result, when the power supply voltage exceeds 95% of the rated value, the backward moving speed of the document table 1 is high, and when it is 95% or less, the backward moving speed becomes relatively slow. Therefore, by appropriately setting the frequency division ratios of the frequency dividers 311 and 312, it becomes 1 when the power supply voltage exceeds 95% of the rating.
The original platen 1 can be moved back so that the copy speed is 30 sheets per minute, and when the power supply voltage is 95% or less of the rated value, the original platen 1 is returned so that the copy speed is 25 sheets per minute. Can be moved.

In the above-described embodiment, the rotation speed of the return motor 33 is controlled with reference to 95% of the rated power supply voltage. However, the reference is set in two stages of 94% and 97% of the rating, and The backward movement speed of the document table 1 by the moving motor 33 can be set in three stages. FIGS. 4 and 5 are a circuit diagram of the voltage detector B and a circuit diagram of the return motor control circuit 32 in that case. In the configuration, the part different from the above-mentioned embodiment is that the voltage detector B is configured in two stages in parallel, and the first stage variable resistor 25 is used.
Is set to 94% of the rating, and the variable resistor 25 'is set to 97% of the rating. Furthermore, the first stage output transistor 2
The combination circuit of the AND gates 50 to 52 and the inverter 53 receives the output of 9 and the output of the output transistor 29 'of the second stage to determine three states, and the frequency dividers 321 to 323 according to each state. One of the divided pulses is guided to the motor drive circuit 329. With such a configuration, the power supply voltage detection signal c becomes "H" when the outputs of the first-stage output transistor 29 and the second-stage output transistor 29 'of the voltage detector B are "H" and "H", respectively. , Similarly, the output of each transistor is “H”,
The signal d becomes "H" when it is "L", and the signal e becomes "H" when the output of each transistor is "L" and "L", respectively. Therefore, the power supply voltage is 94% of the rating.
When it is below, the frequency divider 321 having the largest frequency division ratio
Is selected, the frequency divider 322 is selected when the power supply voltage is between 94% and 97% of the rating, and the frequency divider 323 having the smallest frequency division ratio is selected when the power supply voltage is 97% or more of the rating. To be elected.

Although it is possible to control the backward movement speed of the document table 1 by detecting the decrease of the power source voltage which is the main factor of the surface temperature of the fixing roller 13, the surface of the fixing roller 13 is generally used. In a device provided with a temperature sensor such as a thermistor for detecting the temperature, it is possible to directly detect the variation of the surface temperature from the output of the temperature sensor. The use of such a temperature sensor has an advantage in that the fluctuation of the surface temperature of the fixing roller 13 can include fluctuations of the ambient temperature and humidity in addition to fluctuations of the power supply voltage. In a copying machine using this temperature sensor, the electric power is continuously supplied to the heater when the temperature detected by the temperature sensor decreases, and the electric power supply to the heater is stopped when the surface temperature of the fixing roller reaches a predetermined temperature. Are controlled. Therefore, if the surface temperature of the fixing roller 13 does not reach the predetermined temperature even if the electric power is supplied to the heater for a long time, the amount of heat supplied is insufficient. Therefore, if the time for continuously supplying the electric power to the heater continues for a certain time or longer, it means that the roller surface temperature cannot be controlled to the predetermined temperature. In such a state, the backward movement speed of the document table 1 is reduced.

As the means for detecting the state where the roller surface temperature does not return to the predetermined temperature, it is possible to directly use the temperature sensor without using the continuous power supply time detecting means. In this case, the temperature of the fixing device temporarily drops as the substrate passes, and the temperature sensor can be controlled to a predetermined temperature even when it is not actually necessary to reduce the number of substrates passing through the fixing device 2. If it is in such a state, it may be detected, which is not preferable.

FIG. 6 is a schematic configuration diagram for controlling the copying speed according to the continuous power supply time to the heater described above. In the figure, 60 is a fixing roller, 61 is a heater, 62 is a thermistor, 63 is a control unit, and 64 is a power supply unit. Control unit 6
3 controls the power supply time by the power supply unit 64 based on the temperature detected by the thermistor 62. That is, when the detected temperature decreases, electric power is continuously supplied to the heater 61 via the electric power supply unit 64 to keep the surface temperature of the fixing roller 60 at a predetermined temperature. At this time, the fixing roller 60 is lowered due to a decrease in power supply voltage, a decrease in ambient temperature, or passage of a base material.
If the surface temperature of No. 1 cannot be maintained at the predetermined temperature, the continuous supply time of electric power becomes long. Then, when the continuous power supply time continues for a certain time or longer, the power supply unit 64 considers that the roller surface temperature no longer reaches the predetermined temperature, and outputs a signal corresponding to the continuous time to the return motor control circuit 31 ( Second
Output). With this configuration, it is possible to detect factors such as a decrease in power supply voltage, a decrease in ambient temperature, and an increase in the amount of heat taken by the base material. In response to this detection, the backward movement time of the document table 1 can be lengthened and the number of transfer sheets per unit time passing through the fixing roller can be reduced.

In the embodiment described above, the control of the number of transfer sheets passing through the fixing roller within a unit time, that is, the control of the copying speed is performed by the backward movement speed control of the platen 1. However, the optical system movable copying machine is used. Then, the returning speed of the optical system may be controlled.

[Brief description of drawings]

FIG. 1 is a structural diagram of an electrophotographic copying machine to which a heat fixing device according to an embodiment of the present invention is applied, FIG. 2 is a circuit diagram of a control unit of the copying machine, and FIG. 3 is a circuit diagram of a return motor control circuit. FIG. 4 is a circuit diagram showing another example of the voltage detector of the control section, FIG. 5 is a circuit diagram showing another example of the return motor control circuit, and FIG. 6 is an embodiment of the present invention. 3 is a circuit configuration diagram of a power supply control unit of FIG. 13, 14 (60); fixing rotor, 15 (61); heater,
31; return motor control circuit, 62; temperature sensor, 63;
Control unit, 64; Power supply unit.

 ─────────────────────────────────────────────────── ─── Continuation of front page (56) Reference JP 54-41142 (JP, A) JP 55-146467 (JP, A) JP 57-67970 (JP, A) JP 58- 54365 (JP, A) JP-A-57-118284 (JP, A) JP-A-54-80135 (JP, A)

Claims (1)

[Claims] 1. A heating and fixing device for melting and fixing a powder on a base material by heating the powder on the base material, wherein the powder is heated by supplying electric power to a heater and passes through the base material. By fixing the powder on the base material, the temperature sensor for detecting the surface temperature of the fuser, and the time for supplying electric power to the heater are controlled based on the temperature detected by the temperature sensor. A temperature control circuit for controlling the surface temperature of the fixing device to a predetermined temperature, a continuous power supply time detecting means for detecting a continuous power supply time to the heater, and a continuous power supply time detected by the detecting means. And a unit for reducing the number of the base materials passing through the fixing unit within a unit time in accordance with the length, the heating and fixing device.