JPS6033580A - Temperature controller of heat fixing device of electrophotographic copying machine - Google Patents

Abstract

PURPOSE:To preform constant-temperature control with high precision through simple constitution by controlling the closing of a switch circuit which synchronizes with the zero crossing of an AC source voltage according to a halt rate correlative to the variation rate of the AC voltage, and correcting the halt rate according to the temperature of a heat fixing devie. CONSTITUTION:A halogen lamp 21 as a heating body is connected to a power surce 23 through the switch circuit 22 which is triggered with a trigger pulse PT in accompanying with the zero crossing of the voltage of the AC power source 23. The voltage of this power source 23 is detected through a voltage detector 24 and an A/D converter 25, and the arithmetic processing circuit 26A of a control cricuit 26 calculates the halt rate correlative with the variation rate of the AC voltage and also corrects the halt rate on the basis of the result of the comparison between the heating temperature of the lamp 21 which is detected by a temperature detector 28 at every specific period and a reference temperature. Then, the pulse output PT from a gate circuit 26B which is opened through a pulse generator 27 is controlled in the zero crossing of the AC voltage. Consequently, the constant-temperature control over the heat fixing temperature of the electrophotographic copying machine is carried out through the simple constitution with high precision.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a temperature control device for a heat fixing device of an electrophotographic copying machine. □ [Background of the Invention] The heat fixing device of an electrophotographic copying machine heats a toner image carried on the surface of a transfer material such as paper and fixes it onto the transfer material. Mainly known are a heat roll method that uses contact heat transfer, an oven method that uses convection heat transfer, and a radiant heat method that uses radiation heat transfer. Among these heating methods, the radiant heat method is widely used because the device is relatively simple and there is no deterioration in image quality due to offset or the like. FIG. 1 shows an example of the overall configuration of an electrophotographic copying machine equipped with such a radiant heat type heat fixing device.

In FIG. 1, Patent 1 shows a photosensitive drum that rotates in the direction of arrow A, and around this drum 1 are a primary charger 2 for forming a static latent image, a secondary charger 3, a full-surface exposure device 4, A developing device 5 for developing the latent image into a toner image, a transfer device 6 for transferring the toner image onto a transfer material, and a separating device 7 for separating the transfer paper from the drum are functionally arranged sequentially in the rotational direction of the drum. It is arranged. The transfer material separated from the photosensitive drum 1 by the action of the separating device 7 is transferred to the heat fixing device 9.
sent to. The heat fixing device 9 is formed of a transfer material conveyor 10 and a heater 11 provided opposite to the upper travel path q of the conveyor 10 .

The carrier 10 is a pair of ZOLIs disposed between #1#,
12.12, a plurality of streaking belts 13 stretched between the pulleys, and a suction means 14 provided on the lower surface of the upper strike path of the belt 13, and either one of the above-mentioned Goo IJ-12 The transfer material is transported in the direction of the arrow in the figure by a driver (not shown) engaged with the transfer material. On the other hand, the heater 11 is used as a heating source, e.g.
A reflector plate 16 for effectively irradiating the radiant heat from the radiator 15 onto the toner image on the surface of the transfer material being transferred by the conveyor 10; It is formed to include a cover 17 disposed so as to surround the. lamp 15
has a sufficient amount of heat to melt the toner powder of the toner image, melts the transferred toner powder, and permanently fixes it on the transfer material.

The transfer material with the toner image fixed thereon is discharged to the outside of the electrophotographic copying machine by a discharge roller 18.

The optimum temperature of the toner image surface required to perform the above-mentioned heat fixing, that is, the fixing temperature, depends on the thermal properties of the toner powder material,
It is determined by the thermal properties of the transfer material, etc., and in order to obtain a constant quality, fluctuations in the fixing temperature must be maintained within a specified value. For example, if the standard fixing temperature is approximately 100°C, the fluctuation range is ±
It is desirable to keep the temperature below 5°C.

