JP2903754B2 - Heating furnace for thermal analyzer and temperature control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to
A thermomechanical analyzer used in thermomechanical analyzers that measure the effects of thermal changes by applying an appropriate load to a sample or a thermogravimeter that measures the thermal effects associated with changes in sample weight by heating the sample Heating furnace and its temperature control method.

[0002]

2. Description of the Related Art In a thermal analyzer, the temperature around a heating furnace is cooled to a low temperature range (-100 ° C. or lower), and measurement may be performed while a sample placed in a furnace tube is kept at a constant temperature by a heater. Conventionally, when the heating furnace is cooled in this way, there is a method in which the entire furnace tube is covered with a refrigerant tank and cooled with liquid nitrogen (N ₂ ), or a low-temperature gas of a vaporized refrigerant is blown into the heating furnace to cool the furnace. . However, recently, in consideration of economic cost or cooling efficiency, a refrigerant tank containing a refrigerant that cools only the lower part of the heating furnace main body is arranged, and a liquid level sensor is installed so that the refrigerant liquid level becomes a constant level. In some cases, such control is performed (Japanese Patent Application No. 259889, 1990).

[0003]

The one in which a refrigerant tank is provided below the heating furnace and the liquid level is controlled by a liquid level sensor is efficient and economical, but the liquid level is controlled by the liquid level sensor. By simply controlling the level, the fluctuation of the liquid level differs depending on parameters such as the temperature during the analysis and the elevating temperature, and the base line noise caused by this "fluctuation" becomes an obstacle to the high sensitivity analysis. There is a problem that there is. The present invention has been made in view of such a problem, and an object thereof is to secure a stable liquid level even when the temperature is set in various low-temperature regions and the speed of the elevating temperature is different. An object of the present invention is to provide a heating furnace for a thermal analyzer and a method for controlling the temperature thereof.

[0004]

That is, in order to solve the above-mentioned problems, the present invention provides a heating furnace for a thermal analyzer, which comprises a furnace tube for installing a sample, and a liquid level sensor installed below the furnace tube. A refrigerant tank arranged therein, a refrigerant tank in which a siphon with heater is arranged and a pipe to the refrigerant tank and an electromagnetic valve are piped, and a controller for controlling the liquid level sensor, the siphon with heater and the electromagnetic valve -Characterized by comprising: In the method for controlling the temperature of a heating furnace for a thermal analyzer configured as described above, the ratio of the refrigerant to be supplied to the refrigerant tank may be set to a constant time interval via the controller at each set temperature. And

[0005]

The operation of the heating furnace for a thermal analyzer according to the present invention as described above will be described with reference to the accompanying drawings.

In the thermal analysis measurement, when the liquid level of the refrigerant 4 falls below a certain level due to the influence of the ambient temperature of the refrigerant tank 3, the heating or cooling rate, etc., the liquid level sensor 5 is activated and the controller 10 is operated.
Of the siphon 9 with heater of the refrigerant storage tank through the
Power to the terminal 9a. Then, by heating the heater 9a of the heater-equipped siphon, a part of the liquid nitrogen in the storage tank 6 evaporates and the inside of the tank is pressurized, and the liquid nitrogen is sent to the refrigerant tank 3 by a pressure difference from the atmospheric pressure. Can be When the refrigerant in the refrigerant tank 3 reaches the level at which the liquid level sensor 5 is installed, the controller 10 stops supplying electricity to the heater 9a of the heater siphon 9 and simultaneously activates the solenoid valve 8. Then, the supply of the refrigerant 4 to the refrigerant tank 3 is stopped as “open”. As described above, the refrigerant in the refrigerant tank 3 is maintained at a constant level by repeating the supply of the refrigerant and the stop of the liquid supply. In addition, siphon 9 with heater
The flow rate of liquid nitrogen is increased by increasing the time for energizing the heater 9a and shortening the energizing stop time, thereby shortening the cycle of the refrigerant sending time and the stopping of the liquid sending shown in FIG. You can do it.

Therefore, according to the method using the above means,
The heater of the siphon 9 with the heater is controlled via the controller 10 so as to always have a constant cycle according to the signal from the liquid level sensor 5.
By controlling the ratio (duty ratio) between the current supply to the heater 9a and the current supply stop time (duty ratio), the "fluctuation" of the liquid level can be minimized.

[0008]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing a configuration of a heating furnace for a thermal analyzer according to the present invention. Reference numeral 1 denotes a furnace tube for placing a sample, and a heater 2 is arranged around the tube so that a predetermined temperature can be set. A refrigerant tank 3 containing a refrigerant 4 such as liquid nitrogen is provided below the furnace tube 1, and a liquid level sensor 5 is installed at a predetermined level in the refrigerant tank 3. That is,
The temperature of the sample portion in the core tube is controlled by the refrigerant in the refrigerant tank 3.
Is cooled and heated by the heater 2 so that a predetermined cooling temperature can be set.

Reference numeral 6 denotes a refrigerant storage tank in which a refrigerant 4 such as liquid nitrogen is stored. In the refrigerant storage tank 6, a pipe 7 is connected to the refrigerant tank 3 to supply the refrigerant, and an electromagnetic valve 8 is installed on the other side. Also,
The storage tank 6 is provided with a siphon 9 with a heater. When the amount of the refrigerant 4 in the refrigerant tank 3 decreases due to evaporation or the like, the power is turned on by the liquid level sensor 5 as described later. . Next, reference numeral 10 denotes a controller, which is the heater 9 of the liquid level sensor 5 and the siphon 9 with a heater.
a and the solenoid valve 8.

The heating furnace for a thermal analyzer according to the present invention has the above-described configuration. Usually, during thermal analysis in a certain low-temperature region, the core tube 1 is cooled while the core tube 1 is cooled by the refrigerant in the refrigerant tank 3. The heat analysis is performed by the heater 2 with the measurement sample at a predetermined constant temperature.

Next, at the time of thermal analysis measurement, when the liquid level of the refrigerant 4 falls below a certain level due to the influence of the ambient temperature of the refrigerant tank 3, the heating or cooling rate, etc., the liquid level sensor 5 is activated to activate the controller. The heater 9a of the siphon 9 with a heater in the refrigerant storage tank is energized via 10. Then, a portion of the liquid nitrogen in the storage tank 6 evaporates due to the heating of the heater 9a of the siphon 9 with the heater, the inside of the tank is pressurized, and the liquid nitrogen enters the refrigerant tank 3 due to a pressure difference from the atmospheric pressure. Sent. In addition, refrigerant tank 3
When the refrigerant reaches the level at which the liquid level sensor 5 is installed, the controller 10 turns the heater 9a of the heater siphon 9 on.
The supply of the refrigerant 4 to the refrigerant tank 3 is stopped when the power supply to the refrigerant tank 3 is stopped. As described above, the refrigerant in the refrigerant tank 3 is maintained at a constant level by repeating the supply of the refrigerant and the stop of the liquid supply.

FIG. 2 is a diagram showing the time relationship between the stop of the liquid supply and the supply of the liquid by the controller 10 having the above-mentioned configuration.
It changes depending on the cooling rate and the like. FIG. 3 shows the heater 9 of the siphon 9 with the heater in the refrigerant supply time period shown in the part P of FIG.
FIG. 4 is a diagram showing a relationship between a time for energizing (normally an AC power supply) and an energizing stop time. As can be seen from FIG.
When supplying liquid nitrogen, the controller 10 intermittently supplies current to the heater to control the flow rate of the refrigerant.

FIG. 4 is a diagram showing a case where the interval between the "energization" and "energization stop" during the supply of the refrigerant shown in FIG. 3 is changed, in which the energization time is extended. 5
FIG. 4 is a diagram when the energization time is shortened. The “fluctuation” of the liquid level of the refrigerant tank 3 installed in the furnace tube 1 constituting the heating furnace is the “fluctuation” of the sample temperature in the furnace tube 1.
This "fluctuation" becomes smaller as the cycle of the liquid sending time and the liquid feeding stop time shown in FIG. 2 becomes shorter, and the "fluctuation" becomes larger when the cycle becomes longer. Therefore, as shown in FIG. 4, the time interval between the energizing time and the energizing stop in FIG. 3 is extended by energizing the heater 9a of the heater-attached siphon 9, and the energizing interrupting time is shortened. By increasing the flow rate of the refrigerant and shortening the cycle of the refrigerant supply time and the stop of the liquid supply shown in FIG. Therefore, the signal from the liquid level sensor 5 is supplied to the heater 9a of the siphon 9 with the heater via the controller 10 so as to always have a constant period in consideration of the measured temperature at that time, and the power supply is stopped. By controlling the time ratio (duty ratio), the "fluctuation" of the liquid level can be minimized.

In the above-described embodiment, the heater of the siphon with a heater controls the liquid feeding by controlling the time interval of energization by the AC power supply. However, the heater is controlled by changing the AC voltage value. Is also good.

[0016]

As described above, the heating furnace and the temperature control method for the thermal analyzer according to the present invention are configured as described above in detail.
When the temperature of the sample installed in the furnace tube is set to a predetermined low temperature, precise control of the liquid level can be performed to minimize the "fluctuation" at any set temperature and stabilize the temperature. Therefore, thermal analysis at an extremely low temperature can be accurately performed.

[0017]

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a heating furnace for a thermal analyzer according to the present invention.

FIG. 2 is a diagram showing a time relationship between stoppage of liquid supply and supply by a controller of a heating furnace for a thermal analyzer according to the present invention.

FIG. 3 is a diagram showing a relationship between a time during which power is supplied to a heater of a siphon with a heater and a power supply stop time during supply of a refrigerant shown in a part P of FIG. 2;

4 is a diagram showing a case where the interval between “energization” and “energization stop” during the supply of the refrigerant shown in FIG. 3 is changed, and is a diagram showing a case where the energization time is lengthened.

5 is a diagram showing a case where the interval between “energization” and “energization stop” during supply of the refrigerant shown in FIG. 3 is changed, and is a diagram showing a case where the energization time is shortened.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Furnace tube 2 Heater 3 Refrigerant tank 4 Refrigerant 5 Liquid level sensor 6 Refrigerant storage tank 8
Solenoid valve 9 Siphon with heater 9a Heater
10 Controller

Claims (2)

(57) [Claims] 1. A furnace tube in which a sample is placed, a refrigerant tank disposed below the furnace tube and having a liquid level sensor disposed therein, a siphon with a heater disposed therein and a conduit to the refrigerant tank and an electromagnetic valve. A heating furnace for a thermal analysis apparatus, comprising: a refrigerant storage tank provided with a pipe; a liquid level sensor, a siphon with a heater, and a controller for controlling an electromagnetic valve. 2. A furnace tube for installing a sample, a refrigerant tank disposed below the furnace tube and having a liquid level sensor disposed therein, a siphon with a heater disposed therein, and a pipe line to the refrigerant tank and an electromagnetic valve piped. In a heating furnace for a thermal analysis apparatus comprising a cooled refrigerant tank, a liquid level sensor, a siphon with a heater, and a controller for controlling an electromagnetic valve, the ratio of the refrigerant to be supplied to the refrigerant tank is determined at each set temperature. The temperature control method according to any one of claims 1 to 3, wherein the predetermined time interval is set via the controller.