Thermal analysis device

Abstract

To provide a thermal analysis device capable of accurately measuring materials ranging from a high elasticity modulus to a low elasticity modulus.SOLUTION: A thermal analysis device 1 comprises: a probe 10 applying a load to a sample S; a force generator 5 making the probe generate force; deviation detectors 6a, 6b, 6c detecting dynamical characteristics of the sample by detecting deviation of the probe; a force signal generator 20 generating a force signal which makes the force generator operate; a load detector 7 detecting a load applied to the sample; and heating furnaces 12a, 12b for heating the sample. In the thermal analysis device, the force signal generator includes: a digital signal generator 21 generating a digital signal of a force signal; a plurality of D / A converters 22a, 22b converting a digital signal to an analog signal; and a plurality of amplifiers 23a, 23b amplifying analog signals outputted from the plurality of D / A converters respectively, by a respectively different amplification factor. The force signal generator outputs an analog signal which has been amplified by at least one of the plurality of amplifiers, as a force signal.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a thermal analysis device for measuring the thermal behavior of a sample. [Background technology]

[0002] Traditionally, a method known as thermal analysis has been used to evaluate the temperature characteristics of a sample. The sample is heated and the thermal behavior (physical changes) of the sample is measured as the temperature changes. Thermal analysis is defined in JIS K 0129:2005 "General Rules for Thermal Analysis," and all methods that measure the physical properties of the sample when the temperature of the measurement target (sample) is program-controlled are considered thermal analysis. There are five commonly used thermal analysis methods: (1) differential thermal analysis (DTA) that detects temperature (temperature difference), (2) differential scanning calorimetry (DSC) that detects heat flow difference, (3) thermogravimetry (TG) that detects mass (weight change), (4) thermomechanical analysis (TMA) that detects mechanical properties, and (5) dynamic mechanical analysis (DMA).

[0003] Among these, thermomechanical analysis (TMA) and dynamic mechanical analysis (DMA) apply a load to a sample using a probe, and detect the change in shape of the sample as the displacement of the probe (see, for example, Patent Documents 1 and 2). This makes it possible to measure the elastic modulus or expansion coefficient of the sample as a function of temperature or time. For example, a dynamic mechanical analysis (DMA) device applies a time-varying (oscillating) stress or strain to a sample, measures the resulting strain or stress in the sample, and determines the mechanical properties (elastic modulus) of the sample.

[0004] Taking a dynamic mechanical analysis (DMA) device as an example, the load (force) of the probe is generated as follows: First, the digital signal output from an AC generator, which may be a sine wave, square wave, or triangular wave, is converted to an analog signal by a D / A converter, and the amplitude of this analog signal is adjusted by an amplifier before being input as a current to the coil of the force generator. As a result, an AC force is generated by electromagnetic cooperation between the coil and a magnet provided around it, and this AC force is applied to the sample via the probe. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 6-123722 [Patent Document 2] Japanese Patent Application Publication No. 6-160269 Summary of the Invention [Problem to be solved by the invention]

[0006] In the dynamic viscoelasticity measuring device or thermomechanical analyzer, the relationship between the maximum load that can be applied to a sample and the load resolution, which is the minimum load that can be applied to a sample, is as follows. For example, if the maximum load of the force generator is ±10N, and a D / A converter with a digital resolution of 16 bits (2 to the power of 16) is used, the load resolution = 20N (+ / -10N) / 16 bits = 20N / (2 16 ) = 0.305mN.

[0007] In recent years, there has been progress in the development of lightweight materials with high elastic modulus, such as carbon fiber composite materials. In dynamic viscoelastic measurements of such high elastic modulus samples and thermal analyses such as thermomechanical analysis, there is a demand for improving the maximum load in order to increase the load applied to the sample. However, as mentioned above, if the maximum load is increased, the load resolution also increases proportionally, resulting in a problem of reduced measurement accuracy at low loads close to the load resolution. On the other hand, if the digital resolution of the D / A converter is increased, the load resolution theoretically decreases, but for example, a 24-bit D / A converter would be expensive. As such, it is actually difficult to accurately measure materials with high and low modulus of elasticity using a single thermal analysis device.

