JPH0212412A - Method for detecting intra-machine temperature state of temperature controller - Google Patents

Abstract

PURPOSE:To precisely control the temperature by counting the turning-on or turning-off width of a preliminarily determined power supply control pulse, which is generated after arrival at a first temperature lower than a control target temperature, in time series and detecting the intra-machine temperature state based on this counted value. CONSTITUTION:A counter 12 which counts the turning-on or turning-off pulse width of the control pulse signal in time series based on a count period, a memory 13 in which comparison data to be compared with the counted value is stored, a comparator 14, and an alarm generating circuit 15 which generates alarm at the tie of abnormality are added to a control circuit 6. The first temperature at an arbitrary point on the way of heating is set by the proportional control or the frequency control, and the pulse width or the frequency of the pulse signal after arrival at the first temperature is measured in time series. Thus, this method copes with the intra-machine temperature variance due to not only the external environmental temperature but also trouble of an exhaust fan, clogging of a filter, degradation of a heating body, or the like.

Description

Detailed Description of the Invention "Field of Industrial Application" The present invention relates to an in-machine temperature state detection method applied to a temperature control device that controls energization of a heating element that imparts thermal energy to a heated object, and in particular, The present invention relates to an in-machine temperature state detection method that can easily detect the in-machine temperature or its relative change, in addition to detecting the presence or absence of environmental conditions, deterioration of heating elements, and other abnormalities that prevent normal temperature rise of heated objects.

"Prior Art and its Problems" Traditionally, heating roller fixing devices have been widely used for fixing unfixed toner images due to their miniaturization and ease of control. In recent years, in order to shorten warm-up time and speed up printing, the heating element used as the heat source of the heating roller is a medium that imparts high thermal energy such as a high-power halogen lamp, and the heating roller is a low heat capacity material such as a thin aluminum roller. Since the configuration uses a heated medium, problems such as overshoot and undershoot inevitably become noticeable. However, especially when the undershoot becomes large, it can lead to poor fixing. Shoots lead to deterioration of the non-adhesive layer, such as silicone rubber, coated on the surface of the heat fixing roller, and in any case, unnecessary overshoots and undershoots must be avoided.

For this reason, the temperature control method of conventional heating roller fixing devices requires
A reference temperature lower than the set fixing temperature is set, and continuous power supply heating is performed until the heating roller reaches the reference temperature by heating the heating element, and after reaching the reference temperature, energization with variable pulse width or pulse frequency is performed. Proportional control (PW) switches to a pulse signal and controls the power supply to the heating element while proportionally reducing the on/off width or frequency of the energization pulse as the heating temperature of the heating roller approaches the fixing temperature.
M) method and frequency i (FM modulation) method have been proposed, but as mentioned above, the heat receiving capacity is small compared to the applied heat energy, so the temperature of the heat fixing roller may vary depending on the internal temperature. The rise time (gradient) varies greatly, and if the gradient is particularly large, a non-negligible overshoot will occur even if the temperature control method described above is employed, making precise temperature control impossible. On the other hand, if the gradient is small, for example, when thick paper is inserted, a non-negligible undershoot will occur, leading to poor fixing.

In order to prevent such drawbacks, at the time of starting fixing, in other words, at the time the power switch is turned on, the environmental temperature is measured using a temperature detection means attached to the heat fixing roller, and it is confirmed that the temperature is within a certain environmental temperature range. Although it is possible to perform a fixing operation after confirming the following, this detection method cannot deal with fluctuations in the external environmental temperature during the fixing operation.

In particular, the temperature inside the machine includes not only the external environmental temperature that can be detected at the beginning of fusing, but also deterioration and failure of various parts that occur in or around the fuser, specifically exhaust fan failure and filter failure. It can also occur due to failure or deterioration of various parts such as clogging or deterioration of the heating element, and since these can occur or be discovered only after the fixing operation has started, the above-mentioned environment at the time of starting the fixing Nothing can be detected by temperature measurement alone, and as a result, the temperature rise gradient exceeds the normal range and temperature control is performed, making precise temperature control impossible.

Furthermore, in the event of failure or deterioration of the various parts mentioned above, unlike the external environmental temperature, the internal temperature of the machine will rapidly rise or fall over time, and as a result, thermal energy will be applied to the heat fixing roller. Multiple media exist in addition to the heating element, and in the worst case, temperature control may become completely impossible.

In view of the drawbacks of the prior art, the present invention has been developed to provide a solution for cases in which the temperature inside the machine changes abnormally due to deterioration or failure of various parts inside the machine, in addition to when the external environment temperature exceeds the normal range.
The purpose of this invention is to provide an anomaly detection method that can reliably detect this.

Another object of the present invention is to provide a method for detecting the temperature inside the machine that can easily and accurately grasp the temperature inside the machine around the object to be heated or its relative change. It is possible to accurately vary the reference temperature for starting proportional control and frequency control in accordance with the internal temperature of the machine.
It becomes possible to control temperature closely in layers.

"Means for Solving the Problems" The present invention provides a temperature control device for a heating roller fixing device that employs, for example, a proportional control or frequency control method, in which the pulse width or pulse frequency of a pulse signal that controls the energization of a heating element is fixed. Focusing on 1K, which decreases proportionally as it approaches the fixing temperature, in other words, the on/off period of the pulse signal at the first temperature point lower than the fixing temperature is proportional to the temperature gradient that changes by taking into account the temperature inside the machine. It was invented with a focus on increasing and decreasing the temperature.Firstly, in a temperature control device that adopts a proportional control method, a predetermined temperature that occurs after reaching a first temperature lower than the fixing temperature (control target temperature) is used. Or, in a temperature control device that counts the on/off width of a plurality of energization control pulses in a time coefficient manner and adopts a frequency control method, after reaching a first temperature lower than the fixing temperature (control target temperature). By counting the on/off width of one or more energization control pulses occurring within a predetermined time width of the external whether the environmental temperature is above the normal range;
It is also possible to detect abnormal conditions, such as whether the temperature inside the machine is abnormally changing due to deterioration or failure of each type of component inside the machine.

In this case, the first temperature does not refer only to the reference temperature when switching from continuous power supply heating of one heating element to proportional control or frequency control, but can be set arbitrarily as long as it is between the reference temperature and the control target value. I can do it.

That is, the present invention sets the first temperature at an arbitrary point during heating by the proportional control or frequency control, and measures the pulse width or frequency of the pulse signal after the temperature of the first nucleus is reached in a time coefficient manner. Therefore, not only the external environmental temperature that can be detected at the beginning of the fusing operation, but also the failure of the exhaust fan, clogging of the filter, etc. It is also possible to cope with internal temperature fluctuations that occur due to deterioration or the like.

Incidentally, if the on or off period of the pulse signal increases or decreases in proportion to the temperature gradient that changes by taking into account the temperature inside the machine, it is not necessarily captured in terms of time factor as in the present invention.
Similarly to the above, it is also possible to measure abnormalities in the internal temperature by calculating the number of ON or OFF times within a predetermined time range after passing the first temperature.

However, in such a measurement method, if a noise signal having a minute pulse width is generated within the predetermined time width, this will also be counted incorrectly, and accuracy errors are likely to occur.

In contrast, in the present invention, if the clock period for counting is made larger than the pulse width of the noise signal, there will be no line in which the noise signal is erroneously counted, and even if the clock period for counting is made smaller, the pulse width of the noise signal is extremely small compared to the pulse width of the regular energizing pulse, so when these pulse widths are cumulatively counted, the proportion of noise error in the count value is extremely small. The noise can be virtually ignored.

Therefore, the accuracy of the count value can be improved by increasing the number of energizing pulses to be measured (in the case of the frequency control method, by lengthening the predetermined time width and thus increasing the number of energizing pulses). As a result, it is possible to not only detect the above-mentioned abnormal condition, but also accurately grasp the temperature inside the machine or its relative change, and as a result, it is possible to accurately grasp the temperature inside the machine or its relative change. The reference temperature can be varied with high precision, allowing precise temperature control.

It should be noted that the present invention is not limited to a temperature control device for heating rollers, but can be applied to any temperature control device that employs the proportional control method or frequency control method.

"Embodiments" Hereinafter, preferred embodiments of the present invention will be described in detail by way of example with reference to the drawings. However, the dimensions, materials, shapes, and relative arrangements of the components described in this example are not intended to limit the scope of this invention, unless otherwise specified, and are merely examples of explanation. Not too much.

FIG. 1 is a circuit block diagram of a heat fixing device according to an embodiment of the present invention. To briefly explain the circuit configuration, 1 indicates a pressure roller 1b that rotates in synchronization with each other, and a fixing roller that includes a heater 1c. A temperature sensing means 2 is disposed close to the surface of the fixing roller 1a.

As is well known, the temperature detection means a consists of a fixed resistor and a thermistor that divide the reference circuit voltage, and can output the divided voltage output to the pulse width modulation circuit 3 side as a detection voltage corresponding to the surface temperature of the fixing roller 1a. It consists of

4 is a "threshold generation circuit" that sets each reference voltage corresponding to the fixing set temperature Ta and a reference temperature TO lower than the fixing set temperature Ta, and the reference voltage corresponding to the reference temperature TO is determined by the count value described later. It is configured to be correspondingly variable. Reference numeral 5 denotes a clock generation circuit, and the pulse width modulation circuit 3 outputs an energization control pulse having a pulse period corresponding to an integral multiple of the clock period oscillated by this circuit. Therefore, the count period is preferably set to match the clock period or to an integer fraction thereof, so that the ON or OFF width of the energization control pulse corresponds to an integer multiple of the count period, and the ON or OFF width of the energization control pulse corresponds to an integral multiple of the count period. The width can be measured more accurately as a time factor.

Now, as is well known, when the detected temperature S output from the temperature detection means 2 is below the reference temperature TO, the pulse width modulation circuit 3 continuously sends an ON signal to the control circuit B until the detected temperature S output from the temperature detection means 2 reaches the reference temperature TO. After the detected temperature S reaches the reference temperature ↑0, the pulse width is varied in proportion to the difference between the fixing temperature Ta and the detected temperature S, in other words, the fixing temperature T
A control pulse signal whose ON Hals width is proportionally reduced as it approaches a is transmitted to the control circuit 6 side.

The control circuit 6 is composed of a microcomputer, and the O
A heater on/off signal generated based on the N continuous signal and the control pulse signal (hereinafter both signals are referred to as control signals) is output to the solid state relay SSR, and the relay S
The SR performs on/off control of the AC power source that supplies power to the heater lc, and also performs an internal temperature state detection operation, which will be described later, based on predetermined program control.

The control circuit B includes various devices necessary to smoothly achieve the present invention, specifically, the ON or OFF pulse width of the control pulse signal is controlled by the count period (as described above, the count period is within the control circuit 6). Based on the clock of the clock generation circuit 5, the clock period is equal to or an integer of -
is set to . ), a memory 13 and a comparator 14 for storing comparison data for comparison with the count value, and an alarm generation circuit 15 for generating an alarm in the event of an abnormality are attached. has been done. Note that the timer 11 is used in the frequency control method described later.

Next, the operation procedure based on this embodiment will be explained based on the flowchart of FIG. 2 and the time chart of FIG. 3.

First, power supply to the heater 2 is started by turning on a power switch (not shown), and the fixing roller 1a is continuously heated via the heater 1c until the reference temperature reaches ↑0. After reaching the reference temperature with a temperature gradient corresponding to the temperature inside the machine, a predetermined proportional control is started, and the proportional control uses a coefficient that is substantially differentiating the temperature gradient to control the heating temperature of the fixing roller 1a. An energization control pulse whose on width decreases proportionally as the temperature approaches the fixing temperature Ta is oscillated.

As is clear from the flowchart in Fig. 2, the count starts when the first ON signal (rise trigger) generated after reaching the reference temperature is oscillated.
P 1) After that, continue counting until the off signal (falling trigger) is oscillated (STEP 2)
, and after performing such counting multiple times to improve detection accuracy (5TEP3), output the accumulated count value to the comparator 14! 3TEP 4) First, compare the environmental upper limit data stored in the memory 13.
5) If the data exceeds the data, an upper limit abnormality alarm is generated and the fixing operation is interrupted. (STEP 8) If the count value is less than the environmental upper limit data, then output the environmental upper limit data stored in the memory 13 to the comparator 14 (STEP?) and compare it with the data,
If it is less than this data, a lower limit abnormality alarm is generated and the fixing operation is interrupted (STEP 8).

If the count value is equal to or higher than the environmental lower limit data (STEP 9), the count value is sent to the control circuit 8, and the count value is calculated based on the predetermined algorithm stored in the control circuit B. Select the reference temperature (5TEPIO) and vary the reference voltage corresponding to the reference temperature in "Threshold generation circuit" 4 (STEPII)
.

Thereafter, the above-mentioned operation is repeated every time the proportional control of the fixing operation is restarted.

FIGS. 4 and 5 show other embodiments employing the frequency control method, and the detection operation thereof will be briefly explained.

In the case of the frequency control method, the pulse width is constant, and the pulse frequency is a coefficient obtained by substantially differentiating the temperature gradient, and the energization is proportionally reduced as the heating temperature of the fixing roller 1a approaches the fixing temperature Ta. Since the control pulse is to be oscillated, a predetermined time width is first set by the timer 11, and when the reference temperature is reached, the timer 11 is started (STEP 21). After that, the on-pulse width is generated within the set time of the timer 11. On signal (rising trigger)
Each time oscillates (5TEP22), the comparator 1 calculates the count value accumulated and counted (5TEP24) until time-up (5TEP23).
4) and perform the same operation as above.

In the case of the frequency control method, the number of pulses within the time set by the timer 11 may be counted by a coefficient, but in this case, noise signals are also erroneously detected, resulting in a lack of accuracy.

"Effect" According to this invention, since the change in temperature gradient during the fixing operation is captured as a time variable of the on/off width (period) of the energization control pulse, the external It is possible to deal with not only the environmental temperature, but also fluctuations in the internal temperature of the machine due to deterioration or failure of the heating roller itself or various parts around it, which may occur or be discovered only after the start of the fixing operation. In order to easily and accurately determine that there is an abnormality when the slope exceeds the normal range,
Precise temperature control is the turning point.

Further, according to the present invention, the detection accuracy of the time variable is further improved by increasing the number of energization pulses to be measured.
In addition to detecting the above-mentioned abnormal condition, it is possible to accurately grasp the temperature inside the machine or its relative change, and as a result, the reference temperature for starting proportional control or frequency control can be varied with high precision in response to the detected temperature inside the machine. This allows precise temperature control to be achieved.

Further, according to the present invention, by increasing the number of energization pulses to be measured, noise signals generated during the detection operation are substantially eliminated, and the detection accuracy of the time variable is further improved. In addition to detecting the state, it is possible to accurately grasp the temperature inside the machine or its relative change, and as a result, it is possible to accurately vary the reference temperature for starting proportional control or frequency control in response to the detected temperature inside the machine. - It is possible to precisely control the temperature of each layer.

[Brief explanation of the drawing]

FIG. 1 shows a circuit block diagram of a heat fixing device according to an embodiment of the present invention, FIGS. 2 and 3 show operating procedures when a proportional control method is adopted, and FIG. FIG. 3 is a time chart showing the timing of reading the control signal. 4 and 5 show the operating procedure when the frequency control method is adopted, FIG. 4 is a flowchart, and FIG. 5 is a time chart showing the timing of reading the control signal.

Claims (1)

[Claims] 1) A method for detecting an internal temperature state of a temperature control device that performs temperature control while proportionally reducing the on or off pulse width of a pulse signal that controls energization of a heating element as it approaches a control target temperature. , the on/off width of one or more predetermined energization control pulses that occur after reaching the first temperature lower than the control target temperature is counted in a time coefficient manner, and based on the count value, the in-machine In-machine temperature state detection method characterized by detecting temperature state 2) Temperature control device that performs temperature control while proportionally reducing the frequency of a pulse signal that controls energization of a heating element as it approaches a control target temperature. In the in-machine temperature state detection method, the ON or OFF width of one or more energization control pulses occurring within a predetermined time width after reaching a first temperature lower than the control target temperature is counted in terms of time factor. , A method for detecting the temperature inside the aircraft based on the count value 3) The count value is compared with environmental data corresponding to the upper limit or lower limit temperature in the aircraft, and the temperature inside the aircraft or the change in the temperature inside the aircraft is determined. The method for detecting the cabin temperature state according to claim 1) or 2), characterized in that it is determined whether the temperature exceeds a normal range.