JPH01312575A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent smoking and firing of a fixing heater and the peripheral devices by detecting the temperature of the region of a fixing revolving body corresponding to the part where the maximum heating power of a heating means is obtained, and cutting the electric supply from an electric supplying means when the temperature of the fixing revolving body reaches the specific value or higher. CONSTITUTION:A fixing heater drive circuit 11 is connected with an electric supply cutting means, namely a thermo switch 13, which cuts electric conduction to the fixing heater 8 from the circuit 11 in case of failure occurred, and the thermo switch 13 is installed by abutting on the circumferential surface of a fixing roller 7 in the fixing roller 7 region corresponding to the position where the maximum heating power of the fixing heater 8 is obtained (namely, the position where light distribution quantity is at maximum). When the switch 13 detects that the temperature of the circumferential surface of the fixing roller 7 is at the specific value or higher, it cuts the electric supply for the fixing heater 8 from the fixing heater driving circuit 11. Thus, the smoking and the firing of the fixing heater 8, the fixing roller 7 and the peripheral devices are prevented.

Description

Detailed Description of the Invention -1,000 This invention relates generally to image forming apparatuses, and particularly to electrophotographic copying apparatuses equipped with a fixing device for fixing a visible image formed on a transfer material, and laser beam It relates to an image forming apparatus such as a printer.

- As is well known, in this type of image forming apparatus, a fixing device is provided along with an image forming section, a transfer material conveyance system, etc., and the image formed on the transfer material by the fixing device is A visible image is fixed onto the transfer material. To further explain the above-mentioned fixing device, the fixing device includes charging performed in one image forming section,
When a transfer material on which a visible image corresponding to the original image information has been formed through the image exposure, development, and transfer steps is conveyed by a transfer material conveyance system, this transfer material is transported by a fixing roller and a pressure roller. The image is fixed by being heated and pressed by a pair of rollers. In addition to the above-mentioned fixing roller and pressure roller, the fixing device also includes a fixing heater installed on a rotating shaft that rotatably supports the fixing roller, and a thermistor that detects the temperature of the outer circumferential surface of the fixing roller and pressure roller. , a drive power source that supplies power to the fixing heater, and a drive power source that reads a detection signal output from a thermistor and drives the fixing heater in order to adjust the temperature of the outer peripheral surface to the temperature necessary for image fixing at all times during the image forming sequence. The image forming apparatus includes a control system for controlling the fixing heater, and a thermoswitch, etc. that cuts off power supply to the fixing heater from the drive power source in place of the control system when the control system malfunctions for some reason.

Among the image forming apparatuses having the above configuration, for example, 100
V/l In an image forming apparatus configured to be compatible with a 15V standard power supply (i.e., 100V power supply), the fixing device must perform sufficient image fixation at an applied voltage of 100V. The minimum heater power possible is obtained, and 200V/220V/240V (
7) An image forming apparatus that is configured to be compatible with a standard power supply (i.e., a 200V power supply) is a 240V power supply.
The maximum heater power that allows the fixing device to suppress overshoot, temperature ripple (i.e., the difference between the maximum temperature value and the minimum temperature value), etc., and to perform sufficient image fixing can be obtained at an applied voltage of It looks like this.

To further explain the thermistor and thermoswitch described in iiQ 'y9, the thermistor and thermoswitch are both arranged at a position where the temperature of the outer circumferential surface of the fixing roller can be detected at the location shown in device E in FIG. .

Note that, considering its function, the thermoswitch is connected to a drive circuit that drives the fixing heater so as to be in series with the fixing heater. The reason why the thermistor and thermoswitch are arranged in the manner described above is as follows.

In other words, the temperature of the outer circumferential surface of the fixing roller when the image forming apparatus that missed 10 is in the preparation stage for executing the image forming process is expressed as follows: the vertical axis represents the temperature value, and the horizontal axis represents the axial direction of the fixing roller. It is represented by a temperature curve having two maximum temperature values as shown in FIG. When controlling the temperature of the outer circumferential surface of the fixing roller, which has such a temperature curve, to a predetermined temperature value during the execution stage of an image forming process, it is necessary to It is necessary to minimize the temperature ripple on the outer peripheral surface of the fixing roller. Therefore, in the above-mentioned image forming apparatus, a thermistor for detecting the temperature of the outer circumferential surface of the fixing roller is arranged at a location where a substantially average value of the temperature of the outer circumferential surface of the fixing roller in the axial direction appears (device E in FIG. 5). are doing. Also, regarding the thermoswitch, if the thermoswitch is disposed at a location where the maximum value of the outer circumferential surface temperature of the fixing roller appears, for example, as shown in FIG. 5, device F,
If overshoot occurs when the image forming apparatus moves from the preparation stage to the execution stage of the image forming process, there will be a temperature difference between the part where the thermistor is installed and the part where the thermoswitch is installed. Therefore, there is a risk that the thermoswitch will operate even though there is no failure in the control system such as the drive circuit or control circuit. Therefore, in the image forming apparatus, the thermoswitch is also disposed at a position where it can detect the same temperature value as the temperature value of the outer circumferential surface of the fixing roller detected by the thermistor, that is, at the device E in FIG. It is something.

In order to further improve the image forming apparatus configured as described above, the applicant of the present application has developed a 100V drive power source and a 20OV system drive power source.
We have proposed an image forming apparatus that can prevent the above-described problems from occurring no matter which V-system drive power source is connected.

However, even in the image forming apparatus according to the above proposal, 1
For example, if a failure occurs in the fixing heater drive circuit or control circuit while using a 200V drive power source, and the fixing heater goes out of control, the fixing heater may Because the amount of power supplied is increasing, the rate of temperature rise of the fusing heater is increasing, so the fusing heater and its peripheral equipment are Problems arise in that these devices become extremely hot, causing them to smoke and catch fire. -In order to prevent such problems from occurring.

If the amount of power supplied to the fixing heater is limited when using a 200V system TIjA dynamic power source, the amount of power supplied to the fixing heater when using a 100V system drive power source will be insufficient, so the temperature of the outer peripheral surface of the fixing roller should be Another problem arises in that it is not possible to maintain a predetermined fusing temperature value.

Therefore, the present invention was devised to solve the above-mentioned problems, and the purpose is to solve the problems caused by the difference in temperature rise rate of the fixing heater even when drive power sources with different supply voltage values are used. To provide an image forming apparatus capable of preventing malfunctions such as smoke and ignition of a fixing heater and its peripheral equipment, and capable of maintaining the temperature of the outer circumferential surface of a fixing roller at a predetermined fixing temperature value. That's true.

This is achieved by the image forming apparatus according to the present invention. In summary, the present invention provides a fixing rotor that comes into contact with a pressure rotor and cooperates with the pressure rotor to fix a visible image formed on a transfer material; heating means for heating the fixing rotor, a power supply means for supplying power to the heating means, a temperature detection means for detecting the temperature of the fixation rotor, and a temperature detection signal outputted from the temperature detection means. a control means for controlling driving of the heating means so that the temperature of the fixing rotor reaches a predetermined temperature value over the entire region of the fixing rotor; and a control means for controlling the drive of the heating means so that the temperature of the fixing rotor reaches a predetermined temperature value over the entire region of the fixing rotor, and the fixing means corresponding to a portion where the maximum heat amount of the heating means is obtained. and a power supply cutoff means for detecting the temperature of the fixing rotor in a region of the rotor and for cutting off power supply from the power supply means to the heating means when the temperature of the fixing rotor reaches a predetermined value or higher. This is an image forming apparatus characterized by:

Fruit” 1 case An embodiment of the present invention will be described below with reference to one drawing.

FIG. 2 shows an image forming apparatus according to an embodiment of the present invention.0 Image forming apparatus according to an embodiment of the present invention11t
The outline of M is as follows. That is, in FIG. 2, a rod 100 of one image forming apparatus (hereinafter simply referred to as a "frame 100J")
A transfer material supply mechanism, that is, a paper feed roller 39 and a pair of registration rollers 40 are provided at the lower part of the internal space defined by the transfer material and on the starting end side in the moving direction of the transfer material (on the right side in FIG. 2). On the other hand, the paper feed roller 39 in the frame body 100
A transfer material discharging mechanism, that is, a paper discharging roller 41 is provided at the end (left side in FIG. 2) of the transfer material in the moving direction of the transfer material, which faces the pair of registration rollers 40. In the frame space, a transfer material conveying means, that is, a transfer material conveying belt 33 whose starting end side in a transfer material conveying direction and a terminal end side in a transfer material conveying direction are wound around a drive roller and a fluid roller, and an image forming section, that is, an image forming part, are provided. Forming units I, ■, ■, ■ are provided. The transfer material conveying belt 33 receives and conveys the transfer material fed by the pair of registration rollers 40. It is arranged in close proximity to the transfer material conveyance belt 33 and is configured to sequentially transfer visible images formed on the transfer material moved by the transfer material conveyance belt 33. Further, a fixing means, ie, a fixing device 42 serving as an image fixing mechanism is provided at the terminal end of the transfer material conveying belt 33 in the transfer material conveying direction and close to the paper discharge roller 41. Inside the fixing device 42, there is a fixing rotating body, that is, a fixing roller 7, located at the upper side in FIG. are arranged respectively.

