JPH057611Y2 - - Google Patents

Description

[Detailed description of the invention] (a) Industrial application field The present invention relates to a temperature control device used in a constant temperature bath for analysis.

(b) Prior art In a constant temperature bath temperature control device, for example, a catalyst is placed in a constant temperature bath and heated by applying an electric current to a heater provided around the constant temperature bath to cause a catalytic reaction.
A temperature sensor is used to adjust the temperature of the thermostatic oven, and a fusible temperature fuse is used to cut off the current supplied to the heater in order to prevent the thermostatic oven from overheating.

Most commercially available fusible temperature fuses of this type are designed to be fused at temperatures below about 250°C. Overheating prevention temperature of constant temperature bath is 250℃
When using the above-mentioned fusible temperature fuse in the following cases, place the temperature fuse in a constant temperature bath, and if the constant temperature overheating prevention temperature is 250℃ or higher, the fusible temperature fuse should be placed in a constant temperature chamber. An appropriate location outside the tank is selected for installation.

A conventional example of such a heater overheating prevention device for a constant temperature oven will be explained with reference to FIGS. 1 to 3.

Figure 1 shows how to prevent overheating in a thermostatic oven when the overheating prevention temperature of the thermostatic oven is 250℃ or lower, for example, by adjusting the temperature of the thermostatic oven at a set temperature of 100℃. An example of a device is shown.

In the figure, 1 is a constant temperature bath, 2 is a heater for heating the constant temperature bath 1, and 3 is a temperature sensor for detecting the temperature of the constant temperature bath ₁ and adjusting the temperature. It is connected to a heater power source which will be described later. This temperature sensor 3 is connected to the set temperature of 100°C so that the constant temperature oven 1 maintains the set temperature of 100°C.
℃, the contacts are controlled to open and close, and the current applied to the heater 2 is controlled. 4 is a fusible temperature fuse for preventing overheating of the constant temperature chamber 1 placed in the constant temperature chamber 1, and is connected between the temperature sensor 3 for temperature adjustment and the heater 2 via the lead L ₂ , as will be explained in FIG. connected to.

Figure 2 shows the overheating of a thermostatic oven when the thermostatic oven's overheating prevention temperature is 250℃ or higher, for example, when the thermostatic oven is adjusted to a set temperature of 300℃, and when the thermostatic chamber's overheating prevention temperature is 350℃ or higher. An example of a prevention device is shown.

Reference symbols 1 to 4, l ₁ , and l ₂ in the figure are the same as those labeled with the same symbols in FIG. 1.

Reference numeral 5 denotes an outer box that surrounds the thermostatic oven 1, and the thermostatic oven 1 is placed inside the outer box 5 via a thermally insulating support stand 6. And the fusible temperature fuse 4 is
An appropriate position outside the thermostatic chamber 1 is selected and placed.

FIG. 3 shows an electric circuit used in the conventional thermostat overheat prevention device shown in FIGS. 1 and 2.

Items with reference numbers 2 to 4 in the same figure are:
They are the same as those given the same reference numerals in FIGS. 1 and 2.

7 is, for example, a 100V AC heater power supply,
A power switch 9 is connected in series with this.
Reference numeral 8 denotes an indicator light that indicates whether or not a heating current is being applied to the heater 2, and this indicator light 8 is connected in parallel to the heater 2. A temperature sensor 3 for temperature adjustment and a fusible temperature fuse 4 for preventing overheating of the thermostatic chamber are connected between the power switch 9 and the heater 2.

Now, assuming that the temperature of the constant temperature bath 1 is lower than the set temperature, the temperature sensor 3 for temperature adjustment is closed. In this state, current from the power source 7 flows through the power switch 9, the temperature sensor 3, and the fusible temperature fuse 4 to the heater 2, heating the constant temperature oven 1. When the temperature of thermostatic chamber 1 reaches the set temperature,
The temperature sensor 3 is opened and the current flowing to the heater 2 is cut off. When the temperature of the constant temperature bath 1 becomes equal to or lower than the set temperature, the temperature sensor 3 is closed again and current is supplied to the heater 2. In this way, by opening and closing the temperature sensor 3, the temperature of the thermostatic oven 1 is maintained at the set temperature.

Next, if the constant temperature bath 1 becomes overheated for some reason, the fusible temperature fuse 4 will melt, and the heater 2
The current supplied to the thermostatic chamber 1 is cut off, and overheating of the thermostatic chamber 1 is prevented.

