JPS6330630B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a temperature control device in a heat fixing device or the like.

Conventionally, particularly when temperature is detected by bringing a thermistor into contact with a heat source, the rotation of the heat source may damage the thermistor or break the lead wire supporting the thermistor. In order to prevent this, methods have been taken such as protecting the surface of the thermistor with a heat-resistant tape or bringing the thermistor into contact with the heat source via a springy metal. However, recently there has been a trend to downsize thermistors themselves in order to reduce the mounting volume involved in temperature control, and the thermistor lead wires have also become thinner, which means that the risk of thermistor disconnection and damage is increasing, and thermistors are becoming more and more compact. Measures to prevent disconnection and damage are virtually impossible.

However, when temperature control is performed using a broken thermistor, the thermistor cannot distinguish between the broken wire and the low temperature of the detection section, and continues to supply power to the heat source, causing the temperature of the heat source to rise abnormally.
In this case, the abnormal temperature causes deformation of the fixing roller as a movable part of the heat source and the heat-resistant resin on the surface of the fixing roller, making smooth rotation impossible and normal fixing impossible.

FIG. 1 shows a circuit that is thought to detect a disconnection by determining a difference in the resistance value of a thermistor. This adds R6 and R to the well-known bridge type temperature detection circuit.
A bridge for disconnection detection consisting of 7, R3, and TH1 is added, and a thermistor is connected by operational amplifier Q2.
It detects the disconnection of TH1, turns off transistor Q3, and cuts off the power to heater H1.

In this case, if the entire device including the heater is not supplied with power for a long time and left in a low temperature state, the thermistor TH1 will have a high resistance on the order of 10 MΩ. Therefore, in order to distinguish between this high resistance and the high resistance caused by disconnection, either use an operational amplifier with low offset and high input impedance for operational amplifier Q2, or increase the Vcc voltage to convert a small change in resistance into a large potential difference. This cannot be achieved unless it is detected as such. The former method not only requires an expensive operational amplifier, but also requires noise countermeasures to detect a minute signal indicating a disconnection, distinguishing it from noise, which requires additional equipment. In the latter method, the thermistor may be damaged by the thermistor current that flows when the temperature rises and the resistance value of the thermistor decreases. Therefore, the resistance value R3 is must be determined. However, it is extremely difficult to determine this, and moreover, another type of Vcc power supply is required, which complicates the power supply.

That is, the present invention provides: a detection means for detecting the temperature of a fixing device; a temperature control means for controlling electric power supplied to the heat source of the heated member according to the temperature detected by the detection means; and a detection means for detecting a disconnection of the detection means. disconnection detection means,
interrupting means for interrupting the operation of the temperature control means in response to a detection signal of an abnormal state of conveyance of the sheet, and a detection operation of the disconnection detection means being performed a predetermined time after restarting the temperature control means after the abnormal state is canceled; The present invention provides a temperature control device characterized in that it has a control means for controlling the temperature.

Examples will be explained with reference to the drawings. FIG. 2 is a sectional view of a copying machine to which the present invention can be applied; in the figure, 1 is a platen on which a document is placed and moves back and forth; 2 is a rotatable drum having a seamless photoreceptor;
3 is a lamp for exposing the original image on the platen 1 onto the drum 2; 5 is a corona charger that charges the surface of the photoreceptor in advance; 6 is a corona charger that removes negative charge from the surface of the photoreceptor along with the exposed image; Developing device 9 transfers the developed image to transfer paper 10
11 is a cassette storing a large number of transfer papers 10, which can be detached from the main body; 12 is a stand for manually feeding the transfer paper 10; 13 is a roller for feeding the transfer paper from the cassette; 14 is a manual feed. 1 unit
2 is a roller for feeding the transfer paper, 15 and 16 are micro switches for detecting manual transfer paper, 17 is a registration roller for aligning the leading edge of the transfer paper with the leading edge of the drum image, and 18 is for separating the transfer paper from the drum. 19 is a belt for conveying the transfer paper, 20 is a fixing roller, 21 is a roller for discharging the transfer paper onto the tray 22, 23 is a blade cleaner for removing residual toner from the drum, 4 is a blade 2
A magnetic roller that collects the toner removed in step 3.
7 is a container for storing the toner collected by the roller 4; 24 is a negative corona charger for removing the residual charge on the drum; 25 is a shutter for directly applying the light from the exposure lamp 3 to the exposure surface of the drum for a certain period of time; 26; , 28 is a mirror that applies the light from the lamp 3 directly to the drum surface, and 27 is the lamp 3.
This is a self-occurring lens that focuses the reflected light from the original onto the drum surface.

Explain the operation. When the main switch is turned on, the motor that drives the drum 2 is turned on, the lamp 3 is lit, the shutter 25 is opened, and at the same time the corona charger 6 is turned on to rotate the drum 2. As a result, residual toner, residual charge, and memory on the drum surface are preliminarily cleaned. When the fixing roller 20 reaches a fixable temperature by an internal heater, a copy enable signal is generated. If the copy switch is not turned on, the drum continues to rotate, and the drum stops when a predetermined number of pulses from a rotary encoder, which is provided in the drum drive system and generates n pulses per rotation of the drum, is counted. The above rotation of the drum is referred to as a first pre-rotation.

When the copy switch is turned on while the drum is rotating or stopped, the shutter 25 is closed and the drum 2 is rotated again. After about one rotation (hereinafter referred to as the second pre-rotation), the platen 1 starts moving forward and the original on the platen 1 is slit exposed. Start. The reflected image of the lamp 3 is slit-exposed onto the drum via a self-occurring lens. The photoreceptor of the drum 2 is composed of an insulating layer, a photoconductive layer, and a conductive layer from the surface, and when the surface charged by the charger 5 reaches the exposed surface, the positive charge is removed by the negative charger 6 and the optical image. . When that surface reaches the uniformly exposed surface, the light from the mirror 26 forms a high contrast electrostatic latent image on the drum surface. Toner is applied to the latent image in the development area and the latent image is developed. The visible image is transferred to the transfer paper by the positive potential of the transfer charger in the transfer area. One sheet of transfer paper is separated and fed from the cassette 10 by the timing operation of the paper feed roller 13, and is passed through the transfer area by the registration roller 17 at the same speed as the circumferential speed of the drum. After the transfer, the transfer paper is separated by a roller 18, sent to a fixing roller 20 by a belt 19, where the image is fixed, and then discharged to a tray 22 by a roller 21. After the transfer is completed, the drum surface is then transferred to the blade 2.
3, the charger 24 removes static electricity, and the memory is removed by light from the lamp 3 via the mirror 28. When making continuous copies from the same original, the platen 1 is moved back and forth a number of times set by the ten keys on the copying machine operating section.

Fig. 2-2 is a plan view of the operation section of the copying machine shown in Fig. 2-1, where 39 is a power (main) switch;
41 is a copy start key switch, 41 is a stop key switch to interrupt continuous copying, 42 is a numeric keypad for storing a number in memory to set the number of continuous copies, 43 is a clear key for clearing the number in memory, 44 is the copy tint set lever,
45 is 7 for displaying the number stored in memory
A segment indicator 46 indicates a wait lamp that turns on and off until the fixing roller reaches a fixing temperature; 47 a lamp that commonly displays the cassette and no sheet in the cassette; 48 a cleaner that collects used toner; This lamp is displayed when the toner in the container 7 is full. 49 is a lamp that is displayed when the sheet is jammed. The clear key and numeric keypad do not work when jammed, but the numeric keypad and clear key can be operated while waiting.

The segment display 45 displays 1, which is suppressed to zero by turning on the power switch 39, during the wait period, displays a number subtracted by 1 from the set number each time one copy is completed, and displays the set number again after copying the set number. Displays the number, then displays 1 again after 30 seconds without starting copying. As a result, copying of one sheet can be started without having to perform several sets using the numeric keypad, and copying can be resumed smoothly.

The weight indicator 46 blinks when the power switch 39 is turned on, but if the temperature of the fixing roller has not fallen below the fixing temperature, that is, if the previous operator turned off the power switch 39, It lights up statically, but blinks if the temperature is below the fixing temperature (wait). It also lights up when the fixing roller rises to a predeterminable temperature and the wait time has elapsed. Also, if the temperature detector for controlling the roller to maintain it at the fixing temperature is disconnected, it will blink. When the power switch is turned off, the blinking and lighting status disappears, and the power off status is displayed. Further, when the copy switch is turned on after waiting up, a blinking operation with a longer blinking interval than during the waiting period is performed until shifting to the post-rotation mode. In other words, one wait display can display four states: power-on state, copy-incapable wait state, copy-enabled state, and temperature sensor disconnection state, which saves on the display and reduces the cost of the device. This contributes to

The collected toner overflow indicator 48 is connected to the container 7.
In addition to detecting and displaying the overflow state of the developer container 33, the toner shortage in the developer container 33 is also detected and a static display is displayed. In the former case, the lamp can be blinked, and in the latter case, it can be turned on statically. Further, the paper out indicator 47 blinks when there is no paper, and can be turned on statically when there is no cassette.

In addition, even if a shortage of toner in the container 33 or an overflow in the collection container 7 is detected, if the number of copies set using the numeric keypad is being executed continuously, copying will continue until the set number of copies is completed, and subsequent copies will be continued. This prevents reopening. This prevents a series of copying operations from being delayed by immediately interrupting the copying operation, thereby preventing a reduction in the actual copying speed.

FIG. 3 is an example of a temperature control disconnection detection circuit according to the present invention. In the figure, H21 is a heater inserted into the fixing roller 20, TF is a temperature fuse that shuts off at high temperature, Q30-1 is a triax that turns on and off the power to the heater H21, and Q30-2 is a triax Q3.
Photothyristor Q30 is composed of LEDs for turning on and off 0-1. TH21 is roller 20
Thermistor in contact with R29, R33, R34
is a resistor that forms the bridge with TH21, Q23 is an operational amplifier for temperature control, Q29 is a transistor that controls photothyristor Q30, R28, R
32 is a bias setting resistor for operational amplifiers Q23 and Q24, Q26 and Q28 are transistors for displaying the weight, and Q27 is a thyristor.
R29, R30, R31 are resistors for detecting disconnection of thermistor TH21, Q24 is also an operational amplifier, Q25 is also a transistor, R21,
R22, R23, C21, and Q21 are a resistor capacitor and an operational amplifier that constitute a timer that prevents disconnection detection, and Q22 is a transistor that outputs the timer.
LED22 and LED21 are operational amplifiers Q23 and Q2
Light emitting diode that monitors the output of 4, WAIT
is a wait signal for prohibiting copying, and JAM is a signal that detects a jam on the transfer paper path by a circuit not shown.

Explain the operation.

When the main switch 39 is turned on, this circuit
Immediately after turning on the power to the heater etc., the thermistor TH
Since the resistance value of 21 is high, R29, R33, R34
Due to this bridge, the output of the operational amplifier Q23 becomes high level (hereinafter referred to as H). Therefore, transistor Q29 is turned on and power is supplied to heater H21. As will be described later, since the transistor Q28 is on, WAIT is set to H to prohibit the start of copying. The heater H21 is sufficiently warmed up and the fixing roller 20
When the temperature reaches a fixable temperature, the resistance value of the thermistor TH21 falls below a predetermined value, and the output of the operational amplifier Q23 becomes a low level (L), turning off the transistor Q26, which had been on until then. Therefore, thyristor Q27 is triggered by 24V, turns on, and remains on. This results in transistor Q2
8 is turned off, a wait signal of H until then is sent to the outside.
WAIT is set to L, blockage is set to H, and a wait completion signal is output. That is, once the heater reaches the set temperature, the wait completion signal is held at H regardless of the output of Q23.
The temperature control of the heater H21 is performed in order to keep the surface temperature of the roller 20 constant by controlling the tri-attack according to the output on/off of the operational amplifier Q23.

The thermistor disconnection detection circuit will be explained.
Resistors R30 and R31 are thermistor TH21 of 1M.
It is set so that the output of the operational amplifier Q24 becomes H when the resistance is Ω or more. When the power is first turned on, C21,
Capacitor C21 is charged by the time constant of R23, and the output of operational amplifier Q21 remains H until the voltage of C21 reaches the voltage set by R21 and R22. Therefore, during that time, the transistor Q22 becomes L, resulting in the same effect as when the output of the operational amplifier Q24 becomes L, and the transistor Q25 is turned off regardless of the output of the operational amplifier Q24. Therefore, since no effect is exerted on operational amplifier Q23 via diode D27, transistor Q29 is turned on and off according to the output of operational amplifier Q23 to perform temperature control.

When the capacitor C21 is charged and exceeds the voltage set by R21 and R22, the operational amplifier Q21 becomes L, and the transistor Q22 is turned off. Therefore, if the thermistor TH21 is disconnected when the power is turned on, the output of the operational amplifier Q24 becomes H.
Q25 turns on and Q29 turns off. Therefore, power to heater H21 is immediately cut off. Therefore, the output of operational amplifier Q24 for detecting disconnection is transmitted to Q25 after the timer consisting of R23 and C21 has timed up. By appropriately selecting the constant of the timer, thermistor TH21 can detect the detected temperature. After the resistance becomes sufficiently low due to the rise, Q2
The output of Q4 can be transmitted to Q25. In other words, after the entire device is left at a low temperature, the disconnection is not detected for a while, and the thermistor disconnection is detected after a sufficient period of time has passed after the power is turned on. Therefore, if the thermistor is not disconnected after that time, the resistance has become sufficiently low, so there is no need to distinguish between the high resistance due to the thermistor disconnection and the high resistance of the thermistor after it has been left at low temperatures, so disconnection detection can be performed accurately. Become. Although heating occurs during this time regardless of the thermistor being disconnected, abnormal heating will not occur since this is the prohibited time at the initial power-on. In this embodiment, the timer time is 1 minute, and the resistance value of the thermistor that controls disconnection is 1 MΩ. Furthermore, D21~
D24 is a clamp diode for input protection, C2
2, C23, C24 are noise prevention capacitors,
D25, 26, 27, 28, and 29 are wraparound prevention diodes.

Further, the signal becomes L when the sheet detector 63 does not detect a sheet at a predetermined time, and is transmitted to Q29 via D26 in the event of a device abnormality such as a paper jam.
is turned off, thereby forcibly cutting off the power supplied to the heater H21. Since the power supply continues to be cut off unless the reset process is performed, the temperature of the heater H21 and thermistor TH21 rapidly decreases. Therefore, the disconnection detection timer is also discharged by the signal via D25 and reset instantly, so that the timer always operates for the next time even after being left unused for jam processing.

4 and 5 are operation time charts of FIG. 3. In Fig. 4, power is supplied to heater H21 and thermistor TH2 at the same time as the main switch is turned on.
The resistance value of 1 gradually decreases. At the same time, the disconnection detection prohibition timer C21 is charged. The output of Q21 is H. When the voltage of C21 is sufficiently charged, Q21 becomes L at time _t1 , and the disconnection detection circuit operates. If there is no disconnection, the base of Q25 remains at L, so power continues to be supplied to the heater H21, and therefore the resistance value of the thermistor continues to decrease. When thermistor TH21 becomes less than the set resistance value, it becomes H at time _t2 , and Q23 becomes L.
becomes. Thereafter, control is performed such that the output of Q23 is turned on and off according to the change in the resistance value of the thermistor TH21, and the resistance value converges to the set resistance value. If the wire is disconnected, the base of Q25 becomes H at t ₁ and becomes D.
The anode of 27 becomes L and the heater H2 is connected as shown by the dotted line.
Power to 1 is then cut off, and the signal remains low, preventing copy initiation.

In FIG. 5, when the temperature control operation signal is input, the base of transistor Q29 is set to L via D26, so power to heater H21 is cut off and the charge in C21 is discharged.

Also, if the power switch 39 is turned off during temperature control to stop power supply to the heater and circuit, and then turned on again, the temperature of the roller may not have fallen below the predetermined temperature yet. Regardless of the disconnection, further heating may occur and cause an overtemperature rise. However, the discharge resistance R2 of capacitor C21
1, R23, and R22, the charge remains in the capacitor C21 when the switch 39 is turned on again. Therefore, the prohibition time for detecting disconnection is shortened, and if the thermistor is disconnected, it can be quickly detected, and an excessive rise in temperature can be prevented. In this case, since an amount of charge remains in C21 corresponding to the time the switch 39 is left until it is turned off and turned on again, the timer can be set according to the time required for cooling the roller 20.

Next, copying sequence control and display control based on thermistor disconnection detection will be explained.

FIG. 6 is an operation time chart of the copying machine shown in FIG. 2, and a high level indicates that the copying machine is in operation. The solid line indicates the case where a desired copy is made by repeating the number of copying operations (advancement and backward movement of the original platen) set by the numeric keypad 42, but the thermistor is disconnected during the process of the first sheet of multi-copying. A normal case is shown by a dotted line. As is clear from the figure, when the thermistor is disconnected, the power is not cut off immediately upon detection, but the copying of the first sheet is completed, the drum is rotated and cleaned afterward, and the next restart is prevented.
It is also possible to continue the copying operation for a predetermined number of sheets and then stop the copying operation and prevent it from restarting. The above measures are taken to ensure that the copying speed is not impaired, considering that even if the thermistor is disconnected for some reason during the copying operation, the temperature will not suddenly change for a while. In other words, if a disconnection is detected and the operation of the heater, main motor, etc. is immediately stopped, as in the case of a jam detection, the sheet currently being copied will stop inside the machine, and it will take time and effort to remove it and make the next copy. , this inconvenience can be removed by the above method.

7 and 8 are sequence and display control circuit diagrams.

In the figure, A is the temperature control circuit shown in Figure 3, B is the oscillator for blinking the weight display 46, C is the sequence control circuit, D is the jam detection circuit, E is the operation key, and Q33, Q34, Qn are the main Process loads such as motors Q31 and Q32 are an inverter and an OR gate for operating the weight display 46.

When the power is turned on, a wait signal is generated as described above.
WAIT is H, and therefore the output of Q31 is 0. Therefore, the OR gate causes the LED 46 to blink by the oscillator B, indicating that the roller is not capable of fixing. Even if copy is turned on at the same time, copying cannot be started. When the roller reaches a temperature that allows fixing, WAIT becomes L as described above and LED 46
lights up statically to indicate that copying is possible by turning on the copy key. When the thermistor changes the signal WAIT from H to L as described above before the start of copying or when the copying operation is interrupted, it causes the LED 46 to change to a blinking operation via the gate Q32. Similarly to the above, even if the copy key is turned on, the copy operation does not start. If a copy operation is in progress, no copy cycle will be started after the disconnection.

FIG. 8 shows another example of a circuit, in which the wait indicator 46 is displayed in four states: power supply state, wait state, copy state, and disconnection state.
It is shared for street display. FIG. 9 is an example of a power supply circuit.

Explain the operation. When the power switch 39 is turned on, DC voltages Vc and Vcc are output and the circuit shown in FIG. 8 is put into operation. When the temperature of the fixing roller is low and copying is not possible, wait signal WAIT is sent by voltage Vc.
Output. On the other hand, transistor Q29 is relay K
1 to heat the heater H1. Therefore, even if the copy key 40 is turned on, it is blocked by the gate Q39 and sheet feeding and scanning do not start. However, since the gate Q35 receives the oscillator OSC1 and the copying signal COPY is 0, it outputs a signal synchronized with OSC1 to the gate Q38. Since the other input of the gate Q38 receives the signal 1 based on the COPY 0 signal, the transistor Q40 turns on and off in synchronization with OSC1.
Therefore, the wait display lamp 46 blinks in synchronization with the cycle of OSC1. This alerts the operator to the inability to copy. When the thermistor TH21 reaches the fixing temperature, the thyristor Q27 is turned on by the output of the operational amplifier Q23, so the signal WAIT is activated.
becomes 0. On the other hand, relay K1 is turned off to stop power supply to heater H. The output of gate Q35 is 1
Accordingly, the transistor Q40 is turned on statically by the 1 of the gate Q38, and the lamp 46 is turned on. Since the gate Q39 has one input set to 1, it can accept a copy key and waits in a so-called standby state. In this case, in order to keep the fixing atmosphere at a temperature that allows fixing, the heater H is
Even when on/off temperature control is performed, WAIT remains at 0 due to the thyristor's energization holding action, so the display will not malfunction.

When the power switch 39 is turned off during this standby mode, Vc and Vcc are turned off, so that the weight indicator lamp 46 is turned off and turned off regardless of the above-mentioned holding action of the thyristor. Therefore this lamp 4
6, it is also possible to determine the power supply state to the device.

Then, when the power switch 39 is turned on again, the fixing roller, that is, TH, has not cooled down, so the thyristor is immediately turned on via the operational amplifier, the lamp 46 starts to be lit statically as described above, and the machine is placed in a standby state.

When the copy key 40 is turned on during standby, a start signal is output to the CPU and the main motor is
Starts paper feeding and scanning operations. and
Since the CPU outputs the copy signal COPY, the output of gate Q35 is completely set to 1, and the output of gate Q36 is completely set to 1.
outputs a series of pulses from the oscillator OSC2.
Therefore, gate Q38 connects transistor Q40.
The transistor turns on and off in synchronization with OSC2, so that the transistor can cause the lamp 46 to blink at a repeating cycle longer than OSC1. When the scanning of the preset number of copies is completed and the document table inversion position is reached, the signal COPY is set to 0, so the device goes into standby mode again, lights up the lamp 46 statically, and accepts a copy restart command.

If the copy key is turned on at this time, copying of the previous preset number is resumed without resetting the copy number. This restart is performed in a manner similar to continuous copying in which scanning continues without stopping even when the document table returns to the stop position.

If the power switch 39 is turned off without restarting copying, the lamp 46 is turned off, indicating that the voltage to the loads such as the clutch, main motor, corona charger, etc. has been turned off.

After turning off the power switch 39, this lamp 4
It is also possible to display the OFF state by weakening the amount of electricity supplied to 6. In this case, even if the central control unit CPU turns off the switch 39, it is effective when it is desired to keep the memory operating state alive. In particular, when processing sheet jams, the power switch 39 is often turned off, and in this case it is not desirable to cancel the number of presets in the memory, so it is extremely convenient to use it as an indication of the memory on state.

Next, sequence control will be explained with reference to FIG.

FIG. 10 is an operation control circuit diagram of the copying machine shown in FIG. 2. In the figure, Q ₂ to _{Q 6} operate a clutch that operates the manual feed roller 14, a clutch that operates the registration roller 17, a clutch that operates the cassette roller 13, a clutch that moves the document table 1 backward, and a clutch that moves the document table 1 forward. A flip-flop for control is turned on by a pulse rising signal to port S and turned off by a pulse rising signal to port R. Q ₈ is a flip-flop for determining manual mode, and Q ₂ except that S and R functions are not edge triggers.
is the same as _Q9 is a timer for operating the manual feed roller 14, and requires that the input signal be turned on for a predetermined period of time. Q ₁₀ to _{Q 12} are counters that count clock pulses generated by drum rotation from the time when an input signal is input, and output pulses when a predetermined count is reached. Q ₁₀ and Q ₁₁ are used to determine whether each manual feed roller is turned off or the cassette roller is turned off.
Q ₁₂ is for determining the pre-rotation speed. This clock pulse DCK is generated by the aforementioned rotary encoder at constant N pulses at equal intervals per rotation of the drum.
ke occurs. Q ₁₄ is a counter similar to Q ₁₀ to _{Q 12} above, but in cassette mode, the number of presets is selected according to the cassette size, and in manual mode, the number of presets is manually selected in a different mode than in cassette mode. Select according to the difference sheet size. _G1 to _G10 are AND gates, _G15 to _G25 are OR gates, and _INV1 to _INV6 are inverters.

The signals MRCl, RGCl, CRCl, FWCl, and BWCl are signals that turn on the manual feed roller, registration roller, cassette roller, document platen forward and reverse when they are 1, and turn them off when they are 0, CLK is a clock pulse, and BP is for reversing the document platen. The END signal is a copy cycle stop signal and is based on the stop key, count-up, STB, CTU, PEP, and CEP signals for no paper/cassette. Manual error is a signal indicating the manual mode, JAM is a signal indicating a sheet jam and is generated by jam detection, CTU is a copy counter count-up signal indicating that the preset number of copies has been completed.
The SW detects the SW state using the main switch on signal and outputs it. PS ₁ and PS ₂ are signals output when the manual feed sheet is detected by the detectors 15 and 16;
PF and RG are paper feed signals and registration signals that are generated when the document table turns on the read switches 31 and 32,
CPB and STB are signals generated when the copy button and stop key of the operation unit are turned on, and SP and HP are signals generated when the read switches 30 and 35 of the document table are turned on, indicating the document table advance start position and stop position. PEP
The sheet in cassette 10 is empty when the lamp 60-1
CEP is a signal indicating that the cassette 10 is removed, and is output by the microswitches 50 and 51 whose operation is controlled when the cassette is turned on. TEP is the toner out signal in the developing device 33.
A toner level detector 61 in the developer container detects and outputs that the level has fallen below a certain level;
OVF is a signal indicating the overflow state of collected toner in the collection container 7, and is detected by the level detector 62 and output. WAIT is a thermistor that detects the temperature of the fixing roller with a signal indicating the wait state.
Output by Th.

Explain the operation. During the wait signal WAIT generated by turning on the power source 39, the drum is rotated first. After that, when the wait is up (WAIT is L) and the copy button is turned on while in standby, the main motor is turned on in the same way and the process is started.

Since the sheet is not inserted from the manual feed tray 12, the detector 15 is off, so the flip-flop
Since _Q8 is off, no manual signal is output, gate _G1 is turned off, and flip-flop _Q2 is not set, so manual roller 14 is not turned on either.

When there is no paper PEP 60, no toner TEP 61, overflow OVF 62, etc., a start signal is input to gate G ₂ via gates G ₃ , G ₂₅ , and G ₁₆ when the copy key is turned on. Gate
The other input port of _G2 receives the weight and manual inversion signals (all 1), so it is a flip-flop.
Set _Q4 and turn on the clutch of cassette roller 13. Counter via gate 17
While _Q11 counts a predetermined number of pulses, the roller 13 rotates half a turn and stops, pulls out approximately half of the sheet from the cassette, and then stops.

Counter through gate G ₂₂ at the output of this Q _4
Q12 starts the clock pulse count CLK. When a predetermined number of pulses are counted, which corresponds to approximately one rotation of the drum, flip-flop _Q5 is set via OR gate _G24 , FWcl is turned on, and the document table is advanced. When the reed switch 30 is turned on by the document table, _Q5 is reset through gate _G19 and the clutch FWCl is turned off, while flip-flop _Q6 is set to turn on the clutch signal BWCl and the document table is moved backward. The image exposure lamp 3 is controlled to turn on in synchronization with the main motor, and the intensity of the light amount is controlled in synchronization with the control of BWCl, and becomes strong when BWCl is on. The first slit exposure is completed.
_Q6 reset time is cassette switch 50,
51.

In other words, when the switches 50 and 51 are 1 and 0, the size
Since the A4 sheet is in the cassette, the exposure stroke can be completed with that width. In other words, a counter that counts clock pulses and determines the reversal position.
Set the preset number of _Q14 to n1, which is suitable for A4.
For size B4, switches 50 and 51 are 0 and 1.
Therefore, n2, which is larger than n1, is preset. A3
In this case, 50 and 51 are 1 and 1, so there are even more n3
Set. Note that when 50 and 51 are 0 and 0, a cassette-free signal CEP is outputted via gate _G5 .

The counter _Q14 counts pulses after the registration switch 32 is turned on, but when it reaches the number n1 to n3, it outputs BP, resets the counter _Q6 , and ends the backward movement. Meanwhile via gate G ₂₄ by BP
_Q5 is set to move the document table forward, and when the document table turns on the reed switch 35, _Q5 is reset and the advance is stopped.

Gate G ₁₀ for multiple copies of preset numbers
Q5 will not be turned on even after the process is completed once, so even if the stop switch 35 is turned on, _Q5 will not be reset.
Therefore, the vehicle continues to move forward, and by turning on the start switch 30, _Q5 is reset and the forward movement is stopped. At the same time, set _Q6 again and start the second backward exposure. This gate _G10 receives the signal STB from the stop key 41, and the signal from no paper and no cassette.
PEP, CEP, or preset number copy completion signal
It is turned on by the END signal from each CTU. Therefore, until the copy cycle of the preset number is completed,
In addition, gate _G10 controls the output of the signal HP so that the scan is repeated until an interrupt command is issued due to the stop key, no paper, etc. In addition, Q4 is set via G ₁₄ , G ₂₅ , G ₁₆ , and G ₂ in order to feed the second and subsequent sheets in response to the signal HP.

Furthermore, the same END signal as described above is outputted in the middle of multi-copying via diode D ₅₀ and gate G ₁₈ in response to disconnection detection signal WAIT of the thermistor, stopping the reverse movement at the HP position and preventing restart.

[Brief explanation of the drawing]

Fig. 1 is a conventional temperature control circuit diagram, Fig. 2-1 is a sectional view of a copying machine applicable to the present invention, Fig. 2-2 is a plan view of the operation section of the copying machine shown in Fig. 2-1, and Fig. 3 The figure is a temperature control circuit diagram of the present invention, Figures 4 and 5 are operation time charts of Figure 3, and Figure 6 is a diagram of Figure 2-1.
7 and 8 are sequence and display control circuit diagrams in the present invention,
9 is a power supply circuit diagram of the copying machine shown in FIG. 2, and FIG. 10 is a sequence control circuit diagram in the present invention. In the figure, 20 is a fixing roller, H21 is a heater,
TH21 is a thermistor, C21 is a delay capacitor, Q23 is a temperature control amplifier, Q24 is a disconnection detection amplifier, and WAIT is a wait signal.

Claims (1)

[Scope of Claims] 1. Detection means for detecting the temperature of the fixing device; Temperature control means for controlling power supplied to the heat source of the heated member according to the temperature detected by the detection means; Disconnection of the detection means. disconnection detection means for detecting the abnormal state of conveyance of the sheet; interrupting means for interrupting the operation of the temperature control means in response to a detection signal of an abnormal state of sheet conveyance; A temperature control device comprising: control means for causing the detection means to perform a detection operation.