JP5149081B2 - Fastener with strain measurement function - Google Patents

Description

  The present invention relates to a fastener having a function of measuring a strain corresponding to a stress related to the fastener with high accuracy.

  As a technique for measuring axial strain in fasteners such as bolts, an axial force management bolt is known in which a hole is provided in the axial direction near the axial center of the bolt, and a strain gauge and a temperature sensor are installed inside the hole ( For example, Patent Document 1). In the axial force management bolt described in Patent Document 1, with respect to the produced management bolt, the relationship between the axial force and the strain gauge resistance value change at each ambient temperature is measured in advance and the calibration value is stored in the measuring instrument. It is said that the axial force of a bolt can be easily measured in an actual use environment by connecting a measuring instrument having a calibration processing function with a connector. This axial force management bolt does not constitute a Wheatstone bridge combined with three fixed resistors inside the strain measuring instrument as in the case of normal strain measurement using a strain gauge. Although it has an advantage that it can be measured easily, it also has a drawback that the measurement accuracy is lowered.

  On the other hand, an impurity diffusion resistance controlled to have a predetermined crystal orientation is formed on a silicon single crystal substrate, and a semiconductor strain sensor in which a Wheatstone bridge is configured by combining these resistances is provided in the major axis direction of the bolt. A bolt with a strain amount measuring function installed inside a hole is disclosed (for example, Patent Document 2). In the bolt with strain amount measuring function described in Patent Document 2, the Wheatstone bridge itself can be configured in the bolt by forming the strain detection resistor and the dummy resistor close to each other on the same substrate. It is said that the temperature can be automatically corrected because the temperatures are substantially the same. In addition, since a semiconductor device manufacturing process can be used, a small Wheatstone bridge of about several hundred μm or less can be realized, and it can be used for a bolt having a small diameter.

JP-A-6-347349 JP 2005-114441 A

  In the case of a bolt-type strain measuring device in which a strain gauge or a semiconductor strain sensor is installed inside the hole provided in the axial direction of the bolt as described above, in order to accurately measure strain, a predetermined position / It is important to correctly install a strain gauge and a semiconductor strain sensor in a predetermined direction. Particularly, in the semiconductor strain sensor, since the size of the sensor itself is very small, a great amount of labor is required to correctly install the sensor in a predetermined position and direction inside the hole. In addition, there is a problem that the accuracy and sensitivity of strain measurement vary when the installation of the sensor is deviated.

  Therefore, the object of the present invention is to facilitate the correct installation of the strain sensor inside the hole in a fastener with a strain measurement function provided with a semiconductor strain sensor inside, and as a result, it is possible to measure strain with high accuracy. Another object of the present invention is to provide a fastener with a strain measuring function with small sensitivity variations.

In order to achieve the above object, the present invention is a fastener having a semiconductor strain sensor for measuring the strain amount of the fastener,
A sensor holding member for holding the semiconductor strain sensor;
A stress propagation member for transmitting stress on the fastener to the semiconductor strain sensor and / or the sensor holding member;
The fastener is provided with a hole in an axial direction including a central axis of the fastener,
The sensor holding member holding the semiconductor strain sensor is inserted into the hole,
A fastener with a strain amount measuring function is provided, wherein the stress propagation member is filled between the hole and the sensor holding member.

In addition, in order to achieve the above object, the present invention can make the following improvements and changes in the above-described fastener with a strain amount measuring function according to the present invention. Furthermore, they can be combined.
(1) Stress propagation assisting members are provided in regions on both ends in the axial direction of the sensor holding member as viewed from the semiconductor strain sensor.
(2) The sensor holding member is in contact with the inner wall of the hole of the fastener.
(3) The semiconductor strain sensor is installed on a substantially central axis of the fastener.
(4) The relationship between the Young's modulus E1 of the fastener and the Young's modulus E2 of the stress propagation member is at least “E1 ≧ E2 ≧ 5 GPa”, and the Young's modulus E1 of the fastener and the Young's modulus of the sensor holding member The relationship with E3 is at least “E1 ≧ E3 ≧ 5 GPa”.
(5) The sensor holding member is one of an epoxy resin, a magnesium alloy, aluminum, an aluminum alloy, copper, a copper alloy, or a silicon substrate.
(6) The stress propagation auxiliary member is any of a magnesium alloy, aluminum, an aluminum alloy, copper, a copper alloy, or a silicon substrate.
(7) The sensor holding member is a silicon single crystal substrate, and the semiconductor strain sensor is directly formed on a surface region of the sensor holding member.
(8) In the semiconductor strain sensor, an impurity diffusion resistance is formed in a surface region of a silicon single crystal substrate, and a Wheatstone bridge circuit is configured by the four impurity diffusion resistances.
(9) The impurity diffusion resistor is a p-type impurity diffusion resistor, and in the Wheatstone bridge circuit, two longitudinal directions of the p-type impurity diffusion resistors are parallel to a <110> direction of the silicon single crystal substrate. And the other two longitudinal directions are parallel to the <110> direction and the vertical direction.
(10) The impurity diffusion resistor is an n-type impurity diffusion resistor, and in the Wheatstone bridge circuit, two longitudinal directions of the n-type impurity diffusion resistors are parallel to a <100> direction of the silicon single crystal substrate. And the other two longitudinal directions are parallel to the <100> direction and the vertical direction.

  According to the present invention, it becomes easy to correctly install a semiconductor strain sensor in a predetermined position and direction with respect to a hole provided in an axial direction including the central axis of the fastener, and as a result, strain can be measured with high accuracy. Thus, it is possible to provide a fastener with a strain measuring function that can be performed and has a small sensitivity variation.

  Embodiments according to the present invention will be described below with reference to the drawings. However, the present invention is not limited to the embodiment taken up here.

[First embodiment of the present invention]
(Structure of fastener with strain measurement function)
FIG. 1 is a schematic longitudinal sectional view showing a structural example of a main part of a fastener with a strain measuring function according to a first embodiment of the present invention, and FIG. 2 is a schematic view showing a cross section taken along line AA of FIG. It is. As shown in FIGS. 1 and 2, a fastener (for example, a bolt or a pin) 1 is provided with a hole 1a in the axial direction including the central axis, and a sensor holding member 3 holding a semiconductor strain sensor 4 in the hole 1a. The stress propagation member 2 is filled between the hole 1a and the sensor holding member 3. The semiconductor strain sensor 4 is fixed to a predetermined position of the sensor holding member 3 with a joining member (for example, adhesive, solder, etc.).

  According to the present invention, the semiconductor strain sensor 4 can be accurately and easily installed at a predetermined position and direction of the fastener 1 even when the inner diameter of the hole 1a, which has conventionally been difficult to install the semiconductor strain sensor 4, is small. can do. In other words, since the inner diameter of the hole 1a can be reduced, the influence on the mechanical strength of the fastener 1 can be reduced to a level that can be ignored.

  1 and 2 show the case where the sensor holding member 3 has a substantially cylindrical shape, the sensor holding member 3 may be a prism or a plate. If the flat surface is formed in the location which fixes the semiconductor strain sensor 4, the shape of the sensor holding member 3 will not be specifically limited. Further, in FIG. 1, the hole 1a is provided from the fastener head, but the hole 1a may be provided from the fastening part tail as necessary, or may be a through hole from the fastening part head to the tail.

  Further, as shown in FIG. 1, it is preferable to provide a positioning hole 1b for the sensor holding member 3 at the bottom of the hole 1a. By inserting the sensor holding member 3 into the positioning hole 1b, the positioning of the sensor holding member 3 in the hole 1a can be more reliably performed. A positioning member (not shown) such as a ring may be used instead of the positioning hole 1b. Moreover, it is preferable to seal the vicinity of the opening of the hole 1a with the waterproof / moisture-proof material 5. Thereby, the penetration | invasion of the water | moisture content etc. to the hole 1a can be suppressed, and deterioration of the stress propagation member 2, the sensor holding member 3, etc. by a water | moisture content etc. can be suppressed.

  In the present invention, since the semiconductor strain sensor 4 is not in direct contact with the inner wall of the hole 1a, the stress propagation member 2 and / or the sensor holding member 3 for transmitting the strain of the fastener 1 to the semiconductor strain sensor 4 is an important role. Fulfill. The relationship between the Young's modulus E1 of the fastener 1 and the Young's modulus E2 of the stress propagation member 2 is “E1 ≧ E2 ≧ 5 GPa”, and the relationship between the Young's modulus E1 of the fastener 1 and the Young's modulus E3 of the sensor holding member 3 Is preferably “E1 ≧ E3 ≧ 5 GPa”. On the other hand, when “E1 <E2, E3”, the strain of the fastener 1 is not easily transmitted to the semiconductor strain sensor 4, and the output signal of the semiconductor strain sensor 4 is reduced, so that the measurement sensitivity and accuracy are deteriorated.

  Examples of the material of the sensor holding member 3 include epoxy resin (Young's modulus: about 5 GPa), magnesium alloy (for example, AZ31, Young's modulus: about 45 GPa), aluminum (Young's modulus: about 70 GPa), aluminum alloy ( For example, A7075, Young's modulus: about 70 GPa), copper alloy (for example, C2801, Young's modulus: about 100 GPa), copper (for example, C1020, Young's modulus: about 120 GPa), silicon substrate (Young's modulus of polycrystalline substrate) : About 160 GPa, Young's modulus of a single crystal substrate: about 190 GPa). Moreover, as an example of the material of the stress propagation member 2, resin materials, such as an epoxy resin (Young's modulus: about 5 GPa), are mentioned. For example, when the sensor holding member 3 is made of epoxy resin and the stress propagation member 2 is also made of epoxy resin, “E1 ≧ E2 = E3 ≧ 5 GPa”.

(Manufacture of fasteners with strain measurement function)
The manufacturing method of the fastener with a strain amount measuring function according to the present invention includes a “semiconductor strain sensor fixing step” for fixing the semiconductor strain sensor 4 in a predetermined direction at a predetermined position of the sensor holding member 3, and a semiconductor strain. The “sensor holding member insertion step” in which the sensor holding member 3 to which the sensor 4 is fixed is inserted into a predetermined position inside the hole 1a of the fastener, and the stress propagation member 2 is filled in the hole 1a “stress propagation member Filling step ". If voids such as bubbles are present in the stress propagation member, it is not preferable because the strain of the fastener is difficult to propagate to the semiconductor strain sensor. Therefore, when the absolute value of the hole diameter of the fastener is small (i.e., the space between the hole and the sensor holding member is small), when filling the stress propagation member, bubbles or the like are likely to remain inside the hole, After the “stress propagation member filling step”, the “sensor holding member insertion step” may be performed before the stress propagation member is cured. Thereby, it is possible to suppress the remaining of bubbles and the like inside the hole. In addition, it is advantageous for suppressing the remaining of air bubbles or the like by making the hole 1a of the fastener a through hole from the head of the fastening part to the tail.

[Second Embodiment of the Present Invention]
(Structure of fastener with strain measurement function)
FIG. 3 is a schematic cross-sectional view showing an example of the structure of a fastener with a strain measurement function according to the second embodiment of the present invention, and the same reference numerals are given to the parts common to the first embodiment. In this embodiment, the structure of the main part is the same as that of the first embodiment, but differs from the first embodiment in that the sensor holding member 3 is in contact with the inner wall of the hole 1a. In FIG. 3, a plate-like member is used as the sensor holding member 3, the semiconductor strain sensor 4 is installed on the substantially central axis of the fastener, and the semiconductor strain sensor 4 is embedded in the sensor holding member 3. A fixed example is shown.

  By adopting a structure in which at least two sides of the sensor holding member 3 are in contact with the inner wall of the hole 1a, the positioning of the sensor holding member 3 in the hole 1a is more stable, and variations in strain measurement accuracy and sensitivity are suppressed. Can do. Furthermore, since the stress and strain applied in the shearing direction of the fastener 1 are directly transmitted to the sensor holding member 3, there is an advantage that the accuracy and sensitivity of strain measurement in the shearing direction is improved.

  Moreover, it is preferable that the semiconductor strain sensor 4 is disposed on the central axis of the fastener 1. By installing the semiconductor strain sensor 4 on the central axis that is a neutral line for the bending deformation of the fastener, it is possible to eliminate the influence of excessive compression / tensile strain due to bending deformation and to suppress excessive fluctuations in the sensor output. Therefore, highly accurate strain measurement is possible.

  Moreover, it is preferable that the semiconductor strain sensor 4 is embedded and fixed inside the sensor holding member 3. Since the surface of the sensor holding member 3 becomes gentle, there is an advantage that the remaining of bubbles and the like around the semiconductor strain sensor 4 can be suppressed.

