THERMAL ANALYSIS DEVICE

Abstract

Revealbart is a thermal analysis device capable of accurately measuring the elastic modulus of materials with a high to low elastic modulus. The thermal analysis device comprises a probe for applying a load to a sample S, a force generator for generating and applying a force to the probe, displacement detectors for detecting the probe's displacement to measure the sample's mechanical properties, a force signal generator for generating a force signal to activate the force generator, a load detector for detecting a load applied to the sample, and ovens for heating the sample.The force signal generator comprises a digital signal generator that produces a digital signal of the force signal, a plurality of digital-to-analog converters (DACs) that convert the digital signals into analog signals, and a plurality of amplifiers that amplify each of the analog signals output from the respective DACs by different gain factors. The force signal generator outputs the analog signal, amplified by at least one of the plurality of amplifiers, as the force signal.

Description

[0001] The present disclosure relates to a thermal analysis device that measures the thermal behavior of a sample.

[0002] Traditionally, a method for evaluating the temperature characteristics of a sample is thermal analysis, which involves heating the sample and measuring temperature-dependent thermal behavior (physical changes) of the sample. Thermal analysis is defined in JIS 0129:2005, "General Rules for Thermal Analysis," as all methods for measuring the physical properties of a measurement target (sample) while controlling the temperature of the sample in a programmed manner.There are five commonly used thermal analysis methods: (1) differential thermal analysis (DTA) to measure temperature (temperature difference); (2) differential scanning calorimetry (DSC) to measure heat flow difference; (3) thermogravimetry (TG) to measure mass (weight change); (4) thermomechanical analysis (TMA) to measure mechanical properties; and (5) dynamic viscoelasticity measurement (DMA).

[0003] Among these, thermomechanical analysis (TMA) and dynamic viscoelasticity measurement (DMA) apply a load to a sample using a probe and detect the sample's shape change by measuring the displacement of the probe (see, for example, Patent Literatures 1 and 2). These allow the elastic modulus and expansion coefficient of a sample to be measured as a function of temperature or time.

[0004] For example, a dynamic viscoelasticity (DMA) device applies a stress or strain that varies (oscillates) over time to a sample and measures the resulting stress or strain in the sample to determine the mechanical properties (elastic modulus) of the sample.

[0005] Here, taking a dynamic viscoelasticity measurement (DMA) device as an example, the probe load (force) is generated as described below. First, an AC signal, such as a sine wave, square wave, or triangular wave, which is a digital signal output from an AC generator, is converted into an analog signal by a D / A converter. Then, the amplitude of the analog signal is adjusted by an amplifier and then input as a current to the coil of a force generator.

[0006] Consequently, an AC force is generated by electromagnetic interaction between the coil and a magnet provided around the coil, and this AC force is applied to the sample via the probe. [Related art literature]Patent literature [Patent Literature 1] Japanese Patent Application Publication No. H6-123722 [Patent Literature 2] Japanese Patent Application Publication No. H6-160269

[0007] The relationship between the maximum load that can be applied to a sample and a load resolution, which is the minimum load that can be applied to a sample, in a dynamic viscoelasticity measurement system or a thermomechanical analysis system is as described below.

[0008] For example, if the maximum load in a force generator is set to ±10N, a D / A converter with a digital resolution of 16 bits (two to the power of 16) would produce a “Load resolution = 20N(+ / -10N) / 16 bits = 20N / (2 16 ) = 0.305 mN”.

[0009] In recent years, the development of lightweight materials with high elastic modulus, such as carbon fiber composites, has progressed, and in dynamic viscoelasticity measurement and thermal analysis, such as thermomechanical analysis of such high elastic modulus samples, the maximum load to be applied to a sample must be increased.

[0010] However, as the maximum load increases, the load resolution also increases proportionally, as described above, and the measurement accuracy decreases at low loads close to the load resolution. On the other hand, as the digital resolution of the D / A converter increases, the load resolution theoretically decreases.

[0011] However, a 24-bit D / A converter would be expensive.

[0012] In practice, it is difficult to accurately measure materials with high to low elastic modulus using a single thermal analysis device.

[0013] The present disclosure has been made to solve the above problems, and an object of the present disclosure is to provide a thermal analysis apparatus capable of measuring materials having a wide range of elastic modulus from high to low with high accuracy.

[0014] This object is achieved by a thermal analysis device according to claim 1.

[0015] To achieve the above-mentioned object, the thermal analysis apparatus of the present disclosure includes: a probe extending axially, one end of the probe directly or indirectly contacting a sample to apply a load to the sample; a force generator provided at another end of the probe and generating a force in an axial direction of the probe; a displacement detector detecting a displacement of the probe in the axial direction to measure a mechanical property of the sample; a force signal generator generating a force signal to activate the force generator; a load detector detecting a load applied to the sample;and a furnace for heating the sample, wherein the force signal generator comprises 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 each of the analog signals output from the respective D / A converters by respective different gain factors, and the force signal generator outputs the analog signal amplified by at least one of the plurality of amplifiers as the force signal.;

[0016] With this thermal analysis device, the plurality of amplifiers can amplify each of the analog signals output from the respective D / A converters by different gain factors. This allows the maximum load that can be applied to the sample to be varied and different load resolutions to be set without changing the digital resolution of the D / A converter.

[0017] Consequently, it is possible to accurately measure materials with both high and low elastic moduli.

[0018] In the thermal analysis apparatus of the present disclosure, a difference in amplification factor of each of the plurality of amplifiers may be greater than or equal to twice.

[0019] With this thermal analysis device, the maximum load that can be applied to the sample can be varied significantly due to the large gain difference between each of the plurality of amplifiers.

[0020] The thermal analysis device may include a plurality of digital signal generators each generating a different digital signal, and includes a plurality of D / A converters and a plurality of amplifiers for each of the plurality of digital signal generators.

[0021] With this thermal analysis device, the plurality of digital signal generators can generate different digital signals, so that, for example, one of the digital signal generators can apply a DC force that is constant over time to the sample as a voltage (mechanical tension).

[0022] In the thermal analysis device of the present disclosure, the different digital signals may include an AC signal that oscillates over time and a DC signal that is constant over time.

[0023] According to the present disclosure, it is possible to obtain a thermal analysis device that can accurately measure materials with high to low elastic modulus.

[0024] Preferred embodiments of the present invention are explained in more detail below with reference to the accompanying drawings. They show: Fig. 1 is a view illustrating the structure of a thermal analysis apparatus according to a first embodiment of the present disclosure; Fig. 2 is a view showing load resolutions for different gain factors of an amplifier; and Fig. 3 is a view illustrating the structure of a thermal analysis apparatus according to a second embodiment of the present disclosure.

[0025] In the following, embodiments of the present disclosure are described with reference to the accompanying drawings.

[0026] Fig. 1 is a view illustrating the structure of a thermal analysis apparatus (dynamic viscoelasticity measurement apparatus) according to a first embodiment of the present disclosure.

[0027] A thermal analysis apparatus 1 is equipped with 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, 6b, and 6c that detect a displacement in the axial direction of the probe 10, a force signal generator 20, a load detector 7 that detects a load applied to the sample S, and furnaces 12a and 12b for heating the sample S.

[0028] Ends of the sample S in the vertical direction are held by a sample holding component 11. One end (in Fig. 1 upper end) of the sample holding component 11 is at one end (in Fig. 1 lower end) of the probe 10 and the probe 10 is supported by a probe carrier 15 in such a way that it is movable in the axial direction.

[0029] With this structure, one end of the probe 10 comes into indirect contact with the sample S via the sample holding member 11 and is designed to be capable of applying a load to the sample S.

[0030] Meanwhile, the other end (in Fig. 1 upper end) of the probe is fixed to the force generator 5. Although not shown in the drawings, the force generator 5 includes a coil and a permanent magnet surrounding the coil. When an electric current flows through the coil, it is displaced in the axial direction of the probe 10 to generate a force.

