JPS60123878A - Heat fixing device - Google Patents

Abstract

PURPOSE:To take a copy at a high speed without increasing rated power consumption by controlling the frequency of the reciprocation of an original scanning system or the time of single reciprocation according to the surface temperature of a fixing device or the output of a detector for its variation factor. CONSTITUTION:A variable resistance 25 is set and a return motor control circuit 31 controls the speed of a return motor 33. Namely, a circuit 31 reduces the number of revolution of the motor 33 when a source voltage detection signal (a) is at H so that 25 copies are taken per minute, and increases the rotating speed of the motor 33 when the signal is at L to take 30 copies per minute. Variation in source voltage applied to a fixing device motor 15, i.e. variation factor of the surface temperature of a fixing roller 13 is detected by a voltage detector A to obtain high-speed performance of 30 sheets/min in normal operation in which the source voltage is >=95% of the rated voltage; and the power consumption of a heater 15 is not so large, so the high-speed performance is realized without increasing the power consumption of the fixing device greatly.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a heat fixing device used in copying machines and the like, which melts and fixes powder on a base material by heating the powder on the base material.

<Prior art and its drawbacks> Electrophotographic copying machines, which most commonly use a heat fixing device, are now installed in many offices, etc., but due to the demand for higher speed, the power consumption has increased. A problem has arisen. That is, as the speed of copying machines increases, there is a possibility that the increased power consumption of the heat fixing device will exceed the 15A power capacity of the most common power outlet standard. If you simply increase the capacity of the fixing device without taking any measures, most high-speed machines will probably not be able to be used with a regular power outlet, and special power supply work will be required at the same time as the copying machine is installed. However, performing special power supply work to install a copying machine means that there will be costs for the power supply work in addition to the price of the copying machine, and the actual cost to the user will be the sum of these two. This has the disadvantage of significantly increasing costs.Also, when setting the fixing device, it is normal to take into account fluctuations in the power supply voltage and set it at the worst case, that is, when the voltage is 90% of the rated voltage. However, if this design method is simply applied to a high-speed machine, it will generate more than enough power for the fixing device at the rated voltage, that is, more power than necessary including wasted power. This increases the rated power consumption of the copier as a whole, and if you try to make it compatible with a regular power outlet, the copier's capacity (high speed) will be limited. Ta.

<Object of the Invention> An object of the invention is to provide a heat fixing device that can be used as a faster copying machine without increasing the rated power consumption.

<Structure and Effects of the Invention> The present invention provides a method for fixing bases that pass through the fixing device when the power supplied to the fixing device decreases and the amount of heat emitted from the fixing device becomes unbalanced. This was done by focusing on the fact that the balance between the two can be maintained by reducing the amount of material used, and it is equipped with a detector that detects the surface temperature of the fuser or its fluctuation factors, and a unit time according to the output of the detector. and a means for controlling the number of times the document scanning system reciprocates or the time spent for two reciprocations, the power supplied to the fuser by the detector and the power supplied from the fuser to the base material. The number of substrates that pass through the fixing device within a unit time is changed by determining a level that balances the amount of heat emitted and the amount of heat emitted from the fuser, and controlling the document scanning system in accordance with that level.

According to the present invention, with the above configuration, there is no need to design a device to obtain a certain level of fixing performance under the worst conditions, for example, under conditions where the voltage drops to 90% of the rated voltage, as is the case in the past. If external conditions such as a voltage drop or other external conditions that reduce the surface temperature of the fuser are added, reduce the backward movement speed of the document scanning system or lengthen the stopping time when changing from backward movement to forward movement. By doing so, the number of substrates passing through the fixing device can be suppressed, and constant fixing performance can always be obtained without causing a decrease in surface temperature. Therefore, unlike in the past, there is no need for extra power consumption at the rated time, and by controlling the document scanning system when external conditions change, such as a drop in voltage, the number of substrates passing through the fixing device can be reduced. By simply reducing the power consumption, high speed performance can be obtained without increasing the rated power consumption of the fixing device under normal conditions.