[0008] The present invention has been made to solve the above problems, and has an object to provide a thermal analysis device capable of measuring materials with a wide range of elastic modulus from high to low with high accuracy. [Means for solving the problem]

[0009] In order to achieve the above object, a thermal analysis apparatus of the present invention includes a probe extending in an axial direction, one end of which is in direct or indirect contact with a sample and applies a load to the sample, a force generator provided on the other end of the probe and generating a force in the axial direction of the probe, a displacement detector detecting mechanical properties of the sample by detecting displacement of the probe in the axial direction, a force signal generator generating a force signal to operate the force generator, a load detector detecting a load applied to the sample, and a heating furnace for heating the sample, wherein the force signal generator includes a digital signal generator generating a digital signal of the force signal, a plurality of D / A converters converting the digital signal into an analog signal, and a plurality of amplifiers amplifying the analog signals output from each of the plurality of D / A converters at different amplification factors, and the force signal generator outputs the analog signal amplified by at least one of the plurality of amplifiers as the force signal.

[0010] In this thermal analysis device, multiple amplifiers amplify the analog signals output from the multiple D / A converters at different amplification factors, which allows the maximum load that can be applied to the sample to be changed and allows different load resolutions to be set without changing the digital resolution of the D / A converters. As a result, materials with high elastic modulus to materials with low elastic modulus can be measured with high accuracy.

[0011] In the thermal analysis apparatus of the present invention, a difference between the amplification factors of the plurality of amplifiers may be two or more. According to this thermal analysis apparatus, the difference in amplification factor between the multiple amplifiers becomes large, and the maximum load that can be applied to the sample can be changed significantly.

[0012] The thermal analysis apparatus of the present invention may include a plurality of the digital signal generators, each of which generates a different digital signal, and each of the plurality of digital signal generators may have a plurality of the D / A converters and the amplifiers. According to this thermal analysis apparatus, a plurality of digital signal generators each generate a different digital signal, so that, for example, one of the digital signal generators can apply a constant DC force over time as tension to the sample.

[0013] In the thermal analysis apparatus of the present invention, the different digital signals may be an AC signal that oscillates with time and a DC signal that is constant with time. Effect of the Invention

[0014] According to the present invention, a thermal analysis device capable of measuring materials with high and low moduli of elasticity with high accuracy is provided. [Brief description of the drawings]

[0015] [Figure 1] 1 is a diagram showing a configuration of a thermal analysis instrument according to a first embodiment of the present invention. [Diagram 2] FIG. 13 is a diagram showing the weight resolution when the amplification factor of the amplifier is changed. [Diagram 3] FIG. 4 is a diagram showing the configuration of a thermal analysis instrument according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing the configuration of a thermal analysis instrument (dynamic viscoelasticity measurement (DMA) instrument) 1 according to a first embodiment of the present invention. The thermal analysis apparatus 1 includes a rod-shaped probe 10 extending in the axial direction, a force generator 5 that generates a force in the axial direction of the probe 10, displacement detectors 6a to 6c that detect the axial displacement of the probe 10, a force signal generator 20, a load detector 7 that detects the load applied to the sample S, and heating furnaces 12a, 12b for heating the sample S.

[0017] Both vertical ends of the sample S are fixed and held by a sample holding member 11. One end (the upper end in FIG. 1) of the sample holding member 11 is fixed to one end side (the lower end in FIG. 1) of a probe 10, and the probe 10 is supported by a probe support 15 so as to be movable in the axial direction. This allows one end of the probe 10 to indirectly contact the sample S via the sample holding member 11, making it possible to apply a load to the sample S.

[0018] Meanwhile, the other end of the probe (the upper end in FIG. 1) is fixed to a force generator 5. Although not shown, the force generator 5 includes a coil and a permanent magnet surrounding the coil, and when a current flows through the coil, the probe 10 is displaced in the axial direction to generate a force. Additionally, a core (iron core) 6b made of a conductor is fixed to the outer periphery of the portion of the probe 10 close to the force generator 5, and a differential transformer (primary coil and secondary coil) 6a is disposed around the core 6b. Furthermore, a detector 6c detects the voltage of the differential transformer 6a. When the position of the core 6b (and thus the probe 10) changes relative to the differential transformer 6a, a voltage is generated in the differential transformer 6a in response to the displacement, so that the axial displacement of the core 6b (and thus the probe 10) can be detected. The differential transformer 6a, the core 6b and the detector 6c constitute a "displacement detector."

[0019] A heating furnace consisting of a furnace body 12a and a heater 12b arranged around the furnace body 12a is provided around the sample S, and the temperature of the heating furnace is controlled by a heating furnace controller 14.

[0020] The force signal generator 20 generates a force signal that operates the force generator 5. The force signal generator 20 is, for example, an electronic circuit in which various electronic components and chips are mounted on a circuit board. More specifically, the force signal generator 20 has an AC generator (digital signal generator) 21 that generates a digital signal of the force signal, two D / A converters 22a, 22b that convert the digital signal into an analog signal, two amplifiers 23a, 23b that amplify the analog signals output from the D / A converters 22a, 22b, respectively, and a voltage-current converter 24 that converts the analog signals (voltages) of the amplifiers 23a, 23b into currents and outputs the currents to the force generator 5.

[0021] Then, AC generator 21 generates a sine wave signal (AC signal) that oscillates with time, and this sine wave signal (AC signal) is branched and input to two D / A converters 22a and 22b, where it is converted from a digital signal to an analog signal (voltage). Furthermore, the converted analog signals have their amplitudes adjusted by amplifiers 23a and 23b, respectively, and are then output to force generator 5 via voltage-current converter 24, generating a sine wave force (AC force). The sinusoidal force (AC force) generated by the force generator 5 is applied as a bending (deflection) stress to the sample S via the probe 10 and the sample holding member 11. Meanwhile, the bending (deflection) strain caused in the sample S by this stress is transmitted to the core 6b via the sample holding member 11 and the probe 10, and is detected as a displacement of the position of the core 6b relative to the differential transformer 6a.

[0022] Moreover, the outputs of the amplifiers 23a and 23b are sent to the load detector 7 via a voltage-current converter 24, and the sinusoidal wave force (AC force) generated by the AC generator 21 is detected. A displacement detection signal by the differential transformer 6b and the core 6a is sent to the displacement detector 6c and converted into a displacement signal. A load signal output from the load detector 7 and a displacement signal output from the displacement detector 8 are sent to a calculator 9, which calculates physical quantities (mechanical properties) of the sample, such as storage elastic modulus and loss elasticity.

[0023] Next, the characteristic features of the present invention will be described. In the thermal analysis apparatus 1 of the present invention, the force signal generator 20 includes two D / A converters 22a and 22b, and two amplifiers 23a and 23b that respectively amplify the analog signals output from the D / A converters 22a and 22b. In the present invention, the multiple amplifiers 23a, 23b amplify the analog signals output from the multiple D / A converters 22a, 22b with different amplification factors, respectively. This makes it possible to change the maximum load that can be applied to the sample S, and to set different load resolutions for each of the D / A converters 22a, 22b without changing the digital resolution of the D / A converters 22a, 22b. As a result, materials with high elastic modulus to materials with low elastic modulus can be measured with high accuracy.

[0024] In addition, an amplifier can be set to any gain by combining an OP amp (operational amplifier) ​​with two resistors and changing the resistance value. In other words, to change the gain, you can either replace the resistor or use a variable resistor, but if a high accuracy in the gain is required, it is better to use a non-variable resistor.

