JP3225301B2 - Fixing abnormality diagnosis device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing abnormality diagnosis for diagnosing abnormal lighting of a heating source and stopping runaway based on an output from a surface temperature detecting means attached to a fixing roller of a fixing section of an electronic copying machine or the like. Related to the device.

[0002]

2. Description of the Related Art Conventionally, a so-called heat roller system has been frequently used in a fixing section of an image forming apparatus such as an electronic copying machine, which has a built-in heater as a heating source in one roller and a pair of transfer paper. The toner image is thermally fixed by passing between the rollers. There is an optimum temperature for the thermal fixing of the toner image, and the turning on and off of the heater is automatically controlled so as to maintain a predetermined temperature range including the optimum temperature. In the automatic control, a thermistor as a temperature-sensitive element is slidably contacted with a fixing roller, and the surface temperature of the heat roller is detected by the thermistor and sent to the control unit. However, if the power supply circuit breaks down or the temperature control of the heater is not performed for some reason, a so-called runaway in which the heater is turned on abnormally occurs.

In order to stop the runaway, the conventional fixing unit is provided with a fixing abnormality diagnosing device, and a thermistor is provided at each of a center portion of the fixing roller and a region outside the sheet passing region. The temperature was controlled by the thermistor of No. 1, and the abnormality was determined by the thermistor outside the paper passing area. This is because if the transfer paper is wrapped around the fixing roller, the thermistor inside the paper passing area cannot measure the surface temperature, and the heater is forcibly turned off when the surface temperature outside the paper passing area exceeds a predetermined temperature. It was a configuration to make it.

[0004]

However, since the surface temperature of the fixing roller is controlled by the thermistor at the center, the surface temperature outside the paper passing area, that is, at the end is different from that at the center. Moreover, the difference greatly changed depending on the machine sequence and the paper passing size of the transfer paper. For example, when the central portion is controlled to 200 ° C., the end portion temperature is 170 ° C. at the time of warm-up, but 230 ° C. when the transfer paper having the minimum width is fixed. Therefore, the temperature to be used as the abnormality determination value is at least 240
Degree C.

However, if the transfer paper is wrapped around the fixing roller for some reason, the temperature cannot be controlled by the central thermistor, so that the heater cannot be turned off until the end temperature reaches the abnormality determination value. Was. At this time, the temperature of the central portion surface increased to over 300 ° C., and there was a possibility that the peripheral devices of the fixing roller would be adversely affected.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned drawbacks of the conventional fixing abnormality diagnosis apparatus. The surface temperature of the fixing roller is set to a predetermined temperature or less regardless of the machine sequence or the size of the paper passing width. It is an object of the present invention to provide a fixing abnormality diagnosis device which can suppress the occurrence of runaway and does not damage peripheral devices of the fixing roller even when a runaway occurs.

[0007]

According to a first aspect of the present invention, there is provided an image forming apparatus, comprising: a central part surface temperature detecting means for detecting a surface temperature of a central part of a paper passing area of a fixing roller having a built-in heating source; Detecting means, an end surface temperature detecting means for detecting a surface temperature of the fixing roller outside the paper passing area, and an abnormality of the heating source based on outputs from the end surface temperature detecting means and the central surface temperature detecting means. A runaway control device for diagnosing lighting and turning off the heating source when an abnormality occurs, wherein the runaway control unit determines whether the system is warming up, idling, or fixing. A determination circuit, a paper passing size determination circuit, and a machine sequence for warming up, idling, and fixing at the time of warming up, idling, and fixing the ratio of the end surface temperature and the center surface temperature of the fixing roller. A temperature ratio selection circuit that sets a plurality in advance based on the paper size and specifies the ratio based on the output of the machine sequence determination circuit and the output of the paper passing size determination circuit, and an abnormality determination value of the end surface temperature input in advance. The apparatus further comprises an abnormality determination circuit that corrects with the specified ratio, compares the correction value with the output of the end surface temperature detection means, and determines abnormal lighting of the heating source.

According to a second aspect of the present invention, in the fixing abnormality diagnosing apparatus according to the first aspect, the sheet passing size determination circuit determines whether the sheet passing size is a minimum width, a maximum width, or an intermediate width. Is a circuit that determines

[0009]

According to the first aspect of the present invention, the temperature ratio selection circuit of the runaway control means sets the ratio between the end surface temperature and the center surface temperature of the fixing roller to a machine sequence during warm-up, idling, and fixing. A plurality is set in advance based on the paper size. On the other hand, in the machine sequence judgment circuit and the paper passing size judgment circuit, when warming up, idling,
The machine sequence and paper passing size at the time of fixing are determined, and the results are input to a temperature ratio selection circuit to specify the ratio. Further, an abnormality determination value of the end surface temperature is input to the abnormality determination circuit in advance, and the abnormality determination value is corrected by inputting a ratio specified by the temperature ratio selection circuit. This correction value is compared with the output of the end surface temperature detecting means, and if it is larger than the correction value, it is determined that the heating source is abnormally lit. According to a second aspect of the present invention, the sheet passing size determination circuit determines whether the sheet passing size is a minimum width, a maximum width, or an intermediate width.
Therefore, there are five types of ratios input to the temperature ratio selection circuit: warm-up, idling, maximum width, minimum width, and intermediate width.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of the fixing abnormality diagnosing apparatus of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a schematic configuration diagram of an image forming apparatus including a fixing unit and a fixing abnormality diagnosis device, and FIG.
FIG. 3 is a block diagram of a fixing unit provided with a fixing abnormality diagnosis device, FIG. 3 is a circuit block diagram of a runaway control unit of the fixing abnormality diagnosis device, FIG. 4 is a flowchart for determining abnormal lighting, and FIG. FIG.

The image forming apparatus 1 includes a plurality of paper feed stages 2, each of which accommodates a transfer paper 3. Each paper feed stage 2
On the upper surface of the transfer paper 3, a paper feed roller 4 and a double feed prevention means 5 are provided in parallel, and the transfer paper 3 is sent out one by one to the next process. The transfer paper 3 sent out from each stage is guided by a guide plate (not shown) and inserted into the transport roller 6. The transport roller 6 is linked to and driven by the paper feed rollers 4 of each paper feed stage, and forms a transport path for each paper feed stage 2. The transfer paper 3 sent out from the uppermost transport roller 6 is inserted into a registration roller 7 disposed immediately before the transfer processing section. The transfer paper 3 sent from the registration roller 7 to the transfer area of the transfer processing unit passes through the photosensitive drum 8, the transfer electrode 9, and the separation electrode 10, carries the toner image, and is conveyed through the separation claw 11. The sheet is placed on the belt 12 and sent to the fixing unit 13. The transfer paper 3 heated and pressurized in the fixing unit 13 fixes the toner image and is sent to a discharge tray (not shown).

The fixing section 13 bites and transfers the transfer paper 3 on which a toner image is formed between a cylindrical fixing roller 14 coated with an adhesive material to which toner does not adhere to the surface and a pressing roller 15. A heat lamp 16 serving as a heating source is fixed inside the fixing roller 13. Details of the fixing unit 13 will be described with reference to FIG. Around the fixing roller 14, a roller wrap preventing claw 17 and a cleaning web 1 are provided.
A central temperature sensor 19 and an end temperature sensor 20 supported by a suitable bracket (not shown) are disposed in contact with or close to the roller surface. A small thermistor is used for the center temperature sensor 19 and the end temperature sensor 20, and the output is sent to a control unit 21 which constitutes a runaway control unit of the fixing abnormality diagnosis device. The control unit 21 is connected to an operation panel 22 attached to the image forming apparatus 1. When an automatic paper is selected on the operation panel 22, the size detection unit 24 automatically reads the original placed on the original glass 23. , A paper size signal is input to the control unit 21.

Next, the configuration of the control section 21 which is a runaway control means of the fixing abnormality diagnosis apparatus will be described with reference to FIG. Control unit 2
Reference numeral 1 denotes a machine sequence determination circuit 25 connected to the operation panel 22, a paper passing size determination circuit 26 connected to the operation panel 22 and the size detection means 24, a machine sequence determination circuit 25, a paper passing size determination circuit 26, and the operation panel. A temperature ratio selection circuit 27 connected to the control panel 22; an abnormality determination circuit 28 connected to the operation panel 22, the temperature ratio selection circuit 27 and the end temperature sensor 20 to turn off the heat lamp 16 during runaway; And a temperature control circuit 29 for controlling the surface temperature of the fixing roller 14 in the sheet passing area.

The temperature ratio selection circuit 27 includes a fixing roller 14
A plurality of ratios of the end surface temperature and the center surface temperature of the operation unit 2 are set in advance based on the machine sequence and the sheet passing size.
2 is input. An example of this ratio will be described with reference to FIG. FIGS. 5A, 5B, 5C, and 5D respectively show when the machine sequence is warming up, idling, fixing (maximum width paper passing), and fixing (minimum width paper passing). The temperature distribution of the fixing roller 14 is shown in a graph. Here, the central part surface temperature is T1 = 200 ° C.
, And the end surface temperature T2 at that time is obtained,
The ratio R = T2 / T1 is calculated. This ratio R is warmed up; R (a) = 0.85, idling;
R (b) = 0.95, at the time of fixing (at the time of maximum width paper feeding); R
(C) = 0.98, at the time of fixing (at the time of passing the minimum width); R (d)
= 1.15. Further, an initial value of an abnormality determination value of the end surface temperature is input to the abnormality determination circuit 28 via the operation unit 22 in advance. The initial value is, for example, T2 (SET) = 300 degrees C as shown in FIG.

