JPH02170388A - Temperature control method of heated object - Google Patents

Abstract

PURPOSE:To have accurate temp. control and enhance the image quality when adopted to an image fixation device by setting a plurality of temp. ranges. CONSTITUTION:Two control temp. ranges A, B are set in which objects to be heated are transferred to different target values while current is supplied under control to a heater on the basis of specific pulse signals. These two ranges A, B are set partially overlapped on each other, wherein the control target value of the temp. range A located on the low temp. side is set to the upper limit value UA of the overlapped zone while the control target value of the temp. range B located on the high temp. side is set to the lower limit value LB of the overlapped zone. This enables precision temp. control when adopted to a fixation roller, etc., and the image quality can be enhanced.

Description

Detailed Description of the Invention "Industrial Application Field" The present invention is applicable to a method of controlling the temperature of a pair of heat fixing rollers used in an electrophotographic device, etc., in which a heated body is brought to a predetermined temperature by heating a heater with full current. The present invention relates to a temperature control method for a heated object, which moves the heated object to a control target temperature and maintains the temperature while controlling the heater based on a predetermined pulse signal after startup.

"Prior Art" Conventionally, for example, in the temperature control method for the pair of heat fixing rollers, a so-called 0N-OFF control method has been used in which temperature control is performed while alternately supplying and de-energizing the heater across the target temperature point of the fixing roller. There is also a so-called proportional control method in which the pulse width or pulse frequency of a pulse signal for controlling heater energization is proportionally changed as it approaches the fixing target temperature based on the temperature information of the fixing roller. Although the start-up speed is fast, the heating temperature gradient is linear, so the overshoot is large, and in the latter case, heating control is performed while maintaining thermal balance based on the pulse width or pulse frequency of the pulse signal. Although it is easy to maintain the temperature at the control target value, it has the disadvantage of slow startup speed.

For this reason, conventional control methods have been adopted that combine the advantages of both methods, in which the heated object is heated to a predetermined temperature by full energization heating of the heater, and then temperature control is performed by proportional control over a predetermined temperature range sandwiching the control target temperature. has been done. (Unexamined Japanese Patent Publication No. 58-42079, etc.) ``Problem to be Solved by the Invention'' This control method maintains a predetermined startup speed by the above-mentioned full energization heating, and maintains thermal balance by proportional control to reach the control target value. Accurate temperature control is possible in order to ensure transfer and maintenance, but as the size of the fuser roller pair has become smaller and thinner in recent years in response to the miniaturization of the entire device, it has become possible to control the temperature of the fuser roller pair itself. The storage heat capacity decreases, and as a result, the control temperature may vary greatly by sensitively detecting a slight deviation in thermal equilibrium, such as a voltage change on the heater side or a change in paper thickness on the heat removal side.

Furthermore, as printing speeds have increased in recent years, the amount of heat absorbed per hour has inevitably increased, and the amount of heat supplied has also increased correspondingly. The fact that the accumulated heat capacity of the fixing roller pair itself, which acts as a cushion to maintain thermal balance, is decreasing means that the fluctuation range of the control temperature becomes larger, and this fluctuation can cause fixing defects and greatly affect image quality. It has become.

"Means for Solving the Problems" In view of the above technical problems, the present invention solves various problems caused by a relative decrease in the storage heat capacity of the fixing roller pair itself by setting a plurality of temperature ranges. The first object of the present invention is to provide a temperature control method for a pair of fixing rollers that solves the problems and improves image quality while enabling accurate temperature control. However, the present invention is not limited to this. The purpose of the present invention is to provide a temperature control method that can be applied to all heated devices in which the temperature is controlled by heating with a heater.

The features of the present invention are, as shown in FIG. The point where A and B are set; The point where the two control temperature ranges A and B are set by partially overlapping each other; The control target value of temperature range A located on the low temperature side is set as above. The point where the upper limit value DA of the polymerizing temperature range is set, and the control target value of the temperature area B located on the high temperature side is set to the lower limit value LH of the polymerizing temperature range (preferably, the A point at which power supply to the heater is stopped when the temperature of the object to be heated shifts to the temperature range C where polymerization occurs.

(2) Preferably, the two control temperature ranges A and B are set to a higher temperature range than the full current heating range of the heater.

The temperature control method for the control temperature ranges A and H includes proportionally changing the pulse width or pulse frequency of the pulse signal for controlling the heater energization as it approaches the fixing target temperature.
A known proportional control method may be used, and the heater energization control may be performed based on a pulse signal having a pulse width set in order to maintain each of the control target values UA and LB. A fixed pulse control method may also be used.

"Effect" For example, a virtual reference value C between the upper limit value DA and lower limit value LH
When L is set, even if the actual temperature of the heated object is located in any of the control temperature ranges, the control target values DA and LB will exist at a temperature point exceeding the virtual reference value OL. In order to achieve this, when moving the heated object in the direction of the control target value while controlling the energization of the heater based on a predetermined pulse signal,
``The heated object reaches the virtual reference value CL while always leaving a rising (lowering) surplus by the amount of virtual reference value CL to upper limit (lower limit) value DA, LB J.

Therefore, even when a heated object with a small accumulated heat capacity is used, in addition to the accumulated heat capacity, a heat capacity corresponding to r virtual reference value CL ~ upper limit (lower limit) value DA, LB J is added. The substantial storage heat capacity increases, and even if there is a voltage change on the heater side or a paper thickness change on the heat removal side, it is possible to prevent the control temperature from changing greatly.

Also, if the control target values υA and LB are set at a point that exceeds the virtual reference value CL in this way, an overshoot (undershoot) will occur at the upper limit (lower limit) value corresponding to the control target value.
If this occurs, the temperature of the object to be heated will rise (fall) to such an extent that durability will immediately deteriorate and fixing failure will occur.

Therefore, the present invention eliminates the above-mentioned drawback by stopping the energization of the heater before the temperature of the heated object reaches the control target value, specifically when it moves to the temperature range C where polymerization occurs. I'm trying.

``Example'' A preferred embodiment of the present invention will be described in detail below by way of example with reference to one drawing. However, the dimensions, materials, shapes, relative positions, etc. of the components described in this example are unless otherwise specified.

This is not intended to limit the scope of the invention, but is merely an illustrative example.

FIG. 2 is a schematic block diagram showing the circuit configuration of a heat fixing device according to an embodiment of the present invention. To briefly explain the configuration, l includes a pressure roller 1b that rotates in synchronization with each other and a heater IC. The heating fixing device includes a fixing roller, and a temperature detecting means 2 is disposed close to the surface of the fixing roller.

The temperature detection means 2 consists of a fixed resistor (not shown) that divides the reference circuit voltage, and sends the divided voltage output to the signal generation circuit 5 and the comparators 3A to 3C as a detection voltage corresponding to the surface temperature of the fixing roller. It is configured to enable output.

Reference numeral 4 denotes a reference voltage generation circuit which determines the upper limit temperature UD of the entire current-carrying area based on the read signal from the control circuit 6.

And reference voltages corresponding to the upper limit value DA and lower limit value LB corresponding to each control target temperature in the two control temperature regions A and H are output to each of the comparators 3A to 3C and the signal generation circuit 5.

The comparators 3A to 3C compare each of the reference voltages and the detected voltages, and determine whether the surface temperature T of the fixing roller is the L limit temperature U (for example, 195° C.) in the entire energized area, or the control temperature areas A and H.
When the upper limit value DA (e.g. 203°C) and the lower limit value LB (e.g. 200°C) are exceeded, each comparator 3A
The configuration is such that the corresponding signal from ~3C can be transmitted to the signal generation circuit 5 side.

The signal generation circuit 5 includes the comparator 3A as shown in FIG.
a gate circuit 10 that determines in which temperature range A or H the surface temperature exists based on the output signal from ~3C;
A group of signal generators 20A to 200 that generate various signals are built in, and for example, when the surface temperature of the fixing roller is equal to or lower than the upper limit temperature tln of the entire energized area, any of the comparators 3
Since no output signal is transmitted from A to 3C, a signal is output from the NOAH game) 10 [), and a full energization request signal is transmitted to the control circuit 6 side via the signal generator 200.

The surface temperature becomes the upper limit temperature 00 or more.

If the temperature changes to the control temperature range A,
A signal is output from 10A, and a pulse signal is transmitted to the control circuit 6 side via the signal generator group 20A. Note that 10a is an inverter for signal inversion.

When the surface temperature shifts to the polymerization temperature range between the lower limit value LB and the upper limit value [IA, a signal is output from the AND gate 10C and an off signal is transmitted to the control circuit 6 side via the signal generator 20C. .

When the surface temperature exceeds the upper limit value UA and shifts to the second control temperature region B, a signal is output from the AND gate 10B and a pulse signal is transmitted to the control circuit 6 side via the signal generator 20B. Ru.

Further, the signal devices 20A and 20B have a built-in PWM circuit, and each standard corresponding to the detection voltage from the temperature detecting means 2 and the upper limit value DA and lower limit value LB transmitted from the reference voltage generating circuit 54 as necessary. The control pulse signal is configured to be able to output a control pulse signal whose pulse width is modulated in accordance with the temperature difference while comparing the voltage.

Based on various signals from the signal generating circuit 5, the control circuit 6 outputs a heater on/off signal that changes the ratio of power supply/non-power supply to the heater, a continuous power supply signal for the heater, and an OFF signal to the solid state relay SSR. However, the relay SSR is configured to perform on/off control or continuous energization control of the AC power source 8 that supplies power to the heater.

Next, the operating procedure of this embodiment will be explained based on the flowchart of FIG. 4 and the temperature distribution diagram of FIG. 1.

First, after setting the reference voltages A, 08 and Un, the temperature detection means 2 outputs a detection voltage corresponding to the surface temperature of the fixing roller la to the signal generation circuit 5 and the comparators 3 to 3C, respectively.

If the surface temperature is below the upper limit temperature UD of the entire energized area, (STEP 1) the heater 1c is heated while being continuously energized based on the full energization request signal transmitted from the signal generation circuit 5. Then, the surface temperature is immediately raised to the upper limit temperature of 10 or higher in the entire current-carrying area. (At this time, since the heater IC performs full current heating, there will be some overshoot, but this will be ignored for the purpose of explaining the present invention.) Then, the surface temperature reaches the upper limit temperature of 10 or more, and enters the first control temperature range A. If the transition occurs (5TEP2), pulse width control (temperature increase control u4) is performed with the upper limit value DA as the control target value while controlling the heater lc on/off based on the modulated pulse signal from the signal generation circuit 5. .

When the surface temperature changes from the lower limit value LB to the upper limit value tlA due to the pulse width control (STEP 3), the signal generation circuit 5
The heater 1c is turned off based on the signal, and the residual heat of the heater 1c causes the temperature to gradually shift to the upper limit value UA.

If the upper limit value UA is not reached and the temperature drops to the lower limit value LB, and if the temperature returns to the ring 1 control temperature range (STEP 4), the same pulse width control as described above is performed.

When the surface temperature exceeds the upper limit value υA and shifts to the second control temperature range (STEP 5), the signal generation circuit 5 immediately outputs a modulated pulse signal to control the heater 1c.
While on/off controlling the pulse width control (temperature reduction control) with the lower limit value LB as the control target value.

Furthermore, due to the pulse width control, the surface temperature is increased to the upper limit value UA.
~ When the lower limit value LB is reached (STEP13), the heater IC is turned off based on the off signal from the signal generation circuit 5, and the same control as in 5TEP3 is performed.

Incidentally, the temperature control method for the desired control temperature range ^, B is not necessarily limited to the proportional control method described above.

In other words, without modulating the pulse signals outputted from each of the generators 20A and 20B, it is configured to be able to output a pulse signal having a pulse width necessary to maintain the upper limit value DA or the lower limit value LBtl-, and The heater may be configured to be energized based on the pulse signal.

Furthermore, as an application of the present invention, error checking is also possible by measuring the time taken to reach the control target value.

[Effects of the Invention] As described above, according to the present invention, various problems caused by a decrease in the accumulated heat capacity of the heated object can be effectively solved by setting a plurality of temperature ranges, and accurate temperature control can be achieved. 1K that enables control and improves image quality especially when applied to an image fixing device.

It has various effects such as

[Brief explanation of the drawing]

FIG. 2 is a schematic block diagram showing the circuit configuration of a heat fixing device according to an embodiment of the present invention, FIG. 3 is a circuit diagram of its main parts, FIG. 1 is a distribution diagram showing its temperature change state, and FIG. is a flowchart diagram showing the operating procedure.

Claims (1)

[Claims] 1) Two control temperature ranges in which the heated object is moved to separate control target values while controlling the heater's energization based on a predetermined pulse signal, with parts of the temperature ranges overlapping each other. At the same time, the control target value of the temperature region located on the low temperature side is set to the upper limit value of the temperature region where polymerization is occurring, and the control target value of the temperature region located on the high temperature side is set to the upper limit value of the temperature region where polymerization is occurring. 2) A method for controlling the temperature of a heated object, characterized in that the temperature of the object to be heated is set to the lower limit value, respectively. 2) A method of controlling the temperature of the heated object, characterized in that when the temperature of the object to be heated shifts to the temperature range where the polymerization occurs, energization of the heater is stopped. The temperature control method according to claim 1) 3) The temperature control method according to claim 1), characterized in that the two control temperature regions are set on the high temperature region side of the entire energized heating region of the heater. The temperature control according to claim 1, wherein the temperature control method in the control temperature region is a proportional control method in which the pulse width or pulse frequency of the pulse signal for controlling the heater's energization is proportionally changed as it approaches the fixing target temperature. Method 5) A method for controlling the temperature in the control temperature range is a pulse control method in which energization of the heater is controlled based on a pulse signal having one pulse width set in order to maintain each of the control target values. 1) Temperature control method described