JPH0264680A - Heating and fixing device - Google Patents

Abstract

PURPOSE:To speedily detect abnormality and to relatively readily compose a circuit for detecting abnormality by placing a current detecting sensor on a power supply wiring, reading an output from the current detecting sensor in response to the condition of plural control means, and discriminating the disconnection or shorting of the circuit based on the output. CONSTITUTION:With heating means H-1 and H-2 energized, the corresponding outputs are derived from the current detecting sensor 37, and a discriminating means 42 compares the condition of the control means 33 and 34 with the output from the current detecting sensor 37. When the output therefrom disagrees with the condition of the control means 33 and 34, that is regarded as that the circuit including the heating means H-1 and H-2 and the power supply wiring 35 develops abnormality such as shorting and disconnection, and the discriminating means 42 derives an abnormality detecting output. Thus, abnormality can be detected speedily, and the detecting circuit can be composed relatively readily.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The second invention relates to a heat fixing device in an image forming apparatus such as an electrophotographic copying machine or a laser printer.

<Prior Art> In an image forming apparatus, a heat fixing device for fixing a toner image transferred to a sheet of paper is well known.

Some heat fixing devices of this type conventionally measure the energization time of the heating heater with a timer and determine an abnormality when the energization time becomes longer or shorter than the normal value (Japanese Patent Laid-Open No. 52 (Refer to Publication No.-89331).

In addition, as an improvement to the method for determining abnormalities based on power-on time, a timer that operates when the copier is in standby mode and a timer that operates during copying are provided separately, allowing for faster abnormality detection. (Refer to Japanese Unexamined Patent Publication No. 57-171366)
.

<Problems to be Solved by the Invention> The above-described heat fixing device has a drawback in that it takes a relatively long time to detect an abnormality. For example, in the latter configuration described in the prior art, dedicated timers are provided for standby mode and copy operation, and although the improvement has been made to speed up the time until abnormality detection, it is difficult to identify abnormalities. It takes at least 30 to 40 seconds after the timer starts operating.

On the other hand, if the heating fixing device is short-circuited, a large current will flow through the short-circuited portion, so if the abnormality is not detected promptly, there is a risk that the entire image forming apparatus will be damaged.

Therefore, there is a need for a heat fixing device that can detect abnormalities more quickly than conventional methods.

In addition, many of the recent heat fixing devices are equipped with multiple heat generating means such as heaters, and it is now possible to energize multiple heat generating means simultaneously or selectively depending on the operation mode of the image forming apparatus. The number of things that have been done is increasing. When such a configuration is adopted, if a timer for detecting energization time is provided to detect an abnormality, the number of timers will increase, and the energization time of each heat generating means will change depending on the number of heat generating means to be energized. Therefore, there is also a drawback that it becomes difficult to determine an abnormality based on the energization time.

Therefore, the present invention has been made to solve the above-mentioned problems, and it is possible to quickly detect abnormalities in the heat fixing device, and the circuit configuration for detection can be realized relatively easily. The purpose is to provide a heating fixed stone device.

Means for Solving the Problems> The present invention provides a heat fixing device in an image forming apparatus, which comprises: a heat generating means for heating the heat fixing device; a power supply wiring connected to the heat generating means; a current detection sensor coupled to a supply wiring for detecting the flow of current in the power supply wiring; a control means for controlling energization to the heating means; and a current detection sensor coupled to the power supply wiring in response to a control state of the control means. a determining means for reading the output of the sensor and determining whether the circuit including the heat generating means is disconnected or short-circuited based on the output of the sensor.

The heat generating means may include a plurality of heat generating means connected to a common power supply wiring. In that case, it is preferable that the control means energizes the plurality of heat generating means one by one, and at that time, the determining means determines whether there is a disconnection or a short circuit in the circuit including the heat generating means that is energized. .

Further, the determining means may be configured to determine the disconnection or short circuit based on the output waveform of the current detection sensor.

Effect> When the heating means is energized, a corresponding output is derived from the current detection sensor. The determining means compares the control state of the control means and the output of the current detection sensor. When the output of the current detection sensor does not correspond to the control state of the control means, it can be assumed that an abnormality such as a short circuit or disconnection has occurred in the circuit including the heating means and the power supply wiring. Derive the output.

Even when a plurality of heat generating means are provided, an abnormality thereof can be detected by a current detection sensor connected to a common power supply line.

If an abnormality occurs in the heat generating means, it immediately appears as an output from the current detection sensor, so the abnormality can be detected in real time.