Now, if we consider the fusible temperature fuse 4 used for the purpose of preventing overheating of the thermostatic chamber shown in FIGS. 1 and 2, in FIG. Therefore, if thermostatic chamber 1 is suitable for overheating prevention temperature,
The fusible temperature fuse 4 accurately detects this and melts it.

In the case shown in FIG. 2, as mentioned above, the overheating prevention temperature of the constant temperature bath 1 is set to the fusible temperature fuse 4.
Since the melting temperature is higher than the rated melting temperature of
The location must be selected so that it will melt when the overheating prevention temperature is reached. however,
It is quite difficult to select an appropriate location. Moreover, even if the fusible temperature fuse 4 is placed at an appropriate position, the temperature fuse 4 is affected by fluctuations in the ambient temperature, so when the ambient temperature rises, the temperature fuse 4 The radiant temperature from the constant temperature bath 1 is added to the increase, and there is an inconvenience that the fusible temperature fuse 4 melts even though the constant temperature bath 1 has not reached the overheating prevention temperature.

Furthermore, in the case shown in FIGS. 1 and 2, if the fusible temperature fuse 4 melts,
I had to work to replace it with a new one,
This had the disadvantage of being accompanied by a loss of time.

(c) Purpose The present invention is intended to eliminate the drawbacks of the prior art described above, and is to dispose a second temperature detection means for detecting the abnormal temperature in a thermostatic chamber, so that it is not affected by fluctuations in ambient temperature. Accurately detects abnormal temperatures in thermostatic chambers,
It is an object of the present invention to provide a temperature control device for a thermostatic oven that can prevent the thermostatic oven from reaching an abnormal temperature state by cutting off the supply of heater current to the thermostatic oven.

(D) Configuration The present invention comprises a constant temperature bath equipped with a heater, a first temperature detection means for temperature adjustment that is disposed in the constant temperature bath and opens and closes at a set temperature, and a temperature detection means for controlling the temperature of the first temperature detection means. a second temperature detection means for abnormal temperature of the constant temperature chamber, which is controlled to open and close at a set temperature different from the set temperature;
A relay contact connected in series with the second temperature detection means, and a relay connected in parallel to a series circuit of the second temperature detection means and the relay contact, the first temperature detection means and the second temperature detection means A temperature control device for a constant temperature oven, characterized in that a temperature detecting means is connected, and a relay contact and a heater are connected, and when current flows through the relay, the relay contact is in an open state. This system reliably detects abnormal temperatures in a thermostatic oven without being affected by ambient temperature, and prevents the thermostatic oven from reaching an abnormal temperature state.

(E) Embodiment FIG. 4 shows an embodiment of the temperature control device for a thermostatic chamber of the present invention, and FIG. 5 shows an electric circuit used in the device.

In FIG. 4, 41 is a constant temperature bath, and a heater 42 is provided around it. Constant temperature bath 41
Inside, there is a temperature sensor 43 that is a bimetal contact type first temperature detection means for temperature adjustment, and a bimetal contact type second temperature detection means for detecting the overheating prevention temperature of the constant temperature oven 41. A temperature sensor 44 is arranged. Temperature sensor 43 is connected via lead _l1 to a power switch 50, illustrated in FIG. 5, and temperature sensor 44 is connected via lead _l2 to a relay contact 47, which is also illustrated in FIG. connected between. Note that the set temperature at which the temperature sensor 43 for temperature adjustment opens is set lower than the operating temperature of the temperature sensor 44, which opens when the constant temperature oven 41 reaches the overheating prevention temperature.

In FIG. 5, 45 is a heater power source of, for example, 100 V AC, and 50 is a power switch.
A temperature sensor 43 for temperature adjustment is connected to this power switch 50. Between points A and B, there is a temperature sensor 44 that detects the overheating prevention temperature of the constant temperature bath 41.
A parallel circuit of the relay 46 and an overheat indicator 48 such as a lamp or buzzer that indicates whether or not the relay 46 is activated is connected in parallel to the series circuit of the relay 46 and the relay contact 47. The temperature sensor 43 for temperature adjustment is connected to a temperature sensor 44 for overheat prevention, and the relay contact 47 is connected to a parallel circuit of the heater 42 and an indicator light 49 that indicates whether or not the heater 42 is operating.

The relay contact 47 is a contact that is closed when no current flows through the relay 46, and opens when current flows through the relay 46.

Note that the resistance value of the heater 42 that heats the constant temperature bath 41 is set to be sufficiently smaller than the combined resistance value of the relay 46 and the display 48.

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

In a normal operating state in which the thermostatic chamber 41 does not reach the overheat prevention temperature, the power switch 50, the temperature sensor 43 for temperature adjustment, the temperature sensor 44 for overheat prevention temperature detection, and the relay contact 47 are closed. ing. The current from the power source 45 is transmitted to a power switch 50, a temperature sensor 43 for temperature adjustment,
Constant temperature chamber 41 short-circuited between points A and B
The flow flows to the heater 42 via the temperature sensor 44 for overheating prevention temperature detection and the relay contact 47, and the thermostatic chamber 4
Perform heating in step 1. At this time, the indicator light 49 lights up to indicate that heater current is being supplied to the heater 42. Since points A and B are short-circuited, no current flows through relay 46 and overheat indicator 48, so overheat indicator 48 does not light up and relay 46 is inactive.

Then, when the temperature of the constant temperature bath 41 reaches the set temperature value, the contact of the temperature sensor 43 for temperature adjustment is opened, and the current supply to the heater 42 is cut off. At this time, no current flows through the relay 46, so the relay contact 47 is closed, and the thermostat 41 is closed.
The temperature sensor 44 for detecting the overheating prevention temperature is also closed because the constant temperature bath 41 has not reached the overheating prevention temperature.

Next, when the temperature of the constant temperature bath 41 becomes lower than the set temperature, the contact of the temperature sensor 43 for temperature adjustment is closed, and current is supplied from the power source 45 to the heater 42.
The constant temperature bath 41 is heated. By repeating such operations, the temperature of the constant temperature bath 41 is adjusted to the set temperature.

Next, when the contact point of the temperature sensor 43 for temperature adjustment remains closed due to the seizure phenomenon, and the temperature of the thermostatic oven 41 reaches or exceeds the overheating prevention temperature, the overheating temperature detection sensor 44 of the thermostatic oven 41 opens. Become. As a result, current from the power source 45 flows into the parallel circuit of the relay 46 and the overheating indicator 48 via the power switch 50 and the temperature sensor 43 for temperature adjustment. relay 46
As mentioned above, the combined resistance value of the heater 42 and the overheat indicator 48 is much larger than the resistance value of the heater 42, so a minute current flows through the heater 42. relay 4
6, the relay 46 is energized and the relay contact 47 is opened. Then, the overheat indicator 48 lights up to indicate that the relay 46 is in operation, and the indicator light 49 goes out to indicate that the heater 42 is inactive. In this way, overheating of the constant temperature bath 41 is prevented. At this time, the operator confirms that the thermostatic chamber 41 is overheated by checking the overheating indicator 48 and indicator light 49, and then opens the power switch 50. By opening the power switch 50, no current is supplied to the relay 46, the relay 46 is deenergized, and the relay contact 47 returns to closed. Then, we inspected and repaired the temperature sensor 43 for temperature adjustment, which had remained closed due to the seizure phenomenon, and further
Investigate the cause of the overheating temperature and perform repairs.

The reason for using the switching device consisting of the relay 46 and the relay contact 47 is as follows.

When the switchgear is not used and the contacts of the temperature sensor 43 for temperature adjustment are burned and closed as described above and the thermostatic oven 41 is at the overheating prevention temperature, the temperature sensor 43 44 is opened, but when the temperature of the constant temperature bath 41 becomes below the overheating prevention temperature, the temperature sensor 44 is closed. This means that the temperature of the constant temperature bath 41 is adjusted based on its overheating prevention temperature. In order to prevent this, the relay 46 is energized and the relay contact 47 is opened when the temperature sensor 44 for detecting the overheat prevention temperature of the constant temperature oven 41 is opened.

Next, a description will be given of a transient phenomenon that occurs when the time delay in transmitting heat from the heater 42 to the temperature adjustment sensor 43 is large.

Even if the temperature of the constant temperature bath 41 rises above the temperature adjustment temperature and the temperature adjustment sensor 43 becomes open,
If the temperature of the thermostatic chamber 41 continues to rise due to the large time delay described above and reaches the overheating prevention temperature or higher, the temperature sensor 43 for temperature adjustment is activated.
and the overheating prevention temperature detection temperature sensor 44 are both opened, the current supply to the heater 42 is cut off, the relay 46 is not energized, and therefore the relay contact 47 remains closed, and the overheating indicator 48, Both indicator lights 49 are turned off. After this, the constant temperature bath 41 cools down to below the overheating prevention temperature, and the overheating prevention temperature sensor 44 closes. Even at this time, since the temperature sensor 43 for temperature adjustment is open, the state in which no current is supplied to the heater 42 continues. When the constant temperature bath 41 cools down further and becomes below the set temperature for temperature adjustment, the temperature sensor 43 for temperature adjustment is closed, current is supplied to the heater 42, and heating of the constant temperature bath 41 is restarted. After that, the constant temperature bath 41
The temperature will be adjusted normally at the set temperature. In other words, even if it becomes transiently overheated, it will recover by itself.

With conventional fusible temperature fuses, such transient overheat conditions will cause the temperature fuse to blow and require replacement with a new one.

In addition, although the case of preventing overheating of the thermostatic oven 41 was explained in the above embodiment, the present invention is applicable to the thermostatic oven 4
1. It can also be applied to prevention of supercooling. In this case, it is necessary to set the temperature at which the contacts of the temperature sensor 44 for overheating prevention temperature detection of the constant temperature oven 41 closes to be lower than the temperature at which the contacts of the temperature sensor 43 for temperature adjustment close.

In addition, the temperature sensor 43 for temperature adjustment uses a temperature sensor such as a platinum thermometer, a thermocouple, a thermistor, etc. instead of the method of controlling the current supply to the heater 42 by opening and closing contacts in the above-described embodiment, The detected voltage is applied to a control circuit (not shown), compared with a set voltage in the control circuit, and the polarity of the deviation voltage is discriminated to open and close the contact.
It is also possible to use a method of controlling the current supply to 2.

(F) Effect As explained above, according to the present invention, the first temperature detection means for temperature adjustment is provided in the thermostatic chamber, and the first temperature detection means is provided in the thermostatic chamber.
A second temperature detection means is arranged to control the opening and closing at a set temperature different from the set temperature that controls opening and closing of the temperature detection means, and a relay contact is connected to the second temperature detection means, and the relay contact is connected to the second temperature detection means. By arranging the relays to be activated in parallel, the second temperature detection means can accurately detect abnormal temperatures in the thermostatic oven without malfunctioning due to fluctuations in ambient temperature, unlike conventional devices. By doing so, it is possible to prevent the thermostatic oven from entering an abnormal temperature state, and also prevent the thermostatic oven from adjusting the temperature at the set temperature of the second temperature detection means, that is, the abnormal temperature of the thermostatic oven. Even if the temperature of the bath is transiently abnormal, once the constant temperature bath cools down to below the set temperature for temperature adjustment, it can easily return to the normal temperature adjustment state.

[Brief explanation of the drawing]

Figures 1 to 3 show a conventional overheating prevention device for a constant temperature oven. Figure 1 is a cross-sectional view of a temperature sensor for detecting overheating prevention temperature placed inside the constant temperature oven, and Figure 2 is for detecting overheating prevention temperature. Fig. 3 is a circuit diagram of an electric circuit applied to the device shown in Figs. 1 and 2, and Fig. 4 is a temperature control for a thermostatic oven according to the present invention. FIG. 5, a cross-sectional view of an embodiment of the device, is a circuit diagram of an electrical circuit applied to the device shown in FIG. In the figure, 41 is a constant temperature bath, 42 is a heater, 43 is a temperature sensor for temperature adjustment, 44 is a temperature sensor for overheating prevention temperature detection, 45 is a heater power supply, 46 is a relay, 47 is a relay contact, and 48 is an overheating indicator. vessel, 49
5 is an indicator light indicating whether or not the heater 42 is in operation;
0 indicates a power switch.

Claims (1)

[Scope of Claim for Utility Model Registration] 1. A constant temperature chamber equipped with a heater, and a first temperature adjustment chamber disposed within the constant temperature chamber and opened and closed at a set temperature.
and a second temperature detection means for an abnormal temperature of a constant temperature oven that is controlled to open and close at a set temperature different from the set temperature of the first temperature detection means;
A relay contact connected in series with the second temperature detection means, and a relay connected in parallel to a series circuit of the second temperature detection means and the relay contact, the first temperature detection means and the second temperature detection means A temperature control device for a constant temperature oven, characterized in that a temperature detecting means is connected to the heater, and a relay contact is connected to a heater, and when a current flows through the relay, the relay contact is opened. 2. The temperature control device for a constant temperature oven according to claim 1, wherein the set temperature of the second temperature detecting means is higher or lower than the set temperature of the first temperature detecting means.