JPH035779A - Imaging device - Google Patents

Abstract

PURPOSE:To maintain fixability at a desired value all the time by temporarily raising a pressure roller heating temperature in order to restore the temperature when the temperature of the pressure roller corresponding to fixability drops to a reference temperature. CONSTITUTION:When the temperature of the pressure roller heated by a main heater Hm drops below the reference temperature related to fixability, a subheater Hs is heated via a battery 74 by a main power source 70. On the other hand, when the temperature of the pressure roller exceeds the reference temperature, heating the subheater Hs is stopped. Consequently, the pressure roller heating temperature is temporarily raised to restore the temperature when the temperature of the pressure roller corresponding to fixability drops to the reference temperature. Thus, fixability is maintained all the time.

Description

[Detailed description of the invention] Peel millet saucer public corporation The present invention relates to an image forming apparatus equipped with a heat fixing device.

In order to maintain copy quality in a copying machine, it is important to maintain the fixing performance of the heat fixing device, that is, to maintain the surface temperature of the pressure roller at a desired value during copying.

By the way, when high-speed copying is performed or when a large number of copies are made continuously, the amount of heat absorbed by the copy paper passed between the upper and lower pressure rollers increases, and there is a risk that fixing performance may be impaired. Therefore, when performing such a copying operation, it is necessary to provide means for monitoring the surface temperature of the pressure roller and preventing the temperature from decreasing.

One conventional example of a copying machine equipped with such a means is described in Japanese Patent Laid-Open No. 56-25754 (hereinafter referred to as the first conventional example). In this first conventional example, the surface temperature of the pressure roller is detected by a temperature detection means, and when the surface temperature drops to a reference temperature (a surface temperature slightly higher than a temperature that impairs fixing performance), the heat fixing device is activated. The fixing performance is maintained by reducing the paper passing speed of the copy paper or by increasing the distance between the upper and lower pressure rollers.

Another conventional example is described in Japanese Patent Application Laid-Open No. 59-88760 (hereinafter referred to as the second conventional example). This second conventional example monitors the power supplied from the power supply to the heater that heats the pressure roller, and controls the power supplied from the power supply to other loads to be below a predetermined value, or performs other functions. The timing of energizing the exposure lamp, which is a type of load, and the timing of energizing the heater are staggered to ensure the amount of energization to the heater.

However, in the case of the first conventional example, although the fixing performance can be ensured, the copying speed and the like are reduced, resulting in a disadvantage that the copying performance is impaired.

Further, in the case of the second conventional example, there is a limit in suppressing adverse effects on other loads, and the copy performance is eventually impaired.

In order to satisfy copy quality and copy performance at the same time, it is possible to increase the output of the heater of the pressure roller, but this will increase the power consumption of the entire copying machine, making it difficult to use the copying machine in a normal office, etc. When installing in
This is not practical as it requires replacing the plug etc.

The present invention has been made in view of the current situation, and it is an object of the present invention to provide an image forming apparatus that can save power consumption without impairing copy quality and copy performance.

The present invention is an image forming apparatus equipped with a heat fixing device having a pressure roller incorporating a main heater and a sub-heater,
A main power supply for heating the main heater, a first switching means for switching on/off of the main power supply, a storage battery for heating the sub-heater, a charging means for charging the storage battery, and a connection between the storage battery and the sub-heater. and a second switching means for switching the connection between the storage battery and the charging means, a temperature detection means for detecting the temperature of the pressure roller, and a switch between the first and second switching means based on the detection result of the temperature detection means. and a control means for controlling, when the temperature of the pressure roller heated by the main power source becomes lower than a reference temperature associated with fixing performance, the sub-heater is heated via the storage battery while the temperature is lowered to the reference temperature. The feature is that the sub-heater stops heating when the temperature becomes higher.

Further, the image forming apparatus includes a heat fixing device having a pressure roller with a built-in heater, and includes a power source for heating the heater and driving other loads, a first power supply power, and a first power supply power higher than the first power supply power. a first power control means for controlling the power supplied from the power source to the heater in accordance with the power supplied to the heater; a storage battery that selectively drives the other load with respect to the power supply; a storage battery and the power supply; a second power control means for selectively driving another load according to the pressure roller; a temperature detection means for detecting the temperature of the pressure roller; and a temperature detection means based on the detection result of the temperature detection means;
a control device that controls the first and second power control means, and when the temperature of the pressure roller decreases to a reference temperature associated with fixing performance, the heater is heated by the second power supply. Moreover, it is characterized in that other loads are driven by the storage battery.

In any case, in any of the above configurations, if the temperature of the pressure roller corresponding to the fixing property drops to the reference temperature, the pressure roller should be adjusted in order to recover the temperature. The heating temperature will be temporarily increased. Therefore, fixability can be maintained at all times.

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a front sectional view showing a copying machine to which the present invention is applied. First, the general structure of this copying machine will be explained along with its operation with reference to FIG.

[Schematic configuration of copying machine]

This copying machine has a paper feed tray 30,300 for storing copy paper P and an intermediate tray unit A in the lower part, an image forming part centered on the photoreceptor drum 2 in the middle part, and an optical system 1 in the upper part. By feeding the copy paper P after the first copy to the intermediate tray unit A and refeeding it, double-sided copying or composite copying is possible.

[Image creation system]

The photosensitive drum 2 is rotatable in the direction shown by arrow a, and around it are a charger 20°, a developing device 21,
The transfer charger 22, separation charger 23, cleaning device 24, and eraser lamp 25 are arranged in this order. As the photoreceptor drum 2 rotates in the direction of arrow a, it is uniformly charged by a charging charger 20, receives image exposure from the optical system 1, and forms an electrostatic latent image. Toner is supplied from 21, and a toner image is visualized.

〔Optical system〕

The optical system 1 is capable of scanning in the direction of the arrow below the document platen glass 10, and includes an exposure lamp 11,
Movable mirrors 12a, 12b, 12c and imaging lens 13
and a fixed mirror 12d. The exposure lamp 11 and the movable mirror 12a are connected to the circumferential speed V of the photoreceptor drum 2.
(constant regardless of magnification or variable magnification) vs. V/m (however, m
:copy magnification), and the movable mirrors 12bS 12c integrally move in the direction indicated by the arrow at a speed of (V/2m).

[Paper feed section]

On the other hand, the paper feeding section consists of an upper rotation type paper feed tray 30 and a lower elevator type paper feed tray 300, and the copy paper P stored in each is pushed up by a copy paper push-up tray. 31 drive motor M and elevator lift-up motor M2, respectively.

In addition, 6 is a manual paper feed section, and paper feed tray 30.30
A copy different from the copy paper P stored in 0. Paper can now be used as cents.

[Transportation system] The copy paper P in the paper feed tray 30 is selectively moved by the rotation of the paper feed roller 32, and the copy paper P in the paper feed tray 300 is selectively moved by the rotation of the paper feed roller 302, one of which is selectively transferred to the separation roller. The sheets are sorted and fed one by one by the pair 33 or 303, respectively, and are conveyed by the conveyance rollers 34, 35, 36 or the conveyance roller 30.
4, 305, 306, rollers 37, 38, 39, and timing roller pair 40.

After the copy paper P is temporarily stopped by a pair of timing rollers 40, it is sent to the transfer section in synchronization with the toner image formed on the photoreceptor drum 2, and is transferred to the photoreceptor drum 2 by discharge during transfer charging 22. The fixing bag W (
The toner image is fed to a heat fixing device (thermal fixing device) 26, where a process of melting and fixing the toner image is performed. Note that details of the fixing device 26 will be described later.

A lever 29 for switching the conveyance path of the copy paper P is provided between a conveyance roller pair 27 and a discharge roller pair 28 provided immediately after the exit of the fixing device 26. When ejecting the copy paper P as is, the lever 29 is set to the state shown in the figure, and the copy paper P fed out from the fixing device 26 is
is discharged from the discharge roller pair 28 onto the discharge tray 200.

In addition, when performing double-sided copying or composite copying (described in detail below), the lever 29 is set in a position rotated by a predetermined angle upward to the right from the illustrated state, and the copy paper P is moved from the pair of transport rollers 201 to the guide plate. 202 and is sent to intermediate tray unit 8, which will be described below.

On the other hand, the photosensitive drum 2 after transfer is cleaned by a cleaning device 24.
The remaining toner is removed by the eraser lamp 25, and the remaining charge is removed by light irradiation from the eraser lamp 25, in preparation for the next copying operation.

