JP2009192416A - Thermal analyzer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermal analyzer constituted so as to allow the temperature of a sample to coincide with the hold temperature in a temperature program. <P>SOLUTION: The thermal analyzer is equipped with a heating oven body 1 and an operation control part 2A equipped with a temperature difference calculating function 24 for reading and storing the temperature difference ΔT between a program temperature Tp and a sample temperature Ts, a temperature control period detecting function 25 for detecting a temperature control period and a hold temperature updating function 26 for updating the hold temperature of the temperature program by the detection signal from the temperature control period detecting function 25. The temperature control period detecting function 25 detects the temperature control period before one temperature control period wherein the program temperature Tp reaches the hold temperature, and the temperature difference ΔT at this point of time is added to an initial hold temperature Th to update the hold temperature. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a thermal analysis apparatus that analyzes a sample by performing temperature control of a heating furnace body such as a differential scanning calorimeter, a differential thermal analysis apparatus, a thermogravimetric measurement apparatus, or a thermomechanical analysis apparatus.

  Various thermal analyzers are used to obtain the thermal properties of various materials and to investigate the thermal stability of various inorganic and organic compounds. Among these thermal analyzers, a differential scanning calorimeter (DSC device) is a device for measuring a change in enthalpy of a substance, and is widely used in the field of pharmaceuticals including material science. This differential scanning calorimeter measures the endothermic changes generated in the sample when the sample cell containing the sample and the reference sample and the reference sample cell are placed in symmetrical positions in the heating furnace and the temperature of the heating furnace is raised or lowered. The temperature difference caused by the temperature difference is measured, and the DSC curve specific to the sample is obtained by plotting the heat flow data calculated by the temperature difference with the sample temperature (or time) as a parameter.

The temperature of the heating furnace is controlled based on a temperature program stored in advance. Since this temperature control is normally performed at a furnace temperature Tf different from the sample temperature Ts, the sample temperature Ts is set by the program delay due to the response delay caused by the heat capacity and thermal resistance from the furnace body to the sample temperature detector (eg, thermocouple). As shown in FIG. 5, a deviation occurs with respect to the temperature Tp. Since this deviation becomes apparent at the hold temperature Th of the program temperature Tp, a predetermined temperature is added to the program temperature Tp in advance so as to approach the target temperature. The same applies to other thermal analysis apparatuses such as a differential thermal analysis (DTA) apparatus, a thermogravimetric measurement (TGA) apparatus, or a thermomechanical analysis (TMA) apparatus.
JP 11-23505 A

The conventional differential scanning calorimeter is configured as described above, and a predetermined temperature is added to the program temperature in advance to bring it close to the target temperature. However, the hold temperature can be shifted in various conditions, for example, the temperature range to be used. There is a problem that different values are taken depending on the heating or cooling rate in the previous stage, ON / OFF of cooling, and the like. For this reason, a method of actually measuring this deviation covering all conditions, finely changing the temperature setting and dealing with it is practically impossible, and often deviates from the predicted value due to factors such as congestion, As a result, the hold temperature often does not match the target value.
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a thermal analyzer capable of performing high-accuracy thermal analysis by reducing the deviation between the program temperature and the sample temperature as described above. It is.

In order to achieve the above object, the thermal analyzer of the present invention controls the heating furnace based on a predetermined temperature program in a state where the sample is arranged in the heating furnace, and the thermal change generated in the sample by this temperature control is controlled. In the thermal analyzer to be measured, sample temperature detecting means for detecting the sample temperature, temperature difference calculating means for calculating the temperature difference between the sample temperature and the program temperature set by the temperature program, and a temperature program based on the temperature difference And a temperature program correcting means for automatically correcting.
In addition, the thermal analyzer of the present invention calculates the temperature difference between the program temperature one sample before the temperature control cycle and the sample temperature at the time when the program temperature changes from the temperature increase or decrease state to the hold state. Difference calculation means and hold temperature update means for adding the temperature difference to the hold temperature and updating the hold temperature are provided.

