JPS5811620B2 - heatable device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heating device for heat-treating an object to be heated.

A visible image can be obtained by heating a heat-developable film such as a bubble photographic film or a dry silver film to about 125° C. after exposure.

When this heat-developable film (or sheet) is in the form of a long tape, the exposed heat-developable film is brought into contact with a rotating heating drum while running, and developed by heating it to approximately 125°C. When the speed is high, the amount of heat removed by the film increases in proportion to the speed,
Therefore, it is necessary to increase the heat capacity of the heating dome accordingly.

This heating drum is generally heated by a preheating heater and a temperature control heater, and the capacity is set so that the temperature of the heating drum does not rise to the specified developing temperature with only the preheating heater, and the temperature control heater is set to a thermostat. The heating drum is kept at a predetermined temperature by controlling on/off depending on the temperature detected by a temperature detection element such as a switch.

Figure 2 shows a conventional temperature control circuit.
2 is a heater that heats the heating drum, TS is a thermoswitch that controls on/off the heater H2, and D is a power supply.

The preheating heater H1 is connected so as to be constantly energized, and therefore the capacity of the heater H1 must be set to such an extent that the surface temperature of the heating drum does not rise above a predetermined temperature by itself.

Now suppose that the heating drum is heated to a predetermined temperature of 125°C, and the capacity of the preheating heater H
It is set to 150W in order to satisfy the condition that the power is not exceeded.

Further, when the capacity of the heater required to heat the heating drum to a predetermined temperature when the film is fed at high speed is 1000W, the capacity of the control heater H2 is 850W.

First, when the power switch is turned on, power is started to be supplied to the heating drum, and the film feed speed is set to zero (stopped state), the heating drum is heated by preheating heater H1 at room temperature.
, the control heater H2 is heated by a total of iooow.

If the thermo switch TS is set so that the heater H2 is turned off when the surface temperature of the heating drum reaches a predetermined temperature of 125°C, the thermoswitch TS will be turned off when the surface temperature reaches 125°C, and the control heater will be turned off. Power is no longer supplied to H2, and from then on, the heating drum is heated only by the preheater H1.

Next, when the surface temperature of the heating drum falls below 125°C, the thermo switch TS is turned on again and power is supplied to the control heater H2, and when the surface temperature reaches 125°C, power is no longer supplied again. Repeat the cycle.

Also, when the film is running, the temperature is controlled by repeating the same on and off cycles.

FIG. 4 shows how the surface temperature of the heating drum changes at this time.

When the heating drum, which is at the same temperature as room temperature in FIG. 4, is heated, the temperature of the heating drum changes as shown by the solid line in FIG.

The temperature of the heating drum is a predetermined temperature θ.

(125° C.), the thermostatic switch TS is turned off, power is no longer supplied to the control heater H2, and power is supplied only to the preheating heater H1.

This type of heating method causes a delay in heat transfer.

Actually, after the heater H2 is turned off, the surface temperature of the drum rises above a predetermined temperature, and after a period of time, the surface temperature decreases to a temperature θ.

, the thermo switch TS is turned on and power is supplied to the control heater H2, but as above, the temperature decreases for a certain amount of time, and after that time the temperature rises again, and the temperature θ
.

When this happens, the thermoswitch TS is turned off, and the same cycle as above is repeated.

The variation range of the drum surface temperature due to such control of energization/de-energization of the heater is expressed by the following equation.

α=θP (1-e-〒) Here, θP is the difference between the control amount θ that would be balanced if the thermoswitch TS remained in the on state, and the control amount θ2 that would be balanced if the thermoswitch TS remained in the off state.

L is the aforementioned delay time, and T is a time constant.

The time delay is the wasted time inherent to this control system, and the time constant T
becomes smaller as the capacity of the control heater H2 becomes larger, and becomes larger as the capacity becomes smaller.

In conventional methods, the range of temperature fluctuation on the surface of the heating element is large, making it impossible to heat the object to be heated at a constant rate.

The present invention is intended to reduce the range of temperature fluctuation of the heating element.

The present invention will be explained below using the drawings.

FIG. 1 shows a developing device, in which a heater 2.degree. 3 is embedded in a heating drum 1 for development made of a cylindrical body made of aluminum.

This developing drum has a radial bearing 6 and a thrust bearing 7 so as to freely rotate around a rotating shaft 5.
is maintained.

A slip ring holding member 18 made of an insulating material is arranged below the heating drum 1, and a slip ring 1112 for supplying electric power to the heating drum is provided on the slip ring holding part 18.

An electrode carbon brush 14 is disposed on the heating drum 1 facing the slip ring member 18, and this carbon brush 14 is held by a brush holder 15 made of an insulating material, and is arranged vertically along the brush holder 15. It is possible to move to.