  FIG. 4 is a schematic longitudinal sectional view showing another structural example of the fastener with a strain measuring function according to the second embodiment of the present invention. FIG. 5 is a schematic diagram showing an example of the BB cross section of FIG. 4, and FIG. 6 is a schematic diagram showing another example of the BB cross section of FIG. As shown in FIGS. 4 to 6, by adding the stress propagation auxiliary member 2 ′, the stress and strain applied in the axial direction of the fastener 1 can be easily transmitted to the sensor holding member 3 and / or the semiconductor strain sensor 4. The accuracy and sensitivity of strain measurement in the axial direction is improved. Examples of the material of the stress propagation assisting member 2 ′ include magnesium alloy (for example, AZ31, Young's modulus: about 45 GPa), aluminum (Young's modulus: about 70 GPa), aluminum alloy (for example, A7075, Young's modulus: about 70). GPa), copper alloy (eg C2801, Young's modulus: about 100 GPa), copper (eg C1020, Young's modulus: about 120 GPa), silicon substrate (polycrystalline substrate Young's modulus: about 160 GPa, single crystal substrate Young's modulus: about 190 GPa). Of course, the stress propagation assisting member 2 ′ can be applied to the first embodiment described above. Preferably, the stress propagation assisting member 2 ′ is made of a material having a Young's modulus higher than that of the stress propagation member 2, so that the stress / strain is easily transmitted to the sensor holding member 3 and / or the semiconductor strain sensor 4.

  FIG. 7: is a cross-sectional schematic diagram which shows another structural example of the fastener with a strain measurement function which concerns on the 2nd Embodiment of this invention. As shown in FIG. 7, at least two sides of the sensor holding member 3 are in contact with the inner wall of the hole 1a, and the semiconductor strain sensor 4 is arranged as close as possible to the inner wall of the hole 1a of the fastener. Such a structure has little bending stress to the fastener and is suitable for measuring a small strain in the fastener axial direction with high sensitivity and accuracy.

  In the present embodiment, as shown in FIG. 7, the sensor holding member 3 may be regarded as a partition member, and stress propagation members 21 and 22 made of different materials may be used on the front and back of the sensor holding member 3. In this case, the stress propagation member 21 filled in the smaller distance (space) between the inner wall of the hole 1a of the fastener and the surface of the sensor holding member 3 has the same temperature as the stress propagation member 22 filled in the other. -It is preferable to use a material having a low creep rate under the same stress. Thereby, the strain generated in the fastener 1 can be efficiently transmitted by the semiconductor strain sensor 4.

  When the stress propagation member 21 is filled on the surface 3a side of the sensor holding member to which the semiconductor strain sensor 4 is fixed, the stress propagation member 22 may not be filled on the other surface 3b side. is there. Thereby, the process of filling the stress propagation member can be simplified. In this case, it is preferable to fill the space on the surface 3b side with an inert gas. Thereby, the oxidative deterioration of the sensor holding member 3 and the stress propagation member 21 can be suppressed, and the durability can be improved.

[Configuration of semiconductor strain sensor]
Next, the configuration of the semiconductor strain sensor will be described. In the following description, the case where silicon is used as the semiconductor material will be described. However, the present invention is not limited to the semiconductor strain sensor using silicon, and other semiconductor materials may be used. FIG. 8 is a partially enlarged schematic view showing an example of a semiconductor strain sensor. As shown in FIG. 8, the semiconductor strain sensor 4 is provided at a predetermined position of the sensor holding member 3. The semiconductor strain sensor 4 is made of a silicon single crystal substrate. For example, four p-type impurity diffusion resistors 4a, 4b, 4c, and 4d are formed in the surface region of the same substrate, and these four impurity diffusion resistors are used. A Wheatstone bridge circuit (sometimes simply referred to as a “bridge circuit”) is formed.

  Further, the four p-type impurity diffusion resistors are composed of two impurity diffusion resistors whose longitudinal direction is parallel to the <110> direction of the silicon single crystal and two impurity diffusion resistors perpendicular to them. Yes. By disposing the silicon single crystal <110> direction of the semiconductor strain sensor 4 in parallel with the axial direction of the fastener, the axial strain of the fastener can be measured with high sensitivity.

