JPH01178992A - Detecting device for breaking of wire of heater for fixation - Google Patents

Abstract

PURPOSE:To accurately detect the breaking of the wire of a heater for fixation in a short period of time without any error by detecting the difference between the temperature at the start of the heating of a fixing device and the temperature a specific time after the start of the heating being smaller than a specific value with a signal from a temperature detecting means. CONSTITUTION:This device is equipped with the temperature detecting means 3 and a detecting means 4, and the temperature detecting means 3 detects the temperature of the fixing device 1. The detecting means 4 detects the difference between the temperature at the beating start of the fixing device 1 and the temperature the specific time after the heating start being smaller than the specific value with the signal from the temperature detecting means 3 to detect the breaking of the wire of the fixing heater 2. Consequently, even if the fixing device is already at high temperature when powered on, the breaking of the wire of the fixing heater is detected in a short period of time and even if the fixing device is at extremely low temperature when powered on, the breaking of the wire of the fixing heater is accurately detected without any error.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a fixing heater disconnection detection device used in copying machines, printers, and the like.

(Prior Art) Conventionally, a fuser heater disconnection detection device determines that the fuser heater is disconnected when the temperature of the fuser falls below a certain reference temperature after a certain period of time has elapsed since the power was turned on. JP-A-52-69636, JP-A-57-
This is known from Japanese Patent No. 92363.

However, this fuser heater disconnection detection device determines that the fuser heater is disconnected when the temperature of the fuser falls below a certain reference temperature after a certain period of time has elapsed since the power was turned on. If the fixing device is at a high temperature, it takes 1 time to detect a break in the fixing heater. Conversely, if the fuser is at an extremely low temperature when the power is turned on, the temperature of the fuser may not reach the standard temperature after a certain period of time even if the fuser heater is on. It is mistakenly determined that the fuser heater is broken even though it is not.

(Objective) It is an object of the present invention to provide a fixing heater disconnection detection device that can eliminate the above-mentioned drawbacks and accurately detect a fixing heater disconnection in a short time and without error.

(Structure) As shown in FIG. 1, the present invention provides a fixing device having a fixing device 1 that heats and fixes unfixed paper, and a fixing heater 2 that heats this fixing device 1. The detection means 4 is also provided. The temperature detection means 3 detects the temperature of the fixing device 1, and the detection means 4 detects a predetermined difference between the temperature of the fixing device 1 at the start of heating and the temperature a predetermined time after the start of heating based on the signal from the temperature detection means 3. A disconnection of the fixing heater 2 is detected by detecting that the value is smaller than the value of .

FIG. 3 shows an example of a fixing device in a copying machine to which the present invention is applied.

The fixing roller 11 and the pressure roller 12 constitute a fixing device, and the fixing roller 11 has a core metal 13 and a Teflon layer 14 formed on the surface thereof. The fixing roller 11 is internally heated by a fixing heater 15, and the fixing roller 11 and pressure roller 12 are driven to rotate in opposite directions by a fixing drive motor. The pressure roller 12 has a silicone rubber layer 17 formed on the surface of a core metal 16.

The transfer paper 18 with unfixed toner attached is transferred to the fixing roller 11
and the pressure roller 12, and this fixing roller 11
The toner is fixed by being pressurized and heated by the pressure roller I2.The temperature detection thermistor 19 contacts the surface of the fixing roller 11 and detects its surface temperature. It is placed at a distance and detects the temperature.

FIG. 2 shows an embodiment of the invention.

This embodiment detects a disconnection of the fixing heater I5 in the fixing device, and the two circuit breakers 21 detect an overcurrent in the AC input line and cut off the AC input. A noise filter 22 consisting of a composite circuit of a coil and a capacitor includes a circuit breaker 21 and a contact 23-2 of an electromagnetic relay 23 between the AC power source and the fixing heater 15.
．． 23-3, SSR (solid state relay) 24
This is an electromagnetic relay provided via the fixing heater 1.
Open/close the energizing path to 5.

A small circuit breaker 25 is provided between the noise filter 22, the transformer 26, and the DC power supply section 27, and is connected to the contact 2 of the transformer 26, the DC power supply section 27, and the electromagnetic relay 28.
It operates when there is an abnormality in the circuit consisting of 8-2. Note that the circuit breaker 21 has a large capacity and will not operate if there is some abnormality. The transformer 26 steps down the input voltage from the noise filter 22 to 24V and applies it to the coil 23- of the electromagnetic relay 23.
1, and between both ends of the secondary side there are contacts 28-3 of the electromagnetic relay 28, and a door switch 29-3 of the copying machine.
1 contact 29-3, temperature fuse 20 and electromagnetic relay 2
Three coils 23-■ are connected in series. The electromagnetic relay 28 is connected to the coil 28-1 by the input signal EXT CNT.
is driven to close the contacts 28-2 and 28-3, thereby energizing the DC power supply section 27. At this time, if the contact 29-3 of the door switch 29-1 and the temperature fuse 20 are on, the electromagnetic The relay 23 operates and its contact 23
-2. By closing 23-3, the fixing heater 15 can be energized. The reason why the power supply voltage is stepped down by the transformer 26 is that it is dangerous to use the 200V line of the input power supply as a safety circuit for the temperature fuse 20, contact 29-3 of the door switch 29-1, etc. inside the copying machine. This is because there are many The DC power supply section 27 is the electromagnetic relay 2
When the contact 28-2 of No. 8 closes, AC input is supplied, and power supply voltage is supplied to each part of the machine, the control section 30, and the operation section 31. Further, the DC power supply unit 27 detects an input voltage, which will be described later, and sends an output signal Vin to the control unit 30. The control section 30 and the operation section 31 will be explained in detail later. The temperature fuse 20 is for preventing an abnormal temperature rise in the fixing device, and is blown when the temperature of the fixing device exceeds a predetermined upper limit temperature. The thermistor 32 detects the room temperature or the copying machine temperature and sends a detection signal to the control section 30. The interlock door switch 29-1 has two circuits, and its contact 29-2 sends a signal to the control section 30 when the door of the copying machine is opened, causing the operation section 31 to perform a display or the like. Note that 49 in the figure is a surge absorbing diode.

FIG. 5 shows the internal structure of the DC power supply section 27. As shown in FIG.

From the noise filter 22 to the circuit breaker 25,
The AC input input via the contact 28-2 of the electromagnetic relay 28 is rectified by the rectifier circuit 33, and then sent to the fuse 34.
, 35, a 24V switching circuit 36.5V switching path 37 converts the voltage into alternating current.

The output of this switching circuit 35.37 is the transformer 38
After being stepped down to a low voltage by ゜39, it is rectified again by the rectified voltage detection circuit 40.41 and output as a voltage of 24V and a voltage of 5V.This voltage is detected and the detection signal is sent to the switching circuit 36.37. Sent. The switching circuits 36 and 37 control their outputs based on detection signals from the rectified voltage detection circuits 40 and 41, and these circuits 33 to 4I constitute two DC power supply circuits and a switching power supply circuit.

In addition to the noise filter 22, the circuit breaker 2
5. The AC input that is input through the contact 28-2 of the electromagnetic relay 28 is stepped down by the transformer 43 through the fuse 42, the aftereffect is rectified by the rectifier circuit 44 having a bridge configuration, and then smoothed by the smoothing circuit consisting of the capacitor 45 and the resistor 46. be done. The output of this smoothing circuit is voltage-divided by a semi-fixed resistor 47 and a fixed resistor 48 and output as a Vin signal to the control section 30, where the input voltage is monitored.

FIG. 4 shows the configuration of the control section 30.

The reset clock element 50 includes an oscillator 51, a resistor 52, a capacitor 53, and a diode 54 externally connected to the cPU.
(Central processing unit) 55 supplies a reset signal and a clock signal. This clock signal is a signal for operating the CPU 55, and is a pulse-like signal of 5MIIZ. The reset signal from the reset clock element 50 is generated when the power is turned on, and resets the CPU 55 for only several tens of milliseconds. The reset clock element 50 also supplies a 2.5MH2 clock signal to the timer 56.

The CPU 55 performs overall control, reading the control program □ from the ROM (read-only memory) 57, reading and writing information necessary for control to the RAM (random access memory) 58, and transmitting information through the input/output (Ilo) element 59. External control. The latch element 60 is the CPU 55
(7) Boat ADo-AD7. Since AD8 to ADI5 color address output and data output are output in time division,
The ALE (address latch enable) signal from the decode element 61 causes the CP[J55 boats ADO to AD
7. Latch the address output from AD8 to AD15 and R
Supplies to OM57, RAM58, etc. Decode element 61
decodes the signals SO~s2 output from the CPU 55 and outputs the ALE signal, RD('J-to)ff1, and WR(
Write) signal, INTA (India acknowledge) signal, etc. The RAM 58 stores information written by the CPU 55, and the information specified by the RD multiplied signal input from the CPU 55 via the decode element 61 and the address signal input from the CPU 55 to ports AO to A14 via the latch element 6o. The contents of the address are output to the CPU 55. The ROM 57 has a control program written therein to be executed by the CPU 55, and outputs the control program (machine language) to the CPU 55 based on the RD multiplied signal inputted from the CPU 55 via the decoding element 61. The timer element 56 uses the clock signal supplied from the reset clock element 50 as a basic clock and generates pulses of various frequencies and patterns from the output port 0UTO according to the mode and data instructed by the CPU 55. Input/output (Ilo
) element 59 accesses external input elements (sensors, keys) and output elements (display light emitting diodes, fixing heaters, etc.). This I10 element 59 has A, B, C (
The A and B ports are output caponides and the C port is an input port. l10
The lower 4 bits of the A port of the m-child 59 are connected to an A/D (analog/digital) conversion element 62, and the other output ports are connected to the external fixing heater 15, the fixing drive motor, and the operating section 31 in FIG. A waiting time display section 82, a service man call display section 83, and a fixing temperature set value display section 7 as shown in FIG.
7. Room temperature display section 81. It is connected to the fixing temperature display section 80.

The C input port of the I10 element 59 receives signals from the IO key and clear key 76, temperature display key 79, and fixing temperature setting key 78 as shown in FIG. The DATA signal is input from the A/D conversion element 62 as the bit. The A/D conversion element 62 converts the temperature detection signals from the temperature detection thermistor 19 and thermistor 32 and the Vin signal (analog voltage value) from the DC power supply section 27 into an 8-bit digital value, and converts the temperature detection signal from the thermistor 32 into an 8-bit digital value.
5 through an I10 element 59. CPU55 is I
Four signals are output to the A/D conversion element 62 through the 10 element 59, and the C8 signal to the A/D conversion element 62 is always active (low level) when the A/D conversion element 62 performs A/D conversion. do. ADCL to A/D conversion element 62
The K signal is a signal for outputting data from the A/D conversion element 62. The A/D conversion element 62 has one data terminal.
Since I only have books, I output the data serially and use ADCLK.
Every time one complete signal is input, it is output eight times starting from the highest data.

CP[55 applies the ADCLK signal to the A/D conversion element 62, reads the O-th bit of the C port of the I10 element 59 each time, and repeats this operation eight times to obtain 8-bit data. The Co and C1 signals sent to the AID conversion element 62 are signals for determining which one to select since the A/D conversion element 62 has four built-in A/D conversion circuits. In this embodiment, in order to AID convert the signals from the two thermistors 19 and 32 and the Vin signal from the DC power supply section
The A/D conversion circuit is switched by the O and CI multiplied signals. Further, FIG. 6 shows the configuration of the operation section 31. As shown in FIG.

The operation unit 31 has the functions of 1) setting the fixing temperature, 2) displaying the fixing roller temperature and room temperature, 2) displaying the waiting time until copying is possible, and 2) displaying an abnormality.

(2) To set the fixing temperature, input the set temperature using the 10 key and the clear key 76. However, the fixing temperature can only be set within the range of 175°C to 192°C. The fixing temperature setting value display section 77 displays the temperature input using the IO key and the clear key 76. When the fusing temperature setting key 78 is pressed, the fusing temperature set in the fusing temperature setting value display section 77 at that time is fixed, the self-illuminated lamp of the fusing temperature setting key 78 lights up, and the 10 key and the clear key 76 are pressed. Input is ignored. When the fixing temperature setting key 78 is pressed again, the self-illuminated lamp is turned off and the fixing temperature can be set again using the IO key and the clear key 76.

■For the display of the temperature of the fixing roller and the room temperature, when the temperature display key 79 is pressed, the self-illuminating lamp of the temperature display key 79 lights up, and the temperature of the fixing roller 11 and the room temperature are displayed in the fixing temperature display section 80 and the room temperature display section 81. is started by. The temperature display by the fixing temperature display section 80 and the room temperature display section 81 is updated every 5 seconds. When the temperature display key 79 is pressed again, the temperature display by the fixing temperature display section 80 and the room temperature display section 81 is finished, and the self-illuminated lamp of the temperature display key 79, the fixing temperature display section 80, and the room temperature display section 81 are turned off.

■ Regarding the display of the waiting time until copying is possible, when the power is turned on or when the AC input from the power supply changes from off to on, etc., when the fixing device is waiting for warm-up, it will take several minutes until warm-up is completed. is displayed on the waiting time display section 82. This waiting time display section 82 turns off when the copying machine becomes ready for copying.

■ Regarding abnormality display, in this embodiment, when a disconnection of the fixing heater 15 is detected, the serviceman call indicator 83
lights up and an abnormality display (serviceman call) is made. In this case, the copying machine becomes unable to make copies.

FIG. 7 shows the fixing temperature setting routine of this embodiment. C.P.
U55 first determines whether or not the fixing temperature setting key 78 has been pressed based on the signal from the fixing temperature setting key 78, and if the fixing temperature setting key 78 has been pressed and the current mode is the fixing temperature setting mode, the fixing temperature setting key 78 is pressed. The temperature non-setting mode is set, and if the current mode is the fixing temperature non-setting mode, the fixing temperature setting mode is set. Next, the CPU 55 determines whether the current mode is the fusing temperature setting mode, and if it is the fusing temperature setting mode, it ignores the signals from the 10 key and the clear key 76 and displays it on the fusing temperature setting value display section 77. The temperature set in the fixing temperature setting key 78 is set as the set temperature, and the self-illuminated lamp of the fixing temperature setting key 78 is turned on. Further, if the current mode is the fixing temperature non-setting mode, the CPU 55 recognizes the signal from the 10 key and the clear key 76, changes the display temperature of the fixing temperature setting value display section 77 according to this signal, and changes the display temperature of the fixing temperature setting value display section 77, Turn off the self-illuminating lamp.

In the fixing temperature setting mode, the fixing temperature setting value display section 77
If the temperature displayed is not within the range of 175° C. to 192° C., the CPU 55 does not enter the fixing temperature setting mode but remains in the fixing temperature non-setting mode.

FIG. 8 shows the fixing temperature display routine of this embodiment. C.P.
(155 first determines whether the temperature display key 79 has been pressed, and if the temperature display key 79 has been pressed, if the current mode is display mode, it is set to non-display mode, and if the current mode is non-display mode, it is set to non-display mode.) If so, the CPU 55 turns on the self-illuminated lamp of the temperature display key 79 during the display mode, detects the temperature of the fixing roller 11 and the room temperature every 5 seconds using the signals from the thermistor 19.32, and displays these values. The display temperatures of the fixing temperature display section 80 and the room temperature display section 81 are updated according to the temperature of c.
push turns off the self-illuminated lamp of the temperature display key 79, the fixing temperature display section 80° and the room temperature display section 81.

FIG. 9 shows the waiting time display routine of this embodiment. C.P.
When the power is turned on or when the AC input from the power source changes from OFF to ON, U55 detects this from the signal Vin from the DC power supply section 27, and detects the temperature of the fixing roller 11 at that time from the signal from the thermistor 19, Two types of control are performed depending on this temperature.

First, the temperature of the fixing roller 11 is a constant temperature, for example, 100°C.
If the temperature is less than 1, the CPU 55 checks the temperature of the fixing roller 11 again after a certain period of time, for example, 30 seconds, by checking the temperature of the fixing roller 11 with the thermistor 1.
The temperature increase rate (de) per unit time (1 second) from this temperature detected by the signal from
g/5ee) The zero-order cpuss calculates the difference between the fixing temperature set value and the current fixing temperature, divides this by the temperature increase rate above, calculates the waiting time from this result, and calculates the waiting time. It is displayed on the display section 82.

Also, the temperature of the fixing roller 11 is a constant temperature, for example, 100°.
In the case of C or more, cpuss calculates the difference between the set value of the fixing temperature and the current fixing temperature, and uses this as a pre-prepared general temperature increase rate (obtained by experiment etc., for example 1.71 deg).
/5ee), and the waiting time is calculated from this result and displayed on the waiting time display section 82.

The subsequent processing is common, and after displaying the waiting time on the waiting time display section 82, the CPU 55 subtracts the waiting time by 1 and displays it on the waiting time display section 82 every minute, and then changes the temperature of the fixing roller 11. When the temperature reaches the set value of the fixing temperature, the copying machine is put into a copying ready state and the waiting time display section 82 is turned off.

FIG. 10 shows the abnormality detection display routine of this embodiment. There are several types of abnormality detection, but in this embodiment, the fixing heater 1
Only the disconnection detection in No. 5 will be explained.

When the power is turned on or when the AC input from the power supply changes from OFF to ON, the cpuss detects this from the signal Vin from the DC power supply unit 27, and calculates the temperature T□ of the fixing roller 11 at this time based on the signal from the thermistor 19. Detect and RA
The temperature T2 of the fixing roller 11 is stored in the thermistor 19 after a predetermined period of time (for example, 30 seconds).
The difference Tdeg=(Tt
Find Tz). If this T deg is less than a certain value (for example, 5 deg), the CPU 55 determines that the fixing heater 15 is disconnected, and displays the service man call indicator 83.
lights up.

(Effects) As described above, according to the present invention, in a fixing device that has a fixing device that heats and fixes unfixed paper and a fixing heater that heats this fixing device, temperature detection that detects the temperature of the fixing device is provided. and a signal from the temperature detection means to detect that the difference between the temperature of the fixing unit at the time of heating start and the temperature after a predetermined time from the start of heating is smaller than a predetermined value. Since it is equipped with a detection means for detecting a disconnection, it is possible to quickly detect a disconnection of the fuser heater even if the fuser is already at a high temperature when the power is turned on, and vice versa. To accurately detect a disconnection of a fixing heater without error even in the case of

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of the present invention, FIG. 2 is a block diagram showing an embodiment of the present invention, FIG. 3 is a sectional view showing an example of a fixing device, and FIG. 4 is a control of the above embodiment. FIG. 5 is a block diagram showing the DC power supply section of the above embodiment, FIG. 6 is a plan view showing the operation section of the above embodiment, and FIGS. 7 to 10 are the fixing section of the above embodiment. 3 is a flowchart showing a temperature setting routine, a fixing temperature display routine, a waiting time display routine, and an abnormality detection display routine, respectively. DESCRIPTION OF SYMBOLS 1... Fixing device, 2... Fixing heater, 3... Temperature detection means, 4... Detection means. dust ka zuno 5 Rokukumi obedience'θ Figure 70ze＼ / woθri＼ / O hard-working people

Claims (1)

[Claims] In a fixing device that includes a fixing device that heats and fixes unfixed paper and a fixing heater that heats the fixing device, the fixing device includes a temperature detection device that detects the temperature of the fixing device, and a signal from the temperature detection device that detects the temperature of the fixing device. A detection means for detecting a disconnection of the fixing heater by detecting that the difference between the temperature at the start of heating of the device and the temperature after a predetermined time from the start of heating is smaller than a predetermined value. Fixing heater disconnection detection device.