JPS62231978A - Heating type fixing device - Google Patents

Abstract

PURPOSE:To advance a time point of operation of a thermosensible breaker and to protect a heat roller, etc., from damage caused by overheating, by reducing an overshoot of a surface temperature of the heat roller. CONSTITUTION:A thermistor TH which contact or stands close to the surface of a heat roller 32h detects a surface temperature T1 of the heat roller 32h, and it is concerned in turn-on and turn-off of a heater H. A pressure roller 32p is separated from the heat roller 32h except the time of copying operation, and pressed against the heat roller 32h at the time of copying operation and rotated together with the heat roller 32h. When the surface temperature of the heat roller 32h becomes an abnormally high temperature, a temperature fuse F operates, cuts off an electric conduction line of the heater H and obstructs abnormal overheating of the heat roller 32h. An operating temperature of this temperature fuse F is correlated to the surface temperature T1 of the heat roller 32h, and also, is determined so as to be related to an extended operation time of a main motor M1 and/or an exhaust fan motor M5 for driving a fixing device 32.

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to a fixing VC device of a copying machine, etc., and more specifically, a heat roller with a built-in heating source is used to transfer a copied image to a sheet of paper. The present invention relates to a heating type fixing device that fixes images.

2. Description of the Related Art Conventionally, a so-called heat roll system has been widely used in fixing devices for electrophotographic printers and copying machines. In this method, at least one roller has a built-in heater as a heat source, and the toner image is thermally fixed by passing the floppy paper between these rollers.

By the way, the above-mentioned heater is controlled to turn on and off in relation to the copying operation, but there is an optimum temperature for fusing, and the heater's turning on and off is automatically controlled to maintain this temperature (or temperature range). ing. Automatic control usually uses a thermistor as a temperature-sensitive element, which detects the surface temperature of the heat roller, and is performed by a resistor bridge circuit including the thermistor and a comparator or a microcomputer that processes the thermistor output signal. (Japanese Unexamined Patent Publications No. 53-65743, Unexamined Japanese Patent Application No. 60-1)
15977).

However, if the thermistor malfunctions or for some reason the program that processes the thermistor output signal of the micro pump computer does not operate as designed (including the program running out of control due to noise or lightning surges, etc.), the heater will turn on abnormally. Sometimes. When this abnormal lighting occurs,
The heat roller is heated excessively, and there is a danger that the heat roller may be damaged, members around the heat roller may be damaged, and the copy paper may be ignited, resulting in a fire. Therefore, a temperature-sensitive breaker such as a temperature fuse is usually provided close to the surface of the heat roller, and when the heat roller reaches a predetermined temperature or higher, the temperature-sensitive breaker connected in series with the heater is activated to Safety measures are being explored to cut off the power supply.

The invention is trying to solve the problem! However, in the conventional example, there is a problem in that even if ignition can be prevented, the heat roller whose surface is coated with resin has already been damaged by the time the temperature-sensitive breaker is activated.

This is due to the fact that the responsiveness of temperature-sensitive breakers is low, as it takes a considerable amount of time to blow a temperature fuse, and the second reason is that temperature-sensitive breakers are a last resort for safety measures. This is because the operating temperature is set with an additional margin consisting of the upper limit of temperature change during normal operation of the heat roller.

To explain the latter cause in detail with reference to Fig. 9, the heater is turned on at a high duty cycle as the copy paper heats up during repeated copying operations, but when the copying operation is completed and the main motor stops, , l of heat conduction from the heater to the heat roller surface, ? Due to the delay, overshoeing (O3) always occurs in the heat roller surface temperature (T1) at this point. The operating temperature of a temperature-sensitive breaker such as a temperature fuse is determined based on the design considering this overshoe (O3), for example 1.
I try to set it by adding 0℃. Therefore, when the temperature-sensitive breaker actually operates, the heat roller is in a considerably overheated state, and damage cannot be avoided.

Therefore, an object of the present invention is to reduce the overshoot of the heat roller surface temperature so that the temperature-sensitive breaker is activated earlier than before, thereby protecting the heat roller etc. from damage due to overheating. .

The present invention provides an apparatus for fixing copy paper using a heat roller based on a copying operation, in which the operating temperature is set low in relation to an extended stop time of the main motor and/or the exhaust fan motor at the end of the copying operation. The present invention is characterized by including a circuit in which a thermal breaker is connected in series with the heating source of the heat roller, and based on the knowledge that ventilation inside the machine by the operation of the main motor and/or exhaust fan motor is considerably effective in cooling the heat roller. Based on this, forced cooling by this ventilation reduces the overshading of the heat roller surface temperature after the copying operation, making it possible to set the operating temperature of the temperature-sensitive breaker low.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described in detail with reference to embodiments shown in the accompanying drawings.

First, the structure and operation of a copying machine having one embodiment will be schematically explained with reference to FIG.

At approximately the center of the copy g(too), the photoreceptor drum (
1) is supported so that it can rotate counterclockwise in the figure, and around it are main eraser lamps (2).

A charger (3), a sub eraser lamp (4), a main charger (5), a developing device (6), a transfer charger (7), a separate charger (8), and a cleaning device (9) are installed on the applicant. ing. Photosensitive drum (1
) has a photoreceptor layer on its surface, so this photoreceptor is connected to the eraser lamps (2), (4) and the charger (3).
), (5), it is sensitized and charged, and receives image exposure from the scanning optical system (10) to form an electrostatic latent image on its surface. Note that the main photosensitive drum (1) is driven by a main motor (Ml).

The scanning optical system (10) is connected to the document table glass (on which the document is placed).
It is configured so that the original image can be scanned below 16), and includes an exposure lamp (17), movable mirrors 1), (12), and (13), an imaging lens r (14), and a mirror. (15). The exposure lamp (17)
and the movable mirror (11) adjusts the circumferential speed (
V) (Equal size.

constant regardless of magnification) versus (v/n) (however,
While the movable mirrors (12) and (13) are driven to the left in the figure at a speed of (v/2n), n is the copying magnification. The drive is performed by this scanning motor (M3). In addition, when changing the copy magnification (when changing magnification), a stepping motor (M4)
The imaging lens (14) is moved on the optical axis, and the mirror (15) is also moved and swung.

For copying paper, use the upper and lower paper feeders (21), (22) or the manual paper feeder (23) that accommodate standard paper of different sizes.
) is fed into the machine via the paper feeder vt (20).

Any one paper feed roller (24), (25), <26
) is conveyed by an intermediate roller (27) and temporarily stopped by a timing roller (30).

The stopped copy paper is sent to the transfer section in synchronization with the image formed on the photosensitive drum (1).

The toner image is transferred by a transfer charger (5) and separated from the surface of the photoreceptor drum (1) by a separation charger (6). The sheet is then sent to a fixing device (32) via a conveyance bell (31), where it is thermally fixed, and then ejected onto a paper ejection tray (34) via an ejection roller (33). After the transfer, the photosensitive drum (1) is cleaned of residual toner and electric charge by a cleaning V device (9), an eraser lamp (2), etc., and is ready for the next copying process. Note that the fin motor (Ml) drives rotating parts such as rollers and related operating elements in the copy paper feeding/conveying path. In addition, the exhaust fan (3) is driven by a motor (M5) provided below the conveyor bell (31).
5) The air inside the machine (including ozone generated by the electrostatic process) is exhausted to the outside, and the negative pressure of the exhaust air is used to prevent the waving of the copy paper on the conveyor bell (31). suppress.

