JPS6143820B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heating control device that ensures optimal heating results.

For example, when heating is performed using an electric heating element, such as when toner is heated and fixed in an electrostatic copying machine, the heating is controlled by controlling the power supplied to the heating element. This power supply can be controlled by changing the power supply voltage using a slider, for example.
Alternatively, it may be carried out by switching and controlling the current supplied to the heating element using a semiconductor current control element. Heating control using these sliders and semiconductor current control elements generally does not provide very high accuracy, but conventional methods have been used to improve control precision and accuracy by performing feedback control in a so-called closed loop. It is being carried out a lot. According to this feedback control, the electrical heating element is the control object, the power control means such as the slider or the semiconductor current control element is used as the control element, and a temperature detection means, that is, a feedback element is provided therein, so that fluctuations in the power supply voltage can be controlled. It is possible to perform precise constant temperature heating that faithfully follows the set value (target value) by canceling out disturbances such as changes in temperature and environmental temperature.

However, when closed-loop feedback control as described above is not sufficient,
Or it may not be appropriate. For example, when heat-fixing toner in the electrostatic copying machine described above, an electric heating element such as a resistance wire is used, but the temperature of this heating element is controlled by feedback control as described above. Appropriate heat fixing cannot be achieved simply by keeping the temperature constant. This means that the conditions for the best heat fixing are not uniquely required; for example,
In addition to the environmental temperature, there are complex changes due to humidity, paper quality, etc., and the ultimate goal of control is not the temperature of the heating element itself, but to obtain the best fixing result. This is because it is extremely difficult to quantitatively detect and provide feedback. Furthermore, in this type of system, there are special circumstances in which transmission delays occurring in the feedback system cannot be tolerated. For example, in the heat fixing of the copying machine mentioned above, even if the heating result deviates from the target value and can be compensated for by feedback control, the compensation can only be made from the subsequent heat fixing, and the heating result deviates from the target value. Even the fused portion cannot be compensated for, and in this case, it is not possible to expect the best copying results that are free of defects even in parts.

As mentioned above, when performing heating control,
There are cases where so-called normal closed-loop feedback control is not applicable or is extremely difficult or disadvantageous. In such cases, it may be necessary to perform so-called normal closed-loop heating control instead of closed-loop feedback control as described above.
There are also cases where it is more advantageous. For example, in the above-mentioned copying machine, the power supplied to the heating element is unidirectionally controlled according to past experience data determined individually based on differences in ambient temperature, humidity, paper quality, etc. However, you can get better results, and it is more reliable and easier.

This open-loop heating control method is a very reliable and simple method if the empirical data that is the basis thereof is obtained accurately and precisely in advance. However, in this case, the control of the supplied power is
It must be done faithfully in accordance with the above data, otherwise the results when the data were determined will not be faithfully reproduced and the desired heating result will not be obtained. For example, in the case of the above-mentioned copying machine, the finishing of copies is no longer uniform. In this respect, the conventional method of controlling power to a heating element using a slider or a semiconductor current control element has no particular problem as long as it is applied to the control element of a closed-loop feedback control system. This method is extremely inadequate in terms of reliability and accuracy of settings when applied to places where it is not possible or not possible to use it.

The present invention has been made based on the above background, and its purpose is to provide reliable and accurate feedback control with a simple configuration, even if closed-loop feedback control is not possible or is not possible. It is an object of the present invention to provide a heating control device that allows the best heating results to be obtained at all times.

Bidirectional current control means for controlling the energizing current supplied from the AC power supply to the electric heating element; Environmental condition detection means for detecting the environmental conditions of the electric heating element; Correlation between the environmental conditions of the electric heating element and the amount of energization. a target energization amount calculation means for calculating a target energization amount within a predetermined energization cycle from the empirical data using the detected environmental conditions of the current heating element; continuous energization period setting means for setting the continuous energization period of the electric heating element in units of cycles according to the target energization amount; and bidirectional current control means for continuously controlling conduction over the continuous energization period in each energization cycle. An energization control means is used as a device component, and an embodiment thereof will be described in detail below with reference to the drawings.

FIG. 1 shows the configuration of the heating control section of the heat fixing section of an electrostatic copying machine in which the present invention is implemented. A resistance heating element 1 such as a resistance wire is used, and a commercial An alternating current power source (AC 100 V or 200 V) 2 is used, and this power source 2 is supplied to the heating element 1 through a triax 3, which is a semiconductor bidirectional current control element.
The heat emitted from the heating element 1 also heats and fixes the toner transferred to the copy paper, and the heating control is performed by the controller 4.
This is done based on data written in a ROM (Read Only Memory) 5.

The control device 4 consists of the above-mentioned ROM 5, CPU (central processing unit) 6, and I/O (input/output circuit) 7, and its configuration is extremely simple and compact using one or more LSIs (integrated circuits). being done. The input devices of this control device 4 include a zero voltage detection circuit 8, a voltage detection circuit 9, and a temperature detection circuit 1.
0, a humidity detection circuit 11, etc. are connected thereto. Furthermore, the gate trigger circuit 12 of the above-mentioned triax 3 is connected as its output device. The zero voltage detection circuit 8 detects the timing when the instantaneous voltage of the AC power source 2 passes through a zero value, and is configured to issue a zero detection signal to the AC power source 2 every half cycle. . The voltage detection circuit 9 is for detecting the output voltage of the power supply 2, and fluctuations in the power supply voltage (average voltage) are detected here. The temperature detection circuit 10 is for detecting the environmental (inside the copying machine) temperature using a temperature sensor 10' such as a thermistor, and the humidity detection circuit 11 is for detecting the environmental humidity. These detection circuits 8, 9, 10,
Each detection signal from 11 is input to the control device 4 in the form of digital data. In particular, each detection data from the voltage detection circuit 9, temperature detection circuit 10, and humidity detection circuit 11 is introduced into the address data input side of the ROM 5 via the I/O and the CPU 6. . Thereby, ROM
From 5 onwards, write data corresponding to each detection data can be read.

FIG. 2 shows an example of the write pattern of the ROM 5, and the data column 13 contains data indicating the ratio (%) corresponding to the power supply voltage Vx, temperature Tx, and humidity Hx. Many are written. As described above, the ROM 5 is addressed by each detection data from the voltage detection circuit 9, temperature detection circuit 10, and humidity detection circuit 11, and the data is transferred to the CPU at the specified location.
6. For example, when the CPU 6 determines that the humidity Hx detected by the humidity detection circuit 11 belongs to the representative value H1 shown in the pattern of FIG. detection temperature
Hx is connected to T1, the detection voltage from the voltage detection circuit 9 above
When it is determined that Vx belongs to V1, “100
%” is selected and read. Similarly, Hx=H1, Tx=T2, Vx=
At V1, data indicating "95%" is selected,
Also, when Hx=H1, Tx=T3, Vx=V1, "90
%" is selected and read.

FIG. 3 shows the program configuration of the control device 4. In routines R1, R2, and R3,
Each detection value of the above-mentioned detection circuits 9, 10, and 11
Vx, Tx, Hx are the above typical values (V1~V4, T1, T4,
H1 to H4).
Then, in the next routine R4, the output pattern is selected based on the above judgment result.
The address of the ROM 5 is specified and the corresponding data (%) is selected. In this way, when the data (%) corresponding to various conditions such as voltage Vx, temperature Tx, and humidity Hx are selected, the next routine R
5, based on the selected data (%)
Creating an ON-OFF constant and presetting it into a compare register is done. Its ON-
The OFF constant is the conduction period of the triax 3 interposed between the heating element 1 and the AC power supply 2.
The length of Ton and the length of cutoff period Toff, that is, the duty ratio, are determined as simple integer ratios.
An ON constant Kon that determines the length of the conduction period Ton and an OFF constant Koff that determines the length of the cutoff period Toff are created and preset in the comparison registers Ron and Roff, respectively. Then, in the next routine R6, it is determined whether or not a zero detection signal is generated from the zero voltage detection circuit 8.
If there is no zero detection signal here, the above routine R1
-R5 are repeated, but when a zero detection signal is issued, that is, when a node of the voltage waveform of the AC power source 2 is reached, routine R7 is executed. As shown in detail in FIG. 4, this routine R7 is programmed to be executed by a kind of interrupt caused by the zero detection signal, and when the zero detection signal is first generated, routine R7 is executed. , add 1 to the contents of the interrupt counter IC. Then, in the next routine R72, it is determined whether or not the next section OFF command plug F1, which will be described later, is set. If this flag F1 is not set, routine R73 is executed,
Here, it is determined whether the contents of the interrupt counter IC have reached the ON constant Kon preset in the comparison register Ron. Here, the counter IC
If the content has not reached the preset content, in the next routine R74, a command is issued to drive (ON) the gate trigger circuit 12, and the triax 3 is made conductive from the next node of the AC power waveform. Do it like this. However, when the contents of the interrupt counter IC reach the preset contents (Kon), routines R75 and R76 are executed.
The above next section OFF designation flag F1 is set,
Further, after the contents of the interrupt counter IC are cleared to zero, the routine R74 is executed. On the other hand, if a YES determination is made in the routine R72, that is, the next section OFF designation flag F1
If Roff is set, routine R78 is executed, where the contents of the interrupt counter IC are set to the OFF constant preset in the comparison register Roff.
It is determined whether Koff has been reached. Here, if the contents of the counter IC have not reached the preset contents, in the next routine R74, a command is issued to cancel (OFF) the drive of the gate trigger circuit 12, and the above-mentioned try-out is performed at the node of the AC power supply waveform. or shut it off. but,
In this case as well, when the content of the interrupt counter IC reaches the preset content (Koff), routines R80 and R81 are executed, the next section OFF designation flag F1 is reset, and the interrupt counter IC is After the contents are cleared to zero, the routine R79 is executed. As described above, when the zero detection signal is issued, an interrupt is applied and it is determined whether to turn the above-mentioned triack 3 on or off from the next section. Then, routine R77 is executed, the interrupt state is released, and the execution of routine R7 is completed. When the execution of routine R7 is completed, as shown in FIG. 3, the routine returns to routine R1, and routines R1 to R5 are repeated until the next detection signal is issued again.

As described above, first, various factors that affect the finishing result of heat fixing in an electrostatic copying machine, that is, in this case, the power supply voltage Vx of the heating element 1, the environmental temperature Tx, and the environmental humidity Hx are detected. They are detected by circuits 9, 10, and 11, and the ROM 5 is addressed using these detection results to select the corresponding write data, and a simple integer ratio is calculated according to the selected data. ON and OFF constants are created. Then, the above-mentioned TRIAT 3 is continuously conducted for a number of sections Ton corresponding to the above-mentioned ON constant Ton, and the above-mentioned OFF
Continuous interruption of a number of sections Toff corresponding to the constant Toff is alternately repeated. Figures 5a to 5f show this state.
With respect to the AC power supply radio waveform as shown in FIG. 2, a zero detection signal Po is generated every half cycle t as shown in FIG. Then, as shown in c to f of the same figure, the above ON
Power is supplied to the heating element 1 in a manner that the power is controlled in accordance with the constant Kon and the OFF constant Koff, with the power being controlled every five cycles of the alternating current waveform. For example, as shown in FIG. 5C, the data selected from the ROM 5 is 70.
This is the control waveform when showing %, which was created by Kokiki.
The ratio of the ON constant Kon to the OFF constant Koff is 7:3. Also, Figure d shows the case where the above selection data is 80%, and the created ON constant Kon and
The ratio with the OFF constant Koff is 4:1. Similarly, e in the same figure shows that the selected data is 90% and the ON constant is
The ratio between Kon and the OFF constant Koff is 9:1, and f in the figure shows a case where the selected data is 100%, and the ratio between the two is 10:0. In this way, heating control is performed by controlling the power supplied to the heating element 1. At this time, the setting and control of the supplied power is performed using the half-cycle interval t of the power supply waveform as the minimum unit. Since the number of intervals t is counted digitally, the relationship between the quantitative value and the controlled variable is extremely stable, and as a result, heating control can be performed without relying on closed-loop feedback control. , very reliably and accurately, and complex control elements such as differential elements, integral elements, etc. can be carried out very simply and without intervention. For this reason, the ROM
As long as the empirical data written in advance in Section 5 is accurately determined, the situation corresponding to the precise data will be faithfully reproduced, and the best heating result, that is, in the case of this example, will be achieved. It is possible to reproduce the copy finish.

As explained above, according to the present invention, empirical data showing the correlation between the environmental conditions of the electric heating element 1 and the amount of energization is prepared in advance, and a target is determined from the empirical data using the detected environmental conditions of the electric heating element. By determining the amount of energization, control disturbances are absorbed, and furthermore,
Control accuracy is improved by controlling the energization of the electric heating element in units of half cycles of the energizing AC power supply according to this target energization amount, so that the same heating results of the electric heating element as when empirical data were obtained can be obtained. It becomes possible to reproduce the image faithfully and accurately.

As a result, in the case of a copying machine, the best possible copy is obtained with a uniform finish.

Further, according to the present invention, it is not necessary to control the energization of the electric heating element by feedback control, and in that case, this energization control becomes unilateral, so that the electric heating element is controlled to produce good heating results from the start of the control. It is possible to heat the body.

As a result, in the case of a copying machine, it becomes possible to obtain the best copying results from the original portion, which cannot be guaranteed by feedback control, and therefore the performance and marketability of the copying machine are significantly improved.

Further, according to the present invention, the best heating result of the electric heating element can be obtained even if the control is performed directly without intervening complicated control elements such as differential elements and integral elements in the energization control of the electric heating element. Therefore, it is possible to construct a high-performance device at low cost by simplifying the configuration.

According to the present invention, simple energization control of the electric heating element is performed in which continuous energization and continuous cessation of energization are repeated, thereby making it possible to further simplify the configuration of the device.

As a result, the marketability of copying machines, which are subject to intense competition in terms of performance and price, can be significantly improved.

Further, according to the present invention, since the configuration can be simplified, it is possible to improve the reliability and durability of the device.

As a result, it is possible to provide a copying machine that has extremely few failures, is robust, and is easy to maintain and manage.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a heating control device in which the present invention is implemented, FIG. 2 is a diagram showing an example of a ROM write pattern, and FIG. 3 is a flowchart showing the program configuration of the device. FIG. 4 is a flowchart showing a part of the above flowchart in detail, and FIGS. 5a, b, c, d, e, and f are waveform charts showing examples of the operation of the above device. 1... Heating element, 2... AC power supply, 3... Triack, 4... Control device, 5... ROM, 6...
CPU, 7...I/O, 8...Zero voltage detection circuit,
9... Voltage detection circuit, 10... Temperature detection circuit, 1
1...Humidity detection circuit.

Claims (1)

[Scope of Claims] 1. Bidirectional current control means for controlling the current supplied from the AC power supply to the electric heating element; environmental condition detection means for detecting environmental conditions of the electric heating element; and environment of the electric heating element. A target energization amount calculation that calculates a target energization amount within a predetermined energization cycle from the empirical data using an empirical data setting means in which empirical data indicating a correlation between conditions and energization amount is set in advance, and the detection environmental conditions of the current heating element. means, continuous energization period setting means for setting the continuous energization period of the electric heating element in units of half cycles of the AC power supply according to the target energization amount; and bidirectional current control means for setting the continuous energization period in each energization cycle over the continuous energization period. A heating control device comprising: energization control means for continuously controlling conduction;