JPS61248047A - Heat development control device - Google Patents

Abstract

PURPOSE:To improve the responsiveness of a heating temp. to a target value by determining the current value or voltage between terminals of an electrical heating element as a feedback quantity when the specified value of the voltage between terminals of current of said element is detected. CONSTITUTION:The resistance value R increases when the temp. of the electrical heating element 14 exceeds the target value. Then the current value flowing in the element 14 decreases and the absolute values of a supply current signal I and current signal IR corresponding to the resistance value decrease, resulting in an increase in the value of a phase control signal PC. The shortened pulse width of a gate trigger pulse GP, the decreased firing angle of a triac 12, the decreased average voltage between terminals of the element 14 and the decreased current flowing in the element 14 are therefore resulted, by which the temp. of the element 14 is decreased so as to approach the target value. The operation reverse from the above-mentioned operation takes place when the target value of the element 14 decreases down to the target value or below. The temp. of the element 14 is thereby brought near to the target value. The temp. of the element 14 is thus maintained at the target value.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a thermal development control device that is capable of heat-developing a photothermographic material provided with a layered current-carrying heating element at a constant temperature.

[Conventional technology]

In this type of heat-developable photosensitive material, the resistance value of the heat-developable photosensitive material is determined by changes in ambient temperature and the water content, or heat capacity, of the photothermographic material. fluctuates due to changes in For this reason, it is not possible to maintain the photothermographic material at a constant temperature even if a constant voltage is applied to the current-carrying heating element.Therefore, a thermal development control device that performs feedback control so that the resistance value of the current-carrying heating element remains constant has been proposed. It's being served.

One possible way to control this is to use a resistance detector that outputs the feedback amount to detect voltage and current, divide the voltage value by the current value to find the instantaneous resistance value, and smooth it through a low-pass filter. It will be done.

However, since a low-pass filter is used, the response to the target value is poor, and since the value is smoothed through a low-pass filter, it is not possible to accurately detect the resistance value. Since it is divided by the current value, there is a large error, which has the disadvantage that it is not possible to precisely control the resistance value of the energizing heating element to a constant value, that is, the temperature of the photothermographic material to a constant value.

(Problems to be solved by the invention) The present invention can improve responsiveness to target values,
Moreover, it is an object of the present invention to provide a heat development control device capable of accurately controlling the heating temperature of a heat development photosensitive material to a constant value.

[Means for solving problems]

The heat development control device according to the present invention includes a current supply section that supplies an alternating current to a heat development photosensitive material provided with a current-carrying heating element;
a current detection unit that detects the current flowing through the energized heating element; a voltage detection unit that detects the voltage between the terminals of the energized heating element; and a voltage detection unit that detects the current or voltage when it is detected that the voltage or current is a constant value. a resistance detection section that outputs the current value or voltage value, a resistance setting section that outputs the target value of the resistance of the energized heating element, and a resistance detection section that uses the output of the resistance detection section as a feedback amount and the target value from the resistance setting section. and a control section that controls the current supply section so that the resistance value of the energized heating element matches the target value by comparing the resistance value of the energized heating element with the target value.

[Effect]

Since the current-carrying heating element is supplied with an alternating current, the voltage between the terminals of the current-carrying heating element and the current flowing through the current-carrying heating element change over time. However, since the resistance detection section detects the current or voltage when the voltage or current of the energized heating element becomes a constant value, this current value or voltage value and the resistance value of the energized heating element are have a one-to-one correspondence. Therefore, by controlling this current value or voltage value to be constant, the resistance value of the current-carrying heating element, that is, the temperature of the photothermographic material can be kept constant.

〔Example〕

FIG. 1 shows a control circuit diagram of an embodiment of a thermal development control device according to the present invention. A triac 12, a current heating element 14, and a current detection resistor 16 are connected in series to the AC power source 1o. The firing angle of the triac 12 is controlled so that the power supplied to the energized heating element 14 can be controlled.The 0 energized heating element 14 is held at both ends by an electrode roller and a press roller (not shown). There is.

Here, the resistance value of the energizing heating element 14 increases as the energizing heating element 14 is heated and its temperature rises. This temperature is influenced not only by the current value supplied to the current-carrying heating element 14, but also by the ambient temperature and the water content contained in the photothermographic material. However, the resistance value of the energizing heating element 14 and the heating temperature of the photothermographic material correspond to 1 to 1, and by controlling the resistance value of the energizing heating element 14 to be kept constant, the heating temperature of the photothermographic material can be adjusted. can be kept constant.

A supply voltage signal V is taken out from the connection point between the triac 12 and the energized heating element 14 and is supplied to the comparator 18. Further, the comparator 18 is supplied with a set DC voltage Ev from a voltage setting device 20. The comparator 18 is activated when the supply voltage signal V is larger than the set DC voltage Ev (see Fig. 2).
The down edge detection circuit 22 detects the falling edge of the pulse of the constant voltage detection signal Cv. and supplies the sample-and-hold signal SH to the sample-and-hold circuit 24 (see FIG. 2(C)).
When the voltage between the terminals of the sample-and-hold circuit 24 reaches the set DC voltage Ew, the sample-and-hold signal SH is supplied from the down edge detection circuit 22 to the sample-and-hold circuit 24.