[0025] For example, it is assumed that the maximum load that can be applied to the sample S is ±10 N based on the capacity of the force generator 5, etc. This maximum load is proportional to the current flowing through the coil of the force generator 5, and further proportional to the analog signal (voltage) amplified by the amplifiers 23a and 23b before current conversion by the voltage-to-current converter 24. Therefore, by changing the amplification factor of each of the amplifiers 23a and 23b, the signal (current) output to the force generator 5 can be changed, and the maximum load can be changed. Since load resolution = maximum load / (digital resolution of the D / A converter), the load resolution can be changed without changing the digital resolution of the D / A converter.

[0026] The force signal generator 20 outputs an analog signal amplified by at least one of the amplifiers 23a and 23b as a force signal. In this case, if the user wishes to output only from the amplifier 23a, for example, the user may select this on a selection button or control screen, so that only the amplifier 23a is powered on and operates, and the other amplifier 23b is powered off. The method of switching between the amplifiers 23a and 23b is not limited, but an example of the control is to first output from the amplifier 23b, and then use the amplifier 23a when the load exceeds the maximum value of the amplifier 23b. Another method is to first use the amplifier 23b, and when the amplifier 23b reaches its maximum, output the same value to the amplifier 23a and set the output of the amplifier 23b to 0. Then, when the amplifier 23b reaches its maximum again, the cycle of outputting to the amplifier 23a is repeated.

[0027] As a specific example of changing the maximum load, assume that the maximum load is ±10 N when the output of D / A converters 22a and 22b (in this example, each D / A converter is identical) is 1.0 V and the output of the amplifier is 1.0 V (i.e., amplification factor = 1), as shown in Figure 2. Therefore, if the amplifier output is changed to 0.1V (i.e., amplification factor = 0.1), the maximum load will change to ±1.0N.

[0028] When the digital resolution of the D / A converters 22a and 22b is 16 bits, the maximum load output from the amplifier 23a with an amplification factor of 1 is ±10N, so the load resolution = 20N (+ / -10N) / 16bit = 20N / (2 16 ) = 0.305mN. On the other hand, since the maximum load output from the amplifier 23b with an amplification factor of 0.1 is ±1.0N, the load resolution is 2N(+ / -1N) / 16bit=20N / (2 16 ) = 0.0305mN. This makes it possible to realize, in a single thermal analysis device, a high load mode with a high maximum load of ±10 N and a low load mode with a low maximum load of ±1 N but excellent load resolution.

[0029] Next, a thermal analysis instrument (dynamic viscoelasticity measurement (DMA) instrument) 1B according to a second embodiment of the present invention will be described with reference to Fig. 3. Fig. 3 is a diagram showing the configuration of the thermal analysis instrument 1B. The thermal analysis apparatus 1B is the same as the thermal analysis apparatus 1 according to the first embodiment except for the configuration described below, so the same components are denoted by the same reference numerals and the description thereof will be omitted.

[0030] In the thermal analysis apparatus 1B, the force signal generator 30, like the thermal analysis apparatus 1, includes an AC generator 21, two D / A converters 22a and 22b, and two amplifiers 23a and 23b. Furthermore, the force signal generator 30 has a DC force generator (digital signal generator) 31 that generates a digital signal of the force signal, two D / A converters 32c, 32d that convert the digital signal of the DC force generator 31 into an analog signal, two amplifiers 33c, 33d that amplify the analog signals output from the D / A converters 32c, 32d, respectively, and a voltage-current converter 34 that converts the analog signals (voltages) of the amplifiers 23a, 23b, 33c, 33d into currents and outputs them to the force generator 5.

[0031] When a soft sample such as a film is measured using a dynamic viscoelasticity measuring device, a constant DC force is applied to the sample as tension over time in order to prevent relaxation of the film-like sample and maintain the shape of the sample. The DC force generator 31 generates this tension. In this manner, similar to the first embodiment, a high load mode with a high maximum load and a low load mode with a low maximum load but excellent load resolution can be realized in a single thermal analysis device by using two amplifiers 23a, 23b based on the output of the AC generator 21.