<Embodiment> Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 2 is a sectional view showing a schematic configuration of an electrophotographic copying machine 10 having an embodiment of the present invention.

A document mounting table 11 and a document cover 12 are provided on the top surface of the copying machine 10, and an exposure device 13 is provided in the upper part of the interior. The exposure device 13 is for illuminating the original, guiding light reflected from the original surface to the photoreceptor drum 16, and exposing the surface of the photoreceptor drum 16.

Around the photoreceptor drum 16, there is a charger 17 for charging the surface of the photoreceptor drum 16 to a constant potential, an erase lamp 18 for removing unnecessary charges, and an electric charge formed on the surface of the photoreceptor drum 16 by exposure to light. A developing device 19 for developing an electrostatic latent image into a toner image, a transfer/separation charger 20 for transferring the toner image onto paper and peeling the paper from the photoreceptor drum 16, and residual toner on the surface of the photoreceptor drum 16. A cleaner 21 for removing residual charges on the surface of the photoreceptor drum 16 and a charge eliminating lamp 22 for removing residual charges on the surface of the photoreceptor drum 16 are provided.

In addition, in order to supply paper in conjunction with the movement of the photoreceptor drum 16, etc., a removable paper feed cassette 23, a paper feed roller 24 for taking out paper from the paper feed cassette 23, and a fixed amount of paper to the photoreceptor drum 16 are provided. A pair of registration rollers 25 are provided for secondary feeding of paper at a timing, and a conveyance belt 26 is further provided for conveying the paper to which the toner image has been transferred and has been peeled off from the photoreceptor drum 16.

The heat fixing device 27 according to this embodiment includes a conveyor belt 2
In order to fix the toner image on the paper transported in step 6,
It is arranged on the downstream side of the conveyor belt 26. The heat fixing device 27 includes a heat-generating roller 28 and a pressure roller 29 paired with the heat-generating roller 28. When the paper is conveyed between both rollers 28 and 29, the heat generated by the heat-generating roller 28 causes the paper to be heated. The toner is fused and fixed.

The heat generating roller 28 has two heaters 1 (-1
and H-2, and by energizing these two heaters simultaneously or selectively, the heat generating roller 28 is maintained at a predetermined stable temperature. Further, a thermistor 30 for detecting the temperature of the heat generating roller 28 is provided near the surface of the heat generating roller 28. This thermistor 3
0 may be placed inside the heat generating roller 28.

A pair of ejection rollers 31 is provided downstream of the heat fixing device 27, and an ejection tray 32 for receiving the ejected paper is further provided.

FIG. 1 is a control circuit diagram of the heat fixing device 27 in the copying machine 10. As shown in FIG. The energization of the heater H-1 is controlled by the 5SR33, and similarly, the energization of the heater H-2 is controlled by the 5SR34. 5SR33 and 5SR
34 receives operation commands from the CPU 42. Heater H-1 and heater H-2 are connected in parallel and connected to AC power source 36 via common wiring 35. A current detection sensor 37 is coupled to the common wiring 35 by electromagnetic coupling. The output end of the current detection sensor 37 is connected to a matching circuit 41 via a rectifier diode 38, a voltage dividing resistor 39, and a smoothing capacitor 40, and the output of the matching circuit 41 is provided to the CPU 42. A relay contact 43 is also inserted into the common wiring 35, and the relay contact 43 can be opened and closed by a relay 44 controlled by the CPU 42. Furthermore, the output of the thermistor 30 for temperature detection is provided to the CPU 42.

As is clear from this configuration, in this embodiment, the CPU
42 controls the entire circuit.

FIG. 3 is a characteristic curve showing the relationship between the temperature of the heat generating roller 28 heated by the heaters H-1 and H-2 and time. When the power of the copying machine 1o is turned on, the heat generating roller 28 is rapidly heated by the two heaters H-1 and H-2, and when the temperature reaches a stable temperature, the two heaters or the heater H-1 or H-2 is turned on. Electricity is selectively applied so that the temperature of the heat generating roller 28 settles to a stable temperature.

Figure 4 shows the 5SR33 or 34 in the circuit of Figure 1.
FIG. 3 is a waveform diagram showing the relationship between the current applied to the heater and the output waveform of the current detection sensor 37 at that time. As shown, the current detection sensor 37 derives an output at each instant when energization is initiated by the 5SR 33 or 34.

FIG. 5 is a flowchart showing the control operation of the CF'U 42 of FIG.