The resistance value R1 of the current detection resistor 16 is a constant value, and by detecting the voltage between the terminals of the current detection resistor 16, the current flowing through the energizing heating element 14 can be detected. A supply current signal (2) is taken out from the connection point between the current detection resistor 16 and the AC power supply lO and is supplied to the sample and hold circuit 24. The sample and hold circuit 24 receives the sample and hold signal S from the down edge detection circuit 22.
When receiving H, the value of the supply current signal ■ is held and one current signal corresponding to the resistance value is supplied to the adder 26 (see Fig. 2 (D)). The corresponding current signal II is the current value flowing through the energizing heating element 14 when the voltage between the terminals of the energizing heating element 14 reaches the set DC voltage Ev, and corresponds to the resistance value R of the energizing heating element 14 in a 1:1 ratio. (R-Ev/I*) - The adder 26 is also supplied with a set DC voltage E from the voltage setter 20. The adder 26 receives the set DC voltage E,
and the phase control signal pc which is the sum of the resistance value corresponding current signal 11
is supplied to the comparator 30 of the firing angle control circuit 28 (see FIG. 2(F)).

In other words, the current signal corresponding to the resistance value is the set DC voltage Es
The signal is biased by and supplied to the comparator 30. The set DC voltage Ep is supplied from the voltage setting device 20 to the firing angle control circuit 2.
8 integrators 32. Further, the integrator 32 is supplied with a reset signal R3 from a zero-cross detection circuit 34 connected in parallel to the AC power supply 10 (see FIG.
(Refer to E)), the integrator 32 integrates the signal of the set DC voltage EP, and supplies the comparator 30 with a sawtooth signal SW which is a reset signal when the reset signal R3 is received. (See FIG. 2 (F)), the comparator 30 supplies the gate trigger varis GP to the gate G of the triac 12 when the value of the sawtooth signal SW becomes larger than the value of the phase control signal PC. There is. (Second
(See figure (G)).

Next, the operation of this embodiment configured as described above will be explained.

When the energizing heating element 14 is heated by Joule heat and the temperature of the energizing heating element 14 becomes higher than the target value, the resistance value R increases and the value of the current flowing through the energizing heating element 14 becomes smaller, so that the supply current signal ■, The absolute value of the current signal corresponding to the resistance value becomes smaller, and the value of the phase control signal PC becomes larger. Therefore, the pulse width of the gate trigger Paris CP becomes shorter,
The firing angle of the triac 12 becomes smaller and the energizing heating element 1
4 becomes smaller, the current flowing through the energized heating element 14 becomes smaller, and the temperature of the energized heating element 14 decreases and approaches the target value. 0 If the temperature of the energized heating element 14 falls below the target value, , an operation opposite to the above is performed, and the temperature of the energized heating element 14 attempts to approach the target value. In this way, the temperature of the energized heating element 14 is maintained at the target value.

In this embodiment, unlike the conventional example, a division circuit for dividing the supply voltage signal V by the supply current signal ■ is not provided. A low-pass filter for smoothing is not used, and the current value flowing through the energizing heating element 14 corresponding to the resistance value R of the energizing heating element 14 is detected, so the temperature of the energizing heating element 14 is set as the target. It can be precisely controlled to get close to the value. Furthermore, since no low-pass filter is used, responsiveness to the target value is improved.

In addition, a comparator 18, a voltage setting device 20, an adder 26, a comparator 30. The integrator 32 may be configured with a digital circuit. In this case, the accuracy of temperature control is further improved and the target value can be easily changed. Further, the blocks 18 to 30 may be configured by one microcomputer.Furthermore, contrary to this embodiment, the supply voltage signal V is supplied to the sample and hold circuit 24,
The supply current signal may also be supplied to the comparator 18.

〔Effect of the invention〕

In the heat development control device according to the present invention, the voltage between the terminals of the energized heating element or the current value flowing through the energized heating element or the voltage between the terminals of the energized heating element when it is detected that the current flowing through the energized heating element is a constant value. is detected and used as the feedback amount, which has the excellent effect of improving the responsiveness to the target value of the heating temperature of the energized heating element, and improving the accuracy of control to bring the temperature of the energized heating element closer to the target value. has.

[Brief explanation of drawings]

FIG. 1 is a control circuit diagram showing an embodiment of a thermal development control apparatus according to the present invention, and FIGS. 2(A) to 2(G) are waveform diagrams for explaining FIG. 1. 14... Current heating element, 16... Current detection resistor.

Claims (1)

[Claims] a current supply section that supplies an alternating current to a heat-developable photosensitive material provided with an energized heating element; a current detection section that detects the current flowing through the energized heating element; and a voltage detection section that detects the voltage between the terminals of the energized heating element. , a resistance detection unit that detects the current or voltage and outputs the current value or voltage value when it is detected that the voltage or current is a constant value, and a resistor that outputs a target value of the resistance of the energized heating element. a control unit that uses the output of the setting unit and the resistance detection unit as a feedback amount and compares this with a target value from the resistance setting unit to control the current supply unit so that the resistance value of the energized heating element matches the target value; A heat development control device comprising: