JPH0262573A - Fixing roller device - Google Patents

Abstract

PURPOSE:To confirm whether or not a comparison result is within a specific error range and to control a heating member normally by comparing a value converted into the temperature of a detected voltage from a temperature detecting means with a voltage corresponding to the temperature of a fixing roller from a simulation circuit by the control means of an image forming device. CONSTITUTION:The fixing roller of the image forming device is heated by a heating part 1 and the control means MPU 7 performs the on/off switching of power supply to the heating member 2 of the heating part 1 through a semiconductor relay 4. Further, the temperature detecting means 5 detects the temperature of the heating member 2 at both ends electrically at all times and inputs its output to the control means 7. Further, the simulation circuit 20 reproduces the temperature of the fixing roller at all times and supplies it to the control means 7. Then the control means 7 finds the actual surface temperature of the fixing roller and compares the surface temperature with previously set specific temperature in an internal ROM to supply a command signal for powering on or off the heating member 2 of the heating part 1.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention is utilized in the technical field of thermal fixing devices for image forming apparatuses, and particularly relates to a fixing roller device having a contact type temperature detecting element as a temperature detecting means.

[Prior Art] Conventionally, a heating fixing roller device used in an image forming apparatus using a static photographic process is in contact with a halogen heater as a heat generating member and a fixing roller as a roller. It has a thermistor as a temperature detecting means for detecting the surface temperature of the surface, and when the detection output of the thermistor is manually inputted to a microcomputer (hereinafter referred to as the cap 11J) as a control means including an A/D converter, the temperature of Ml) U calculates the surface temperature of the fixing roller from the input data, and controls the surface temperature of the heat roller by turning on and off the halogen heater as needed.

[Problems to be Solved by the Invention] However, in the conventional fixing roller device, a thermistor or Itri line is used to detect the surface temperature of the fixing roller. As is well known, a thermistor has a very large resistance value when the temperature is low.

If the thermistor is disconnected, the detected temperature will become lower and the resistance value will increase. Therefore, the MPU controls the halogen heater to raise the temperature.

As a result, the halogen heater overheated, eventually leading to a fire.

In order to solve this problem, the value of the thermistor is checked after a certain period of time has passed after the halogen heater starts being energized. I was checking the IT line.

However, if the power switch of the image forming apparatus is turned off before the disconnection check is performed, the MPU is cleared, and the thermistor disconnection detection is performed from the beginning when the power is turned on next time.

In this case, since the halogen heater has already been heated by the previous energization, when the halogen heater is further energized, the temperature increases further. Therefore, if this operation is repeated, the halogen heater will overheat and become dangerous.

Additionally, if the thermistor that is in contact with the fixing roller comes off the fixing roller while the MPU is controlling the temperature of the halogen heater, the thermistor will not function as intended and its detection sensitivity will decrease. There was a problem with the halogen heater or the overripe because it was difficult to find out.

An object of the present invention is to solve the above-mentioned particular problems and provide a fixing roller device that can detect abnormalities in temperature control of a halogen heater.

[Means for Solving the Problems] According to the present invention, the following features are provided: A roller that includes a heat generating member and rotates in a predetermined direction, and a switch that switches between energizing and cutting off the power to the heat generating member. With means.

a temperature detection means for detecting the surface temperature of the roller; and a temperature detection means for determining the actual surface temperature of the roller from the output signal of the temperature detection means, and calculating the actual surface temperature and a predetermined value preset in the temperature control program. In the fixing roller device, the fixing roller device includes a control means for supplying a command signal to the switching means to open or release the switching means, When a command signal is supplied, a simulation circuit is provided that electrically reproduces the temperature characteristics of the heat generating member by energizing or cutting off the current in accordance with the command signal, The pseudo surface temperature corresponding to the surface temperature of the roller is compared with the actual surface temperature, and it is determined whether the actual surface temperature and the pseudo surface temperature are within a predetermined error range. This is achieved by having a circuit that determines whether or not it is being controlled normally.

[Function] When the fixing roller device configured as described above is started, the control means converts the detection voltage input from the temperature detection means into temperature, and also electrically detects the temperature of the fixing roller from the simulation circuit. Take in the voltage that appears.

Then, the temperature after conversion described in 1 and the simulated voltage are compared, and it is determined whether each is within a predetermined error range, and it is determined whether the heat generating member is being controlled normally. do.

[Example] The present invention will be described in detail below based on the accompanying drawings.

Referring to FIG. 1, there is shown a circuit configuration of a fixing roller device as a first embodiment of the present invention.

The heating unit l is a fixing roller (not shown) of the image forming apparatus. This is a heating circuit for heating, and includes a halogen heater 2 as a heat generating member, an AC power supply 3, and a semiconductor relay (SS
R) 4, and a temperature detection element (hereinafter referred to as a thermistor) 5 as a temperature detection means for measuring the surface temperature T of the fixing row, which are connected as shown in the figure.

In addition, the heating part l is connected to one terminal, read-only memory (ROM), random access memory (HA)4),
and an input port AN2 of a one-chip microcomputer (hereinafter referred to as MPU) 7 as a control means having an A/D converter, and the other terminal is connected to an output port AN2 of the MPU 7.

As is well known, the resistance value of the thermistor 5 decreases as the temperature increases. Therefore, when the voltage is raised to the power supply voltage VCC by the resistor 6, the voltage v7 across the thermistor 5 decreases as the temperature T increases.

The simulation circuit 20 is a circuit that electrically reproduces the temperature of the fixing roller at all times, and includes a transistor 9. which charges the capacitor H1. A resistor 11 that limits the charging current to the capacitor 10, and a resistor that discharges the capacitor 10.
2 and are connected as shown.

Further, one terminal of the simulation circuit 20 is connected to the input port ANI of the MP lower mentioned above, and the other terminal is connected to the output port ANI.

The reset circuit 8 is connected to I(ESET) of the MPIJ 7, and is a circuit that resets the MPU 7 when the power source is turned on for about 1 minute.

Next, the relationship between the surface temperature T of the fixing roller and the voltage vA across the capacitor lO will be explained.

Assuming that T is the maximum temperature of the fixing roller, To is the initial temperature, and T is the temperature rise time constant, the temperature T of the fixing roller after the halogen heater 2 is energized (unplugged) is T = (T,
, -T,)[1-exp(-1/τ,)]. Also, when the surface temperature decreases, the temperature decrease time constant is τd, the initial temperature is To, and the surrounding outside temperature is Te, then T = (
T, −Te) exp(−L/τd).

Here, the relationship between the charging and discharging voltage vA of the capacitor IO will be explained.

The temperature change of the fixing roller is sufficiently faster at the rise than at the fall, so the charging time constant of the capacitor IO is set to
Set it so that it is sufficiently faster than the time constant. As a result, resistor 11 becomes sufficiently smaller than resistor 12, and the charging time constant. is the value of the resistor 11 and the capacitor lO. Also, the discharge time constant 8 is the capacitor lO and the resistor 12
It is the product of the values of

On the other hand, if the voltage when charging the capacitor IO is V, which is the maximum voltage reached, this is the power supply voltage v, . . . c minus the saturation voltage between the collector and emitter of the transistor. The charging voltage VAI is the initial voltage, VA
+ = (Vs+Vo) [1-exp(t/τ
It's June.

Further, the discharge voltage VA2 of the capacitor lO is set to an initial voltage of V. Then, VA2=Voexp(-t#e).

Here, ■ is T1 and Vo is T. and τ0=τ. , τ
If 6=τ1 and the outside temperature Te is a constant value that is sufficiently small compared to v, then the temperature T can be expressed by the voltage vA of the capacitor.

The relationship is shown in FIG. As is clear from the figure, when the power is turned off, it can be seen that the temperature T decreases and the voltage vA changes almost in the same way.

Referring to FIG. 3, a flow chart of the operation of the MPU 7 is shown.

When the power is turned on, the MPU 7 is reset by the reset circuit 8. When the reset is completed, MP (17 is the voltage V of the heating unit l input via the input port AN2)
The analog data of A is A/D converted and further converted into temperature T (101).

Note that this temperature T is converted into a value proportional to the actual temperature so that it can be compared with a voltage vA input from ANI, which will be described later.

Next, from the input boat AN, the simulation circuit 20
The analog data of the pressure vA is taken in and converted to/D (102). Step 101 and step 1112
Compare the manually input temperature T and voltage vA, and check whether each is within the predetermined error range (10:l)
. If the temperature T and the voltage vA are not equal within a predetermined error range, the process moves to step 104, and the energization of the halogen heater 2 is prohibited until the value ①=0.

Then, an abnormality in temperature control is displayed on a display device (not shown) such as an LED lamp (105).

Further, when it is determined in step 1 that the temperature T and the voltage vA are equal within a predetermined error range, the surface temperature T
Since the value is as estimated by the simulation circuit 20, it is determined that the data of voltage v7 inputted from AN2 is correct, and temperature control is started.

First, it is determined whether the temperature T is lower than the temperature Tc to be controlled (106), and if it is determined that the temperature T is lower than the temperature Tc, the output 02 is set to high level so as to turn on the semiconductor relay (SSII) 4. do. At this time, the output device also becomes high level and charges the capacitor 10 at the same time.

If it is determined in step 106 that the temperature T is higher than the temperature Tc, the output device and 02 are set to low level.

By repeating this operation, the voltage vA of the capacitor 10 can always follow the roller temperature T.

Referring to FIG. 4, a circuit configuration of a fixing roller device as a second embodiment of the unreleased uI+ is shown.

It should be noted that the configurations of the reset circuit 8 and the heating section 1 are the same as those of the first embodiment, and therefore are omitted for brevity of explanation.

In this embodiment, the capacitor 1 of the simulation circuit 20
The MPU 7 calculates the charging characteristics of 0, converts the calculated result into a digital-to-analog converter (D/A converter), and applies it to the capacitor 10 via the emitter follower of the transistor 9. It is something to do.

In the first embodiment described above, the maximum voltage V, , or the power supply voltage V
In this example, the maximum voltage V,
can be freely selected. Also, in the first embodiment, it was necessary to make a complicated adjustment to match the two time constants for charging and discharging, but in this embodiment, it is only necessary to make adjustments during discharging. Note that an operational amplifier may be used as the transistor 9.

Furthermore, in this embodiment, when an abnormality in temperature control is detected,
By charging the voltage of the capacitor 10 sufficiently high at that moment and taking a long time to discharge after turning off the power, the time during which energization to the halogen heater 2 is prohibited until the power is turned off and turned on again after an abnormality is discovered is reduced. You can do this by taking a long enough time.

[Effects of the Invention] As described above, according to the present invention, the control means constantly simulates the surface temperature of the fixing roller using a simulation circuit composed of a simple circuit, and uses the result as the fixing roller detected by the temperature detection means. Since the actual surface temperature of the roller is compared with the actual surface temperature of the roller, it is possible to detect breakage of the heater arranged inside the fixing roller, pJr line of the temperature detection means, or foreign matter getting between the temperature detection means and the fixing roller. Abnormalities such as a decrease in temperature detection sensitivity can be immediately detected.

In addition, even if the power to the device is cut off and then immediately turned on again, the surface temperature of the fixing roller during the cut-off can be simulated, so when the power is turned on again, abnormalities such as the above-mentioned wire breakage can be detected immediately. What you can know is what you can do.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of the fixing roller device according to the first embodiment of the present invention, and FIG. 2 shows the correlation between the voltage of the capacitor of the simulation circuit and the temperature of the fixing roller when the device of FIG. 1 is operated. Figure 3 shows the M of the device 11:i4.
FIG. 4, a flowchart showing the operation of the PU, is a circuit diagram of a fixing roller device according to a second embodiment of the present invention. l...Heating part 2...Heating member (halogen heater) 5...Temperature detection means (Thermistor) 7... Control means (MPU)
IO・・・・・・・・・Capacitor 11, 12・
·····resistance

Claims (3)

[Claims] (1) A roller equipped with a heat generating member and rotating in a predetermined direction; a switching means for switching between energization and cutoff of the heat generating member; a temperature detecting means for detecting the surface temperature of the roller; and a temperature detecting means for detecting the surface temperature of the roller; The actual surface temperature of the roller is determined from the output signal of the detection means, the actual surface temperature is compared with a predetermined value preset in the temperature control program, and the switching means is closed. and a control means for supplying a command signal to open or open the fuser roller. A simulation circuit is provided that electrically reproduces the temperature characteristics of the heat generating member by performing the following steps, and the control means is configured to control a pseudo surface temperature corresponding to the surface temperature of the roller obtained by the simulation circuit and the actual surface temperature. and a circuit for determining whether or not the actual surface temperature and the pseudo surface temperature are within a predetermined error range, and determining whether or not the heat generating member is normally controlled. A fixing roller device characterized by: (2) The fixing roller device according to claim 1, wherein the simulation circuit is configured by combining at least one resistor and a capacitor. (3) When charging the capacitor of the simulation circuit, the control means calculates the charging characteristics of the capacitor based on the set calculation formula, and controls the charging of the capacitor according to the calculated result. Claims (
2) The fixing roller device according to item 2).