Figure 2 shows the main parts of the operation panel of the copying machine (100), where (71) is the print key that is operated when starting copying, and (72) is 7 which displays the number of copies and the status of the copying machine.
Segment type display, (80) to (89) are numeric keys for setting the number of copies, (90) is an interrupt key during multi-copying, and (91) is a clear/stop key for canceling the number setting or stopping the copy operation. ,(93),
(94) is a 7-tube key for setting image density, (92)
) are vapor size selection keys, (92a) to (92d
) are display portions of the selected vapor size.

Although not shown, a key for setting a copy magnification and a display section related thereto are also provided.

As shown in FIG. 3, the copying machine (100) having the above configuration has an fplI CPU (201), a tpJ2
It is associated with a control device (200) including a microcomputer so that the operation is controlled by C (202).

f:tSI Cr'U (201) is a copying machine (100)
Numeric keys (80) to (89) arranged on the operation panel of
, print key (71), other keys (90) to (9
4) A display section (72) that displays the number of copies and the state of the copier according to the operation of the numeric keys (80) to (89), and various displays. It is connected to the light emitting diodes (92a) to (92cl), etc. for use via defoog (203).

Further, the first CPυ (201) has an output port as a main motor (Ml) in order to control the operation of the copying machine.

It is individually connected to drive circuits (not shown) such as the developing motor, various clutches, charters, and exhaust fan motor (M5), and is also connected to an interrupt signal input/output terminal (INT
) and data input/output terminals (Sin) and (Sout), it is connected to the second CI''U (202).

The second CPU (202) executes operation control of the scanning optical system (10) of the copying machine (100), and controls the operation of the scan motor (M3) and the scan motor (M3).
It is connected to a borrowed lens control circuit (205), various optical system detection switches (Sn), (S, ), etc.

J: Note m'l Cr'U (201) 1. t*r:,
Fuser ft? (32) Controls automatic temperature control 3819. First, a more specific configuration related to temperature control of the fixing device (32) is shown in FIG. In the figure, a cylindrical heat roller (321+) whose surface is coated with a non-adhesive agent (32hC) that does not allow toner to adhere is heated from the inside by a tube-shaped heater (H) fixed inside the cylindrical shape. . Thermistor (Tl+) fixed and supported by a suitable bracket and in contact with or close to the surface of the heat roller (32h)
is the surface temperature (T1) of this heat roller (321+)
The pressure roller (32p) is separated from the heat roller (32b) except during the copying operation, and is connected to the heat roller (32b) via a clutch etc. during the copying operation. 321+) and rotates together with the heat roller (32b).
1) (see Figure 1), the copy paper (40) is conveyed while being sandwiched between both rolls (32b) and (32p), and the toner image (401) is turned into a permanent image by the heat roller (32h). The image is then thermally fixed onto the copy paper (40). (F)
is a temperature fuse, which is installed close to the surface of the heat roller (32h).

When the surface temperature of the heat roller (321+) becomes abnormally high, the temperature fuse (F) is activated to cut off the energization line of the heater (H) and prevent abnormal overheating of the heat roller (32b). The operating temperature of this temperature fuse (F) is correlated with the surface temperature (T1) of the heat roller (321+), and in this embodiment, the main motor (Ml) driving the fixing device (32) and/or It is defined in connection with the extended operating time of the exhaust fan motor (M5). Conventionally! In this embodiment, the temperature is set to 160°C, for example, in a similar configuration, whereas the temperature was set at 69'C.

OnRIII'JE l! m Figure 3 m I CPU
(201) Kaji 71゜That is, the fluctuation voltage (■,) of the thermistor (Tl+>) based on temperature changes is always input to the ^/D conversion input port (Vref is the ^/D built in the CPU).
The first CI"U (201) converts this input voltage into digital data and compares it with predetermined data. The predetermined data is the surface temperature of the heat roller suitable for fixing (Ttl+) This is a digital digital datater for the thermistor voltage (VL!+) that is predetermined in association with the heat row 2 surface temperature (TI).
) is a high level signal (rll
J) is output to the driver (IC2), a solid state relay (SSR) such as a thyristor is made conductive, and the heater (
Light up the lights. Conversely, when the voltage (vl) falls below (VLh), the output cap-) (PI+) goes to low level (rLJ).
, the relay (ssr+) is activated and the heater (T
4) Turn off the light. A temperature fuse (F) is connected to the heater (H) in series with the commercial power supply of ^ctoov, and if the surface temperature of the heat roller becomes abnormally high regardless of changes in the thermistor voltage (V,), the atmosphere based on the The current supply line to the heater (H) is cut off depending on the temperature (for example, 160° C.).

FIG. 5 shows another embodiment of the temperature control circuit suitable for the case where the first CPU (201) does not have a built-in ^/D converter. The comparison 25 (ICI) compares the thermistor voltage (vth) as a reference voltage with the varying voltage (Vl), and controls the drive of the driver (Ice) using the comparison output.

The circuit ([3) is an interface section between the circuit (A) and the CPU, and when the output port (PORT2) becomes rHJ, the output of the driver (IC3) becomes rLJ, the diode (DI) becomes conductive, and the comparator ( ICI) output is rL
J, and the heater (II) is forcibly turned off.

On the other hand, the output of the output port (PORT2b5'rL J tonaruto, driver (Ic3) is [11,l), and this part becomes high impedance due to the diode (Dl), and the heater (H) is controlled by the circuit (A). The input capo (PORTI) is the comparator (PORTI).
The output section of ICI) is for monitoring rHJ and rLJ. For example, by using this port (PORTI), it is possible to perform controls such as detecting the rising edge of rLJ after a copy operation and stopping the main motor (Ml).

Next, a procedure for controlling the operation of the copying machine by the control device (200) will be explained using a tjSO diagram and a chart 70 in FIG. 7.

FIG. 6 shows the copy executed by m I CPU (201)!
(100) is a flowchart generally showing the operation control.

When the power is turned on, the CPU is reset, and the program is started, initial settings are first performed in step (#1). The initial setting is the number of copies displayed (72
) processing and CP for setting variable operation items for the copying machine (100) to the standard state, such as setting the display to "1"
Processing to clear RAM, registers, etc. in U and CP
Processing such as setting the initial values of various timers built into the U.

In the next step (Step 2), an internal timer built into the CPU and whose value has been set in advance as an initial setting is started.

Step (#3) is an input processing routine that detects key operations on the copying rock harvesting panel and inputs data. At step (#3'), press the print switch (print start key).
When the ON edge of 71)) is detected, step (I4)
Then, set the copy start flag to "1" to start the copy operation. At the timing when the SW is not ON, the process proceeds to step (#5).

Step (well 5) is a copying operation routine that enables each operating element in the copying machine (100) and controls the conveyance of copy paper as well as the scanning optical system (10). Details are shown in Figure @7. show.

In the step (#6), the second CPU (202) is connected via the interrupt terminal ([NT).
CPU? ' - perform mutual communication between data.

In step (#7), processing related to copying operations other than those described above is performed. Includes temperature control processing in the fixing device.

In step (#8), the end of an internal timer (hard timer) set so that the processing time of the program in the first CPU (201) remains constant regardless of the processing content is determined, and each time the program ends, step ( Return to #2) and repeat the above processing routine.

Note that various timers used in each routine are counted (timer = counter) based on the length of time it takes to go around this loop, and the end of the time is determined by how many times this loop has been counted. .

In FIG. 7 showing details of the copy operation subroutine,
First, in step (#530), it is determined whether the copy start flag is [11]. [If it is 11, in step (#531), the main motor, the developing motor, the charger, and the transfer charger are given an A-1 signal, and the copy 11 start flag is reset while the copying operation is in progress. Set the copy flag to "1" and set the timer (T-^)
and set the timer (T-D).

In steps (#532) to (#535), it is determined which of the upper and lower paper feed cassettes is selected, and if the upper paper feed cassette is selected, its roller clutch (CL) is ONL, If the lower paper feed cassette 7) is selected, its roller clutch (CI, ) is turned on. In step (#536), the timer (T-Δ) which gives the clutch operating time is judged, and if it is the timing to end, the upper or lower roller clutch 7 is turned off in step ($537).

In the dog step (#538), a timer (T-8>) is activated, which gives the time until the scanning optical system (1o) starts operating, and when it is time to finish, the scan starts in step (#539). Set the signal to "1".

As a result, the scan clutch (CL) is turned on and scanning starts, as shown in the timing chart of figure f:A8.

In the following step (#547L (#548)), the fed copy paper is temporarily stopped before the timing roller (3o), waits for a timing signal output as the scanning optical system (1o) moves, and The timing roller (3o) is operated at the output timing of the timing signal to synchronize the leading edge of the copy paper and the leading edge of the image.

In step (#549), (I55o), after a certain period of time counted by the timer (T-C) while timing No. 43 is being output, the charger is turned off, the scan signal is set to 101, and the timing roller clutch ( C
L) is turned off to stop image formation.

In step (#551>), the scanning optical system (1o) returns to its original position.
- Determine whether the l side number is rll, and if it is in the process of returning, determine whether copying for the set number of sheets has been completed in step (#552). If it has not finished, set the copy start flag to [1] and proceed to step (#556).
Proceed to. When it is determined in step (#552) that the multi-copy is completed, in step (#553) the localization value signal "1" output when the scanning optical system (10) returns to its original position is detected. , turn off the developing motor and transfer charger, turn off the main motor stop timer (T-D
) (step (#555)).

When the end of the timer (TD) is determined in step (#556), the fin motor (Ml) is stopped at that timing (step (#557)). Step (#5
In step 58), the results of the processing up to now are output.

By the way, in the above step (#555), a predetermined time value (L) is set in the timer (T-D), but as shown in the in8 diagram, it is set to the conventional value (L1 bar, for example, 5 seconds). On the other hand, in the example, this is extended (t2) (
For example, 8.5 seconds). This means that after the copy operation ends (corresponding to the copy flag becoming [0]), the operation of the main motor (Ml) is extended for (L2-Ll) to continue ventilation inside the copying machine (100). This is to make it happen.

Due to this ventilation, as can be seen by comparing Figures 9 and 10, the heat roller is cooled down after the copying operation is completed.
The surface temperature (T,) forms one maximum peak (P2) during the operation of the main motor (Ml), and gradually decreases from there. Therefore, if the main motor (Ml) is stopped before reaching the reference temperature (TLI+) of the heat roller surface, the overshoot after that point will be offset by the temperature drop, and the temperature will not rise suddenly to T2 as before. It is 5 to 10 degrees Celsius lower, at most T3. From now on, even if the temperature rise up to this temperature T3 is taken into account, the operating temperature of the temperature fuse (F) can be set lower by the amount by which the overshoot is reduced.

tpJ11 and FIG. 12 show other embodiments.

In Figure 11, after the copy operation is completed, the main motor (
Ml) continues to operate, and the heat roller surface temperature (T, )
reaches the maximum peak (P2) and descends, and continues to descend until it falls below the base sail temperature (TLb) only once. When the temperature falls below this base temperature (Tth), the thermistor voltage (vl) exceeds the reference value (Vtb) at this point, and the heater (H') lights up (ON) for a very short time.

The heat roller (32b) is heated a little, its surface temperature (T, ) rises slightly, and the thermistor voltage (■1
) is below (VLI+). The heater (H) is turned off (OFF) at this point. The main motor (Ml) is controlled to be turned off based on the time when the light goes out. Even if the main motor (Ml) is turned off in this way,
The heat roller is already sufficiently cooled by the extended stop time, and even if overshoot occurs after the stop time, the temperature T is the same as or slightly lower than that of the previous embodiment. Also, like this, turn the heater on to 0N.
By setting the temperature to 10FF, it is possible to quickly return to the temperature gradient of the steady temperature cycle in the standby state of the copying machine, which is not during copying operation.

Fig. fjS12 shows specific means for this control. The step of setting the copy flag to "0" (
#555) Next, the heater (H) is 0N10FF I
, a step (#560) is provided to determine the inside of the main motor (Ml), and when 0N10FF is confirmed in this step (#560), the process proceeds to step (#557) and
This is to turn off.

In this embodiment, the 0N10FF of the heater is checked only once, but the process may proceed to step (#557) after checking a plurality of predetermined times.

Based on this, determine whether the heater (+() operates normally or not (
It is also possible to determine whether there are any failures such as wire breaks. Also, in this embodiment, the timer (T-D) is set in step 2 (#555), and the end is determined in step (#556). The time is set to be longer than the maximum value of the time (L3) in Fig. 11 in order to prepare for an unexpected failure of the detection means in step (1$560). This is because the detection means may be 0N10FF of the heater lighting signal, or may directly confirm the rise and fall of the temperature detection level No. 47, or only the fall.

In the above embodiment, in order to cool the heat roller, the time when the main motor stopped +h was extended to continue ventilation. However, the exhaust fan motor (M
5) may also be used. Furthermore, it would be more effective if both of them extended their stopping points. In addition, if the fixing device is of a type in which the heat roller and pressure roller are separated when the copying operation is completed, in addition to cooling by using ventilation, heat rollers can be heated by extending the time in which the heat roller is in contact with the pressure roller. The heat of the roller is absorbed by the pressure roller,
Cooling of the heat roller after the lobby operation may be accelerated.

λ absorption phenomenon As is clear from the above explanation, according to the present invention, overshoot of the heat roller surface temperature at the end of the copying operation is suppressed, so that the operating temperature of a temperature-sensitive breaker such as a temperature fuse is lower than that of the conventional one. The rising temperature can also be set low, and therefore, in the event of a heater malfunction or lamp malfunction, the temperature-sensitive breaker operates much faster than in the past, thereby protecting the heat roller and the like from damage caused by overheating.

Further, since the present invention requires only slight changes to the control program related to copy operations, no cost is incurred (
Tin (regardless of the combination of these two), it not only greatly improves the protection ability of the machine when the heater is turned on abnormally, but also has excellent effects such as facilitating the heat-resistant design of the heat roller and surrounding parts. .

[Brief explanation of drawings]

FIG. 1 is a schematic sectional view of a copying machine to which an embodiment of the present invention is applied, FIG. 2 is a vertical plan view of its operation panel, FIG. 3 is a circuit diagram of the control device of the copying machine, and FIG. 4 is a perspective view of the main parts of the fixing device, fjS5 is a diagram showing other examples of the temperature 7f'l fDIJ control circuit, FIGS. 6 and 7 are flowcharts, ff1
Figure 8 is a timing chart, Figure 9 is an explanatory diagram of a conventional example,
FIG. 10 is an explanatory diagram of one embodiment, FIG. f511 is an explanatory diagram of another embodiment, and FIG. 12 is a 70-chart of another embodiment. 100... Copying machine, 32... Fixing device, 3211.
...Heat roller, 35...Exhaust fan, Ml...
Main motor, M5...Exhaust fan motor, TH...
- Thermistor, H... Heater, F... Temperature fuse, 201... Microcomputer (1st CPU). Figure 1 Figure 2 Figure 11 Figure 5 Figure 6 Figure 7

Claims (1)

[Claims] (1) In a device that fixes copy paper using a heat roller based on a copying operation, the main motor and/or
Alternatively, a heating type fixing device comprising a circuit in which a temperature-sensitive breaker whose operating temperature is determined to be low in association with the extended stop time of the exhaust fan motor is connected in series with the heat source of the heat roller.