[0032] At the same time, based on the output of the DC force generator 31, the two amplifiers 33c, 33d can apply tension to the sample in high load mode and low load mode, respectively, allowing measurements to be performed while maintaining the sample shape in response to changes in load from the high load mode to the low load mode. From the viewpoint of applying tension to the sample in both the high load mode and the low load mode, since a higher tension (DC force) is required in the high load mode, it is preferable that the difference in the amplification factor of the two amplifiers 33c, 33d is the same as the difference in the amplification factor of the amplifiers 23a, 23b. For example, in FIG. 2, the difference in the amplification factor of the amplifiers 23a, 23b in the high load mode and the low load mode is 10 times, but it is preferable that the difference in the amplification factor of the amplifiers 33c, 33d corresponding to the high load mode and the low load mode, respectively, is also 10 times.

[0033] Also, for example, in the high load mode, the voltage-to-current converter 34 combines the sine wave signal (voltage, which is an AC signal) output from the amplifier 23a and the DC signal (voltage) output from the amplifier 33c, converts it into a current, and outputs it. In this case, for example, when the user selects the high load mode using a selection button or a control screen, the power supply for each amplifier is turned on and off so that only the amplifiers 23a and 33c are in operation.

[0034] The present invention is not limited to the above-described embodiments. For example, by replacing the AC generator 21 in the first embodiment with a DC force generator, the present invention can be applied to a thermomechanical analysis (TMA) device. Furthermore, the number of D / A converters and corresponding amplifiers may be two or more. One end of the probe may be in direct contact with the sample to apply a load to the sample. The difference between the amplification factors of the plurality of amplifiers is preferably about 10 times, and more preferably at least 2 times.

[0035] The D / A converters may be the same or different, and the digital resolution of each D / A converter may be the same or different. It is preferable to provide one digital signal generator, such as an AC generator or a DC generator, for multiple D / A converters that are to output a specific type of digital signal, such as AC or DC. For example, providing a separate AC generator for each of multiple D / A converters increases costs and there is a risk that the phases of the AC for each D / A converter will not match. Examples of the AC signal include a sine wave, a square wave, and a triangular wave. "At least one of the multiple amplifiers" may mean one, two, or all of the multiple amplifiers. [Explanation of symbols]

[0036] 1,1B Thermal analyzer 5 Force Generator 6a, 6b, 6c Displacement detector 7 Load detector 10 Probes 12a, 12b Furnace 20,30 Force signal generator 21,31 Digital signal generator 22a, 22b, 32c, 32d D / A converters 23a, 23b, 33c, 33d Amplifiers S sample

Claims

1. a probe extending in an axial direction, one end of which directly or indirectly contacts a sample and applies a load to the sample; a force generator provided on the other end side of the probe and configured to generate a force in the axial direction of the probe; a displacement detector that detects a displacement of the probe in the axial direction to thereby detect a mechanical property of the sample; a force signal generator for generating a force signal for operating the force generator; A load detector for detecting a load applied to the sample; a heating furnace for heating the sample; In a thermal analysis apparatus comprising: the force signal generator includes a digital signal generator that generates a digital signal of the force signal, a plurality of D / A converters that convert the digital signal into an analog signal, and a plurality of amplifiers that amplify the analog signals output from the plurality of D / A converters at different amplification factors, and wherein the force signal generator outputs the analog signal amplified by at least one of the plurality of amplifiers as the force signal.

2. 2. The thermal analysis apparatus according to claim 1, wherein the difference between the amplification factors of the plurality of amplifiers is two or more.

3. a plurality of the digital signal generators are provided, each of the digital signal generators generating a different digital signal; 3. The thermal analysis apparatus according to claim 1, further comprising a plurality of said D / A converters and said amplifiers for each of said plurality of digital signal generators.

4. 4. The thermal analysis apparatus according to claim 3, wherein the different digital signals are an AC signal that oscillates with time and a DC signal that is constant with time.

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