<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, ■ is a document table on which the document table 2 is placed and moves back and forth; 3 is a photoconductor drum that rotates clockwise; 4 is a charger that uniformly charges the surface of the photoconductor; 5 is a developer; and 6 1 is a transfer device that transfers the image formed on the photoreceptor onto the transfer paper 7, 8 is a cleaner, 9 is an exposure lamp, and 1o is a plastic fiber lens that exposes the light reflected from the original 2 onto the surface of the photoreceptor. , 11 is a cassette that stores the transfer paper 7; 12 is a paper feed roller that narrows down the transfer paper one by one from the cassette 11; 13 and 14 are fixing rollers; With the above configuration, when the copy button is pressed, the document table 1 moves to the left, and at the same time, the photoreceptor drum 3 rotates, and the document 2 is exposed onto the photoreceptor and transferred to the developing device. The image visualized by 5 is transferred to transfer paper 7, and the transfer paper passes through fixing rollers 13 and 14 and is ejected.When the document table 1 completes its forward movement, a switch (not shown) turns this on. This is detected and the document table 1 is moved backwards.Then, one copy is completed when the document table 1 returns to the home position.During multi-copy, the above operation is continuously repeated to fix the fixing rollers 13 and 14. The transfer paper 7 is fed at regular intervals.

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

The power supply voltage supplied from the power outlet 20 is supplied to the primary sides of the voltage detection circuit transformer Z1 and the control circuit transformer 22. The turns ratio is set so that the secondary voltage of the transformer 21 is rated 8■, and the full-wave rectifier 2
Join 3. The capacitor 24 smoothes the full-wave rectified voltage to convert the secondary side voltage 8cm into a DC voltage of approximately tOV.

The smoothed voltage is divided by a variable resistor 25 and a resistor 26, and the divided voltage is applied to the gate of a 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 5 and the base-emitter voltage of the transistor 27 with the voltage across the variable resistor 25. , you're trying to control it off. Transistor 29 receives the output of transistor 27, turns on and off in response to on and off of transistor 27, and outputs power supply voltage detection signal a. With the above configuration, the variable resistor 25.
Resistance 26. A circuit combined with transistors 27 and 29 and Zener diode 28 constitutes voltage detector A that detects fluctuations in power supply voltage.

The secondary output of the transformer 22 is stabilized by a DC stabilizing circuit 30, and is stabilized by a double-acting motor control circuit 31 and a control circuit 3.
2. A double-acting motor control circuit 31 receives the output of the output transistor 29 of the voltage detector and controls the speed of the double-acting motor 33. The control circuit 30 also controls the double-acting motor control circuit 31 and loads 34 such as solenoids, relays, clutches, motors, etc.

The power supply voltage obtained from the power outlet 20 is further supplied to the fuser heater 15 via a relay contact 35 and to the exposure lamp 37 via a relay contact 36 . Relay contacts 35 and 36 are included in the load 34 and control circuit 3? On by.

Controlled off.

The fuser heater 15 has a rating of 900W. Generally, in a high-speed copying machine with a copying speed of 30 sheets per minute, a certain level of fixing performance cannot be obtained unless 800 W of power is continuously supplied to the fuser heater. Therefore, by using the fuser heater 15 with a rating of 900 W, a margin of 100 W can be obtained.Next, the setting position of the variable resistor 25 of the voltage detector will be explained. If a 900 W heater is used as the fuser heater 15 as described above, the heater output will be exactly 800 W when the power supply drops to 95% of the rated power. Therefore, at a voltage of 95% to the rated voltage, sufficient fixing performance 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 condition of the power supply, the heater output will be approximately 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 drop during continuous copying. According to experiments, when the power supply voltage is rated at 90% of the rated value, sufficient fixing performance can be obtained by setting the copying speed to 25 sheets per minute. Therefore, when using a fuser heater with a rating of 900W, copying should be possible at a high copying speed of 30 sheets per minute until the power supply voltage drops to 95%, and when the power supply voltage drops to 95% or less, By lowering the copying speed to 25 sheets per minute, constant fixing performance can be obtained regardless of the amount of variation in 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 its rating.