However, the temperature often changes beyond this narrow tolerance range due to fluctuations in power supply voltage.

Therefore, in order to maintain the temperature of the toner image surface within a specified value, in practice, the temperature of the toner image surface is estimated by detecting the temperature of a predetermined part in the fixing device, and the lander 5 is turned on according to the detected temperature. , it is conceivable to perform off control to control the amount of heat generated during a certain period of time to be constant.

However, in general, lamps have a small heat capacity, so they are turned on.
In response to the turning off, the temperature of the heated area, that is, the surface of the toner image changes drastically. Therefore, even if the average calorific value and average temperature are maintained at predetermined values over a relatively long period of time, the temperature at the surface of the toner image will fluctuate greatly, resulting in unfixed or insufficient fixing of the toner image. It has the disadvantage of being stored away.

In addition, in order to eliminate the drawbacks of such on/off control, phase control is performed using semiconductor switching elements,
A method is known in which the input power of the lamp is controlled to a predetermined value by this method, but this method has the drawbacks that noise radiation is generated due to ignition control and the device becomes complicated.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a temperature control device for a heat fixing device of an electrophotographic copying machine, which has a simple configuration and can maintain a predetermined heat fixing temperature with high accuracy.

[Summary of the invention]

The present invention connects a heating element as a heating source to an alternating current power source via a switch circuit, and turns on this switch circuit from All Sus in synchronization with the zero cross of the alternating current power voltage waveform. The pulse is paused in accordance with the fixed rate determined in correlation to the voltage fluctuation rate, and the temperature of a predetermined part of the heat fixing device is compared with a reference temperature at each fixed correction period. By correcting the pause rate by increasing or decreasing it by a fixed rate based on the comparison result, the control accuracy of the heat fixing temperature is improved and the configuration is simplified.

[Embodiments of the invention]

Hereinafter, the present invention will be explained based on examples.

FIG. 2 shows a block diagram of one embodiment of the present invention.

As shown in the figure, Halodan Lande 2 as a heating element
1 is connected to an AC power source 23 via a switch circuit 22 that is opened and closed by a pulse PT. The power supply voltage eI of the AC power supply 23 is detected by the voltage detection circuit 24, digitally converted by the AD converter 25, and then inputted to the arithmetic processing circuit 26A of the control circuit 26. The pulse generation circuit 27 takes in the power supply voltage eN of the AC power supply 23, detects the phase in which the polarity of the AC waveform changes, that is, the zero cross, and outputs a timing pulse Po synchronized with the phase.

This timing no 9rus P. is outputted as a pulse PT to the switch circuit 22 via the r-t circuit 26B of the control circuit 26, and outputted as a timing signal to the arithmetic processing circuit 26A, and -. A temperature detector 28 is provided near the printer 21, and detects the temperature of the heat fixing area, and also detects the detected temperature T8 and the reference temperature T. When Ts≧To, it is “high (H)” and when Ts<T. In this case, the temperature signal T at the "low (L)" level is sent to the arithmetic processing circuit 26A.
It is designed to output to . The arithmetic processing circuit 26A uses the input detection voltage VD and the preset reference voltage ■
Based on the voltage fluctuation rate R of the voltage e1 and the voltage e1, an f-to-gate opening/closing signal G having a pulse pause rate S added in advance according to this fluctuation rate R is formed, and this signal G is further processed. It is adapted to be corrected according to the temperature signal T and output to the inverting input terminal of the dart circuit 26B.

Note that the switch circuit 22, the voltage detection circuit 24, and the
Specific detailed circuit diagrams of the pulse generation circuit 27 are shown in FIGS. 3 and 5, respectively.