Next, with reference to FIGS. 1 to 4, the operation of the heating fixing device 27 will be explained according to the flow shown in FIG. 5.

The CPU 42 first closes the relay contact 43 using the power relay 44 (step S1), and then controls the 5SRs 33 and 34 to turn off both the heaters H-1 and H-2 (into a non-conducting state) (step S2). .

In this state, the output of the current detection sensor 37 is read and the output state of the sensor 37 is determined (step S3). If the circuit is normal, no current flows from the AC power supply 36 to the heaters H-1 and H-2 via the common wiring 35, and there is no output from the current detection sensor 37, so in this case step 312 Proceed to.

If there is an output from the current detection sensor 37, the CPU
42 stores the output of the current detection sensor 37 (step S4).

Next, the CPU 42 controls the 5SR33 to turn on the heater H-
1, and read the output waveform of the current detection sensor 37 at that time (step S5).

This output waveform has a constant period as shown in FIG. Then, the read output waveform is transferred to the previous step S.
The waveform is compared with the waveform stored in step 4 (step S6).

If the two waveforms match, it means that the current is flowing through the common wiring 35 regardless of whether the heater H-1 is energized. (In many cases, there is a ground fault to the body of the machine 10.) If so, step S7) turns off all heaters and stops the machine (step S8).

If the detected waveform and the stored waveform do not match in step S6, heater H-1 is turned off and only heater H-2 is energized (step 89).

Then, the output of the current detection sensor 37 is read again, and the read waveform is compared with the waveform stored in step S4 (step 5IO).

If the two waveforms match, it means that current is flowing through the common wiring 35 regardless of whether or not the heater H-2 is energized, so the CPU 42 determines that the heater H-2 is short-circuited (step 5ll). Turn off all heaters and stop the machine (step S8) In this way, a short circuit in heater H-1 or heater H-2 is detected as soon as power is turned on to the circuit.

If the circuit is normal, the process proceeds to step S12 as described above, and the heater H-1 is turned on by the 5SR33. Then, the output of the current detection sensor 37 is read (step 81
3). If there is no output pulse from the sensor 37 at this time, it means that no current from the AC power source 36 is flowing through the circuit including the heater H-1, so the CPU 42
-1 is disconnected (step 514), all heaters are turned off and the machine is stopped (step S8).

In step 313, if there is an output pulse from the current detection sensor 37, the energization to the heater H-1 is stopped, and conversely, the 5SR 34 energizes the heater H-2 (step 515). Then, the output of the 7IXA detection sensor 37 is read, and if there is no output pulse from the sensor 37, the CPU 42 determines that the circuit including the heater H-2 is on a new line (step S16.517), and turns all the heaters off. The power is turned off to stop the machine (step S8).

In steps S13 and S16, if there is an output waveform from the current detection sensor 37, it is determined that the circuit including the heaters H-1 and H-2 is normal. Based on this result, the CPU 42 turns on the heaters H-1 and H-2 using the 5SRs 33 and 34, and rapidly heats the heat generating roller 28 until it reaches a stable temperature (step 518). A thermistor 30 detects whether the heat generating roller 28 has reached a stable temperature.

When the heat generating roller 28 reaches a stable temperature (step 51)
9), the CPU 42 stops energizing the heaters H-1 and H-2 (step 523), ? Determine whether there is an output waveform of the ti current ratio detection sensor 3 (step 524)
. If the circuit is normal, there is no output waveform from the current detection sensor 37. Therefore, in this case, the CPU 42 determines that the circuit is normal (step 525) and returns to step S19.
Return to.

In step S24, if it is determined that there is an output waveform from the current detection sensor 37, the CPU 42 stores the waveform of the output waveform (step 826).
(The output waveform of the current detection sensor 37 is read with only -1 energized (step 527).Then, the read output waveform is compared with the waveform stored in the previous step S26 (step 528).

If the two waveforms match, it means that current is flowing through the common wiring 35 regardless of whether or not the heater H-1 is energized, so the CPU 42 determines that the heater H-1 is short-circuited (step 529). , all heaters are turned off and the machine is stopped (step S8).

If the detected waveform and the stored waveform do not match in step S28, heater H-1 is turned off, and conversely heater H-2 is turned off.
energize the current detection sensor 37 and read the output of the current detection sensor 37 again (
Step 530), and the read waveform is compared with the waveform stored in step S26 (step 531).