[0031] A core (iron core) 6b made of a conductor is fixed to the periphery of the probe 10, which is close to the power generator 5, and a differential transformer (primary and secondary coils) 6a is placed around the core 6b. A detector 6c detects the voltage of the differential transformer 6a. When the relative position of the core 6b (i.e., the probe 10) with respect to the differential transformer 6a changes, a voltage corresponding to the displacement is generated in the differential transformer 6a, and the displacement of the core 6b (i.e., the probe 10) in the axial direction can be detected.

[0032] The differential transformer 6a, the core 6b and the detector 6c form the “displacement detector”.

[0033] A heating furnace consisting of a furnace body 12a and a heating element 12b arranged around the furnace body 12a is provided around the sample S. The temperature of the furnace is controlled by a furnace controller 14.

[0034] The force signal generator 20 generates a force signal to activate the force generator 5. The force signal generator 20 is, for example, an electronic circuit composed of a circuit board and various electronic components and chips mounted on the circuit board.

[0035] The force signal generator 20 includes an alternating current (AC) generator (digital signal generator) 21 that generates a digital signal of the force signal, two D / A converters 22a and 22b that convert the digital signals into analog signals, two amplifiers 23a and 23b that amplify the analog signals output from the respective D / A converters 22a and 22b, and a voltage-current converter 24 that converts each of the analog signals (electrical voltages) output from the amplifiers 23a and 23b and outputs the current to the force generator 5.

[0036] The AC generator 21 generates a sinusoidal signal (AC signal) that oscillates over time. This sinusoidal signal (AC signal) is branched and input to two D / A converters 22a and 22b, which convert a digital signal into an analog signal (electrical voltage). The generated analog signals are output to the force generator 5 via the voltage-to-current converter 24 after the amplitudes of the analog signals are adjusted by the respective amplifiers 23a and 23b, and the force generator 5 generates a sinusoidal force (AC force).

[0037] The sinusoidal force (AC force) generated by the force generator 5 is applied to the sample S as a bending (deflection) stress through the probe 10 and the sample holding member 11. The bending (deflection) stress generated in the sample S by the stress is transmitted to the core 6b through the sample holding member 11 and the probe 10 and is detected as the positional displacement of the core 6b relative to the differential transformer 6a.

[0038] The outputs of the amplifiers 23a and 23b are sent to the load detector 7 via the voltage-current converter 24, and the sinusoidal force (AC force) based on the sinusoidal signal generated by the AC generator 21 is detected.

[0039] The displacement detection signal generated by the differential transformer 6b and the core 6a is sent to the displacement detector 6c and is converted into a displacement signal.

[0040] The load signal, which is the output of the load detector 7, and the displacement signal, which is the output of the displacement detector 8, are sent to a computing unit 9, where physical quantities (mechanical properties) of the sample, such as storage modulus and loss of elasticity, are calculated.

[0041] The features of the present disclosure are described below.

[0042] In the thermal analysis device 1 of the present disclosure, the force signal generator 20 includes two D / A converters 22a and 22b and two amplifiers 23a and 23b that amplify the analog signals output from the respective D / A converters 22a and 22b.

[0043] In the present disclosure, the plurality of amplifiers 23a and 23b can amplify each of the analog signals output from the respective D / A converters by different gain factors. This allows the maximum load that can be applied to the sample to be varied, and different load resolutions can be set without changing the digital resolutions of the D / A converters 22a and 22b.

[0044] Consequently, it is possible to accurately measure materials with high and low elastic moduli.

[0045] The amplifier can be adjusted to any gain by changing the resistance value, for example by combining an operational amplifier and two resistors.

[0046] In other words, to change the gain, the resistors can be replaced or variable resistors can be used. However, if gain accuracy is required, non-variable resistors must be used.

[0047] For example, assume that the maximum load that can be applied to sample S is ±10N, based on the capability of force generator 5, etc.

