JP2006337129A - Thermal analyzer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce consumption of coolant liquid and useless energy in a heating process, and to prevent disturbance of thermal analysis data in the heating process. <P>SOLUTION: In a measurement control part 30, a waiting time required for disappearance of a coolant having the liquid height detected by a liquid level sensor 8 by evaporation from stop of coolant supply by a pump 5 is set. The measurement control part 30 controls driving of the pump 5 so that the coolant liquid level in a cooling tank 2 becomes constant based on a signal of the liquid level sensor 8 when performing measurement in a cooling process, stops driving of the pump 5 when performing measurement in the heating process, and then starts current application to a heater 14 in a furnace body 1 after elapse of the waiting time. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a thermal analyzer such as a differential thermal analyzer and a differential scanning calorimeter.

  In a thermal analysis device such as a differential scanning calorimeter, a sample to be measured and a thermally inactive reference sample are accommodated in the furnace body, and these are changed in the same thermal environment by changing the temperature of the furnace body. Change. In the process of the temperature change, information related to the temperature change of the sample to be measured and the reference sample is detected by a sensor or the like provided in the furnace, and the thermal property of the sample to be measured is measured. In such a thermal analysis device, the temperature of the sample is raised to a high temperature (for example, about 500 ° C.) or lowered to a low temperature (for example, about −140 ° C.). A heating device such as a heater for heating is provided, and a cooling device is provided to perform measurement in a temperature region below room temperature. As the cooling device, a device using a Peltier element or a device provided with cooling means for directly or indirectly cooling the furnace body using a refrigerant such as liquid nitrogen has been put into practical use (see Patent Document 1). ).

  A furnace body that is equipped with a heating device and can receive information from the sample relating to temperature changes by containing the sample therein, and a liquid level sensor that is thermally connected to the furnace body and detects the liquid level of the refrigerant And a refrigerant supply mechanism for supplying the refrigerant to the refrigerant tank, and driving the heating device for the furnace body and driving the refrigerant supply mechanism to change the sample temperature according to a predetermined program. A thermal analyzer provided with a measurement control unit has also been proposed (see Patent Document 2).

In such a thermal analyzer, the refrigerant is necessary in the cooling process, but not in the temperature raising process. Therefore, the measurement of the cooling process is finished, and the driving of the refrigerant supply mechanism may be stopped when performing the measurement in the temperature rising process. However, in the conventional heat measurement device, the driving of the refrigerant supply mechanism must be stopped manually. . Since a certain amount of refrigerant is stored in the refrigerant tank during the cooling process, it is difficult to ensure that the refrigerant does not evaporate at the time of shifting to the measurement during the temperature raising process. Usually, either the refrigerant still remains at the time of shifting to the measurement in the temperature raising process, or the refrigerant has already run out before entering the temperature raising process. In either case, the heat measurement data is disturbed and measurement with good reproducibility cannot be performed.
Therefore, conventionally, the supply of the refrigerant is continued even in the temperature rising process, and the temperature rising process is measured by supplying more heat to the furnace body than the amount of heat consumed by the evaporation of the refrigerant from the heating device of the furnace body. Yes.
JP 2001-183319 A Utility Model Registration No. 3109216

In the conventional measurement method in which the supply of the refrigerant continues even in the temperature rising process, excessive consumption of the refrigerant liquid in the temperature rising process and useless energy for that are required.
An object of the present invention is to eliminate the consumption of refrigerant liquid and waste of energy during a temperature rising process in a thermal analysis apparatus, and to prevent disturbance of thermal analysis data during the temperature rising process.

In the thermal analyzer of the present invention, the refrigerant tank has an open structure capable of releasing the refrigerant vapor, and the refrigerant at the liquid level detected by the liquid level sensor in the measurement control unit is evaporated from the refrigerant supply stop by the refrigerant supply mechanism. The waiting time required to disappear is set, and when the measurement control unit performs measurement in the cooling process, the liquid level of the refrigerant in the refrigerant tank is made constant based on the signal of the liquid level sensor. When the drive of the refrigerant supply mechanism is controlled and measurement is performed in the temperature rising process, the drive of the furnace body heating device is started after the standby time has elapsed after the drive of the refrigerant supply mechanism is stopped. It is characterized by being.
The driving of the refrigerant supply mechanism can be stopped after the furnace temperature reaches a predetermined low temperature in the cooling process, for example.

  The amount of refrigerant in the refrigerant tank only needs to be in the cooling process. In the present invention, since there is no refrigerant in the temperature raising process, if there is more refrigerant than necessary, the standby time for shifting to the temperature raising process becomes long and unnecessary time is required. Therefore, in order to ensure that the amount of refrigerant in the refrigerant tank is set to an optimum amount, in a preferred embodiment of the present invention, a cable penetrating from the outside to the inside of the refrigerant tank is provided, and the tip of the cable is provided in the refrigerant tank. The liquid level sensor is mounted on the outside of the refrigerant tank, and an index is provided on one side of the refrigerant tank and the cable, and a scale is provided on the other, and the scale is disposed opposite to the position that can be indicated by the index. The height position of the liquid level sensor is made variable by making the length of the cable in the tank adjustable.

In the thermal analysis apparatus of the present invention, a standby time required for the refrigerant in the refrigerant tank to disappear from evaporation from the refrigerant supply stop by the refrigerant supply mechanism is set, and when the standby time elapses, the heating device for the furnace body is driven. Since the temperature rise measurement can be started from the point when the refrigerant in the refrigerant tank has just run out, the excessive measurement of the refrigerant due to unnecessary refrigerant liquid injection during the heating process while suppressing the disturbance of the heat measurement data. Consumption can be eliminated and the power of the heating device can also be reduced. In addition, the refrigerant tank is usually covered with a heat insulating material, and condensation and frost are generated around the heat insulating material when the refrigerant is continuously supplied to the refrigerant tank even during the temperature rising process. Since no refrigerant remains in the refrigerant tank in the temperature rising process, condensation and frost around the heat insulating material can be suppressed, and a clean measurement environment can be maintained.
If the height position of the liquid level sensor in the refrigerant tank is made variable, the amount of refrigerant in the refrigerant tank in the cooling process can be set to an optimal amount, and the waiting time when shifting from the cooling process to the temperature rising process Can be shortened.

An embodiment will be described with reference to a schematic configuration diagram of a differential scanning calorimeter (DSC) in FIG.
Although not shown, the furnace body 1 is configured to be able to store a sample therein and to detect a temperature change of the sample. The furnace body 1 has a heater 14 as a heating device, and a lower part thereof is in close contact with the heat transfer plate 3. The heat transfer plate 3 is in close contact with the close contact portion with the furnace body 1, and the refrigerant tank 2 is in close contact with the upper surface thereof, and the furnace body 1 and the refrigerant tank 2 are thermally connected to each other through the heat transfer plate 3. Are combined.

  The refrigerant tank 2 contains liquid nitrogen as a refrigerant, and is insulated from the outside air and insulated by the refrigerant tank airtight lid 21 and the heat insulating member 13. The refrigerant is stored in the refrigerant storage container 4 and is appropriately supplied to the refrigerant tank 2 through the refrigerant supply hose 6 by the pump 5 of the refrigerant supply mechanism. Nitrogen vaporized in the refrigerant tank 2 passes through the exhaust hose 7 and is released into the atmosphere. The refrigerant supply hose 6 and the exhaust hose 7 are respectively insulated by a supply hose heat insulation tube 61 and an exhaust hose heat insulation tube 71.

  A penetration tube 9 penetrates through the refrigerant tank secret lid 21 and the heat insulating member 13, and a rubber plug 10 is provided on the outer end of the refrigerant tank. The cable 81 passes through the inside from the outside of the refrigerant tank into the refrigerant tank. A liquid level sensor 8 is provided at the tip of the cable 81 and is held near the refrigerant liquid level in the refrigerant tank. The liquid level sensor 8 is a platinum thermistor, for example, and detects the liquid level of the refrigerant based on the detected temperature. The signal line from the liquid level sensor 8 passes through the inside of the cable 81 and is taken out of the refrigerant tank.

  The cable 81 is provided with a scale 12 and penetrates the rubber plug 10 and is fixed. An index 11 is provided near the outer end of the through tube 9 outside the refrigerant tank, and the position of the liquid level sensor 8 in the refrigerant tank is easily predicted by the index 11 and the scale 12. When changing the detection position of the liquid level of the refrigerant remaining in the refrigerant tank 2, the rubber plug 10 is loosened, and the cable 81 is taken in and out of the refrigerant tank while referring to the index 11 and the scale 12, thereby the sensor 8. Then, the rubber plug 10 is fixed again at the desired position.

  When the remaining amount of the refrigerant is detected by the liquid level sensor 8 and the remaining amount is smaller than a predetermined amount, the liquid supply mechanism 5 pumps out the liquid nitrogen in the refrigerant storage container 4 and supplies it to the refrigerant tank 2. Here, since the refrigerant detection position can be easily changed from the outside of the refrigerant tank to an appropriate position, thermal analysis measurement can always be performed at the optimal detection position, and wasteful consumption of refrigerant can also be reduced. .

The scale and index may be configured to be equal to the height position of the liquid level sensor 8 from the bottom surface of the refrigerant tank at the time of insertion, or may be configured to indicate an appropriate position depending on the measurement conditions.
Reference numeral 30 denotes a measurement control unit. The measurement control unit 30 is set with a standby time required for the refrigerant at the liquid level detected by the liquid level sensor 8 to disappear due to evaporation from the refrigerant supply stop by the pump 5. The sample control temperature in the furnace body 1 and the temperature detected by the liquid level sensor 8 are input to the measurement control unit 30, and energization control to the heater 14 of the furnace body and drive control of the pump 5 are performed according to the measurement program.

When performing measurement in the cooling process, the measurement control unit 30 controls the driving of the pump 5 based on the signal from the liquid level sensor 8 so that the liquid level of the refrigerant in the refrigerant tank 2 is constant, When performing the measurement in the temperature raising process, the drive of the pump 5 is stopped, and then energization to the heater 14 of the furnace body 1 is started when the standby time has elapsed.
The driving of the pump 5 may be stopped after the furnace temperature reaches a predetermined low temperature in the cooling process.

  According to this embodiment, if the insertion depth of the cable 81 is changed with reference to the scale 12 and the index 11 of the cable 81, the position of the liquid level sensor 8 can be adjusted from the outside of the refrigerant tank 2. Since the position can be confirmed, the liquid level position of the detected refrigerant can be easily changed to a desired position, and the effect of reducing wasteful consumption of the refrigerant such as liquid nitrogen can be obtained.

The operation in the cooling to heating measurement program in this embodiment will be described with reference to FIG.
(1) Cooling process measurement sequence:
The refrigerant supply pump 5 is turned on to supply the refrigerant to the refrigerant tank 2 and the temperature of the furnace body 1 is lowered.
When the liquid level sensor 8 detects the accumulation of refrigerant, the pump 5 is turned off or the supply amount is reduced, and when the liquid level of the refrigerant leaves the liquid level sensor 8, the liquid level sensor 8 is turned on again. Thus, the supply amount by the pump 5 is controlled so that the refrigerant liquid level becomes constant.
When the furnace body 1 reaches the set temperature, the pump 5 is turned off because the measurement in the cooling process is finished.

(2) Measurement sequence for temperature rising process:
When the set standby time has elapsed after the pump 5 is turned off, the furnace body temperature is raised while controlling the heating rate by the heater 14 of the furnace body 1.
If the refrigerant remains in the refrigerant tank 2 at the time of shifting to the heating process, the refrigerant is unnecessary, but this standby time is set so that the refrigerant will not evaporate. Does not affect the control of furnace temperature.

  FIGS. 3 and 4 show DSC measurement examples in the cooling to heating process in this example, and both show cases where the setting of the standby time is intentionally shifted. In any of the figures, t1 is a time when the refrigerant is completely exhausted after the pump 5 is turned off, t2 is a time when heating by the heater 14 is started, A is a DSC curve, and B is a temperature curve.

  The data in FIG. 3 is for a case where the set standby time is about 1 minute shorter. At the time when heating by the heater 14 is started, the refrigerant has already disappeared, and the heating has already started slightly before the heating by the heater 14, but the DSC curve is disturbed.

  On the other hand, the data in FIG. 4 is for the case where the set standby time is about 3 minutes longer. Even when heating by the heater 14 is started, the refrigerant remains, and even when heating by the heater 14 is started, a temperature increase according to a scheduled program is not seen, and a temperature increase until the refrigerant runs out is suppressed, Thereby, also in this case, the DSC curve is disturbed.

  The present invention eliminates such a timing shift, and by setting the standby time correctly, the heating by the heater 14 is started from the point in time when the refrigerant is completely exhausted in the refrigerant tank. Therefore, the temperature is raised and the DSC curve is not disturbed.

  The waiting time cannot be determined only by the liquid level of the refrigerant in the refrigerant tank. This is because the supply of the refrigerant remaining in the refrigerant supply hose 6 continues for a while even if the refrigerant supply by the pump 5 is stopped. The refrigerant supply that continues even after the pump 5 is stopped depends on the pump feed amount.

FIG. 5 shows the result of obtaining the waiting time by experiment with respect to the setting of the refrigerant feed amount of the pump 5 and the liquid level of the refrigerant (by setting the height of the liquid level sensor 8). Numerical values (3.6, 3.8, 4) attached after the pump indicate the refrigerant feed amount of the pump 5, respectively, and the larger the value, the greater the feed amount. The LN2 level that is the liquid level of the refrigerant indicates the height from the bottom surface of the refrigerant tank 2.
In this embodiment, an optimum standby time is obtained according to the refrigerant feed amount of the pump 5 and the liquid level of the refrigerant, and is set in the measurement control unit 30 to perform measurement without disturbing the DSC curve.

  The present invention can be used for a thermal analyzer such as a differential thermal analyzer or a differential scanning calorimeter.

It is a schematic block diagram which shows the differential scanning calorimeter of one Example. It is a flowchart figure which shows the operation | movement of the Example. It is a graph which shows the example of 1 measurement of DSC in the cooling-heating process in the Example. It is a graph which shows the other measurement example of DSC in the cooling-heating process in the Example. It is a graph which shows the relationship between the refrigerant | coolant feed amount of a pump, the liquid level of a refrigerant | coolant, and standby time.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Furnace 2 Refrigerant tank 3 Heat transfer plate 5 Pump 6 Refrigerant supply hose 7 Exhaust hose 8 Liquid level sensor 9 Through tube 10 Rubber plug 11 Index 12 Scale 13 Heat insulation member 14 Heater 21 Refrigerant tank airtight cover 30 Measurement control part 81 Cable

Claims (3)

A furnace body that is equipped with a heating device and is capable of taking out information from the sample relating to temperature changes by accommodating the sample inside;
A refrigerant tank that is thermally connected to the furnace body and includes a liquid level sensor that detects a liquid level of the refrigerant;
A refrigerant supply mechanism for supplying a refrigerant to the refrigerant tank;
In a thermal analysis apparatus comprising: a measurement control unit that controls driving of the furnace body heating device and driving of the refrigerant supply mechanism to change a sample temperature according to a predetermined program;
The refrigerant tank has an open structure capable of releasing refrigerant vapor,
In the measurement control unit, a standby time required for the refrigerant at the liquid level detected by the liquid level sensor to disappear due to evaporation from the refrigerant supply stop by the refrigerant supply mechanism is set,
The measurement control unit controls the driving of the refrigerant supply mechanism so that the liquid level of the refrigerant in the refrigerant tank is constant based on the signal of the liquid level sensor when performing measurement in the cooling process, The thermal analysis is characterized in that when the measurement in the temperature raising process is performed, the driving of the heating device for the furnace body is started after the standby time has elapsed after the driving of the refrigerant supply mechanism is stopped. apparatus. The thermal analysis apparatus according to claim 1, wherein the driving of the refrigerant supply mechanism is stopped after the furnace temperature reaches a predetermined low temperature in the cooling process. A cable penetrating from the outside to the inside of the refrigerant tank is provided, and the liquid level sensor is attached to the tip of the cable inside the refrigerant tank, and an indicator is provided on one side of the refrigerant tank and the cable outside the refrigerant tank, and the other The scale is provided at a position where the scale can be pointed by the indicator, and the height of the liquid level sensor can be adjusted by adjusting the length of the cable in the refrigerant tank. The thermal analysis apparatus according to claim 1 or 2, wherein the thermal analysis apparatus is variable.

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