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

As mentioned above, the voltage across the capacitor 24 is IOV at the rated power supply voltage. Therefore, when the power supply voltage drops to 95% of the rating, the voltage across the capacitor 24 will be 9.5%.
It decreases to 5■. On the other hand, the Zener diode 28 is selected to have a Zener voltage of 5. Therefore, the setting position of the variable resistor 25 is now set to 5 V when the voltage across the capacitor 24 is 9.5 V, plus the zener voltage of 5 V and the base-emitter voltage of the transistor 27 of 0.65 V.
If the power supply voltage is set to 5.5V, which is the sum of the power supply voltage, the transistor 27 will remain off when the power supply voltage is 95% or less, and turn on when it exceeds 95%. That is, the power supply voltage detection signal a becomes "H" when the power supply voltage is 95% or less of the rating, and becomes "L" when it exceeds 95%.

By setting the variable resistor 25 as described above, the double-acting motor control circuit 31 can control the speed of the double-acting motor 33 at 95% of the rated power supply voltage. That is, when the power supply voltage detection signal a is "H", the double-acting motor control circuit 31 lowers the rotation speed of the double-acting motor 33 to set the copying speed to 25 copies per minute. Also, the power supply voltage detection signal a is L.
'', the rotation speed of the double-acting motor 33 is increased to 3 minutes per minute.
Set the copy speed to 0.

By detecting the variation in the power supply voltage applied to the fuser heater by the voltage detector A as described above, that is, the cause of variation in the surface temperature of the fixing roller 13, it is possible to detect It can demonstrate high-speed performance of 30 sheets per minute, and within this range, the excess power consumed by the fuser heater 15 is not that large (because there is not, it is normal to not have to increase the power consumption of the fuser so much after all). It is possible to obtain a copying machine that can exhibit high-speed performance with a power supply voltage of .

Next, the double-acting motor control circuit 31 will be explained with reference to FIG. This figure is a circuit diagram of the double-acting 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 ANDs the power supply voltage detection signal a and the output of the frequency divider 311, and the AND gate 3.14 logics the signal obtained by inverting the power supply voltage detection signal a by the inverter 315 and the output of the frequency divider 312. Multiply. The OR gate 316 is the AND gate 313, 3
14, and an AND gate 317 ANDs the logical sum output and the backward movement permission signal S from the control circuit 32, and outputs the result to the motor drive circuit 318.

Further, the output of the motor drive circuit 318 is supplied to the double-acting 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,
When the power supply voltage detection signal a is “H”, the frequency divider 31
1 is led to the motor drive circuit 318. Frequency divider 3
11 has a larger frequency division ratio than the frequency divider 312, so the frequency of the divided pulses guided to the motor drive circuit 318 is higher when the power supply voltage detection signal a is "H" than when it is "L". becomes smaller. That is, the reciprocating gj motor 33 rotates 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 rhythmic speed of the document table 1 is fast, and when it falls below 95%, the backward movement speed becomes relatively slow. Therefore, by appropriately setting the frequency division ratio of the frequency dividers 311 and 312, it is possible to move the document table 1 back so that the copying speed is 30 sheets per minute when the power supply voltage exceeds 95% of the rated value. Also, when the power supply voltage drops below 95% of the rated value, set the original platen 1 so that the copying speed is 25 sheets per minute.
can be reversed.

In the above embodiment, the rotation speed of the double-acting motor 33 was controlled based on 95% of the rated power supply voltage, but the reference was set to two levels, 94% and 97% of the rated value, and the The rhythmic speed of the document table 1 by the dynamic motor 33 can be set in three stages. 4 and 5 are circuit diagrams of the voltage detector B and the double-acting motor control circuit 32 in that case. The difference in the configuration from the above embodiment is that the voltage detectors B are arranged in two stages in parallel, and the variable resistor 25 in the first stage is
94% of the rated value is set for the variable resistor 25', and 97% of the rated value is set for the variable resistor 25'. Furthermore, the first stage output transistor 2
9 and the output of the second stage output transistor 29' are received by a combination circuit of AND gates 50 to 52 and an inverter 53, three states are determined, and frequency dividers 321 to 323 are applied depending on each state. Either one of the divided pulses is guided to the motor drive circuit 329. With this configuration, the first stage output transistors 29 and 2 of the voltage detector B
The outputs of the output transistors 29' in each stage are "H".
, when it is “H”, the power supply voltage detector 1ic is “H”
Similarly, the output of each transistor is "H", -L"
When the signal d becomes "H", the signal e becomes "H" when each transistor output is "L" and "L" respectively.
However, when the power supply voltage is 94% or less of the rating, the frequency divider 321 with a large division ratio is selected, and when the power supply voltage is between 94% and 97% of the rating, the frequency divider 321 is selected. 322 kami were selected, and the power supply voltage was rated 9
When it is 7% or more, the frequency divider 3 with the smallest frequency division ratio
23 is selected.゛The return speed of the document table 1 can be controlled as described above by detecting the drop in the power supply voltage, which is the main cause of change in mV of the surface temperature of the fixing roller 13. Temperature fluctuation factors include fluctuations in ambient temperature and humidity in addition to fluctuations in power supply voltage. For example, if the ambient temperature is low, the temperature of the transfer paper itself is also low, so the amount of heat absorbed by the paper increases when it passes the fixing roller. Therefore, maintaining the fixing surface at a constant temperature requires more power than when the ambient temperature is high. The same can be said about humidity. When the humidity is high, the amount of water contained in the transfer paper increases, so the amount of heat absorbed during classification increases, and more electricity is required than when the humidity is low.