[0048] This maximum load is proportional to the current flowing through the coil of the force generator 5 and is also proportional to the analog signals (voltages) amplified by the amplifiers 23a and 23b before the analog signals are subjected to current conversion by the voltage-current converter 24.

[0049] Therefore, by changing the gain of each of the amplifiers 23a and 23b, the signal (current) output to the power generator 5 can be changed and the maximum load can be changed. Based on the fact that 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.

[0050] The force signal generator 20 outputs the analog signal amplified by at least one of the plurality of amplifiers 23a and 23b as the force signal. In this case, for example, if the user wishes to output an analog signal only from the amplifier 23a, only the amplifier 23a can be turned on and operated, and the other amplifiers 23b can be turned off according to the user selection made via the selection button or control screen.

[0051] The method for switching between amplifiers 23a and 23b is not limited, but the switching may be performed such that amplifier 23b outputs a signal first, and then amplifier 23a is used only when the load exceeds the maximum load of amplifier 23b. Alternatively, the switching may be performed such that amplifier 23b is used first, and when amplifier 23b is operating at its maximum load, the same value is output to amplifier 23a and the output of amplifier 23b is set to 0.

[0052] Then, when amplifier 23b reaches its maximum load, amplifier 23a begins performing an output. This cycle is repeated.

[0053] A specific example of changing the maximum load is described. When the outputs of the D / A converters 22a and 22b (in this example, the D / A converters are identical) are 1.0 V and the outputs of the amplifiers are 1.0 V (i.e., gain = 1), as shown in Fig. 2, the maximum load is ±10N.

[0054] Therefore, when the amplifier output is changed to 0.1 V (i.e., gain = 0.1), the maximum load changes to ±1.0 N.

[0055] If the digital resolutions of the D / A converters 22a and 22b are 16 bits, the maximum load output from the amplifier 23a with a gain of 1 is ±10 N and the load resolution = 20N (+ / -10N) / 16 bits = 20N / (2 16 ) = 0.305 mN.

[0056] On the other hand, since the maximum load output from the amplifier 23b with a gain of 0.1 is ±1.0 N, the load resolution = 2N(+ / -1 N) / 16 bits = 20N / (2 16 ) = 0.0305 mN.

[0057] Therefore, a single thermal analysis device can realize both 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 and excellent load resolution.

[0058] Next, with reference to Fig. 3, a thermal analysis device (dynamic viscoelasticity measurement (DMA) device) 1B according to a second embodiment of the present disclosure is described. Fig. 3 is a view showing the structure of the thermal analysis apparatus 1B.

[0059] The thermal analysis apparatus 1B is identical to the thermal analysis apparatus 1 of the first embodiment except for the configuration described below.

[0060] In the thermal analysis device 1B of the present disclosure, the force signal generator 30 includes an AC generator 21, two D / A converters 21a and 22b, and two amplifiers 23a and 23b, as in the thermal analysis device 1.

[0061] In addition, the force signal generator 30 includes a direct current (DC) generator (digital signal generator) 31 that generates a digital signal of the force signal, two D / A converters 32c and 32d that convert the digital signals into analog signals, two amplifiers 33c and 33d that amplify the analog signals output from the respective D / A converters 32c and 32d, and a voltage-current converter 34 that converts each of the analog signals (electrical voltages) output from the amplifiers 23a, 23b, 33c, and 33d and outputs the current to the force generator 5.

[0062] When a soft sample, such as a film, is measured with a dynamic viscoelasticity measurement device, a DC force that is constant over time is applied to the sample as a voltage to prevent the film-like sample from sagging and to maintain the sample shape. DC generator 31 generates this voltage.

[0063] In this way, as in the first embodiment, due to the two amplifiers 23a and 23b operating based on the output of the AC generator 21, a high load mode with a high maximum load and a low load mode with a low maximum load and excellent load resolution can be realized in a single thermal analysis device.