Further, a brush holder cap 16 made of a conductive material is provided on the top of the brush holder 15, and the cap 16 is always in contact with the carbon brush 14.

The carbon brush 14 is always pressed against the spring 11.12 with a constant pressure by the compression spring 17.

Further, a lead wire 13 connected to a power source is connected to the springs 11 and 12, and the heaters 2 and 3 are connected to the spring 1.
Electric power is supplied from a power source via 1, 12, a carbon brush 14, and a cap 16.

In addition, thermoswitches 9 and 9', for example, are embedded in the heating drum as temperature detection means, and the surface (outer periphery) of the heating drum is turned on and off according to the temperature detected by these thermoswitches. ) is controlled to a predetermined temperature.

Further, when changing the set temperature on the surface of the heating drum, the set temperature can be changed by adjusting the rethermo switches 9, 9' through the hole 10 made in the lid 8 provided at the top of the heating drum 1.

When the outer peripheral surface of the heating drum 1 reaches a predetermined temperature, the film 4 is brought into contact with the heating drum 1 to heat the film,
Forms a visible image on the film.

FIG. 3 shows the temperature control circuit of the above-mentioned apparatus. One thermoswitch 9 is set to turn off when it detects a temperature lower than the predetermined temperature of 125° C. required to properly develop the film. The other thermoswitch 9' is set to turn off when a predetermined temperature of 125° C. is detected.

FIG. 5 shows how the surface temperature of the heating drum changes as controlled by this control circuit.

When the heating drum 1 at room temperature is heated by the heaters 2 and 3, the temperature rise until the drum 1 reaches the predetermined temperature θ2 (125° C.) is the same as that shown in FIG.

Then, the thermo switch 9 is turned off at the set temperature θ2,
Power is no longer supplied to the heater 2.

After this, heating is performed by the heater 3 to a predetermined temperature θ.

When this happens, the thermo switch 9' is turned off and power is no longer supplied to the heater 3.

However, as described above, the drum surface temperature rises for a certain period of time, then the temperature decreases, and the temperature of the heating drum reaches θ again.

When this happens, the thermo switch 9' is turned on and the heater 3 is energized, but in this case as well, the surface temperature decreases for a certain period of time as shown in the figure, and then rises until the temperature reaches θ.

When this happens, the thermoswitch 9' is turned off, and this cycle is repeated thereafter.

In this case, the variation range of the surface temperature due to on/off control is expressed as α=θP(1-e-〒) as described above.

In this case, the control heater 3 is the heater H2 in the case of FIG.
Since the capacitance can be made smaller than the capacitance, the time constant T becomes larger.

Therefore, compared to the conventional temperature control method, in the case of the temperature control method of the present invention, the capacity of the temperature control heater 3 can be made smaller, so each coefficient changes as follows.

θP: smaller than in the conventional case.

T: Larger than in the conventional case.

Therefore, e-〒 becomes larger than before (1-e-〒
) becomes smaller.

The following relationship holds true for the temperature fluctuation range.

α2 (in the case of the present invention) and α1 (in the conventional case) Therefore, the fluctuation width of the surface temperature is smaller in the present invention than in the conventional case.

For example, in Fig. 3, the capacity of preheater 2 is 500W.
, the temperature setting of the thermoswitch 9 is 115°C, the capacity of the control heater 3 is 500W, and the setting temperature of the thermoswitch 9' is 125°C, the heating drum will rise from room temperature to 115°C.
℃ is heated by a 1000W heater, and when the temperature reaches 115℃, the 500W preheating heater 2 is turned off, and the control 500W heater is turned off.
It is heated only by the heater 3, and thereafter it is controlled to a predetermined temperature by turning the control heater 3 on and off.

Therefore, it is clear that the fluctuation range for a predetermined temperature is smaller when the 500 W heater is turned on and off than when the 850 W control heater is turned on and off as in the conventional case shown in FIG.

As described above, the present invention connects temperature detection means to at least two heaters, and sets the set temperature of one temperature detection means lower than the set temperature of the other temperature detection means, thereby increasing the temperature of the surface of the heating body. It is possible to reduce the fluctuation range,
The object to be heated can be subjected to constant heat treatment.

[Brief explanation of drawings]

Fig. 1 is a sectional view of a developing device to which the present invention is applied, Fig. 2 is a conventional temperature control circuit diagram, Fig. 3 is a temperature control circuit diagram of the present invention, and Figs. 4 and 5 are the surface of the heating drum. Each figure shows a state of temperature change. 1... Heating drum, 2, 3... Heater, 9, 9'... Thermo switch.

Claims (1)

[Claims] 1. It has at least two heaters for heating a heating element that heat-processes an object to be heated, and a temperature detection means for controlling each heater, and heating is performed by controlling each heater at a different temperature by the temperature detection means. A heating device characterized by reducing the range of body temperature fluctuations.