Thermal analysis device

Abstract

A thermal analyzer is provided. A thermal analysis device (1) is provided with: a probe (10) that applies a load to a sample (S); a force generator (5) that causes the probe to generate a force; displacement detectors (6a, 6b, 6c) that detect the mechanical properties of the sample by detecting the displacement of the probe; a force signal generator (20) for generating a force signal for operating the force generator; a load detector (7) that detects a load applied to the sample; and heating furnaces (12a, 12b) for heating the sample, the force signal generator having: a digital signal generator (21) for generating a digital signal of the force signal; a plurality of D / A converters (22a, 22b) for converting the digital signal into an analog signal; and a plurality of amplifiers (23a, 23b) that amplify 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 a force signal.

Description

Technical Field

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

[0002] In the past, as a method for evaluating the temperature characteristics of a sample, a method called thermal analysis has been performed. In this thermal analysis, the sample is heated and the thermal behavior (physical change) of the sample accompanying the temperature change is measured. Thermal analysis is defined by JIS K0129:2005 "General Rules for Thermal Analysis", and all methods for measuring the physical properties of the sample under program control of the temperature of the measurement object (measurement sample) are thermal analysis. Commonly used thermal analyses include (1) differential thermal analysis (DTA) for detecting temperature (temperature difference), (2) differential scanning calorimetry (DSC) for detecting heat flow difference, (3) thermogravimetric measurement (TG) for detecting mass (weight change), (4) thermomechanical analysis (TMA) for detecting mechanical properties, and (5) dynamic viscoelasticity measurement (DMA).

[0003] Among them, in thermomechanical analysis (TMA) and dynamic viscoelasticity measurement (DMA), a load is applied to a sample by a probe, and the shape change of the sample at this time is detected as the displacement of the probe (for example, refer to Patent Documents 1 to 2). In this way, the elastic modulus and expansion coefficient of the sample can be measured as a function of temperature or time.

[0004] For example, a dynamic viscoelasticity measurement (DMA) apparatus applies stress or strain that changes (vibrates) over time to a sample, measures the resulting strain or stress of the sample, and determines the mechanical properties (elastic modulus) of the sample.

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

[0006] Thus, a force based on alternating current is generated by electromagnetic interaction between the coil and a magnet provided around the coil, and this force is applied to the sample via the probe.

[0007] Prior art literature

[0008] Patent Literature

[0009] Patent Document 1: Japanese Patent Application Laid-Open No. 6-123722

[0010] Patent Document 2: Japanese Patent Application Laid-Open No. 6-160269 Summary of the invention

[0011] Problems to be solved by the invention

[0012] However, the relationship between the maximum load that can be applied to a sample and the minimum load that can be applied to the sample, that is, the load resolution, in a dynamic viscoelasticity measuring device or a thermomechanical analysis device is as follows.

[0013] For example, when the maximum load in the force generator is set to ±10N, if a D / A converter with a digital resolution of 16 bits (2 to the 16th power) is used, the load resolution = 20N (+ / -10N) / 16 = 20N / (2 16 )=0.305mN.

[0014] Furthermore, in recent years, lightweight and high elastic modulus materials such as carbon fiber composite materials have been developed. In order to increase the load applied to the sample in thermal analysis such as dynamic viscoelasticity measurement and thermomechanical analysis of such high elastic modulus samples, it is required to increase the maximum load.

[0015] However, if the maximum load is increased, the load resolution is proportionally increased as described above, and there is a problem of reduced measurement accuracy in measurements 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 will theoretically decrease, but the cost of a 24-bit D / A converter, for example, will increase.

[0016] Thus, it is actually difficult to perform high-precision measurements on both high elastic modulus materials and low elastic modulus materials using one thermal analysis device.

[0017] The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a thermal analysis device capable of measuring materials ranging from high elastic modulus materials to low elastic modulus materials.

[0018] Means for solving problems

[0019] In order to achieve the above-mentioned object, the thermal analysis device of the present invention comprises: a probe extending in an axial direction, one end side of which is in direct or indirect contact with a sample to apply a load to the sample; a force generator, which is arranged on the other end side of the probe and generates a force in the axial direction of the probe; a displacement detector, which detects the mechanical properties of the sample by detecting the displacement of the probe in the axial direction; a force signal generator, which generates a force signal for causing the force generator to operate; a load detector, which detects the load applied to the sample; and a heating furnace, which is used to heat the sample, characterized in that the force signal generator has: a digital signal generator, which generates a digital signal of the force signal; a plurality of D / A converters, which convert the digital signal into an analog signal; and a plurality of amplifiers, which amplify the analog signals outputted from 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.

[0020] According to the thermal analysis device, the plurality of amplifiers amplify the analog signals outputted from the plurality of D / A converters at different amplification factors, thereby making it possible to change the maximum load that can be applied to the sample and set different load resolutions even without changing the digital resolution of the D / A converters.

[0021] As a result, both high elastic modulus materials and low elastic modulus materials can be measured with high accuracy.

[0022] In the thermal analysis device of the present invention, the difference in the amplification factor between each of the plurality of amplifiers may be two times or more.

[0023] According to this thermal analysis apparatus, the difference in amplification factor among the plurality of amplifiers becomes large, and the maximum load that can be applied to the sample can be greatly changed.

[0024] The thermal analysis device 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 include a plurality of the D / A converters and the amplifiers.

[0025] According to this thermal analysis apparatus, since the plurality of digital signal generators generate respective different digital signals, for example, one of the digital signal generators can apply a force based on direct current that is constant with respect to time to the sample as tension.

[0026] In the thermal analysis device 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 respect to time.

[0027] Effects of the Invention

[0028] According to the present invention, it is possible to obtain a thermal analysis device capable of measuring materials ranging from high elastic modulus materials to low elastic modulus materials with high accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a diagram showing the structure of the thermal analysis device according to the first embodiment of the present invention.

[0030] Figure 2 It is a graph showing the load resolution when the gain of the amplifier is changed.

[0031] Figure 3 It is a diagram showing the structure of a thermal analysis device according to a second embodiment of the present invention.

[0032] Description of Reference Numerals

[0033] 1.1B: Thermal analysis device

[0034] 5: Force generator

[0035] 6a, 6b, 6c: Displacement detectors

[0036] 7: Load detector

[0037] 10: Probe

[0038] 12a, 12b: Heating furnace

[0039] 20, 30: Force signal generator

[0040] 21, 31: Digital signal generator

[0041] 22a, 22b, 32c, 32d: D / A converter

[0042] 23a, 23b, 33c, 33d: Amplifier

[0043] S: Sample DETAILED DESCRIPTION

[0044] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0045] Figure 1 It is a diagram showing the structure of a thermal analysis device (dynamic viscoelasticity measurement (DMA) device) 1 according to the first embodiment of the present invention.

[0046] The thermal analysis device 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~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.

[0047] The sample S is fixedly held at both ends in the vertical direction by the sample holding member 11. Figure 1 The upper end of the probe 10 is fixed to one end side ( Figure 1 The probe 10 is supported by the probe support 15 so as to be movable in the axial direction.

[0048] Thus, one end side of the probe 10 can indirectly contact the sample S via the sample holding member 11 , so that a load can be applied to the sample S.

[0049] On the other hand, the other end side of the probe ( Figure 1 The probe 10 is fixed to the upper end thereof (at the upper end thereof) on the force generator 5. Although not shown in the figure, the force generator 5 includes a coil and a permanent magnet surrounding the coil, and generates force by passing a current through the coil to displace the probe 10 in the axial direction.

[0050] In addition, a core (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 arranged around the core 6b. And the 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 corresponding to the displacement, so that the axial displacement of the core 6b (and thus the probe 10) can be detected.

[0051] The differential transformer 6a, the core 6b and the detector 6c constitute a "displacement detector".

[0052] A heating furnace including a furnace body 12 a and a heater 12 b disposed around the furnace body 12 a is provided around the sample S, and the temperature of the heating furnace is controlled by a heating furnace controller 14 .

[0053] The force signal generator 20 generates a force signal for operating 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.

[0054] In more detail, the force signal generator 20 has: an AC generator (digital signal generator) 21 that generates a digital signal of a force signal; two D / A converters 22a, 22b that convert digital signals into analog signals; two amplifiers 23a, 23b that respectively amplify the analog signals output from the D / A converters 22a, 22b; and a voltage-to-current converter 24 that converts the analog signals (voltage) of the amplifiers 23a, 23b into current and outputs it to the force generator 5.

[0055] Furthermore, a sinusoidal wave signal (AC signal) vibrating according to time is generated by the AC generator 21, and the sinusoidal wave signal (AC signal) is branched and input to two D / A converters 22a and 22b, and converted from a digital signal to an analog signal (voltage). Furthermore, the converted analog signal is adjusted in amplitude by amplifiers 23a and 23b, respectively, and then output to the force generator 5 via the voltage-current converter 24, thereby generating a sinusoidal wave force (force based on AC power).

[0056] The sinusoidal wave force (force based on alternating current) generated by the force generator 5 is applied to the sample S as bending (flexural) stress via the probe 10 and the sample holding member 11. On the other hand, the bending (flexural) deformation generated in the sample S due to the stress is transmitted to the core 6b via the sample holding member 11 and the probe 10, and is detected as the displacement of the position of the core 6b relative to the differential transformer 6a.

[0057] The outputs of the amplifiers 23 a and 23 b are sent to the load detector 7 via the voltage-current converter 24 , and the sinusoidal wave force (AC power) generated by the AC generator 21 is detected.

[0058] The displacement detection signal based on the differential transformer 6a and the core 6b is sent to the displacement detector 6c and converted into a displacement signal.

[0059] The load signal as the output of the load detector 7 and the displacement signal as the output of the displacement detector 6 c are sent to the calculation unit 9 , and physical quantities (mechanical properties) of the sample such as storage modulus and loss elasticity are calculated.

[0060] Next, the characteristic features of the present invention will be described.

[0061] In the thermal analysis device 1 of the present invention, the force signal generator 20 includes two D / A converters 22a and 22b and two amplifiers 23a and 23b for amplifying analog signals output from the D / A converters 22a and 22b, respectively.

[0062] In the present invention, the plurality of amplifiers 23a and 23b amplify the analog signals outputted from the plurality of D / A converters 22a and 22b at different amplification factors, thereby making it possible to change the maximum load that can be applied to the sample S, and even without changing the digital resolution of the D / A converters 22a and 22b, different load resolutions can be set.

[0063] As a result, both high elastic modulus materials and low elastic modulus materials can be measured with high accuracy.

[0064] In addition, the amplifier can be set to any gain factor by combining an OP amplifier (operational amplifier) ​​and two resistors and changing the resistance value. That is, the resistor can be replaced or a variable resistor can be used to change the gain factor, but when the accuracy of the gain factor is required, a non-variable resistor can be used.

[0065] For example, it is assumed that the maximum load that can be applied to the sample S is ±10 N, based on the capability of the force generator 5 and the like. This maximum load is proportional to the current flowing through the coil of the force generator 5 and is further proportional to the analog signal (voltage) amplified by the amplifiers 23 a and 23 b before the current conversion by the voltage-to-current converter 24.

[0066] Therefore, by changing the amplification factor of each amplifier 23a, 23b, the signal (current) output to the force generator 5 can be changed, and the maximum load can be changed. Load resolution = maximum load / (digital resolution of D / A converter), so the load resolution can be changed without changing the digital resolution of the D / A converter.

[0067] In addition, the force signal generator 20 outputs the analog signal amplified by at least one of the plurality of amplifiers 23a and 23b as a force signal. At this time, for example, if it is desired to output only from the amplifier 23a, when the user selects this on the selection button or control screen, the power of the amplifier 23a can be turned on only, and the power of the other amplifier 23b can be turned off.

[0068] The method of switching amplifiers 23a and 23b is not limited, and for example, the following control can be cited: amplifier 23b is output first, and amplifier 23a is used in the case of a load exceeding the maximum value of amplifier 23b. In addition, as another method, amplifier 23b is used first, and when amplifier 23b reaches the maximum, the same value is output to amplifier 23a, and the output of amplifier 23b is set to 0. In addition, a method of repeating the step of outputting to amplifier 23a when amplifier 23b reaches the maximum again is cited.

[0069] As a specific example of changing the maximum load, Figure 2 As shown, when the output of the D / A converters 22a and 22b (in this example, the D / A converters are identical) is 1.0V and the output of the amplifier is 1.0V (ie, amplification factor = 1), the maximum load is ±10N.

[0070] Therefore, if the output of the amplifier is changed to 0.1 V (ie, amplification factor = 0.1), the maximum load change is ±1.0 N.

[0071] When the digital resolution of the D / A converters 22a and 22b is 16 bits, the maximum load output from the amplifier 23a with a gain of 1 is ±10N. Therefore, the load resolution = 20N (+ / -10N) / 16bit = 20N / (2 16 )=0.305mN.

[0072] On the other hand, since the maximum load output from the amplifier 23b with amplification factor = 0.1 is ±1.0N,

[0073] Load resolution = 2N (+ / -1N) / 16bit = 2N / (2 16 )=0.0305mN.

[0074] Thus, a high load mode with a maximum load of up to ±10N and a low load mode with a maximum load as low as ±1N but excellent load resolution can be achieved with one thermal analysis device.

[0075] Next, refer to Figure 3 , a thermal analysis device (dynamic viscoelasticity measurement (DMA) device) 1B according to a second embodiment of the present invention will be described. Figure 3 It is a diagram showing the structure of a thermal analysis device 1B.

[0076] The thermal analysis device 1B is the same as the thermal analysis device 1 according to the first embodiment except for the following configuration, and thus the same components are denoted by the same reference numerals and description thereof will be omitted.

[0077] In the thermal analysis device 1B, the force signal generator 30 includes the AC generator 21 , two D / A converters 22 a and 22 b , and two amplifiers 23 a and 23 b , similarly to the thermal analysis device 1 .

[0078] In addition, the force signal generator 30 has: a DC force generator (digital signal generator) 31 that generates a digital signal of a force signal; two D / A converters 32c and 32d that convert the digital signal of the DC force generator 31 into an analog signal; two amplifiers 33c and 33d that respectively amplify the analog signals output from the D / A converters 32c and 32d; and a voltage-current converter 34 that converts the analog signal (voltage) of each amplifier 23a, 23b, 33c, and 33d into a current and outputs it to the force generator 5.

[0079] Here, when a soft sample such as a film is measured by a dynamic viscoelasticity measuring device, a DC force that is constant over time is applied to the sample as tension in order to prevent the film sample from loosening and maintain the sample shape. The DC force generator 31 generates the tension.

[0080] Thus, similarly to the first embodiment, based on the output of the AC generator 21, the two amplifiers 23a and 23b can realize a high load mode with a high maximum load and a low load mode with a low maximum load but excellent load resolution using one thermal analyzer.

[0081] At the same time, based on the output of the DC force generator 31, tension can be applied to the sample in high load mode and low load mode respectively through two amplifiers 33c and 33d, and the following measurement can be performed, in which the sample shape is maintained according to the load change from high load mode to low load mode.

[0082] In addition, from the perspective of applying tension to the sample in high load mode and low load mode respectively, higher tension (DC-based force) is required in high load mode, so the difference in amplification factors of the two amplifiers 33c and 33d is preferably the same as the difference in amplification factors of amplifiers 23a and 23b.

[0083] For example, in Figure 2 In the embodiment, the difference between the amplification factors of the amplifiers 23a and 23b in the high load mode and the low load mode is 10 times, and the difference between the amplification factors of the amplifiers 33c and 33d corresponding to the high load mode and the low load mode may also be 10 times.

[0084] In the case of the high load mode, for example, the voltage-current converter 34 synthesizes the sine wave signal (voltage as an AC signal) output from the amplifier 23a and the DC signal (voltage) output from the amplifier 33c, converts the synthesized signal into a current, and outputs the synthesized signal.

[0085] In this case, for example, when the user selects the high load mode using a selection button or a control screen, the power of each amplifier may be turned on / off so that only the amplifiers 23 a and 33 c are operated.

[0086] The present invention is not limited to the above-described embodiments.

[0087] 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) apparatus.

[0088] Furthermore, the number of D / A converters and corresponding amplifiers may be two or more.

[0089] Alternatively, one end of the probe may be brought into direct contact with the sample to apply a load to the sample.

[0090] The difference in the amplification factor between the plurality of amplifiers may be approximately 10 times, but is preferably at least 2 times.

[0091] The D / A converters may be the same or different, and the digital resolutions of the D / A converters may be the same or different.

[0092] It is preferable to provide a digital signal generator such as an AC generator or a DC generator for a plurality of D / A converters that are intended to output a specific type of digital signal such as AC or DC. For example, if an AC generator is provided separately for each of a plurality of D / A converters, the cost is increased, and the phase of the AC corresponding to each D / A converter may be inconsistent.

[0093] Examples of the AC signal include a sine wave, a rectangular wave, and a triangular wave.

[0094] "At least one of the plurality of amplifiers" may be one, two, or all of the plurality of amplifiers.

Claims

1. A thermal analysis device comprising: A probe extending in the axial direction, one end of which is in direct or indirect contact with the sample to apply a load to the sample; a force generator, which is disposed on the other end side of the probe and generates a force in the axial direction of the probe; A displacement detector for detecting the mechanical properties of the sample by detecting the displacement of the probe in the axial direction; a force signal generator, which generates a force signal for causing the force generator to act; a load detector for detecting a load applied to the specimen; as well as a heating furnace for heating the sample, It is characterized in that 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 signals outputted from the plurality of D / A converters at different amplification rates. Furthermore, 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 device according to claim 1, characterized in that The difference in the amplification factor between the plurality of amplifiers is greater than or equal to 2 times.

3. The thermal analysis device according to claim 1 or 2, characterized in that: The thermal analysis device comprises a plurality of digital signal generators, each of which generates a different digital signal. Each of the plurality of digital signal generators has a plurality of the D / A converters and a plurality of the amplifiers.

4. The thermal analysis device according to claim 3, characterized in that The different digital signals are an AC signal that oscillates according to time and a DC signal that is constant with respect to time.

Images