[Intermediate tray for double-sided copying and composite copying] Next, a schematic configuration of the intermediate tray unit A will be described. The intermediate tray unit A is composed of a switching block, a conveying block, a reversing block, an intermediate tray block, and a paper refeeding block, and is integrated into a unit. Both left and right ends of the intermediate tray unit (A) are supported by rails (not shown), and are constructed so that they can be pulled out from the front of the copying machine main body.

The switching block includes a pair of transport rollers 203 and a switching lever 20.
4, and switches the conveyance path of copy paper P in double-sided copy mode and composite copy mode.

Note that the switching block is not the intermediate tray unit) A, but
It may also be provided in the main body of the copying machine.

The transport block includes transport rollers 205, 206, 207.
208 and a guide plate, and forms a conveyance path in double-sided copying mode.

The reversing block has reversing conveyance rollers 209.21O1 and a reversing guide 211, and has a function of reversing the copy paper P conveyed via the conveying block and sending it to the intermediate tray 212.

The paper refeeding block includes a holder, a paper refeeding roller 213, separation rollers 214 and 215, and a guide plate, and refeeds the copy sheets P on the intermediate tray 212 one by one.

The double-sided copy mode and composite copy mode are selected by operating a mode selection key on an operation panel (not shown) provided on the top of the copying machine main body. When one of the copy modes is selected, the lever 29 is switched to a predetermined position, and the copy paper P, on which one side or a portion thereof has been copied, is guided from the transport roller pair 201 by the guide plate 202 to the transport roller pair. 203.

On the other hand, in the double-sided copy mode, the switching lever 20
4 is set in the predetermined position, and the copy paper P is moved to the switching lever 2.
04 is guided by the upper surface of the transport block 205, 206.
The paper is conveyed to the left side in the figure at 207 and 208, then reversed by reversing conveyance rollers 209 and 210 and a reversing guide 211, and sent to the intermediate tray 212 with the copy side facing up.

Then, the sheets are aligned on the intermediate tray 212, and the sheets are re-fed one by one by clockwise rotation of the re-feed roller 213.

On the other hand, in the composite copy mode, the switching lever 204 is switched to a predetermined position, and the copy paper P is guided by the lower surface of the switching lever 204 immediately after passing the conveying roller pair 203, and is directly copied onto the intermediate tray 212. It is sent face down. Then, as in the double-sided copy mode, the sheets are re-fed one by one by clockwise rotation of the re-feed roller 213.

The re-fed copy paper P is separated by the separation rollers 214, 215 and conveyed to the timing roller pair 40 via the conveyance rollers 37, 38, 39, and thereafter is subjected to a double-sided copying operation or a normal copying operation. A composite copy operation is performed. Note that the refeed roller 213 is positioned in three stages and is swingable, so that the copy paper P is moved to the intermediate tray 21.
When the copy paper P is fed onto the intermediate tray 212, it is positioned at the upper stage or the middle stage, and when the paper is re-fed, it is pressed against the copy paper P on the intermediate tray 212 with an appropriate pressure.

[Fixing device]

As shown in FIG. 1, the main components of the fixing device 26 are an upper pressure roller 26a and a lower pressure roller 26b, which are arranged vertically to face each other, between which the copy paper P that has undergone the transfer process is passed. The basic structure is as follows.

As shown in FIG. 1, thermistors T and I for detecting the surface temperature of the upper pressure roller 26a are mounted in opposing positions on the outer peripheral surface of the upper pressure roller 26a. On the other hand, inside the upper pressure roller 26a, as shown in FIG. 2, a main heater H consisting of a halogen heater and a sub-heater H3 are inserted and connected. Both the main heater H8 and the sub-heater H8 heat the upper pressure roller 26a, and maintain the surface temperature of the upper pressure roller 26a at the reference temperature.

Specifically, this heating control is performed by the CPU 5 (see FIG. 3) to which the temperature detection signal of the thermistor T is input, via the heater control circuit shown in FIGS. 4 and 5.
is the control center of this copying machine, and performs drive control of the image forming system, conveyance system, etc. in addition to the heating control. Note that the details of the heating control will be described later.

[Configuration of copying machine control system]

FIG. 3 is a block diagram showing the control system of this copying machine.
When the thermistor T inputs a temperature detection signal to the CPU 5, the CPU 5 receives the signal and issues predetermined control command signals to the control terminals A and B via the output interface 52 to control the heater control circuit described later. The configuration is such that the surface temperature of the upper pressure roller 26a is set to a desired value corresponding to the copying process.

Similarly, the CPU 5 also controls the driving of the image forming system, transport system, etc. via the output interface 52. Therefore, the control port of the output interface 52 for setting control procedures etc. is connected to the CPU 5 via the decoder 51.

[Heater control circuit]

4 and 5 are circuit diagrams showing the heater control circuit, of which FIG. 4 shows the main part of the heater control circuit, and FIG. 5 shows the circuit configuration around the thermistor voltage.

As shown in FIG. 4, the main heater H has a line 71a,
71b to the AC power supply 70, and the line 7
An SSR (semiconductor relay) 72 is connected in series in the middle of 1b. 5SR72 is connected to the control terminal A, and adjusts the heating temperature of the main heater HN by controlling the on/off of the main heater at zero cross according to the control command signal from the CPU 5.

Specifically, when the CPU 5, which monitors the temperature detection signal of the thermistor T shown in FIG. It has become. In addition, instead of on/off control, the phase (conduction angle) of the power supplied to the main heater is controlled by tritic or cyrisk.
Control may be performed to control the heating of the main heater HH.

Tracks 75 pulled out from the middle of tracks 71a and 71b, respectively
A charger 73 is connected to the other ends of a and 75b. The charger 73 is connected to the storage battery 74 via on-off switches S+ and Sz, and charges the storage battery 74 when the on-off switches St and St are turned on. On the other hand, storage battery 7
4 is the sub-heater H5 via the open/close switch S, , S,
The sub-heater H5 is heated when the open/close switches S, , S, are turned on. On/off switch (relay contact) S8, St, Sl, S4
The turning off is performed by the CPU 5 via the relay Rv, which will be described below.

Note that the ratio of power consumption between the main heater Hs and the sub-heater H8 is set to about 800 W for the former and about 200 W for the latter. In this way, the maximum power consumption can be achieved by l that is regularly used in a normal office or the like.

This is because the power consumption can be kept below 5KW.

As shown in FIG. 5, a voltage dividing resistor R5 and a thermistor TN are connected in series between lines 81a and 81b, one end of which is connected to a reference power source (12V DC power source) 80. The operational amplifier O connected between T and
P detects the thermistor voltage VT) and outputs this thermistor voltage VT to the output terminal C and the A/
The configuration is such that the data is input to the CPU 5 via the D converter 50.

And, at the other end of the line 81a, the opening/closing switch St,
A relay RV is connected to control the on/off of St, St, and S4. The relay R7 is connected to the CPU 5 via a drive IC 82 that controls its on/off state, the control terminal B, and the output interface 52.

In this circuit configuration, when relay Rv is turned off based on a control command signal from CPU 5, open/close switch S+ SSt is turned on as shown in FIG. 4, thereby connecting charger 73 and storage battery 74. will be charged.

In addition, in this state, as shown in the figure, the open/close switch S1,
S4 is in an off state.

On the other hand, when relay R7 is turned on, open/close switch S, ,
St is turned off, and the open/close switches S1 and S4 are turned on, the storage battery 74 and the sub-heater H5 are connected, and the storage battery 74 heats the sub-heater H8.

This heating is performed when the surface temperature of the upper pressure roller 26a detected by the thermistor T8 falls below the reference temperature during copying. That is, when the surface temperature decreases, C which monitors the thermistor voltage 7 of thermistor TN
The PU5 issues a control command signal to restore the surface temperature at the time of detection to the reference temperature or higher, and the main heater H8
The configuration is such that the sub-heater H8 is heated together with the heating of the sub-heater H8.

[Specific control procedure for heating control]

The heating control of the heater described above is performed according to the flowcharts shown in FIGS. 6 and 7. However, FIG. 6 is a main flow showing a control procedure of the CPU 5 including heating control, and FIG. 7 is a subroutine showing a heater control procedure.

First, the main flow will be explained. When the CPU 5 is reset and the built-in control program starts, the CPU 5 first initializes itself and makes initial settings to put the copying machine into the initial mode (Sl). Specifically, this initial setting is performed by clearing the memory contents of the RAM, setting various registers (none of which are shown), etc.

Next, the CPU 5 starts an internal timer (not shown) (S2) and executes a heater control routine to be described later (S3).

When the heater control routine is completed, the copy operation routine performed in the above series of steps is executed (S4), and then other processing routines (various processing routines associated with the copy operation) are executed (35), and When all of these processing routines are completed, the process waits for the internal timer to expire (S6), completes one routine, and returns to step S2.

The length of this one routine is used to count the various timers that appear in the subroutine shown in Figure 6. Here, each timer determines the end of the timer depending on how many times this one routine is repeated. to decide.

Next, the heater control routine will be explained according to FIG. The CPU 5 reads the thermistor voltage ■7 of the thermistor T8 at a predetermined sampling pitch (S31), and uses the read thermistor voltage ■7 and the reference value ■ inputted in advance. (See FIG. 8) (S32).

As a result, the surface temperature T of the pressure roller 26a changes to the reference temperature T.
If it is determined that the temperature is lower than 0, the relay Ry is turned on, that is, the open/close switches S1 and S4 are turned on, and the sub-heater H8 is heated by the storage battery 74 (S33).

On the other hand, in step S32, if T≧T0,
Turn off the relay RV, that is, turn on the open/close switch S1, st, and turn off the sub-heater H8 (836), Step 33
Proceed to 4. At this time, the storage battery 74 is charged by the charger 73.

Next, in step S34, the temperature T is set to the reference temperature T by comparing the thermistor voltage v and the reference value ■1.
Determine whether it is 1 or more. As a result, if T<T, the main heater H9 is turned on (535), and then the process returns to the main flow.

Further, in step S34, if To>Tt, the surface temperature of the upper pressure roller 26a is sufficiently high, so the main heater H14 is turned off (537) and the process returns to the main flow.

In the control described above, the reference temperature T0 is set to the minimum required upper pressure roller 26a without impairing fixing performance.
The surface temperature is set slightly higher than that of
Further, the reference temperature T+ is set to a value higher than To, with a further margin. FIG. 8 shows an example of changes in temperature T. In normal use of the copying machine, the temperature T is controlled by steps S34, 35, and 37 in FIG.
As shown in the range a in FIG. 8, the temperature is maintained near the reference temperature T. However, when a large number of copies are made continuously, heating by the main heater H,4 is not enough, and the temperature T decreases even though the main heater H,4 is turned on (in the range marked with a circle in the figure). . Temperature T is reference temperature T
, the sub-heater H3 is turned on and the surface temperature T of the pressure roller 26a is maintained near the reference temperature T0 (range g!i of C in the figure). Then, when the above-mentioned continuous copying is completed, By heating the main heater H8, the temperature T
increases as shown in the range d in the figure, and the reference temperature T,
to return to.

When performing such heating control, it is convenient for suppressing maximum power consumption. In other words, since it is rare that a large number of copies (several hundred copies or more) are made continuously in actual use, the power consumption of the main heater that is constantly used is reduced to normal usage B (not making extremely large copies). When the temperature drops to a predetermined temperature T0 lower than the normal control temperature T1, the maximum power consumption is suppressed by temporarily turning on the sub-heater H5 using the storage battery 74 in order to recover the temperature. At the same time, it is possible to perform copy operations with high precision.

In the above embodiment, in the on/off control of each heater, if the surface temperature of the upper pressure roller 26a is higher than the reference temperature (for example, To), the heater (for example, sub-heater HS) is turned on, and if it is lower, the heater is turned off. Although the control was performed, the reference voltage for turning off each heater may be set higher than the reference voltage for turning on each heater, and may be set separately.By doing this, the frequency of turning on and off the heaters can be reduced. The degree of fatigue of the heater can be suppressed.

9 to 12 show an embodiment according to the invention as claimed in claim 2, and in this second embodiment, the sub-heater H
8 is not provided, and when the surface temperature of the upper pressure roller 26a falls to the reference temperature, the power supplied to the heater (main heater) is increased, and other loads such as the image forming system and the transport system are It is driven by a storage battery and has a configuration that saves power consumption.