The switch circuit 22 is configured as shown in FIG. 3, and the trigger pulse PT is inputted to the base of the transistor 102 via the terminal 101. The emitter of the transistor 101 is grounded, and the collector is connected to a DC power supply VCC through a series circuit consisting of a light emitting element 103A of a photothyristor coupler 103 and a resistor 104. The anode of the light receiving element 103B of the photothyristor Casilla 103 is connected to the rectifier circuit 1 via a resistor 105.
06, the cathode is connected to the other input of the rectifier circuit 106. Further, the light receiving element 103B is connected to the cathode via a parallel circuit consisting of a resistor 107 and a capacitor 108.

One output of the rectifier circuit 106 is connected to one electrode of the triac 109, and the other output is connected to one electrode of the triac 109.
connected to the tart. A resistor 110 is connected between the other electrode of triac 109 and the gate.

Further, a series circuit consisting of a triac 109KU capacitor 111 and a resistor 112 is connected in parallel.

Further, terminals 113 and 114 are input terminals of the switch circuit 22 and are connected to the power supply 23. Also terminal 114.115
is an output terminal of the switch circuit 22 and is connected to the lamp 21.

The voltage detection circuit 24 is constructed as shown in FIG. 4, and the AC power supply voltage e■ is input to the primary terminals 122, 123 of the transformer 121. The output end of the transformer 121 is input to a rectifier circuit 124, and the output of the rectifier circuit 124 is connected to one terminal of a capacitor 126, 127 and a variable resistor 128 via a resistor 125. Rectifier circuit 124
The other output terminal of the capacitor 12 is grounded, and the other output terminal of the capacitor 12
6 and the other end of a capacitor 127, and is also connected to the other end of a variable resistor 128 via a resistor 129. A sliding terminal of variable resistor 128 is connected to terminal 130.

The pulse generating circuit 27 is constructed as shown in FIG. 5, and the output of the rectifying circuit 134 for rectifying the AC power supply voltage J is connected in series to a resistor 135 and a light emitting element 136A of a phototransistor coupler 136. The collector of the light receiving element 136B of the phototransistor coupler 136 is connected to a DC power supply vCC, and the emitter is grounded via a resistor 137. The emitter of the light receiving element 136B is connected to the base of a transistor 138, the emitter of this transistor 138 is grounded, and the collector is connected to a resistor 139.
It is connected to the DC power supply vCC and the output terminal 140 via.

Regarding the operation of the embodiment circuit configured in this way, the sixth section
This will be explained below with reference to the time chart shown in the figure and the flow chart shown in FIG.

The voltage detection circuit 24 detects the voltage of the AC power supply 23 and outputs an analog detection voltage signal V to the AD converter 25. The AD converter 25 converts the detected voltage signal vA into a digital detected voltage signal VD and outputs it to the arithmetic processing circuit 26A. On the other hand, the pulse generating circuit 27 connects the phototransistor coupler 136 in response to the AC voltage waveform eI shown in FIG.
Then, the transistor 138 is turned on and off as shown in FIG. 6, and a timing pulse PO% synchronized with the off timing of the transistor 138, that is, a timing pulse PO% synchronized with the timing when the polarity of the AC voltage waveform at changes, is generated. route is output.

The operation of the arithmetic processing circuit 26A to which the detected voltage signal VD and the timing pulse Po are input will be explained according to the flowchart shown in FIG. VD is taken in, and the average power supply voltage VD is calculated for a certain period of time, for example, an 8-north pulse interval. Next, in step 152, the fluctuation rate R of the power supply voltage is calculated based on the following equation +11.

Note that in formula (1), V. represents the reference voltage,
For example, a voltage of 90 cm, which is the rated power supply voltage, is selected.

Next, in step 153, a dart opening/closing signal G correlated to the fluctuation rate R is formed. The turn G is stored as a table in the memory within the control circuit 26.

In other words, as shown in Table 1, the fluctuation rate R is divided into steps of, for example, 5 ticks, and the pulse pause rate is set to 5J (J=0, 1, 2, etc.) corresponding to each step. ) is determined, and four turns G for dirt opening/closing are set in advance in correspondence to S. ) t"-T opening/closing 1? Turn GJ is the timing pulse P.
has been established. In addition, the number of pauses M is 2
In the above case, it goes without saying that the timing of the pause pulses is set at equal intervals. Next, the process moves to step 154, where the temperature signal T is captured at every predetermined correction period, and in step 155, it is determined whether the temperature signal T is rHJ or "L", and if T=H, the step The process moves to step 156 and correction is made by subtracting 1 from J. If T=L, the process moves to step 157 and no correction is performed. Subsequently, in step 158, the dart opening/closing pattern ( ) J corresponding to the corrected J is searched from the chiffle. And step 15 'JjC o.

A dart opening/closing signal 0 is formed based on the dart opening/closing pattern G retrieved by the search, and is output to the ff-to circuit 26B.

As shown in FIG. 6, this dart opening/closing signal G is a step signal with a constant width that matches the timing of the bird to be stopped. As shown in FIG. 6, the bird blocks the output of the pulse PT. When the trigger pulse PT having the pulse pause rate S determined based on the voltage fluctuation rate R is input to the switch circuit 22 in this way, the transistor 102 of the switch circuit 22 is turned on in response to the pulse PT, Furthermore, the rectifier circuit 10 is connected via the photothyristor coupler 103.
6 is generated and the triac 109 is turned on. In this way, the AC voltage output from the switch circuit 22 has the waveform of the output voltage 13Q shown in FIG.

As described above, according to this embodiment, the lamp output is held constant and the heating is When the temperature of the fixing area is higher than the reference temperature, the lamp output is reduced at a fixed rate to maintain the temperature of the heat fixing area, which has the effect of accurately maintaining the temperature of the heating fixing area at a constant level. .

Further, according to this embodiment, since the operating point of the switch circuit 22 is the zero cross, noise radiation due to switching is removed, and temperature control accuracy is further improved.

In addition, although an example was shown in which the voltage fluctuation rate R was divided into steps of 5 inches in the above-mentioned section 1, it is possible to further improve the accuracy of temperature control by dividing the voltage fluctuation rate into even smaller steps.
i Needless to say.

〔Effect of the invention〕

As described above, according to the present invention, the control accuracy of the heat fixing temperature can be improved and the configuration can be simplified.

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram of an electrophotographic copying machine as an example to which the present invention can be applied, FIG. 2 is a block diagram of an embodiment of the present invention, and FIGS. FIG. 6 is a time chart for explaining the operation of the embodiment shown in FIG. 2, and FIG. 7 is a flowchart showing the control procedure of the embodiment shown in FIG. 2. ...Lamp, 22...Switch circuit, 23.
...AC power supply, 24...voltage detection circuit, 25...
AD converter 26...control circuit, 27...arm pulse generation circuit, 28...temperature detector. Agent: Tatsuyuki Unuma (and 1 other person) Figure 1 - Figure 6 - Rigaherusp, -■---11''-11i'i-ζ
AQ-

Claims (1)

[Claims] (1) In a temperature control device for an electrophotographic copying machine heat fixing device whose heat source is a heating element connected to an AC power source via a switch circuit; a voltage for detecting the voltage of the AC power source and outputting a detected voltage signal; a temperature detector; a temperature detector that detects the temperature of a predetermined portion of the heat fixing device and outputs a temperature signal that becomes high level when the detected temperature is equal to or higher than a reference temperature; a /4' pulse generating circuit that forms and outputs a synchronized timing pulse; and has a /4' pulse pause rate that is synchronized with the timing pulse and determined in correlation to a fluctuation rate of the detected voltage signal with respect to a reference voltage signal. a control circuit that forms a trigger pulse and outputs it to the switch circuit, receives the temperature signal at fixed correction intervals, and performs correction to lower the pulse pause rate by a fixed rate when the temperature signal is at a high level; 1. A temperature control device for a heat fixing device of an electrophotographic copying machine, comprising: