JPH03200187A - Detection of life of heat fixing device - Google Patents

Abstract

PURPOSE:To allow the exact detection of a service life and to prevent the erroneous recognition of an old fixing device as a brand new fixing device by forcibly shorting a circuit to blow a fuse, then detecting the life of the heat fixing device in accordance with the detecting voltage from a detecting circuit. CONSTITUTION:For example, a temp. detecting element TH for life detection 10 and a fixed resistor R 1 are connected in series to constitute the detecting circuit. The fuse FU is connected in parallel to at least one resistance element R 2 constituting the detecting circuit. A synthesized resistor for voltage dividing is thereby formed of the fuse FU and the resistance elements R 1, R 2. The detecting voltage at the point of the time when the fuse FU is connected in parallel, therefore, approximates to the voltage of a circuit 30 for control or 0v. The presence or absence of the fuse FU can be decided easily by impressing the circuit voltage to the detecting circuit. The circuit is forcibly shorted if there is the fuse FU. The exact life detection is executed in this way in accordance with the detecting voltage from the detecting circuit and the erroneous recognition of the old fixing device as the brand new fixing device is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for detecting the lifespan of a thermal fixing device that thermally fixes an unfixed toner image, and particularly relates to a method for detecting the lifespan of a thermal fixing device that thermally fixes an unfixed toner image, and particularly relates to a method for detecting the lifespan of a thermal fixing device that thermally fixes an unfixed toner image. Concerning a method for detecting the lifespan of a device.

"Prior Art" For example, a roller-type heat fixing device consisting of a combination of a fixing roller with a built-in heater and a pressure roller has been known, and in this type of fixing device, the temperature is controlled at a high temperature of around 180 to 200 degrees Celsius. In order to achieve image fixation while passing a recording paper carrying an unfixed toner image between the pair of rollers, even if the roller surface is coated with a heat-resistant material such as silicone rubber, the bearings thereof are For this reason, it is difficult to maintain good fixing performance unless the fixing device is replaced as appropriate.

The determination of when to replace the fuser is generally based on the fuser (
This is done using a print number counter, but even if the number of prints is the same, the fixing operation time differs between intermittent printing and continuous print cycles, and it is not always possible to accurately detect the lifespan.

For this reason, in the known fixing device, the number of sheets counted for life detection is set to the lowest common multiple assuming the worst case scenario. This is undesirable in terms of resource conservation, as it indicates that the product is at the end of its lifespan.

On the other hand, when replacing the pair of fixing rollers after the expiry of their service life, it is necessary to provide a means for checking whether the replaced fixing roller is new.For this reason, in the conventional apparatus, for example, as shown in FIG. , a resistor R1, and a fuse Fu, and by installing the fixing device in the printer, the voltage terminal 5
1 to control voltage.

Further, the downstream side of the fuse Fu is connected in parallel with the emitter side of the transistor Tr whose collector side is grounded and the control boat, respectively, so that the presence or absence of the control voltage is first confirmed from the control boat (A), and the control voltage is If is OV, it is determined that the old fuser has been installed, and a replacement signal is displayed again. On the other hand, if the control voltage is 5V, it is determined that a new fuser has been installed, and the life detection counter is At the same time, by applying a base voltage (B) to the transistor Tr based on a signal from the control unit side, an excessive current is caused to flow through the collector of the transistor T to the fuse Fu to blow it out, I was trying to discard the new state.

``Problem to be Solved by the Invention'' However, according to such conventional technology, whether or not the fuser is new is determined only by the presence or absence of the fuse Fu, so the user only needs to replace the fuse Fu of the old fuser to continue using it. This was an extremely important issue from the standpoint 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 number counter, and
To provide a method for detecting the lifespan of a fuser, which prevents a user from mistakenly recognizing that the fuser is a new fuser even if the user replaces the fuse of the old fuser.

"Means for Solving the Problems" The present invention focuses on the fact that when a fixing roller deteriorates, the degree of temperature rise is different between the deteriorated part and the normal part when a predetermined thermal energy is applied. For example, when the bearing deteriorates, the fixing pressure between the pressing roller and the opposing pressure roller decreases, and as a result, the amount of heat absorbed by the pressing roller and the paper decreases, resulting in an increase in temperature. Therefore, by disposing a temperature detection circuit at a location where the fixing roller deteriorates quickly, it is possible to detect the lifespan based on the detected temperature.

For example, the deterioration of the fixing roller is faster at the end where the bearing is attached than at the center, so it is possible to detect the temperature of both sections and determine that there is an abnormality when boarding occurs at both detected temperatures. It becomes possible.

Note that the lifespan detection can also be performed by keeping the amount of heat supplied constant and detecting the temperature change over time without measuring a plurality of temperature points.

It should be noted that even when an old fuser whose life has come to an end is installed, it is uneconomical to constantly apply thermal energy to detect the life of the fuser, and a fuse for replacement detection is still necessary.

Therefore, it is necessary to create a structure that can always determine the presence or absence of the fuse before the detection circuit detects the lifespan.

Therefore, in the present invention, a detection circuit is configured by connecting a temperature detection element for life detection and a fixed resistor R1 in series, and the fuse is connected in parallel to at least one resistance element constituting the detection circuit. This is the characteristic of

As a result, a combined resistance for voltage division is formed by the fuse and the resistance element, so the detected voltage at the time when the fuses are connected in parallel approximates the control circuit voltage or OV. By applying the circuit voltage to the detection circuit when installed, it is possible to easily determine the presence or absence of a fuse.

Furthermore, if there is a fuse, the fuse can be blown by forcibly short-circuiting the circuit, thereby making it possible to accurately detect the life of the thermal fixing device based on the voltage detected by the detection circuit. .

As mentioned above, providing multiple detection means for detecting the surface temperature at different locations on the fixing roller makes use of the difference in the detected temperature between the two detection means to detect abnormalities in the detection means themselves or the heater heating means. This is preferable since it is possible to easily determine the presence or absence of .

"Embodiments" Hereinafter, preferred embodiments of the present invention will be described in detail by way of example with reference to the drawings. However, unless otherwise specified, the dimensions, materials, shapes, and relative arrangements of the components described in this example are not intended to limit the scope of this invention, but are merely illustrative examples. It's nothing more than that.

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 consists of a combination of a fixing roller la with a built-in heater 2 and a pressure roller lb. A detection element 3 for temperature control is located in the center of the surface of the fixing roller 1a, and a bearing is located on the shaft end side near the part. A life detection body 10 including a thermistor TH and a fuse Fu is attached to the body, and these components are configured to be replaceable as a unit.

On the other hand, on the device main body side, there is a temperature control circuit 21 (PWM) that generates a signal for controlling the energization of the heater 2 in response to the detection voltage from the detection element 3, and a temperature control circuit 21 (PWM) that receives the detected voltage from the detection element 3 and generates a signal for controlling the energization of the heater 2. a temperature control system consisting of 5SR22, and a detection section 30 that compares the detection voltages of the detection element 3 and the life detection body 10 with a reference voltage. It consists of a determining section 40 that performs various abnormality detections in addition to life span detection based on the detection signal from the detecting section 30, a display section 50 that displays a predetermined display based on the signal from the determining section 40, and the transistor Tr. It consists of a lifespan/abnormality detection system consisting of a fuse blowout circuit II.

Next, the detailed configuration of the lifespan/abnormality detection system will be explained based on FIG. 2.

The life detector 10 has a thermistor TI (and a fuse F) between a pair of fixed resistors R1 and R2 connected in series to a control voltage terminal.
u are connected in parallel, and the cathode side of the fixed resistor R2 is grounded, while the thermistor TH and the fuse Fu
between the parallel connection part of and fixed resistor R2 (hereinafter referred to as voltage dividing terminal)
is connected to the emitter side of the transistor Tr. still,
The resistance values of fixed resistors R1 and R2 are set to be R2)R1.

The detection unit 30 consists of a group of comparators 31a that compare the comparison voltage from the voltage dividing terminal or thermistor TH with the reference voltage from the reference voltage setting circuit Vs set as described later and output a comparison signal. .

Note that the reference voltage is, for example, 4.5V from above when the control voltage is set to 5V.

3.5V, 2V, 0.5V, 2.2V, 3.3
It is set to V.

The determining unit 40 is formed of CPtJ and is configured to display a predetermined lamp based on the comparison signal from the comparator 31a.

Next, the operation of this embodiment will be explained.

First, when a new fuser with a fuse Fu is installed, the life detector IO detects that the thermistor TH and the fuse Fu are connected in parallel, and because of R2) R1, the voltage from the voltage dividing terminal is a value close to the control voltage 5V. As a result, a comparison output is output from the comparator I to the judgment section 40, and the judgment section 40 judges that a new fixing device has been installed.
By applying a base voltage to the transistor Tr, the collector of the transistor T is grounded, causing an excessive current to flow through the fuse Fu and blowing it out, thereby canceling the new state.

As a result, the life detection body 10 has a fixed resistance R connected in series.
1. A voltage dividing circuit consisting of thermistor TI and fixed resistor R2 is formed.

And a detection element 3 for detecting voltage and temperature control corresponding to the thermistor TH for life detection obtained by the voltage dividing circuit.
Before performing a predetermined lifespan detection while comparing the detected voltages, it is first determined whether or not there is an abnormality in the thermistor TH itself for lifespan detection.

That is, when the thermistor TH is short-circuited or short-circuited, the detected voltage is 4.5V or more or 0.5V or more.
5V or less, the corresponding comparators 31a and 31d
The determination unit 40 determines the comparison output and displays the result.

Next, heating control of the fixing device is started, and if the detected voltage during the heating control is within the range of 2.2 to 3.3■ and 2 to 3.5■, the corresponding comparators 31b-c , 31e-
Based on the comparison output from f, 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 where the bearing is attached than at the center, so when the end of the roller deteriorates due to long-term heating control, the detection voltage on the voltage dividing terminal side increases. , even though the detection voltage for temperature control is within the normal range, the detection voltage exceeds 3.5V, and in this case, the determination unit 40 It is determined that the life has come to an end, and the life is displayed.

Incidentally, if both of the above-mentioned detection voltages are out of the normal range, this is displayed because it is an abnormality on the temperature control side such as a failure of the heater 2 or the SSR.

Now, if you replace only the fuse Fu of the fuser that has reached the end of its lifespan, after blowing it by passing an excessive current through the fuse Fu as described above, the detection voltage and the detection voltage for temperature control are compared and the specified lifespan is replaced. Because of the detection, it can be easily determined that the fuser has reached the end of its life.

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

"Effects of the Invention" As described above, according to the present invention, it is possible to accurately detect the lifespan without using a sheet number counter, and even if the user replaces the fuse of the old fuser, it is possible to use a new fuser. In addition, by providing multiple detection means to detect the surface temperature of the fixing unit, the difference in temperature detected by both detection means can be used to detect the detection means itself and It is also possible to determine whether there is an abnormality in the heater heating means.

It has various effects such as

[Brief explanation of drawings]

FIG. 1 is a schematic block diagram showing a fuser according to an embodiment of the present invention and the main circuit configuration around the fuser on the apparatus main body side, and FIG. 2 is a circuit block diagram showing the detailed configuration of the life/abnormality detection system.
FIG. 3 is a circuit block diagram showing the detailed configuration of a conventional life detection system.

Claims (1)

[Claims] 1) A surface temperature detection circuit formed by connecting at least one resistance element in parallel with a replacement detection fuse is attached to the heat fixing device, and when the fixing device is installed in the main body of the apparatus. 2) A method for detecting the lifespan of a thermal fuser, comprising: forcibly short-circuiting the circuit to blow the fuse, and then detecting the lifespan of the thermal fuser based on the voltage detected by the detection circuit. 2) The detection circuit. The lifespan according to claim 1), wherein a sensing body for detecting the surface temperature of the fixing device is provided separately from the fuser, and the lifespan of the fixing device is determined based on a state of deviation between the temperatures detected by the sensing body and the detection circuit. Detection method