However, Fig. 9 is a circuit diagram showing the power control circuit of the heater, Fig. 10 is a circuit diagram showing the switching circuit of the storage battery, Fig. 11 is a flowchart showing the main flow similar to Fig. 6 above, and Fig. 12 is a circuit diagram showing the power control circuit of the heater. 3 is a flowchart showing a control routine. Further, since the other configurations are the same as those of the previous embodiment, corresponding parts are designated by the same numbers and illustrations are omitted.

[Power control circuit]

First, the schematic configuration of the power control circuit will be explained according to FIG. 9. This power control circuit has a general configuration in which a phase control circuit 91 controls power supplied to a heater H connected to an AC power source 90 via a main switch 94. That is,
As shown in the figure, the phase control circuit 91 has a three-terminal bidirectional thyristor 92, a bridge rectifier circuit 93, and an operational amplifier 02 as main circuit components. The phase (conduction angle) of the supplied power is controlled in synchronization with the heater H.
It is configured to control the power supplied to the

The control command signals given from the CPU 5 to the phase control circuit 91 include a power supply switching command signal that determines the magnitude of power supplied to the heater H, and an on/off command signal that controls turning on and off of the heater H. , the former is the output interface 52, control terminal A and drive IC.
The signal is applied to the phase control circuit 91 via 95. On the other hand, the latter is the output interface 52, control terminal B
and is applied to the phase control circuit 91 via the drive IC 96.

Specifically, when a feed power switching command signal of "H" level is output from the CPU 5 to the phase control circuit 91, the heater H
When the power to be fed to is set to be large and the "L" level feed power switching command signal is output, the power to be fed is set to be small.

On the other hand, when the CPU 5 outputs an on/off command signal of "L'" level to the 3-terminal bidirectional thyristor 92, the 3-terminal bidirectional thyristor 92 is turned on, the heater H is lit, and the level is "H". When the on/off command signal is output, the three-terminal bidirectional thyristor 92 is turned off, and the heater H is turned off.

[Storage battery switching circuit]

Next, details of the storage battery switching circuit will be explained. A.C.
A 24V load (driving load for an imaging system, transport system, etc.) 102 is connected to the power supply 90 via lines 104a and 104b, and a 24V DC power supply 100, a charger 73, A storage battery 74 and a relay R7 for switching the storage battery 74 are connected in parallel.

Note that the feed power switching command signal is sent to the relay R7 via the control terminal A and the drive IC 95 from the CPU 5.
It is designed to be output from.

Further, a changeover switch 101 controlled by a relay R7 is provided in the middle of the line 104a.

The changeover switch 101 is a load 102 provided by a DC power supply 100.
and the drive of the load 102 by the storage battery 74, and is in a normal state (when the relay RY is not in operation), in which a "L" level power supply switching command signal is applied from the CPU 5 to the relay R7 via the control terminal A. situation)
, it is switched to the DC power supply 100 side.

At this time, the storage battery 74 will be charged, but this charging may be carried out over time with a small amount of current, or it may be carried out by rapid charging while the copying machine is on standby. .

In this circuit configuration, “H” is applied to control terminal A.
When the power supply switching command signal of level is output, relay R
V is activated, the selector switch 101 is switched to the storage battery 74 side, and the storage battery 74 drives the load 102, thereby saving power consumption as a whole. Note that in the normal state when the changeover switch 101 is switched to the DC power supply 100 side, the charger 73 charges the storage battery 74.

[Specific control procedure for power control]

Next, specific procedures for power control will be explained according to FIGS. 11 and 12. However, since the main flow shown in FIG. 11 is the same except that the power control routine shown in step 5300 is different from the heater control routine shown in step S3 of FIG. 6, the explanation will be omitted, and the power control routine shown in FIG. Only the control routine will be explained.

The CPU 5 first checks the thermistor voltage ■7 of the thermistor T.
is read at predetermined sampling (S301), and the read thermistor voltage v7 is set to the reference value V0 shown in FIG.
5302), as a result, the upper pressure roller 26
If it is determined that the surface temperature T of the upper pressure roller 26a is lower than the reference temperature T, the surface temperature of the upper pressure roller 26a should be increased. 90 to the heater H, which is larger than the normal power supply (first power supply electrode).
In addition to setting the power supply, the load 10 is set by the storage battery 74.
2 drive is performed (S303).

On the other hand, in step 5302, if it is 'rag're, a "L" level power supply switching command signal is issued to the control terminal, the power supply mode to the heater H is set to the first power supply, and the load A selector switch 101 is connected so that 102 is driven by the DC power supply 100.
(S306).

After executing the process in step 5303, the thermistor voltage V7 is then compared with the reference value Vl shown in FIG.
04), if T<TI, an "H rubel on/off command signal is issued to the control terminal B, the heater H is turned on (S305), and the process returns to the main flow." - On the other hand, in step 5304 , TkT, turn off the heater H (5307) and return to the main flow.

In this second embodiment, a main heater and a sub-heater may be provided as in the above embodiment, and the sub-heater may be controlled on/off based on the reference temperature.

In the case of the present invention as described above, when the temperature of the pressure roller corresponding to fixing properties drops to the reference temperature, the heating temperature of the pressure roller is temporarily increased in order to recover the temperature. Because of this configuration, fixing performance can be maintained at a desired value at all times.

Furthermore, since there is no need to reduce the image forming speed, etc., image forming quality such as copy quality is not impaired.

Furthermore, since fixing performance can be maintained without increasing the power consumption of the image forming apparatus itself, there is an advantage that there is no need to replace plugs or the like during installation, and the image forming apparatus can be directly connected to an existing power source in a normal office.

Further, particularly in the case of the image forming apparatus according to the second aspect, since the load other than the heater is temporarily driven by the storage battery, there is an advantage that the power supply mode can be made efficient. Moreover, it only requires a small capacity storage battery.
, which is convenient for reducing costs.

[Brief explanation of drawings]

Fig. 1 is a front sectional view showing a copying machine to which the present invention is applied, Fig. 2 is a perspective view showing details of the upper pressure roller, Fig. 3 is a block diagram showing the control system of the copying machine, and Fig. 4 is a A circuit diagram showing a heater control circuit that controls heating of the main heater, FIG. 5 is a circuit diagram showing a heater control circuit that controls heating of a sub-heater, FIG. 6 is a flowchart showing the main flow of the CPU, and FIG. A flowchart showing the control routine, FIG. 8 is a graph showing changes in thermistor voltage vT,
Figure 9 is a circuit diagram showing the heater power control circuit, Figure 10 is a circuit diagram showing the storage battery switching circuit, Figure 11 is a flowchart showing the main flow similar to Figure 6, and Figure 12 is the power control routine. FIG. FIG. 2 5...CPU, 26...Fixing device, 26a...Upper pressure roller, 70.90...AC power supply, 72...
S.S.R. 73...Charger, 74...Storage battery, 92...3-terminal bidirectional thyristor, 82.95.96...Drive IC. 102...Load, HN...Main heater, Hs...
・Sub-heater H,,H...Heater, 'Rv...'Relay, SI%S, ,S, ,S4...Opening/closing switch, T,...Thermistor.

Claims (2)

[Claims] (1) An image forming apparatus equipped with a heat fixing device having a pressure roller with a built-in main heater and a sub-heater, comprising a main power supply for heating the main heater, and a first power supply for switching on/off the main power supply. a switching device; a storage battery that heats the subheater; a charging device that charges the storage battery; a second switching device that switches connections between the storage battery and the subheater and between the storage battery and the charging device; The pressure roller is heated by the main power source, and includes a temperature detection means for detecting temperature, and a control means for controlling the first and second switching means based on the detection result of the temperature detection means, and the pressure roller is heated by the main power source. An image forming apparatus characterized in that when the temperature drops to a reference temperature associated with fixing performance, the sub-heater is heated via the storage battery, and when the temperature becomes higher than the reference temperature, heating of the sub-heater is stopped. . (2) An image forming device equipped with a heat fixing device having a pressure roller with a built-in heater, comprising: a power source for heating the heater and driving other loads; and a first power supply power higher than the first power supply power. a first power control means that controls the power supplied from the power source to the heater over a second power supply; a storage battery that selectively drives the other load with respect to the power supply; a second power control means for selectively driving the load; a temperature detection means for detecting the temperature of the pressure roller; and a second power control means for controlling the first and second power based on the detection result of the temperature detection means. and a control device for controlling the means, and when the temperature of the pressure roller falls to a reference temperature associated with fixing performance, the heater is heated by the second power supply, and the other load is heated by the storage battery. An image forming device characterized in that the image forming device is configured to drive.