In this embodiment, the fixing roller 7 has a plate thickness of 1.4 mm.
The pressure roller 9 has an outer diameter of 20 mm and a total pressure of 6 kg. Paper feed roller 39 of the frame 100. An opening is formed on the side where the registration roller pair 40 is provided.

A removable transfer material storage cassette 38 is fitted into the opening. On the other hand, an opening is also formed on the side of the frame body 100 where the paper discharge roller 41 is provided, and the transfer material discharged to the outside of the frame body 100 by the paper discharge roller 41 is stored in the opening. A removable discharge tray 37 is fitted therein.

The image forming process performed by the image forming apparatus having the above-mentioned configuration is already well known as the Carlson electrophotographic process.

The explanation will be omitted.

FIG. 1 shows the configuration of a control system included in an image forming apparatus according to the present invention.As is clear from FIG. Driven by a control unit 20 having a control means, that is, a CPUI, a ROM 2, and a voltage determination circuit 14, a main motor system that is driven by a motor drive circuit 12, and a power supply means, that is, a fixing heater drive circuit 11. It is roughly divided into a heating means, that is, a fixing heater 8 system. The motor drive circuit 12 forming the main motor system described above is connected to the outlet 5. It receives power from a drive power source (not shown) connected to the image forming apparatus via the low-voltage power source 4, and also receives power from a CPU
The drive means, ie, the main motor 10, is driven based on a drive command signal output from the main motor 10. In the embodiment according to the present invention, the main motor 10 has a rotating shaft that connects the fixing roller 7 and pressure roller 9 of the fixing device 42, the photosensitive drums 35C of each of the image forming units I to (3), etc. It is connected to a power transmission mechanism (not shown) that transmits the driving force of the main motor 10 to the transfer material conveyance belt 33 and paper feed roller 39. The fixing heater drive circuit 11 receives power from the drive power source via the outlet 5 and drives the fixing heater 8 disposed inside the fixing roller 7 based on a drive command signal output from the CPUI.
It is what drives the. The fixing heater 8 has a rating of 2.
A 40V, 100W halogen heater is used. Further, a power supply cutoff means, that is, a thermoswitch 13 is connected to the fixing heater drive circuit 11 to cut off power supply from the fixing heater drive circuit 11 to the fixing heater 8 when the fixing heater drive circuit 11 fails. ing. Near the outer peripheral surface of the fixing roller 7, a temperature detecting means, ie, a thermistor 6, is arranged to detect the temperature of the fixing roller 7 and output an electric signal corresponding to the detected temperature to the CPUI. The thermoswitch 13 and the thermistor 6 will be described in detail later. A 100V/115V drive power source is added to the aforementioned low voltage power source 4,
A changeover switch is provided so that a 200V/220/240V (F) driving power source can be freely connected to the image forming apparatus. The low voltage power source 4 is configured to not only supply driving power to the motor drive circuit 12 but also to the control unit 20 described above. The outlet 5 has a voltage of 100V/115V for the image forming apparatus.
The one used when connecting the V drive power supply, and the one used when connecting the 20V drive power supply.
There are two types, one used when connecting a 0v/22oV/240V drive power source, and each type can be attached or removed from the image forming apparatus depending on the rating of the connected drive power source.

The ROM 2 of the control unit 20 described above has a built-in control program, etc. (for example, a temperature control sequence for controlling the outer peripheral surface temperature of the fixing roller 7 to a predetermined fixing temperature value), and also stores necessary data. ing. The data stored in the ROM 2 includes, for example, data regarding the temperature value of the fixing roller 7 (i.e.,
A plurality of fixing temperature value data that allow image fixing by the fixing device W142) and the voltage determination circuit 14 (to be described later) by the CPU
The outer circumferential surface temperature of the fixing roller 7 is set at a preset temperature increase rate (for example, 3°C/
There is temperature monitoring time data, monitoring temperature value data, etc. that are set for each rated voltage value of the drive power source that can be used so that the temperature can be controlled by sec). The temperature control sequence described above is performed to suppress overshoot that occurs when a 200V drive power source is used in the image forming apparatus, for example.

The temperature control sequence is performed by reading the temperature detection signal outputted from the thermistor 6 several times in each cycle with the temperature monitoring time stored in the ROM 2 as one cycle, and the temperature value detected in each cycle becomes the monitoring temperature. The fuser heater 8 continues to be driven until the temperature reaches the temperature value, and when the monitored temperature value is reached within each temperature monitoring time, the drive of the fuser heater 8 is stopped for the remaining time of each temperature monitoring time. This is called constant temperature increase rate control. By setting the temperature monitoring time and the monitoring temperature value to appropriate values, the outer periphery of the fixing roller 7 can be adjusted to It is now possible to keep the rate of increase in surface temperature approximately constant, and furthermore, in the preparation stage for executing one image forming process, the temperature distribution in the axial direction of the fixing roller rough (shown by the horizontal axis in Figures 3 and 7) can be approximately maintained. It is possible to equalize. Under the control of the CPU, the voltage determination circuit 14 determines that the voltage of the drive power supply supplied via the outlet 5 and the low-voltage power supply 4 is 100V.
It is configured to determine whether it is a system or a 200V system and output the determination result to the CPUI. The CPU performs arithmetic operations and logical operations.The CPU controls the temperature control sequence stored in the ROM 2 so that the outer circumferential surface temperature of the fixing roller 7 reaches a predetermined fixing temperature based on the temperature detection signal output from the thermistor 6. The so-called constant temperature increase rate control is performed so that the temperature rises at a constant temperature.

Further, according to an embodiment of the present invention, the thermistor 6 has 1
A region where a substantially average temperature value of the fixing roller 7 appears in the image forming process preparation stage (i.e., a region of the apparatus C in FIG. 3).
or the area shown in Figure 5 IIE),
The thermoswitch 13 is arranged in an area of the fixing roller 7 (i.e., the area 11A in the third figure) corresponding to the area where the maximum amount of heat generated by the fixing heater 8 is obtained (i.e., the area where the amount of light distribution is maximum).
or B, the area shown by ff1F in Figure 5, which is the highest temperature area in the event of runaway), and is disposed in contact with the outer circumferential surface of the fixing roller 7. The thermoswitch 13 is configured to cut off the power supply to the fixing heater q from the fixing heater drive circuit 11 when it is detected that the temperature of the outer peripheral surface of the fixing roller 7 has reached a predetermined value or higher. Even if the thermistor 6 and thermoswitch 13 are arranged in this way, the CPUI performs the so-called constant temperature increase rate control as described above from the preparation stage of the image forming process until the completion of the image forming process. Therefore, the temperature of the outer circumferential surface of the fixing roller 7 is approximately uniform over the entire axial direction, so that in the steady driving state, the temperature detected by the thermistor 6 and the ambient temperature of the thermoswitch 13 are approximately concave.
becomes. Therefore, even though the fuser heater drive circuit 11 and the control unit 20 are not malfunctioning, the thermo switch 13 malfunctions and the power supply from the fuser heater drive circuit IT to the fuser heater 8 is cut off. It can be prevented. On the other hand, if the fixing heater drive circuit 11 or the control unit 20 breaks down, the fixing heater 8 from the fixing heater drive circuit 11
Even if it becomes impossible to control the power supply to
3, the fixing heater 8 and the fixing roller 7
The power supply can be cut off before the device and its peripheral devices emit smoke or catch fire.

In an image forming apparatus configured as described above.

If the fixing heater 8 runs out of control while using the 240V drive power source, the power supply to the fixing heater 8 from the fixing heater drive circuit 11 is cut off through the process described below. When the fixing heater drive circuit 11 and the control unit 20 are in a failure state,
When power continues to be supplied from the drive power source 24-'OV through the outlet 5, the fixing heater 8 rapidly heats the fixing roller 7 with the heater power of iiow (the fixing roller l during this heating is The temperature rise rate is 10~b, and the light distribution of the fixing heater 8 (i.e., halogen heater) is such that the maximum value of the light distribution exists at both ends in the axial direction as shown in FIG. Therefore, the temperature distribution of the fixing roller 7 during runaway also has maximum temperature values at both ends in the axial direction, as shown in FIG.
When the heater power is set to 1100W, the fixing roller 7 generated between the third figure IA or B and the positions 1c and D
If the thermoswitch 3 is disposed near position C in FIG. 3 as in the conventional image forming apparatus, when the thermoswitch 13 operates, The temperature at B becomes quite high.1 For example, if the fixing heater 8 is
oow, if a halogen heater with a light distribution of 160% is used and a thermoswitch 13 with an operating temperature of 210°C is installed at the position C, the temperature at the position C will be 32°C.
When the temperature reaches about 0 to 330°C, the thermoswitch 13 will be activated. However, the temperature at the positions A and B at this point has reached approximately 370° C., and there is an extremely high risk of smoke or light emission. However, in the embodiment according to the present invention, the thermoswitch 13 is disposed at the position IA or B, so that the temperature value of the portion where the maximum temperature value of the fixing roller 7 appears can be adjusted from 320°C to 33°C.
Since the temperature can be suppressed to about 0°C, the risk of smoke and ignition can be eliminated.