  The thermal analysis apparatus of the present invention does not predict and correct the program temperature based on the past temperature measurement value, but the sample temperature and the program (target) temperature measured in real time one control cycle before the hold temperature reaching point. Is used as the correction amount of the target hold temperature, so that even if various conditions such as the temperature range to be used and the heating or cooling rate in the previous stage are different, a correction operation that always follows it is performed. The deviation between the sample temperature and the program temperature can be suppressed to a minimum in most cases.

  Embodiments of a thermal analyzer according to the present invention will be described with reference to the drawings. The thermal analyzer shown in FIG. 1 is a differential scanning calorimeter that controls the furnace body temperature Tf of the heating furnace body 1 and the heating furnace body 1 for heating the sample, and the temperature difference (DSC) between the sample S and the reference sample R. And an arithmetic control system 2 for measuring the signal) and calculating the amount of absorbed and generated heat. The heating furnace body 1 has a heater 3 wound around a furnace body 1a, and an aluminum sample cell 4 containing a sample S and a reference sample R and a reference sample cell 5 are inserted in the center and symmetrical with each other. A plate 6 made of a thermocouple material alloy (e.g., Constantan) placed in a positional relationship is installed.

  Thermocouples (for example, chromel and alumel wires) 7 and 8 that can correspond to the required temperature range are arranged immediately below the sample cell 4 and the reference sample cell 5 of the plate 6, respectively, and the sample temperature Ts is obtained from the output signal of the thermocouple 7. The temperature difference between the sample S and the reference sample R can be measured from between the chromel wires 7a and 8a of the thermocouples 7 and 8, and accompanying the physical and chemical changes generated in the sample S based on the temperature difference. Enthalpy change can be obtained.

  FIG. 2 is a block diagram showing the configuration of the arithmetic control system 2, and FIG. 3 is a response curve diagram showing the characteristics of the program temperature Tp, furnace temperature Tf, and sample temperatures Ts, Ts' obtained by the functions of the arithmetic control system 2. . The related operation of each function of the arithmetic control system 2 will be described below with reference to FIGS. A thermocouple 9 for detecting the inner wall temperature of the furnace body 1a is embedded in the vicinity of the heater 3 of the heating furnace body 1, and the output signal and the output signals of the thermocouples 7 and 8 are respectively the furnace body temperature of the arithmetic control system 2. A / D conversion is performed by the converter 10, the sample temperature converter 11, and the temperature difference converter 12, and the result is input to the arithmetic control unit 2 </ b> A mainly composed of a microcomputer.

  When measurement is started by pressing a measurement start button (not shown), a start signal X is input to the arithmetic control unit 2A and the temperature program 21 is activated, and a program temperature Tp set according to the temperature program as shown in FIG. Rises at a predetermined speed. This program temperature Tp is subtracted by the furnace body temperature Tf obtained by converting the output signal of the thermocouple 9 into a digital signal by the furnace body temperature converter 10 and the deviation detection function 22, and the deviation is PID operation by the PID calculation function 23. In addition, for example, when an AC power supply is used, it is converted into a firing angle by a firing angle converter 13. This firing angle is updated at every constant period τ to change the duty of the current supplied to the heater 3, and the temperature of the heating furnace body 1 is controlled.

  With the above temperature control, the furnace body temperature Tf rises following the program temperature Tp as shown in FIG. Further, the sample temperature Ts obtained by converting the output signal of the thermocouple 7 into a digital signal by the sample temperature converter 11 is lower than the program temperature Tp due to heat loss caused by the thermal resistance and heat capacity generated from the furnace body 1a to the sample cell 4. Follow with temperature.

The temperature difference ΔT between the sample temperature Ts and the program temperature Tp is calculated by the temperature difference calculation function 24 at regular intervals, and the previous value is updated and stored. Further, the temperature control cycle detection function 25 detects that the program temperature Tp has reached a time t1 one temperature control cycle τ before the time t0 when it reaches the hold temperature Th, and transmits a detection signal to the hold temperature update function 26. Then, the hold value Th is updated to Th ′ shown by the equation (1).
Th ′ = Th + ΔT (1)
As a result, as shown in FIG. 3, the program temperature Tp continues to rise at a constant rate until it reaches the hold temperature Th ′, and as a result, both the furnace temperature Tf and the sample temperature Ts continue to rise (each Tf ′ Ts ′) and the temperature actually held by Ts ′ are close to the original target hold temperature Th. Further, the output signal between the chromel wires 7a and 8a of the thermocouples 7 and 8 is converted into a temperature difference by the temperature difference converter 12, and further converted into an absorbed and exothermic flow rate (DSC signal) by the absorbed and exothermic amount conversion function 27. Analysis is performed.

  FIG. 4 is a flowchart showing the temperature control procedure of the arithmetic control unit 2A. When the temperature program is started and energization of the heater 3 is started (ST1), temperature control is performed based on the temperature program (ST2). When the temperature program reaches one sampling period before the transition from the temperature rising state to the hold state (ST3), the temperature difference ΔT (= Tp−Ts) between the program temperature Tp and the sample temperature Ts is measured and calculated. (ST4), the program hold temperature Th is rewritten to Th ′ (= Th + ΔT) (ST5). Thus, the temperature rising temperature control at a predetermined speed is continued until the program temperature Tp reaches Th ′ (ST6). When the program temperature Tp reaches Th ′, the control is switched to the hold temperature control (ST7), and the hold time at the predetermined temperature ends (ST8). Further, it is checked whether or not the next temperature program is executed (ST9). If yes, the next temperature program is repeatedly executed. If not, the process is terminated (ST10).

  In the above embodiment, the differential scanning calorimeter has been described. However, temperature control is similarly performed for other thermal analysis apparatuses that heat the furnace body temperature by a temperature program. Although the temperature program is described as shifting from the temperature rising state to the hold state, temperature control is performed in the same manner when the temperature falling state is shifted to the hold state. Further, the present invention is not limited to the above embodiment. For example, the input to the furnace temperature converter 10, the sample temperature converter 11, and the temperature difference converter 12 is switched by a multiplexer, and then one A / D converter sequentially. A / D conversion may be performed.

  It is used in a thermal analyzer such as a differential thermal analyzer, a differential scanning calorimeter, a thermogravimetric analyzer, or a thermomechanical analyzer.

It is a schematic block diagram of the differential scanning calorimeter by the Example of this invention. It is a block diagram of the arithmetic control system 2 which concerns on the Example of this invention. It is a various temperature characteristic figure of the differential scanning calorimeter by an Example. It is a flowchart which shows the procedure of the temperature control which concerns on an Example. It is various temperature characteristic diagrams of a conventional differential scanning calorimeter.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Heating furnace main body 1a Furnace body 2 Operation control system 2A Operation control part 3 Heater 4 Sample cell 5 Reference sample cell 6 Plate 7 Thermocouple 7a Chromel wire 8 Thermocouple 8a Chromel wire 9 Thermocouple 10 Furnace temperature converter 11 Sample temperature Converter 12 Temperature difference converter 13 Firing angle converter 21 Temperature program 22 Deviation detection function 23 PID calculation function 24 Temperature difference calculation function 25 Temperature control cycle detection function 26 Hold temperature update function 27 Absorption / heat generation amount conversion function R Reference sample S Sample X Start signal

Claims (2)

  Sample temperature detection means for detecting the sample temperature in a thermal analyzer that controls the heating furnace based on a predetermined temperature program in a state where the sample is arranged in the heating furnace, and measures the thermal change generated in the sample by this temperature control. And a temperature difference calculating means for calculating a temperature difference between the sample temperature and a program temperature set by the temperature program, and a temperature program correcting means for automatically correcting the temperature program based on the temperature difference. A thermal analyzer.   Temperature difference calculation means before one temperature control period for calculating the temperature difference between the program temperature and the sample temperature before one temperature control period when the program temperature changes from the temperature rising or falling state to the hold state, and hold the temperature difference 2. The thermal analyzer according to claim 1, further comprising hold temperature update means for updating the hold temperature by adding to the temperature.

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