JPH04301552A - Heating furnace for thermal analysis equipment and temperature control method - Google Patents

Abstract

PURPOSE:To minimize a fluctuation according to each low temperature setting and stabilize temperature by supplying coolant to a coolant reservoir at specified time intervals via a controller for each temperature setting in controlling temperature of a heating furnace. CONSTITUTION:At the time of measurement, if a liquid level of coolant 4 is at a certain level or lower due to influence of ambient temperature of a coolant reservoir 3, its rate of change, etc., a liquid level sensor 5 activates to supply power to a heater 9a of a heater siphon 9 of a coolant storage tank 6. This heat vaporizes a part of the coolant 4 in the tank 6, and pressure is applied to inside the tank 6, so that the coolant 4 is fed to the coolant reservoir 3 by differential pressure from an atmospheric pressure. The coolant 4 in the coolant reservoir 3 reaches a set level of the liquid level sensor 5, whereby a controller 10 stops supplying power to the heater 9a and also opens a solenoid valve 8 to stop supplying the coolant 4. This is repeated to maintain the coolant 4 in the coolant reservoir 3 at a constant level. Therefore, in any low temperature set region with a speed of raising/lowering temperature differed, a stable liquid level can be secured.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] This invention is applicable to
Thermal analysis equipment used in thermomechanical analysis equipment that applies an appropriate load to a sample and measures the effects associated with thermal changes, and thermogravimetry equipment that heats the sample and measures the thermal effects associated with changes in sample weight. This invention relates to a heating furnace for use in heating and its temperature control method.

0002

[Prior art] In a thermal analyzer, the area around the heating furnace is a low-temperature area (
The sample is cooled down to -100°C or lower) and placed in the reactor core tube, and the sample is sometimes measured while being maintained at a constant temperature with a heater. Conventionally, when cooling a heating furnace in this way, the entire furnace core tube was covered with a refrigerant tank and cooled with liquid nitrogen (N2), or the heating furnace was cooled by blowing low-temperature gas of vaporized refrigerant. However, recently, considering economic cost or cooling efficiency, a refrigerant tank containing refrigerant that cools only the lower part of the heating furnace body is installed, and a liquid level sensor is installed to keep the refrigerant liquid level at a certain level. There is also a device in which the control is performed using the following methods (Patent Application No. 259889, 1990).

0003

[Problems to be Solved by the Invention] A system in which a refrigerant tank is installed at the bottom of a heating furnace and the liquid level is controlled by a liquid level sensor is efficient and economical. If only the level is controlled, fluctuations in the liquid level will vary depending on parameters such as the temperature during analysis and temperature rise and fall, and the baseline noise caused by this fluctuation will become an obstacle during high-sensitivity analysis. There is a problem that there is. This invention was made in view of the above problem, and its purpose is to ensure a stable liquid level even when the temperature is set in various low temperature ranges, and even when the rate of rise and fall of temperature is different. An object of the present invention is to provide a heating furnace for a thermal analyzer and a temperature control method thereof.

0004

[Means for Solving the Problems] In other words, in order to solve the above-mentioned problems, this invention has the following features: (1) A heating furnace for a thermal analyzer includes a core tube in which a sample is placed, and a liquid level sensor installed at the bottom of the core tube. A refrigerant tank in which a siphon with a heater is arranged, a refrigerant tank in which a siphon with a heater is arranged and a conduit to the refrigerant tank and an electromagnetic valve are arranged, and the liquid level sensor, the siphon with a heater, and the electromagnetic valve are controlled. It is characterized by consisting of a controller. In addition, (1) the method for controlling the temperature of a heating furnace for a thermal analyzer having the above configuration includes controlling the proportion of refrigerant supplied to the refrigerant tank at regular intervals via the controller at each set temperature; Features.

[0005]

[Operation] The operation of the heating furnace for a thermal analyzer according to the present invention as the above means will be explained using the reference numerals in the accompanying drawings.

During thermal analysis measurement, when the liquid level of the refrigerant 4 falls below a certain level due to the influence of the ambient temperature, heating or cooling rate of the refrigerant tank 3, the liquid level sensor 5 is activated and the controller 10 is activated.
The heater of the heater siphon 9 of the refrigerant storage tank is
9a is energized. Then, a part of the liquid nitrogen in the storage tank 6 evaporates due to the heating of the heater 9a of the heater-equipped siphon, and the inside of the tank is pressurized, and the liquid nitrogen is sent to the refrigerant tank 3 due to the pressure difference with atmospheric pressure. It will be done. Further, when the refrigerant in the refrigerant tank 3 reaches the level at which the liquid level sensor 5 is installed, the controller 10 stops energizing the heater 9a of the heater siphon 9, and at the same time operates the solenoid valve 8. The supply of the refrigerant 4 to the refrigerant tank 3 is stopped by setting it to "open". In this way, the refrigerant in the refrigerant tank 3 is maintained at a constant level by repeating the feeding and stopping of the refrigerant. In addition, the siphon 9 with heater
By increasing the time during which the heater 9a is energized and shortening the time during which the energization is stopped, the flow rate of liquid nitrogen is increased, and the period between the refrigerant feeding time and the stopping of the liquid nitrogen shown in Fig. 2 is shortened to reduce "fluctuation". You can.

[0007] Therefore, according to the method using the above means,
The heater of the siphon 9 is controlled via the controller 10 so that the signal from the liquid level sensor 5 always has a constant cycle.
By controlling the ratio (duty ratio) between the energization time and the energization stop time to the tank 9a, "fluctuations" in the liquid level can be minimized.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing the 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 core tube 1, and a liquid level sensor 5 is installed in the refrigerant tank 3 at a fixed level position. That is,
The temperature of the sample inside the core tube is controlled by the coolant in the coolant tank 3.
A predetermined cooling temperature can be set by cooling and heating with the heater 2.

A refrigerant storage tank 6 contains a refrigerant 4 such as liquid nitrogen. A conduit 7 is connected to the refrigerant tank 3 to supply refrigerant to the refrigerant storage tank 6, and a solenoid valve 8 is installed on the other side. Also,
A siphon 9 with a heater is disposed in the storage tank 6, and when the refrigerant 4 in the refrigerant tank 3 decreases due to evaporation or the like, the liquid level sensor 5 turns on the power, as will be described later. . Next, 10 is a controller which controls the liquid level sensor 5 and the heater 9 of the heater-equipped siphon 9.
a and the solenoid valve 8.

The heating furnace for a thermal analysis device according to the present invention has the above-described configuration, and normally, during thermal analysis in a certain low temperature region, the furnace core tube 1 is cooled by the refrigerant in the refrigerant tank 3 while the surroundings are cooled. Thermal analysis measurement is performed by keeping the measurement sample at a predetermined constant temperature using the heater 2.

Next, during thermal analysis measurement, when the liquid level of the refrigerant 4 falls below a certain level due to the influence of the ambient temperature, heating or cooling rate of the refrigerant tank 3, the liquid level sensor 5 is activated and the controller is activated. 10, the heater 9a of the heater-equipped siphon 9 of the refrigerant storage tank is energized. Then, a part of the liquid nitrogen in the storage tank 6 evaporates due to the heating of the heater 9a of the heater-equipped siphon 9, and the inside of the tank is pressurized, and liquid nitrogen flows into the refrigerant tank 3 due to the pressure difference with 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 activates the heater 9a of the heater siphon 9.
At the same time, the electromagnetic valve 8 is operated and opened to stop supplying the refrigerant 4 to the refrigerant tank 3. In this way, the refrigerant in the refrigerant tank 3 is maintained at a constant level by repeating the feeding and stopping of the refrigerant.

FIG. 2 is a diagram showing the time relationship between stopping and supplying liquid by the controller 10 having the above-mentioned configuration, and the period in this case depends on the temperature measured by the thermal analyzer, the heating and
It changes depending on the cooling rate, etc. FIG. 3 shows the heater 9 of the heater-equipped siphon 9 during the refrigerant supply period shown in section P of FIG.
FIG. 3 is a diagram showing the relationship between the time when electricity is applied (usually an AC power supply) to a and the time when electricity is stopped. As can be seen from this Figure 3,
When supplying liquid nitrogen, the controller 10 intermittently energizes the heater to control the flow rate of the refrigerant.

Furthermore, FIG. 4 is a diagram showing a case where the interval between "energization" and "energization stop" during refrigerant supply shown in FIG. 5
is a diagram when the energization time is shortened. The liquid level of the refrigerant tank 3 installed in the core tube 1 constituting the heating furnace.
"Fluctuations" cause "fluctuations" in the temperature of the sample part in the reactor core tube 1, and the shorter the period of liquid feeding time and liquid feeding stop time shown in Figure 2, the smaller this "fluctuation" becomes. The ``fluctuation'' also increases. Therefore, as shown in FIG. 4, the time interval between the energization time and the energization stop time shown in FIG. It is possible to reduce the "fluctuation" by increasing the flow rate and shortening the period between the refrigerant feeding time and the stopping of the liquid feeding shown in FIG. Therefore, depending on the signal from the liquid level sensor 5, the heater 9a of the heater-equipped siphon 9 is energized and de-energized via the controller 10 at a constant cycle, taking into account the measured temperature at that time. By controlling the time ratio (duty ratio), "fluctuations" in the liquid level can be minimized.

[0015] In the above embodiment, the heater of the heater-equipped siphon was controlled by controlling the time interval at which it was energized by the AC power supply, but it was also possible to control the liquid supply by changing the AC voltage value. Also good.

[0016]

[Effects of the Invention] Since the heating furnace for a thermal analyzer and the temperature control method according to the present invention are configured as detailed above,
When setting the temperature of the sample installed in the reactor core tube to a predetermined low temperature, it is possible to precisely control the liquid level and stabilize the temperature by minimizing fluctuations at any set temperature. Therefore, thermal analysis can be performed accurately at extremely low temperatures.

[0017]

[Brief explanation of drawings]

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

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

3 is a diagram showing the relationship between the time when the heater of the heater-equipped siphon is energized and the time when the energization is stopped during refrigerant supply shown in section P of FIG. 2; FIG.

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

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

[Explanation of symbols]

1 Furnace core 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)

[Claims] Claim 1: A reactor core tube in which a sample is placed, a refrigerant tank installed at the bottom of the reactor core tube in which a liquid level sensor is arranged, a siphon with a heater arranged, and a conduit to the refrigerant tank and a solenoid valve. 1. A heating furnace for a thermal analysis apparatus, comprising a piped refrigerant tank, and a controller for controlling the liquid level sensor, a siphon with a heater, and an electromagnetic valve. [Claim 2] A reactor core tube in which a sample is placed, a refrigerant tank installed at the bottom of the reactor core tube and in which a liquid level sensor is arranged, a siphon with a heater arranged, and a conduit and an electromagnetic valve connected to the refrigerant tank. In a heating furnace for a thermal analyzer, which consists of a tank containing refrigerant, the liquid level sensor, a siphon with a heater, and a controller that controls an electromagnetic valve, the proportion of refrigerant supplied to the refrigerant tank is controlled at each set temperature. A temperature control method characterized in that the temperature is controlled at regular intervals via the controller.