[0064] In addition, due to the two amplifiers 33c and 33d operating based on the output of the DC generator 31, it is possible to apply a voltage to the sample in both the high and low load modes, allowing measurements while maintaining the sample shape even though the load changes from high to low.

[0065] From the point of view of applying a voltage to the sample in both the high and low load modes, it is preferable that the difference between the gains of the two amplifiers 33c and 33d be the same as that of the amplifiers 23a and 23b, since a higher voltage (DC force) is required in the high load mode.

[0066] For example, in Fig. 2, the difference between the gains of amplifiers 23a and 23b in the high and low load modes is ten times. The difference between the gains of amplifiers 33c and 33d in the high and low load modes must also be ten times.

[0067] For example, in the high load mode, the voltage-current converter 34 combines the sinusoidal signal (voltage which is an AC signal) output from the amplifier 23a and the DC signal (voltage) output from the amplifier 33C, converts the combined signal into a current, and outputs the current.

[0068] In this case, for example, when the user selects the high load mode on the selection knob or control screen, each of the amplifiers can be turned on and off so that only the amplifiers 23a and 33c can be operated.

[0069] The present disclosure is not limited to the above embodiments.

[0070] For example, the present disclosure can be applied to a thermomechanical analysis (TMA) apparatus by replacing the AC generator 21 in the first embodiment with a DC generator.

[0071] The number of D / A converters and the number of corresponding amplifiers can be two or more.

[0072] One end of the probe can be in direct contact with the sample to apply a load to the sample.

[0073] The difference in the amplification factor of each of the plurality of amplifiers is preferably about ten times, but it is sufficient if the difference is at least a factor of 2.

[0074] The D / A converters can be identical or different from each other. The digital resolution of each D / A converter can be the same or different.

[0075] A digital signal generator, such as an AC generator or DC power generator, should be dedicated to a plurality of D / A converters that output a specific type of digital signal, such as AC or DC. For example, if AC generators are dedicated to individual D / A converters, the cost increases and the AC phases of the D / A converters may not match.

[0076] AC signals include sine waves, square waves, and triangular waves.

[0077] “At least one of the plurality of amplifiers” can be one, two, or all amplifiers. 1.1 B thermal analysis device 5 Power generator 6a, 6b, 6c Displacement detector 7 Load detector 10 probe 12a, 12b Oven 20, 30 force signal generator 21, 31 Digital signal generator 22a, 22b, 32c, 32d D / A converters 23a, 23b, 33c, 33d amplifiers S Sample QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] JP 6-123722

[0006] JP 6-160269

[0006]

Claims

[1] Thermal analysis device (1, 1B) having the following features: a probe (10) extending in an axial direction, one end side of the probe contacting a sample (S) directly or indirectly to apply a load to a sample; a force generator (5) provided at another end side of the probe and adapted to generate a force in the axial direction of the probe; a displacement detector (6a, 6b, 6c) that detects a displacement of the probe in the axial direction to measure a mechanical property of the sample; a force signal generator (20, 30) that generates a force signal to activate the force generator; a load detector (7) which detects a load applied to the sample; and an oven (12a, 12b) for heating the sample; wherein the force signal generator comprises 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 signal output from each of the plurality of D / A converters by different gain factors, respectively; and the force signal generator outputs the analog signal amplified by at least one of the plurality of amplifiers as the force signal. [2] The thermal analysis apparatus according to claim 1, wherein a difference in amplification factor of each of the plurality of amplifiers is greater than or equal to twice. [3] A thermal analysis device according to claim 1 or 2, wherein the thermal analysis device (1B) comprises a plurality of digital signal generators (21, 31) each generating a different digital signal, and a plurality of said D / A converters (22a, 22b, 32c, 32d) and a plurality of said amplifiers (23a, 23b, 33c, 33d) for each of the plurality of digital signal generators. [4] A thermal analysis device according to claim 3, wherein the different digital signals comprise an AC signal that oscillates over time and a DC signal that is constant over time.

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