If the two waveforms match, fltE is flowing through the common wiring 35 regardless of whether the heater H-2 is energized, so the CPU 42 determines that the heater H-2 is short-circuited. is turned off to stop the machine (step S8).

In this manner, a short circuit in the heater H-1 or H-2 is detected every time the heating roller 28 reaches a stable temperature, thereby preventing damage to the entire apparatus.

In step S31, if the detected waveform and the stored waveform do not match, the control moves to step S19 again and abnormality detection is performed again.

After the heat generating roller 28 reaches a stable temperature, the copying machine 10 performs a copying operation and the heat fixing device 27 fixes the toner image on the paper, the heat from the heat generating roller 28 is taken away and the heat generating roller 28 becomes stable. temperature drops below. If the temperature of the heat generating roller 28 falls below the stable temperature, the CPU
42 determines the operating state of a motor (not shown) for rotating the exposure device 13 or the photosensitive drum 16 (step 520), and when the lamp or motor is operating, the H-
If the lamp and motor are both stopped, heaters H-1 and H-2 are energized (step 521).
Both are energized (step 522) to raise the temperature of the heat generating roller 28 to a stable temperature.

The reason why only the heater H-1 is energized while the lamp or motor of the exposure device 13 is in operation is to take into consideration the capacity of the circuit wiring of the entire copying machine 10. More specifically, in order to energize both heaters H-1 and H-2 while the lamp or motor is operating,
When designing the circuit of the copying machine 1o, the wiring 82 must be made large. This would result in high wiring costs for the entire copying machine 1o, which is why the above considerations are taken in this embodiment.

In the above embodiment, in order to heat the heat generating roller 28, two
Although an example in which two heaters are provided has been described, a single heater or three or more heaters may be provided. Even if there are multiple heaters, the current detection sensor 3
By coupling 7 to the common wiring of the heater, a circuit can be configured with a single current detection sensor.

In the above description, a heat fixing device applied to a copying machine has been described, but the present invention is not limited to copying machines, but can be widely applied to heat fixing devices for printers and other image forming apparatuses.

<Effects of the Invention> Since the present invention is configured as described above, abnormalities in the heat fixing device can be quickly detected. In particular, if the heating means is short-circuited, there is a risk that a large current will flow through the entire device, but whether or not the heating means is short-circuited is always detected each time the heating means is intermittently turned off, allowing for early detection of abnormalities. It is possible.

Further, even if the number of heating means increases, abnormality can be detected by a single current detection sensor, so the circuit can be configured relatively easily.

[Brief explanation of the drawing]

FIG. 1 shows an example of a circuit configuration of a heat fixing device according to an embodiment of the present invention. FIG. 2 shows a copying machine 10 in which an embodiment of the present invention is adopted.
FIG. 2 is a schematic cross-sectional view of the configuration. FIG. 3 is a characteristic curve showing the relationship between the temperature of the heat generating roller 28 and time. FIG. 4 is a waveform diagram showing the relationship between the current applied to the heater and the output waveform of the current detection sensor at that time. FIG. 5 is a flowchart showing the operation of the control circuit in one embodiment of the present invention. In the figure, 10... Copying machine, 27... Heat fixing device, 28... Heat generating roller, 30... Thermistor, 3
3゜34...SSR, 35...Common wiring, 36.
...AC power supply, 37...Current detection sensor, 42...
CPU is shown. Patent applicant Hiroshi Kamei, representative of Sanda Kogyo Co., Ltd., patent attorney
Win (2 idiots)

Claims (1)

[Scope of Claims] 1. A heat fixing device in an image forming apparatus, comprising: a heat generating means for heating the heat fixing device; a power supply wiring connected to the heat generating means; and a power supply wiring coupled to the power supply wiring. , a current detection sensor for detecting the flow of current in the power supply wiring; a control means for controlling energization to the heating means; reading an output of the current detection sensor in response to a control state of the control means; A heat fixing device comprising: a determining means for determining whether a circuit including the heat generating means is disconnected or shorted based on the output of the sensor. 2. The heat fixing device according to claim 1, wherein the heat generating means includes a plurality of heat generating means connected to a common power supply wiring. 3. The heat fixing device according to claim 2, wherein the control means energizes the plurality of heat generating means one by one, and at this time, the determining means determines whether a circuit including the heat generating means related to the energization is disconnected. or to determine a short circuit. 4. The heat fixing device according to claim 2 or 3, wherein the determining means determines the disconnection or short circuit based on the output waveform of the current detection sensor.