On the other hand, if the fixing heater 8 runs out of control while using a 100V drive power source, the following will occur. The heater power amount of the fixing heater 8 when a 100V drive power source is used is considerably smaller than when a 200V drive power source is used, and is about 285W in this embodiment. Heater power is about 2
The temperature increase rate of the fixing roller 7 due to the heating from the fixing heater 8 set at 85 W is quite slow (in this embodiment, it is about 3° C./sec), and the temperature increase rate of the thermoswitch 13 itself is quite slow. In other words, the difference between the temperature increase rate of the fixing rotare and
The temperature value between the temperature of the fixing roller 7 and the temperature near the fixing roller IA becomes smaller. Therefore, the temperature near position A of the fixing roller 7 is approximately equal to that of the thermoswitch 13.
For example, the fixing heater 8 is a halogen heater with a rating of 240°C, tioow, and a light distribution of 160%, and the thermoswitch 13 is set to an operating temperature of 210°C. When the fixing roller 7 is used, the thermoswitch 13 is activated when the temperature near the fixing roller 7 reaches about 250°C.

As is clear from the content explained above, according to an embodiment according to the present invention, a 1oov system drive! ! No matter which drive power source is used, either the lI'11 source or the 200V drive power source, it is possible to prevent the fuser heater 8 and its peripheral devices from emitting smoke or catching fire due to runaway of the fuser heater 8. Ta.

In this embodiment, the thermoswitch 3 is disposed in contact with the outer circumferential surface of the fixing roller 7, but instead of the thermoswitch 13, a thermofuse of a thermal dye type is installed on the outer circumferential surface of the fixing roller 7. Even if one type of drive power source is used, the fixing heater 8 may have a high heater power (e.g., about too low). If so, the present invention can be effectively applied. Furthermore, in addition to the above-described constant temperature increase rate control, there is also a control method that can control the humidity increase rate of the fixing roller 7 to be substantially constant in the preparation stage of the image forming process when a plurality of drive power sources with different rated voltages are used, for example. , the rate of temperature rise of the fixing roller 7 is determined at the beginning of the execution preparation stage of the image forming process, and the voltage value of the drive power source is determined by the voltage determination circuit 14, and from the middle of the execution preparation stage of the image forming process, the determination result is responded to. There is no problem in controlling the temperature increase rate to be variable.

As explained above, according to the present invention, even if drive power sources with different supply voltage values are used, the heating means and its peripheral equipment will not emit smoke due to the difference in the temperature rise rate of the heating means. Accordingly, it is possible to provide an image forming apparatus that can prevent problems such as fire, and can maintain the temperature of the outer circumferential surface of the fixing rotor at a predetermined fixing temperature value.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a control system included in an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a longitudinal sectional view showing the overall configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 3, FIG. 4, and FIG. 5 are explanatory views of the operation of an image forming apparatus according to an embodiment of the present invention. 6: Thermistor Ward 7 "Fusing 0-Ra Cu11: Fusing heater drive circuit 13: Thermoswitch 20: Control unit

Claims (1)

[Claims] 1) A fixing rotor that comes into contact with the pressure rotor and cooperates with the pressure rotor to fix the visible image formed on the transfer material; A heating means for heating, a power supply means for feeding power to the heating means, a temperature detection means for detecting the temperature of the fixing rotor, and a temperature detection signal outputted from the temperature detection means over the entire area of the fixing rotor. control means for controlling the driving of the heating means so that the temperature of the fixing rotor reaches a predetermined temperature value; Image formation characterized by comprising a power supply cutoff means that detects the temperature of the fixing rotary body and cuts off power supply from the power supply means to the heating means when the temperature of the fixing rotary body reaches a predetermined value or higher. Device.