JP2885320B2 - Thermal fuser life detection method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting the life of a heat fixing device for thermally fixing an unfixed toner image, and more particularly, to a method of detecting the temperature of different portions of a heat roller surface of a heat fixing device. The present invention relates to a method for detecting the life of a thermal fixing device that determines the life of the fixing device based on a state of deviation.

`` Prior art '' Conventionally, a roller type heat fixing device composed of a combination of a fixing roller and a heating roller with a built-in heater is known, and in this type of fixing device, the temperature is controlled to a high temperature of about 180 to 200 ° C. In order to fix the image while inserting the recording paper carrying the unfixed toner image between the pair of rollers, even if the roller surface is coated with a heat-resistant member such as silicon rubber, especially the bearing portion etc. Deteriorates,
For this reason, it is difficult to maintain good fixability unless the fixing unit is replaced as appropriate.

In general, such fixing unit replacement timing is determined by a fixing (print) number counter. However, even if the number of prints is the same, the fixing operation time differs between the intermittent printing and the continuous printing cycle. I can't do it.

For this reason, in the known fixing device, the number of counts for the life detection is set to the least common multiple assuming the worst, but with such a configuration, although the fixing device is still usable, It indicates that it is the end of life, which is not preferable in terms of resource saving.

On the other hand, when the fixing roller pair is replaced after the end of the service life, it is necessary to provide a means for confirming whether the replaced fixing roller is new or not. Therefore, in the conventional apparatus, for example, as shown in FIG. 51, resistor R1, and fuse
A thermal fixing device provided with a checking means consisting of Fu is prepared, and a control voltage is applied to the voltage terminal 51 by mounting the fixing device in the printer, and a transistor Tr whose emitter side is grounded on the downstream side of the fuse Fu. And the control port (B) is connected in parallel, whereby the presence or absence of the control voltage is first checked from the control port (B), and when the control voltage is 0 V, the old fixing device is installed. And the replacement signal is displayed again.On the other hand, if the control voltage is 5 V, it is determined that a new fixing device has been installed, the life detection counter is reset, and a signal from the control unit side is output. By applying a voltage to the base (A) of the transistor Tr based on the current, an excessive current flows through the fuse Fu through the collector of the transistor Tr to blow the fuse Fu, thereby destroying a new state. It had.

[Problem to be Solved by the Invention] However, according to such a conventional technique, whether or not a fuse Fu is new is determined only by the presence or absence of the fuse Fu. Therefore, the user continues to use the fuse Fu of the old fuser only by replacing the fuse Fu. This has become a very important issue in terms of system quality and safety measures.

In view of the drawbacks of the prior art, the present invention enables accurate life detection without using a sheet counter, and prevents a user from erroneously recognizing that a new fuser is a new fuser even if a fuse of an old fuser is replaced. It is an object of the present invention to provide a method for detecting the life of a fixing device.

“Means for Solving the Problems” The present invention focuses on the fact that, when the fixing roller is deteriorated, the degree of temperature rise when a predetermined heat energy is applied is different between the deteriorated part and the normal part. is there.

For example, when the bearing is deteriorated, the fixing pressure between the pressure roller and the opposing pressure roller decreases, so that the amount of heat taken by the pressure roller and the sheet decreases, and as a result, the temperature increases.

Therefore, by arranging a temperature detecting circuit having a temperature detecting means in a portion where the fixing roller deteriorates quickly, the life can be detected based on the detected temperature.

For example, the detection circuit includes a first detection circuit having first detection means for detecting the temperature of the end of the heating roller, and a second detection means having a second detection means for detecting the temperature of a portion other than the end of the heating roller. 2 detection circuit, and the deterioration of the fixing roller is detected by a second detection unit in a portion other than the end portion,
For example, the temperature of the both ends is detected because the end side where the bearing is attached degrades faster than the center portion, and it is possible to determine that there is an abnormality when a deviation occurs between the detected temperatures.

Hereinafter, "" is deleted. "In the life detection, it is also possible to perform the life detection based on the time-series temperature change while keeping the supplied heat amount constant without measuring a plurality of temperature points." Even when a fixing device is mounted, it is uneconomical to always detect the life by applying heat energy, and a replacement detection fuse is necessary.

Therefore, it is necessary to provide a structure that can always determine the presence or absence of the fuse before performing the life detection by the detection circuit.

Therefore, for example, a second feature is that a fixed resistor R2, a temperature detecting element for life detection and a fixed resistor R1 are connected in series to form a detecting circuit, and the fuse is connected in parallel to the temperature detecting element. Accordingly, a combined resistance for voltage division is formed by the fuse and the fixed resistors R1 and R2. Therefore, the detection voltage at the voltage dividing point 32 at the time when the fuses are connected in parallel approximates the control circuit voltage. Also, when the fuse is disconnected, indicates a divided voltage of the temperature detecting element and the fixed resistor R2,
By applying the detection voltage to the detection circuit when the fixing device is mounted on the apparatus main body, the presence or absence of the fuse can be easily determined.

Further, by forcibly short-circuiting the circuit when there is a fuse, the fuse can be blown, whereby the life of the thermal fixing device can be accurately detected based on the detection voltage from the detection circuit. .

As described above, providing a plurality of detecting means for detecting the surface temperature in different places of the fixing roller is based on the difference between the detected temperatures of the two detecting means, and the abnormality of the detecting means itself or the heater heating means. Is easily determined, which is preferable.

Hereinafter, preferred embodiments of the present invention will be illustratively described in detail with reference to the drawings. However, unless otherwise specified, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention thereto, but are merely illustrative examples. It's just

FIG. 1 is a schematic block diagram showing a fixing device according to an embodiment of the present invention and a main circuit configuration around the fixing device on the apparatus main body side.

The fixing device is composed of a combination of a fixing roller 1a having a built-in heater 2 and a pressure roller 1b, and a detector 12 having a temperature control detecting element 3 is provided at the center of the surface of the fixing roller 1a.
The thermistor TH and fuse at the shaft end near the bearing
A life detecting body 10 including Fu is attached, and these are configured to be exchangeable as one.

On the other hand, a temperature control circuit 21 (PWM) that receives a detection voltage from the detection element 3 and generates an energization control signal for the heater 2 on the apparatus body side, and turns on / off a heater power supply 23 in response to the signal.
A temperature control system comprising an SSR 22 for performing control, a detection unit 30 for comparing a detection voltage of the detection element 3 and the life detection body 10 with a reference voltage, and a life detection based on a detection signal from the detection unit 30. Determining unit 40 for detecting various abnormalities, and a display unit for performing a predetermined display based on a signal from the determining unit 40
50, and a fuse blowing circuit comprising the transistor Tr
It consists of 11 life / abnormality detection systems.

Next, the detailed configuration of the life / abnormality detection system will be described with reference to FIG.

The life detector 10 connects a parallel connection of a pair of thermistors TH and a fuse Fu connected in series between a solid resistance R1 having one end connected to a control voltage terminal and a fixed resistance R2 having one end grounded. A connection between the parallel connection of the thermistor TH and the fuse Fu and the fixed resistor R2 (hereinafter referred to as a voltage dividing terminal 32 ) is connected to the collector of the transistor Tr, and one of the comparators 31a in the detection unit 30 described later. Connected to input terminal. The resistance values of the fixed resistors R1 and R2 are set so that R2 >> R1.

The detecting unit 30 compares the voltage from the voltage dividing terminal of the resistor connected in series with the temperature detecting element 3 or the voltage from the thermistor TH to the reference voltage from the reference voltage setting circuit Vs set as described later, and generates a comparison signal. It comprises a group of comparators 31a to 31f to output.

Incidentally, the reference voltage, when the control voltage is set to 5V, for example, the reference voltage from the top 4.5V, 3.5V, 2V, 0.5V,
It is set to 2.2V and 3.3V.

The determination unit 40 is formed by a CPU, and is configured to display a predetermined lamp based on comparison signals from the comparators 31a to 31f.

 Next, the operation of the embodiment will be described.

First, when a new fuser with a fuse Fu is installed, the life detector 10 has the thermistor TH and the fuse Fu connected in parallel, and because of R2 >> R1, the voltage from the voltage dividing terminal 32 approximates the control voltage 5V. The comparison output is output from the comparator 31a to the determination unit 40 side, and the determination unit 40 determines that the new fixing device is installed, and the base voltage is applied to the transistor Tr of the fuse melting circuit 11. Is applied, the collector of the transistor Tr is grounded, so that an excessive current flows through the fuse Fu to blow it out, and a new state is discarded.

As a result, the life detector 10 has a fixed resistance R connected in series.
1. A voltage dividing circuit composed of the thermistor TH and the fixed resistor R2 is formed.

The detection voltage corresponding to the life detecting thermistor TH obtained by the voltage dividing circuit and the temperature control detecting element 3
Before performing a predetermined life detection while comparing the detection voltages, it is first determined whether the life detection thermistor TH itself is abnormal.

That is, when the thermistor TH is short-circuited or disconnected, the detection voltage becomes 4.5 V or more or 0.5 V or less, and the comparison output from the corresponding comparators 31a and 31d is determined by the determination unit 40. Is displayed.

Next, the heating control of the fixing device is started, and when the two detection voltages are in the range of 2 to 3.5 V and 2.2 to 3.3 V during the heating control, the corresponding comparators 31b to 31c and 31e to 31f output the same. Based on the comparison output, the determination unit 40 determines that the temperature is normal, and performs normal temperature control.

On the other hand, the deterioration of the fixing roller 1a is faster at the end side where the bearing is mounted than at the center, so if the roller end side deteriorates due to long-term heating control, the detection voltage at the voltage dividing terminal 32 side increases. However, even though the detection voltage for temperature control is within the normal range, the detection voltage exceeds 3.5 V. In this case, the determination unit 40 based on the comparison output from the corresponding comparator 31a-b. Is determined to have reached the end of its life, and the life is displayed.

If both of the detected voltages deviate from the normal range, it is indicated as an abnormality on the temperature control side such as a failure of the heater 2 or the SSR.

In the case where only the fuse Fu of the fixing unit whose service life has expired is replaced, as described above, after the fuse Fu is blown by flowing an excessive current, a predetermined service life is compared while comparing the detection voltage with the detection voltage for temperature control. Since the detection is performed, it can be easily determined that the life of the fixing device has expired.

Therefore, according to this embodiment, the above-described operation of the present invention can be smoothly achieved.

[Effects of the Invention] As described above, according to the present invention, accurate life detection can be performed without using a sheet counter,
Even if the user replaces the fuse of the old fuser, it can accurately detect the life of the fuser without erroneously recognizing it as a new fuser, and provide multiple detection means for detecting the surface temperature of the fuser. By utilizing the difference between the detected temperatures of the two detectors, it is possible to determine whether or not the detector itself or the heater heater is abnormal.

And so on.

[Brief description of the drawings]

FIG. 1 is a schematic block diagram showing a fixing device according to an embodiment of the present invention and a main circuit configuration around the fixing device on the apparatus main body side. FIG. 2 is a circuit block diagram showing a detailed configuration of the life / abnormality detection system.
FIG. 3 is a circuit block diagram showing a detailed configuration of a conventional life detecting system. 3 detection element (second detection means), 10 life detection object (detection circuit), 11 fuse blowing circuit, 12 detection object (detection circuit), 31 comparator (comparison circuit), TH ... Thermistor (first detection means)

Claims (2)

(57) [Claims] A detecting circuit for detecting a surface temperature of a heating roller of the heat fixing device; a detecting circuit configured to detect a temperature of a different portion of the heating roller; A method for detecting the life of a thermal fixing device, wherein the life of the fixing device is determined based on a state of divergence of a plurality of detected temperatures detected by the detecting device, wherein the detecting circuit has a first detecting means for detecting a temperature of an end portion of a heating roller. A comparison comprising a first detection circuit and a second detection circuit having second detection means for detecting a temperature of a portion other than the end portion of the heating roller, wherein the first detection circuit has a plurality of different thresholds Circuit, a fuse is connected in parallel to the first detection means, and a control voltage applied to the first detection circuit depending on the presence or absence of the fuse, or a voltage lower than the voltage but higher than 0 V is applied to the comparison circuit. To And a fuse blowing circuit capable of blowing the fuse in a state where the thermal fixing device is installed in the image forming apparatus. A method of detecting the life of the heat fixing device, which is capable of judging whether the heating roller is new or old and judging the life of the fixing device from the output of the comparison circuit based on a voltage change which varies depending on the presence or absence of the heat roller. A plurality of detecting circuits each having a detecting means for detecting a surface temperature of a heating roller of the heat fixing device, wherein the detecting means is configured to detect a temperature of a different portion of the heating roller; A method for detecting the life of a thermal fixing device, wherein the life of the fixing device is determined based on a state of divergence of a plurality of detected temperatures detected by the detecting device, wherein the detecting circuit has a first detecting means for detecting a temperature of an end portion of a heating roller. A comparison comprising a first detection circuit and a second detection circuit having second detection means for detecting a temperature of a portion other than the end portion of the heating roller, wherein the first detection circuit has a plurality of different thresholds When the first detecting means is short-circuited, a voltage near the control voltage applied to the first detecting circuit is applied, or when the first detecting means is disconnected, a voltage near 0 V is applied to the comparing circuit. Will be entered in Measuring the terminal voltage or the voltage corresponding to the temperature of the first detecting means, and determining the life of the fixing device together with the life of the first detecting means based on the output of the comparing circuit. A method for detecting the life of a heat fuser.