JPH077235B2 - Temperature controller for heat fixing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention is used in an electrophotographic copying machine, an electrophotographic printer, or the like, and a temperature control device of a fixing device for fixing a recorded image on recording paper by heating. Regarding

More specifically, the fixing temperature detecting means for detecting the surface temperature of the heating roller for fixing the unfixed image on the recording paper, and the heating roller for the heating roller based on the comparison result of the temperature detected by the fixing temperature detecting means and the set temperature. The present invention relates to a temperature control device for a heating and fixing device, which is provided with a heating control means for controlling the operation of a heater on and off.

[Conventional technology]

The temperature controller of the fixing device described above starts the heater operation when the surface temperature of the heating roller becomes lower than the set temperature,
Further, when the surface temperature of the heating roller becomes higher than the set temperature, the operation of the heater is controlled to be turned on and off so that the operation of the heater is stopped so that the surface temperature of the heating roller is maintained near the set temperature. .

In such a temperature control device of the heating and fixing device, if some abnormality occurs in the heater or the signal for controlling the operation of the heater is not normally transmitted, even if the surface temperature of the heating roller exceeds the set temperature. Keep rising,
On the contrary, a situation may occur in which the temperature continues to drop even if it falls below the set temperature. If the surface temperature of the heating roller continues to rise, the offset preventing liquid may evaporate, the recording paper may be burnt, and the heating roller may be damaged. On the other hand, if the surface temperature of the heating roller continues to drop, fixing failure may occur or low temperature offset may occur.

Therefore, a fixing abnormality detecting means is generally provided so as to detect that the surface temperature of the heating roller is not normally controlled and avoid the occurrence of the above-mentioned trouble. Conventionally, as such fixing abnormality detecting means,
A fixing upper limit temperature higher than the set temperature and a fixing lower limit temperature lower than the set temperature are set, and the surface temperature of the heating roller detected by the fixing temperature detecting means is compared with the fixing upper limit temperature and the fixing lower limit temperature, respectively, and heating is performed. It is known to output a fixing abnormality generation signal when the surface temperature of the roller exceeds the fixing upper limit temperature and when it falls below the fixing lower limit temperature.

[Problems to be solved by the invention]

However, the conventional configuration described above has the following problems.

That is, the surface temperature of the heating roller sharply drops due to contact with the recording paper having a large heat capacity. Further, the change region of the surface temperature of the heating roller changes depending on the ambient temperature. Therefore, in such a state, in order to prevent an erroneous determination that the fixing temperature is abnormal despite the fact that the temperature is actually changed normally, the surface due to a change in the surrounding environment, etc. In consideration of fluctuations in the rate of change of temperature, it is unavoidable to set the fixing upper limit temperature and the fixing lower limit temperature to temperatures considerably separated from the set temperature.

In the conventional configuration, the occurrence of the fixing temperature abnormality is detected only when the surface temperature of the heating roller reaches the fixing upper limit temperature or the fixing lower limit temperature. Therefore, when a fixing abnormality occurs in an environment in which the rate of change in surface temperature is small, it takes a considerable amount of time to detect it. Therefore, there is a possibility that the heat roller may be damaged due to heat accumulated for a long period of time.

In view of the above situation, an object of the present invention is to make it possible to detect an abnormality in the fixing temperature as quickly as possible even in an environment in which the rate of change in surface temperature is small.

[Means for solving problems]

The temperature control device of the heat fixing device according to the present invention is characterized in that the fixing temperature detecting means detects the surface temperature of the heating roller at regular intervals, and the temperature detected by the fixing temperature detecting means and the previous detection. Based on the result of comparison with the temperature, the counting means counts when the temperature difference is equal to or more than a predetermined amount, and the count value by the counting means from the output of the on / off control signal to the heater by the heating control means is the set value. There is provided a fixing abnormality detecting means for outputting a fixing abnormality generating signal when the value exceeds the limit.

[Work]

In other words, if the on / off control signal for the heater is output when the surface temperature of the heating roller exceeds or falls below the set temperature, the surface temperature continues to rise or fall for a while, but normal operation is performed. After a certain period of time, the surface temperature will change in the opposite direction.
On the other hand, when a trouble such as that the temperature control is not normally performed occurs, a phenomenon occurs in which the surface temperature does not change in the opposite direction forever. Since the heat capacity of the heating roller is constant, the switching timing of the surface temperature change becomes earlier in the environment where the surface temperature change rate is small.

Therefore, the set value that causes the fixing abnormality occurrence signal to be output when the count value by the counting means exceeds the surface when the normal temperature control is performed in an environment where the rate of change of the surface temperature of the heating roller is large. By setting so as to match the timing of switching of the temperature change, it is possible to detect that the abnormality of the fixing temperature has always occurred at the same timing and at the earliest timing.

Moreover, only comparison and counting are required, and the configuration for detecting an abnormality in the fixing temperature can be made extremely simple.

〔Example〕

 Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 is a schematic sectional view of a heat fixing device (F) provided in a part of the electrophotographic copying machine.

A heating roller (1) and a pressure roller (2) are arranged opposite to each other in the passage of the recording paper (P). The recording paper (P) having the unfixed image adhered on the upper surface is sent out from a transfer device (not shown), and then guided by a conveying device (3) to a guide (4).
And is fed between the rollers (1) and (2).

The heating roller (1) has a surface coated with silicone rubber, and is rotated clockwise by a driving device (not shown). Further, a heater (1a) is provided inside thereof, and the recording paper (P) passing between the rollers (1) and (2) is heated by the operation of the heater (1a). On the other hand, the pressure roller (2) has a silicone rubber layer on its surface, is rotatably supported and is in pressure contact with the heating roller (1), and the passing recording paper (P) is applied to the heating roller (1). It is designed to be pressed.

And, by the cooperative action of both rollers (1) and (2),
The toner that forms an unfixed image on the recording paper (P) is heated and melted to be fixed on the recording paper (P). After the toner is fixed, the recording paper (P) has two rollers (1),
After passing between (2), it is separated from the surface of the heating roller (1) by the separating claws (5a) and (5b), and is guided (6).
And is discharged to the outside of the copying machine by a pair of discharge rollers (7a) and (7b).

The surface of the heating roller (1) is provided with a cleaning device (8) for removing the toner attached to the surface of the recording paper (P) by heating the recording paper (P) by sliding contact with the felt (8a). It is attached. A thermistor (9) is in sliding contact with the surface of the heating roller (1). Then, based on the detected surface temperature information from the thermistor (9),
As will be described later, the operation of the heater (1a) in the heating roller (1) is controlled.

Next, operation control of the heater (1a) will be described.

FIG. 1 is a block diagram of a temperature control device whose main part is composed of a microcomputer (C).

The thermistor (9) is connected in series with the resistor (R) and divides the DC power supply voltage (Vcc) by both. Then, the higher the surface temperature of the heating roller (1), the lower this partial pressure value (Vd). The divided voltage value (Vd) is converted into 8-bit detected temperature data (Dd) by the AD converter (10), and then the CPU (12) of the microcomputer (C) is transferred via the I / O interface (11). ) Is entered.

The AD converter (10) receives an AD conversion start signal (ADCS) from the I / O interface (11) every several hundred msec, and the surface temperature of the heating roller (1) is every few hundred msec. It is configured to be detected and input to the CPU (12) as detected temperature data (Dd). That is, the thermistor (9),
The resistance (R), the AD converter (10), the I / O interface (11) and the like constitute a fixing temperature detecting means (FD).

In the ROM (13) of the microcomputer (C), in addition to a temperature control program described later, a sequence program for each device, and 8-bit set temperature data (Ds) corresponding to the set temperature that is the control target, etc. Is remembered.
The microcomputer (C) further includes a RAM (14) for storing data, a clock generator (15) for generating clock pulses, and the like.

In the CPU (12), input detected temperature data (Dd) and R
Compare with the set temperature data (Ds) in OM (13). Based on the result, the CPU (12) outputs a heater operation control signal (HCS) that controls the operation of the heater (1a) to the heater drive unit (16) via the I / O interface (11). . The heating control means (12a) of the CPU (12) performs this operation.

The heater drive control signal (HC
When S) starts the operation of the heater (1a) at "H" level, the trigger signal (TS) is output in synchronization with the separately input zero cross signal (ZCS) and SSR (17) is set to " Set to "ON" state. When the heater operation control signal (HCS) is "L" level and the operation of the heater (1a) is stopped, the trigger signal (TS) is not output and the SSR (17) is in the "OFF" state.
In the figure, (18) is an AC power source and (19) is a thermal fuse.

Also, the detected temperature data (Dd) input to the CPU (12)
Is stored in the RAM (14) and is stored in the previous RAM (14)
And the previous detected temperature data (Dp) stored in a register (not shown) and compared. An address for a counter (CM) as counting means is provided in the RAM (14). The counter (CM) is configured to count up when the difference between the previously detected temperature data (Dp) and the current detected temperature data (Dd) is a predetermined amount or more.

That is, the heating roller (1) has a heat capacity, and it takes time to transfer the heat from the heater (1a). Also, the thermistor (9) has a response delay. Therefore, even if the heater (1a) is stopped from the operating state, the surface temperature of the heating roller (1) once rises and then begins to fall. Further, even when the heater (1a) is operated from the stopped state, the surface temperature of the heating roller (1) is once lowered and then starts to rise.

Therefore, when the heater operation control signal (HCS) is at "L" level to stop the operation of the heater (1a), the surface temperature of the heating roller (1) continues to rise, that is, the previously detected temperature data. This counter (CM) is incremented while the detected temperature data (Dd) of this time is smaller than (Dp). When the detected temperature data (Dd) of this time becomes larger than the detected temperature data (Dp) of the previous time, this counter (CM) is cleared.

On the other hand, when the heater operation control signal (HCS) is at "H" level to start the operation of the heater (1a), the surface temperature of the heating roller (1) continues to decrease, that is, the previously detected temperature data. This detected temperature data (D
This counter (CM) is incremented while d) is large. The counter (CM) is cleared when the detected temperature data (Dd) of this time becomes smaller than the previously detected temperature data (Dp).

When the surface temperature of the heating roller (1) shows normal behavior based on the operation control of the heater (1a), heating is performed within a predetermined time after the heater operation control signal (HCS) reaches any level. The surface temperature of the roller (1) changes from a rising state to a falling state or vice versa, and the above-mentioned counter (CM) is cleared.

However, for example, when the heater (1a) is broken or the thermistor (9) has a poor contact, the counter (CM) is not cleared and continues counting up. Therefore, when the count value by the counter (CM) exceeds the set value, the CPU
The fixing abnormality detection means (HTF) of (12) outputs a fixing abnormality occurrence signal to display a display to that effect on a display device (not shown) and to stop the energization of all circuits except the display device. Is configured to do.

This set value is set differently before the wait is completed and after the wait is completed.

That is, it is considered that the surface temperature of the heating roller (1) is almost equal to the temperature of the surrounding environment when the power switch (not shown) is turned on before the completion of weighting. Then, for a while after the operation of the heater (1a) is started, heat is taken by the pressure roller (2) and its surroundings, so that the surface temperature of the heating roller (1) rises slowly. Further, the resistance value of the resistor (R) for dividing the power supply voltage (Vcc) and exchanging it into an analog voltage is often set to a value substantially equal to the resistance value of the thermistor (9) at the set temperature. . Therefore, the digitized detected temperature data (Dd) may not change until the surface temperature of the heating roller (1) reaches a certain temperature.

From the above, the set value before completion of the wait is set larger than the set value after completion of the wait.

The control operation by the controller of the heater (2) having the above configuration will be described based on the flowchart shown in FIG.

When the main switch of the electrophotographic copying machine is closed and recording is possible, this "fixing temperature control" subroutine is called from the main routine that controls the overall flow of copy operation every few hundreds of milliseconds. It is like this.

In this flowchart, <DTTMP> is the detected temperature data (D
d) storage area, <CTTMP> is a storage area for the count value by the counter (CM), and <FWAIT> is a storage area for a wait flag indicating whether the wait is completed or not. ) Is addressed to. When the main switch is closed, <DTTMP> is [F
F _(H) ], <CTTMP> to [0 _(H) ], and <FWAIT>
Are initialized to [FF _(H) ] respectively.

Also, <EMGTMP>, <WUPTMP>, <HITMP>, <LOWTMP
> Indicates high temperature abnormal temperature data, wait completion temperature data, high temperature side set temperature data, low temperature side set temperature data, which are each digitized into 8 bits, and are respectively stored in the ROM (13).
It is stored in. And <C> indicates a general-purpose register in the CPU (12).

When the "fixing temperature control" subroutine is called,
The previous detected temperature data (Dp) stored in DTTMP> is loaded into general-purpose register <C>(# 1), and then AD converted to AD converter (10) via I / O interface (11). The start signal (ADCS) is output, the surface temperature of the heating roller (1) detected by the thermistor (9) is digitized and captured (# 2), and the detected temperature data (Dd) is stored in <DTTMP>(# 3). .

Next, the data of <DTTMP> and the data of <EMGTMP> are compared (# 4). If the data of <DTTMP> is less than the data of <EMGTMP>, that is, if the detected surface temperature is higher than the abnormal high temperature, If there is, call the subroutine of "high temperature abnormality",
The display is performed by the display device, and after the power supply to the parts other than the display device is stopped (# 5), the process returns to the main routine. If the detected surface temperature is lower than the abnormal high temperature, then the wait flag <FWAIT> is checked (# 6).

If the wait flag <FWAIT> is not [0 _(H) ], that is, if the wait is not completed, the data of <DTTMP><WUP
TMP> data is compared (# 7). If the data of <DTTMP> is less than or equal to the data of <WUPTMP>, that is, if the detected temperature is the wait completion temperature or more, the wait flag <FWAIT> and <CTTMP> are cleared as the wait completion (# 8, # 9) After setting the heater operation control signal (HCS) to the “L” level to stop the operation of the heater (1a) (# 10), the process returns to the main routine.

If the data of <DTTMP> is larger than the data of <WUPTMP> in the judgment of the step (# 7), that is, if the detected temperature is lower than the wait completion temperature, then <DTTMP>.
> Data is compared with the data in the general-purpose register <C>(# 11). That is, the input detected temperature data (Dd) is compared with the previous detected temperature data (Dp).

If the data of <DTTMP> is more than the data of general register <C>, it means that the detected surface temperature has not changed or dropped for several hundred msec. In that case, the data of <CTTMP> is incremented (# 1
2). Then, the data of <CTTMP> is compared with the set value data <α> for detecting the fixing abnormality before the completion of the weight (# 13).

If the data of <CTTMP> is equal to the set value data <α>, the surface temperature of the heating roller (1) does not rise even if a predetermined time has elapsed after the heater operation control signal (HCS) changed to "H" level. It is shown that. In this case, it is determined that some trouble has occurred, a subroutine "low temperature abnormality" is called to display the fact and stop energization (# 14), and then return to the main routine. <CTTM
If the data of P> has not reached the set value data <α>, after setting the heater operation control signal (HCS) to the “H” level to start the operation of the heater (1a) (# 16),
Return to the main routine.

Then, when it is determined in the comparison in the step (# 11) that the data of <DTTMP> is smaller than the data of the general-purpose register <C>, the surface temperature of the heating roller (1) is rising. And clear <CTTMP>(# 15),
After setting the heater operation control signal (HCS) to "H" level (# 1
6) Return to the main routine.

On the other hand, if the wait flag <FWAIT> is [0 _(H) ] in the judgment of the step (# 6), that is, if the wait is completed, the data of <DTTMP> and the data of <HITMP> Are compared (# 17).

If the <DTTMP> data is less than or equal to the <HITMP> data,
That is, if the detected temperature is equal to or higher than the set temperature on the high temperature side, then the data of <DTTMP> and the data of the general-purpose register <C> are compared (# 18). That is, the detected temperature data (D
Compare d) with the previous detected temperature data (Dp).

If the data of <DTTMP> is equal to or less than the data of general register <C>, that is, it means that the detected surface temperature has not changed or increased for several hundred msec. At this time, the data of <CTTMP> is incremented (# 1
9). Subsequently, the data of <CTTMP> is compared with the set value data <β> for detecting the fixing abnormality at the time of the heater operation stop control after the completion of the weight (# 20).

If the data of <CTTMP> is equal to the set value data <β>, the surface temperature of the heating roller (1) will not drop even if a predetermined time has elapsed after the heater operation control signal (HCS) changed to the “L” level. It is shown that. In this case, it is determined that some trouble has occurred, a subroutine "high temperature abnormality" is called to display the fact and stop energization (# 21), and then return to the main routine. <CTTM
If the P> data has not reached the set value data <β>, set the heater operation control signal (HCS) to the “L” level to stop the operation of the heater (1a) (# 16),
Return to the main routine.

When it is determined in the comparison in the step (# 18) that the data of <DTTMP> is larger than the data of the general-purpose register <C>, the surface temperature of the heating roller (1) has dropped. After clearing <CTTMP>(# 22) and setting the heater operation control signal (HCS) to the “L” level (# 2)
3) Return to the main routine.

Also, if the data of <DTTMP> is larger than the data of <HITMP> in the judgment of the step (# 17), that is, if the detected temperature is the high temperature side set temperature or less, the data of <DTTMP> and <DTTMP> Compare with the data of LOWTMP>(# 24). <DT
If the data of TMP> is more than the data of <LOWTMP>, that is, if the detected temperature is less than the set temperature on the low temperature side, then
The data of DTTMP> is compared with the data of general register <C>(# 25). That is, the input detected temperature data (Dd)
And the previous detected temperature data (Dp) are compared.

If the data of <DTTMP> is more than the data of general register <C>, it means that the detected surface temperature has not changed or dropped for several hundred msec. At this time, the data of <CTTMP> is incremented (# 2
6). Subsequently, the data of <CTTMP> is compared with the set value data <γ> for detecting the fixing abnormality during the heater operation start control after the completion of the weight (# 27).

If the data of <CTTMP> is equal to the set value data <γ>, the surface temperature of the heating roller (1) does not rise even if a predetermined time has passed after the heater operation control signal (HCS) changed to "H" level. It is shown that. In this case, it is determined that some trouble has occurred, a subroutine "low temperature abnormality" is called to display the fact and stop energization (# 28), and then return to the main routine. <CTTM
If the data of P> has not reached the set value data <γ>, set the heater operation control signal (HCS) to "H" level to start the operation of the heater (1a) (# 29),
Return to the main routine.

Then, when it is determined in the comparison in the step (# 25) that the data of <DTTMP> is smaller than the data of the general-purpose register <C>, the surface temperature of the heating roller (1) is rising. And clear <CTTMP>(# 29),
After setting the heater operation control signal (HCS) to "H" level (# 3
0), return to the main routine.

Further, if the data of <DTTMP> is smaller than the data of <LOWTMP> in the judgment in step (# 24), that is, if the detected temperature is higher than the set temperature on the low temperature side, the detected heating roller (1) Indicates that the surface temperature of is between the high temperature set temperature and the low temperature set temperature. At this time, the data of <CTTMP> is incremented (# 3
1). Then, the data of <CTTMP> is input to the thermistor (9)
The set value data <δ> for detecting the abnormal condition is compared (# 32).

If the data of <CTTMP> is equal to the set value data <δ>, it indicates that the detected surface temperature obtained from the heating roller (1) does not change even after a lapse of a predetermined time. In this case, it is judged that some trouble has occurred in the thermistor (9), and after calling the subroutine of "Thermistor error" to display that fact and stop energization (# 33),
Return to the main routine. If the data of <CTTMP> has not reached the set value data <δ>, nothing is done and the process returns to the main routine.

In this flowchart, a case has been described in which two high temperatures and low temperatures are set as the set temperatures, and an abnormality in the thermistor (9) can be detected. Actually, the difference between the two set temperatures is about 2 to 3 ° C., but only one set temperature may be set in order to reduce the temperature ripple. In this case, (# 24) and (# 31) in the previous flowchart
It suffices to omit each step of (~).

As the thermistor (9) for detecting the surface temperature of the heating roller (1), the one having a negative characteristic has been described in the above embodiment, but a one having a positive characteristic may be used instead. Further, a platinum resistance temperature detector or a magnetic temperature sensor may be used instead of the thermistor (9), and an AD converter (10) using a crystal temperature sensor that can obtain a digital output.
May be omitted. Further, a non-contact type temperature detector such as a radiation thermometer may be used, and the specific configuration of the fixing temperature detecting means (FD) can be appropriately changed.

The temperature control device of the present invention is used in laser beam printers, microfilm printers, etc. in addition to electrophotographic copying machines.
It can be applied to a heat fixing device that fixes a visible image on a recording paper by heating.

〔The invention's effect〕

As described above, the temperature control device of the heating and fixing device according to the present invention is configured to detect the surface temperature of the heating roller at regular intervals by the fixing temperature detecting means, and detect the temperature detected by the fixing temperature detecting means. Based on the result of the comparison between the detected temperature and the previous detected temperature, the counting means counting when the temperature difference is a predetermined amount or more, and the count value by this counting means from the time when the heating control means outputs the on / off control signal to the heater. Is provided with fixing abnormality detecting means for outputting a fixing abnormality occurrence signal.

Then, the set value that causes the fixing abnormality occurrence signal to be output when the count value by the counting means exceeds the surface when the normal temperature control is performed in an environment where the rate of change of the surface temperature of the heating roller is large. By setting so as to match the timing of changing the temperature change, it is possible to detect that the abnormality of the fixing temperature has always occurred at the same timing and at the earliest timing.

As a result, when a fixing error occurs in an environment where the surface temperature change rate of the heating roller is small due to the ambient temperature, etc., it can be detected earlier than before, and damage to the heating roller etc. due to heat accumulation can be detected. I can do less.

[Brief description of drawings]

The drawings show an embodiment of a temperature control device for a heating and fixing device according to the present invention. FIG. 1 is a block diagram, FIG. 2 is a schematic sectional view of the heating and fixing device, and FIG. 3 is a flowchart of the temperature control operation. (1) ... heating roller, (12a) ... heating control means, (F
D) …… Fixing temperature detection means, (CM) …… Counting means, (HT
F) …… Fixing abnormality detection means.

Continuation of front page (56) Reference JP-A-60-217380 (JP, A) JP-A-60-191280 (JP, A) JP-A-60-22168 (JP, A) JP-A-61-156079 (JP , A) JP 60-115977 (JP, A) JP 58-11978 (JP, A) JP 57-171366 (JP, A) JP 55-146467 (JP, A) JP 55-76371 (JP, A) JP-A-57-92363 (JP, A) JP-A-57-144578 (JP, A)

Claims (1)

[Claims] 1. A fixing temperature detecting means for detecting a surface temperature of a heating roller for fixing an unfixed image on a recording sheet, and a heating roller for a heating roller based on a comparison result between a temperature detected by the fixing temperature detecting means and a set temperature. In a temperature control device of a heating and fixing device provided with heating control means for controlling on / off of the operation of a heater, the fixing temperature detection means is configured to detect the surface temperature of the heating roller at regular time intervals, and the fixing temperature detection is performed. The counting means counts when the temperature difference is greater than or equal to a predetermined amount based on the result of comparison between the temperature detected by the means and the previous detected temperature, and the temperature control means outputs the ON / OFF control signal to the heater. A heating and fixing device provided with fixing abnormality detecting means for outputting a fixing abnormality occurrence signal when the count value by the counting means exceeds a set value. Temperature control device.