FIG. 6 is a circuit diagram of a temperature detector that controls the double-movement speed of the double-movement motor 32 in accordance with fluctuations in ambient temperature, using fluctuations in ambient temperature as a factor for fluctuations in the surface temperature of the fixing roller. The difference in the configuration from the voltage detector shown in FIG. 2 is that a thermistor 100 whose resistance value decreases as the temperature rises is connected instead of the resistor 26. With this configuration, when the desired ambient temperature is set, the output transistor 29
If the variable resistor 25 is set so that the temperature is turned on, the temperature detection signal a' becomes "L" when the ambient temperature exceeds the set temperature.
If the temperature is below the set temperature, it becomes "H". By outputting this signal to the double-acting motor control circuit 31 shown in Figure 2, the copying speed can be changed depending on whether the ambient temperature is above or below the set temperature. With a multi-stage configuration, it is easy to set the copying speed to multiple stages.

If a humidity detection sensor is connected in place of the thermistor 100, the copying speed can be changed even with changes in humidity using the same circuit configuration as above. Furthermore, as shown in FIG.
If the circuit shown in the figure is connected to a power supply circuit as shown in FIG. 2, it is possible to simultaneously detect fluctuations in power supply voltage and temperature, and change the copying speed in accordance with these fluctuations. 8th
The figure shows an example of an experiment using the circuit shown in FIG. In the figure, the numbers in the table represent the number of copies per minute.

In the embodiments described above, the number of transfer sheets passing through the fixing roller within a unit time, that is, the copying speed, was controlled by controlling the backward movement speed of the document table; however, in an optical mobile copying machine, What is necessary is to control the backward movement speed of the optical system. In addition, instead of controlling the backward movement speed of these document scanning systems, the forward movement speed, or both the forward movement and backward movement speeds may be controlled, or even the movement from forward movement to backward movement may be controlled. Sometimes, the time for stopping the document table or the document scanning system of the optical system may be controlled, or the time for stopping the document table when moving from backward movement to forward movement may be controlled. In short, it is sufficient to control the number of times the document scanning system reciprocates within a unit time or the baking time spent on one reciprocation.

[Brief explanation 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 the control section of the copying machine, FIG. 3 is a circuit diagram of the double-acting motor control circuit, and FIG. 4 shows another example of the voltage detector of the control section. The figure shows another example of the double-acting motor control circuit. Furthermore, FIG. 6 is a circuit diagram of a temperature detector, and FIG. 7 is a circuit diagram of a temperature and voltage generator. Further, FIG. 8 is a diagram showing an example of controlling the copying speed when the circuit shown in FIG. 7 is used. 13.14 Fixed roller, 15-heater, A, B-1
! Pressure detector. Applicant Sharp Corporation Agent Patent Attorney Hisao Komori Figure 1 Figure 2 Figure 1\ /

Claims (1)

[Claims] (1) A fixing device that melts and fixes the powder on the substrate by heating the powder, a detector that detects the surface temperature of the fixing device or its fluctuation factors, and the detector A heating fixing device comprising: means for controlling the number of times a document scanning system reciprocates within a unit time or the time spent in one reciprocation according to the output of the document scanning system.