  Further, an amplifier 6 for amplifying the output of the bridge circuit may be provided on the same substrate of the semiconductor strain sensor 4. By providing the amplifier 6 on the same substrate as the bridge circuit, since the output of the bridge circuit is immediately amplified, there is an advantage that noise resistance is improved and distortion measurement accuracy is improved.

  Further, a temperature sensor 7 made of, for example, a pn junction may be provided on the same substrate of the semiconductor strain sensor 4. As a result, the output fluctuation due to the temperature of the output of the semiconductor strain sensor 4 can be corrected, so that more accurate strain measurement can be performed.

  FIG. 9 is a partially enlarged schematic view showing another example of the semiconductor strain sensor. As shown in FIG. 9, a bridge circuit is constituted by four p-type impurity diffusion resistors 4a, 4b, 4c, and 4d, and the silicon single crystal <110> direction of the semiconductor strain sensor 4 is relative to the axial direction of the fastener. It is arranged parallel to the 45 degree direction. Thereby, the shear strain of the fastener can be measured with high sensitivity.

  FIG. 10 is a partially enlarged schematic view showing another example of the semiconductor strain sensor. As shown in FIG. 10, as the semiconductor strain sensor 6, four n-type impurity diffusion resistors 6a, 6b, 6c, 6d are formed on a silicon single crystal substrate, and a bridge circuit is formed by these four impurity diffusion resistors. Has been. At this time, the n-type impurity diffusion resistor is formed so that the longitudinal direction thereof is parallel and perpendicular to the <100> direction of the silicon single crystal. By disposing the silicon single crystal <100> direction of the semiconductor strain sensor 6 in parallel with the axial direction of the fastener, the axial strain of the fastener can be measured with high sensitivity. On the other hand, when the silicon single crystal <100> direction of the semiconductor strain sensor 6 is arranged in parallel with the 45-degree direction with respect to the axial direction of the fastener, the shear strain of the fastener can be measured with high sensitivity.

  As the semiconductor strain sensor used in the present invention, in addition to the above-described example, a strain sensor described in JP-A-2005-114441 “Bolt with strain amount measuring function” can be used.

[Third embodiment of the present invention]
(Structure of fastener with strain measurement function)
FIG. 11 is a schematic longitudinal sectional view showing an example of the structure of the main part of a fastener with a strain measuring function according to the third embodiment of the present invention, and the same reference numerals are used for parts common to the first embodiment. It was attached.

  In the first and second embodiments, the example in which the semiconductor strain sensor 4 is fixed to the sensor holding member 3 with a bonding member such as an adhesive has been described. In contrast, in the present embodiment, a semiconductor single crystal substrate is used as the sensor holding member 13, and the semiconductor strain sensor 14 is directly formed in a surface region at a predetermined position of the sensor holding member 13. That is, the sensor holding member 13 itself also serves as a semiconductor strain sensor.

  Similar to the semiconductor strain sensor 4 described above, the semiconductor strain sensor 14 introduces impurities such as arsenic, phosphorus, and boron into the surface of the silicon single crystal substrate (here, the sensor holding member 13) to form an impurity diffusion resistance, It is formed by configuring a bridge circuit with the impurity diffusion resistance. Further, as shown in FIG. 11, in addition to the semiconductor strain sensor 14, the sensor holding member 13 may be formed with, for example, an arithmetic circuit 15 or a pad 16 for taking out an electric signal to the outside. Furthermore, it is preferable that a wiring 17 for electrically connecting the semiconductor strain sensor 14, the arithmetic circuit 15, the pad 16 and the like is also formed on the sensor holding member 13.

  Although not shown in FIG. 11, the electrical signals of the amplifier for amplifying the bridge circuit output, the temperature sensor for temperature correction, and the semiconductor strain sensor 14 as shown in FIG. Other electrical circuits, such as a wireless circuit for transfer, can be formed on the sensor holding member 13 (on the same silicon single crystal substrate). In addition, regarding the installation of the sensor holding member 13 in the hole 1a, the methods and structures described in the first and second embodiments can be applied.

  In the present embodiment, since the semiconductor strain sensor 14 is provided directly on the surface region of the sensor holding member 13, an inclusion (for example, a bonding member such as an adhesive) for fixing the semiconductor strain sensor to the sensor holding member. ) Is not necessary. That is, there is an advantage that a fastener with a strain measuring function having high durability (long-term reliability) can be obtained without worrying about deterioration of the joining member. Further, in addition to the same effects as those of the first and second embodiments, the strain applied to the sensor holding member 13 can be directly detected, so that the strain can be measured with higher sensitivity and higher accuracy.

[Effect of the embodiment]
According to the above embodiment of the present invention, the following effects can be obtained.
(1) Since the fastener with a strain measuring function according to the present invention uses a sensor holding member, the semiconductor strain sensor can be used even when the hole diameter of the holder is small, which is conventionally difficult to install the semiconductor strain sensor. It can be installed accurately and easily at a predetermined position and direction of the fastener.
(2) Since the fastener with a strain measurement function according to the present invention can accurately install the semiconductor strain sensor at a predetermined position and direction of the fastener, the strain measurement can be performed with high sensitivity and high accuracy.
(3) The fastener with strain measurement function according to the present invention has a structure in which at least two sides of the sensor holding member are in contact with the inner wall of the hole of the fastener, so that the positioning of the sensor holding member in the hole is more stable. Variations in strain measurement accuracy and sensitivity can be suppressed. Furthermore, since the stress and strain applied in the shearing direction of the fastener are directly transmitted to the sensor holding member, the accuracy and sensitivity of strain measurement in the shearing direction are improved.
(4) The fastener with strain measurement function according to the present invention is provided with a semiconductor strain sensor on the central axis, which is a neutral line for the bending deformation of the fastener, so that the influence of excessive compression / tensile strain due to bending deformation can be reduced. Since it can be eliminated and an extra fluctuation of the sensor output can be suppressed, a highly accurate strain measurement can be performed.
(5) The fastener with a strain measuring function according to the present invention is such that the surface of the sensor holding member becomes gentle by embedding and fixing the semiconductor strain sensor inside the sensor holding member. Residuals such as bubbles can be suppressed, and highly sensitive strain measurement can be performed.
(6) The fastener with a strain measuring function according to the present invention uses a semiconductor single crystal substrate as a sensor holding member, and a strain applied to the sensor holding member by directly providing a semiconductor strain sensor portion on the surface region of the sensor holding member. Can be directly detected, so strain measurement with higher sensitivity and accuracy is possible. Moreover, since it is not necessary to provide a joining member for fixing the semiconductor strain sensor to the sensor holding member, there is no deterioration of the joining member, and a fastener with a strain measuring function having high durability (long-term reliability) can be obtained.

  Embodiments of the present invention will be described below with reference to the drawings. However, the present invention is not limited to the embodiments taken up here.

(Effect of sensor holding member)
A commercially available iron bolt (Young's modulus: about 200 GPa) was prepared as the fastener 1, and a hole 1a was provided in the axial direction including the central axis. The semiconductor strain sensor 4 is fixed to the surface of the epoxy resin-made sensor holding member 3 with an adhesive so as to have the same structure as that of the first embodiment described above (see FIG. 1). A sample prepared by filling the stress propagation member 2 made of an epoxy resin so as not to leave bubbles after being inserted into the hole 1a was taken as Example 1. On the other hand, a sample prepared by inserting the semiconductor strain sensor 4 directly into the hole 1a without using the sensor holding member and then filling it with the stress propagation member 2 made of epoxy resin so as not to leave bubbles was designated as Comparative Example 1. 12 is a longitudinal cross-sectional image diagram showing the structure of the main part of the fastener with a strain measurement function of Comparative Example 1. FIG.

  The strain sensitivity was measured by measuring the sensor output when the bolts with strain measuring function of Example 1 and Comparative Example 1 were tightened with a known torque using a torque wrench. The measurement was performed for 5 samples each. In all the samples, the output of the sensor increased linearly as the tightening torque value increased. FIG. 13 is a schematic diagram showing an example of a strain sensitivity measurement graph. As shown in FIG. 13, the bolt strain sensitivity was calculated from the slope of the graph.

  FIG. 14 is a graph showing the strain sensitivity measurement results of Example 1 and Comparative Example 1. The vertical axis of the graph is expressed as “normalized strain sensitivity = strain sensitivity of each bolt / maximum value of strain sensitivity”. As apparent from FIG. 14, when the sensor holding member 3 is not provided (Comparative Example 1), the strain sensitivity varies by about 25%, whereas when the sensor holding member 3 is provided (Example 1), It can be seen that the variation in strain sensitivity is reduced within about 5% and is stable. Further, the maximum sensitivity (normalized strain sensitivity = 1) was obtained in Example 1, and the strain sensitivity was lowered in all Comparative Examples 1. From this, it is considered that in the first comparative example, the direction deviation of the semiconductor strain sensor 4 occurred as shown in FIG.

(Influence of Young's modulus of sensor holding member)
A commercially available iron bolt (Young's modulus: about 200 GPa) was prepared as the fastener 1, and a hole 1a was provided in the axial direction including the central axis. The semiconductor strain sensor 4 is fixed to the surface of the sensor holding member 3 with an adhesive so as to have the same structure as that of the second embodiment described above (see FIG. 3), and the sensor holding member 3 is inserted into the hole 1a. Thereafter, a stress propagation member 2 made of an epoxy resin was filled so that no bubbles remained, thereby preparing a sample.

  At this time, as the sensor holding member 3, an epoxy resin (Young's modulus: about 5 GPa) is used as Example 2, and a magnesium alloy (AZ31, Young's modulus: about 45 GPa) is used as Example 3. Example 4 using aluminum (Young's modulus: about 70 GPa) and Example 5 using copper alloy (C2801, Young's modulus: about 100 GPa), oxygen-free copper (C1020, Young's modulus) : About 120 GPa) was designated as Example 6. A sensor holding member 3 that uses a silicon single crystal substrate (Young's modulus: about 190 GPa) was used as Example 7 so as to have the same structure as in the third embodiment (see FIG. 11). .

  Each sample was subjected to a tensile test using a universal testing machine, and the ratio between the strain applied to the fastener 1 and the strain detected by the semiconductor strain sensor 4 was evaluated as a strain transmission rate (unit:%). In any sample, the output of the semiconductor strain sensor increased linearly as the amount of strain applied to the fastener 1 increased as in FIG. From this, it was confirmed that the amount of strain applied to the fastener 1 can be accurately detected by considering the strain transmission rate as a coefficient. The results are shown in FIG. FIG. 15 is a graph showing the relationship between the strain transmission rate and the Young's modulus of the sensor holding member in Examples 2-7. As shown in FIG. 15, it was found that as the Young's modulus of the sensor holding member increased, the strain transmission rate also increased, and that the Young's modulus of the sensor holding member was about 45 GPa or more and the strain transmission rate exceeded 50%. From this, it can be said that the Young's modulus of the sensor holding member is preferably about 45 GPa or more in order to detect a minute strain with higher accuracy.

It is a longitudinal cross-sectional schematic diagram which shows the structural example of the principal part of the fastener with a strain measurement function which concerns on the 1st Embodiment of this invention. It is a schematic diagram which shows the AA cross section of FIG. It is a cross-sectional schematic diagram which shows the structural example of the fastener with a strain measurement function which concerns on the 2nd Embodiment of this invention. It is a cross-sectional schematic diagram which shows another structural example of the fastener with a strain measurement function which concerns on the 2nd Embodiment of this invention. It is a schematic diagram which shows an example of the BB cross section of FIG. It is a schematic diagram which shows another example of the BB cross section of FIG. It is a cross-sectional schematic diagram which shows another structural example of the fastener with a strain measurement function which concerns on the 2nd Embodiment of this invention. It is a partial expansion schematic diagram showing an example of a semiconductor strain sensor. It is a partial expansion schematic diagram which shows the other example of a semiconductor strain sensor. It is a partial expansion schematic diagram which shows the other example of a semiconductor strain sensor. It is a longitudinal cross-sectional schematic diagram which shows the structural example of the principal part of the fastener with a strain measurement function which concerns on the 3rd Embodiment of this invention. It is a longitudinal cross-sectional image figure which shows the structure of the principal part of the fastener with a strain measurement function of the comparative example 1. It is a schematic diagram which shows an example of a strain sensitivity measurement graph. It is a graph which shows the strain sensitivity measurement result of Example 1 and Comparative Example 1. It is the graph which showed the relationship between the strain transmission rate in Examples 2-7, and the Young's modulus of a sensor holding member.

Explanation of symbols

1 ... Fastener, 1a ... hole, 1b ... positioning hole,
2, 21, 22 ... Stress propagation member,
3 ... Sensor holding member, 3a, 3b ... Sensor holding member surface,
4 ... Semiconductor strain sensor, 4a, 4b, 4c, 4d ... p-type impurity diffusion resistance,
5 ... Waterproof / moisture-proof material, 6 ... Amplifier, 7 ... Temperature sensor,
8 ... Semiconductor strain sensor, 8a, 8b, 8c, 8d ... n-type impurity diffusion resistance,
13 ... sensor holding member, 14 ... semiconductor strain sensor,
15 ... arithmetic circuit, 16 ... pad, 17 ... wiring.

Claims (11)

A fastener having a semiconductor strain sensor for measuring a strain amount of the fastener,
A sensor holding member for holding the semiconductor strain sensor;
A stress propagation member that transmits stress applied to the fastener to the semiconductor strain sensor and / or the sensor holding member;
The fastener is provided with a hole in an axial direction including a central axis of the fastener,
A positioning hole for the sensor holding member is further provided at the bottom of the hole,
Before SL said sensor holding member which holds the semiconductor strain sensor is entirely the Rutotomoni one end is inserted into the hole plugged into the positioning hole,
The stress propagation member is filled between the hole and the sensor holding member ,
The relationship between the Young's modulus E1 of the fastener and the Young's modulus E2 of the stress propagation member is “E1 ≧ E2 ≧ 5 GPa”, and the relationship between the Young's modulus E1 of the fastener and the Young's modulus E3 of the sensor holding member Is a fastener with a strain measurement function, characterized in that “E1 ≧ E3 ≧ 45 GPa” . In the fastener with a strain amount measuring function according to claim 1 ,
The fastener with a strain amount measuring function, wherein the sensor holding member is in contact with an inner wall of a hole of the fastener. In the fastener with a strain amount measuring function according to claim 1 or 2 ,
The fastener with a strain amount measuring function, wherein the semiconductor strain sensor is installed on a substantially central axis of the fastener. In the fastener with a strain amount measuring function according to any one of claims 1 to 3 ,
The fastener with a strain amount measuring function, wherein the sensor holding member is one of magnesium alloy, aluminum, aluminum alloy, copper, copper alloy, or silicon substrate. In the fastener with a strain amount measuring function according to any one of claims 1 to 4 ,
A fastener with a strain amount measuring function, characterized in that stress propagation assisting members are provided in regions at both axial ends of the sensor holding member as viewed from the semiconductor strain sensor. In the fastener with a strain amount measuring function according to claim 5,
A fastener with a strain amount measuring function, wherein the Young's modulus of the stress propagation auxiliary member is higher than the Young's modulus of the stress propagation member. In the fastener with a strain amount measuring function according to claim 5 or 6 ,
The stress propagation auxiliary member is any one of a magnesium alloy, aluminum, an aluminum alloy, copper, a copper alloy, and a silicon substrate, and a fastener with a strain amount measuring function. In the fastener with a strain amount measuring function according to any one of claims 1 to 7 ,
The sensor holding member is a silicon single crystal substrate, and the semiconductor strain sensor is formed directly on the surface region of the sensor holding member. The fastener with a strain amount measuring function according to claim 8 ,
The semiconductor strain sensor, which diffusion resistance is formed on the surface region of the silicon single crystal substrate, characterized in that by the impurity diffusion resistors of the four in which the Wheatstone bridge circuit is configured Fastener with strain measurement function. The fastener with a strain amount measuring function according to claim 9 ,
The impurity diffused resistor is a p-type impurity diffused resistor,
In the Wheatstone bridge circuit, two longitudinal directions of the p-type impurity diffusion resistors are parallel to the <110> direction of the silicon single crystal substrate, and the other two longitudinal directions are the <110> direction. A fastener with a strain measurement function, characterized by being parallel to the vertical direction. The fastener with a strain amount measuring function according to claim 9 ,
The impurity diffusion resistance is an n-type impurity diffusion resistance,
In the Wheatstone bridge circuit, two longitudinal directions of the n-type impurity diffusion resistors are parallel to the <100> direction of the silicon single crystal substrate, and the other two longitudinal directions are the <100> direction. A fastener with a strain measurement function, characterized by being parallel to the vertical direction.

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