Next, an abnormal lighting judgment flow of the runaway control means will be described with reference to FIGS. In the control unit 21 in which the predetermined ratio and the initial value are set as described above, a signal is input from the operation unit 22 or the size detection unit 24 to the machine sequence determination circuit 25 and the sheet passing size determination circuit 26, and the machine sequence and the The paper size is determined. The result is input to the temperature ratio selection circuit 27, and one of the preset ratios is specified.

In the abnormality determination circuit 28, the corrected abnormality determination value T2S = T2 (SET) * R (a) based on the initial value T2 (SET) of the abnormality determination value and a specified ratio, for example, R (a).
Ask for. If R (a) = 0.85, T2S = 30
0 * 0.85 = 255. When the abnormality determination value T2S is compared with the end surface temperature T2 and T2> T2S, it is determined that the heating source is abnormally lit, and the heat lamp 16 is forcibly turned off.

Accordingly, when the end surface temperature is lower than the center surface temperature in the sequence or the sheet passing size, the end surface temperature T2 is turned off at a temperature lower than the initial value of the abnormality determination value. When the temperature is relatively high, the heat lamp 16 is turned off at a temperature higher than the initial value. In any case, it is possible to prevent the surface temperature of the fixing roller 14 from exceeding 300 ° C. and running away.

[0018]

As described above, according to the first aspect of the present invention, the runaway control means increases the ratio of the end surface temperature to the center surface temperature of the fixing roller when warming up, idling, and fixing. In addition, by setting a plurality of values in advance based on the paper passing size and correcting the abnormality determination value of the end surface temperature input in advance based on the specified ratio, the machine sequence at the time of warm-up, idling, fixing, and the width of the paper passing width are corrected. Regardless of the size, the surface temperature of the fixing roller can be suppressed to a predetermined temperature or lower, and even when runaway occurs, peripheral devices of the fixing roller are not damaged.

In the fixing abnormality diagnosing device according to the second aspect, the surface temperature of the fixing roller can be suppressed under all conditions by classifying the sheet passing size into three types, a minimum width, a maximum width, and an intermediate width. it can.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an image forming apparatus including a fixing unit and a fixing abnormality diagnosis device.

FIG. 2 is a configuration diagram of a fixing unit provided with a fixing abnormality diagnosis device.

FIG. 3 is a circuit block diagram of a runaway control unit of the fixing abnormality diagnosis device.

FIG. 4 is a flowchart of determination of abnormal lighting.

FIG. 5 is an explanatory diagram of a temperature distribution state of a fixing roller.

[Explanation of symbols]

 13 Fixing Unit 14 Fixing Roller 16 Heat Lamp 19 Central Temperature Sensor 20 End Temperature Sensor 21 Control Unit 25 Machine Sequence Judgment Circuit 26 Paper Feed Size Judgment Circuit 27 Temperature Ratio Selection Circuit 28 Abnormality Judgment Circuit

Claims (2)

(57) [Claims] 1. A central part surface temperature detecting means for detecting a surface temperature of a central part of a paper passing area of a fixing roller having a heating source built therein, and an end part detecting a surface temperature of the fixing roller outside the paper passing area. Surface temperature detecting means, and runaway control means for diagnosing abnormal lighting of the heating source based on outputs from the end surface temperature detecting means and the central part surface temperature detecting means and turning off the heating source when an abnormality occurs. In the fixing abnormality diagnosis device, the runaway control unit includes a machine sequence determining circuit that determines whether the warm-up is performed, the idling is performed, or the fixing is performed, a paper-passing size determining circuit, and an end surface temperature of the fixing roller. A plurality of the center surface temperature ratios are set in advance based on the machine sequence during warm-up, idling, and fixing, and the paper passing size, and the machine sequence determination cycle is set. And a temperature ratio selection circuit that specifies the ratio based on the output of the sheet passing size determination circuit, and an abnormality determination value of the end surface temperature that is input in advance is corrected by the specified ratio. An abnormality determining circuit for comparing the output of the surface temperature detecting means to determine abnormal lighting of the heating source. 2. The fixing abnormality diagnosis apparatus according to claim 1, wherein the sheet passing size determination circuit determines whether the sheet passing size is a minimum width, a maximum width, or an intermediate width. A fixing abnormality diagnosis device, characterized in that: