JP2011133298A - Load cell for high pressure, and high-pressure material strength testing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a load cell that can be used for a long time under high pressure and moreover, under a corrosive atmosphere, such as hydrogen. <P>SOLUTION: The load cell for high pressure includes strain gauges 1a, 1b, 1c, 1d; and a housing 3 for storing the strain gauges 1a, 1b, 1c, 1d by forming an internal closed space. The load cell for high pressure has internal pressure of the internal closed space synchronized with the external pressure, by injecting or discharging an inert medium into the internal closed space via a medium flow channel 4. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a load cell used under a high-pressure gas environment, and more particularly to a load cell used under a high-pressure corrosive gas environment. The present invention also relates to a high-pressure material strength test apparatus using such a load cell.

  A load cell is a sensor in which a strain gauge is attached to an elastic body called a strain body with an adhesive in a housing in an inert gas atmosphere. Hereinafter, it is referred to as an “electrical signal”) and is a device for measuring stress. Here, the strain gauge is obtained by sandwiching a metal foil such as a Cu-Ni alloy having a thickness of several μm processed into a predetermined shape with an insulating film mainly composed of a resin such as polyimide or epoxy.

  On the other hand, there is an increasing need to measure the amount of strain in a high pressure environment in various test apparatuses. For example, since various materials such as hydrogen gas storage containers, pipes, and injection valves used in fuel cell systems are required to have high corrosion resistance in a high-pressure hydrogen environment of 35 MPa or higher, high-pressure corrosion is required. A strength test apparatus for measuring tensile strength, fatigue strength, etc. in a gas environment has been proposed.

  FIG. 7 is a schematic view showing a conventional high-pressure material strength test apparatus. As shown in FIG. 7, the conventional high-pressure material strength test apparatus 110 supports a pressure vessel 120 that houses a subject 160, a support member 130 that supports one end of the subject 160, and the other end of the subject 160. The pull rod 140 that applies tensile or compressive stress to the subject 160, load loading means (not shown) for controlling the movement of the pull rod 140, and the pressure vessel lid 150 having a through hole 151 for inserting the pull rod 140, And a corrosive gas supply pipe 170 for supplying corrosive gas into the pressure vessel 120.

  In this apparatus, first, in a state where the subject 160 is fixed to the support member 130 and the pull rod 140, the pressure vessel 120 is placed on the pressure vessel lid 150 and the inside of the pressure vessel 120 is sealed by tightening a bolt. The state shown in FIG. 7 is assumed. Thereafter, hydrogen gas or other corrosive gas is introduced from the corrosive gas supply pipe 170 into the pressure vessel 120, the internal pressure of the vessel is increased to a desired test pressure, and the state is maintained, and a fatigue test or other material test is performed. Is done. Since hydrogen gas deteriorates a metal material or the like, the corrosive gas includes hydrogen gas in a broad sense.

  At this time, the sealing properties between the pressure vessel 120 and the pressure vessel lid 150 and between the pressure vessel lid 150 and the pull rod 140 are ensured by O-rings 152, 153 and 154 as sealing members, respectively. In this test apparatus, a load cell is attached for the purpose of accurately measuring the stress applied to the subject 160.

  However, the above-described normal load cell is not intended for use in a high-pressure environment, and therefore the load cell cannot be mounted in the pressure vessel. Although it is conceivable to attach the load cell to the pull rod outside the pressure vessel, the stress value applied to the test piece is usually accurate due to the resistance of the sealing material (such as an O-ring) between the pressure vessel and the pull rod and other factors. Cannot be measured. In addition, although it is conceivable to attach a strain gauge to the pull rod or test piece in the pressure vessel with an adhesive, there is a problem that the adhesive is eroded by hydrogen in a corrosive environment such as hydrogen gas and the strain gauge peels off. In some cases, the metal foil constituting the strain gauge is eroded.

  In order to solve this problem, Patent Document 1 proposes an invention using a strain gauge whose insulating layer is made of ceramics, and Patent Document 2 discloses a Cu-Ni metal foil gauge having a thickness of 10 to 25 μm or a thickness of 10 There has been proposed an invention using a strain gauge comprising a ~ 25 μm Fe-Cr-Al metal foil gauge, and further using a strain gauge coated with a thin film by a material comprising at least one selected from aluminum, gold and zinc.

JP 2006-349487 A JP 2008-64569 A

  Patent Document 1 is said to have been made based on the knowledge that “ceramics do not transmit hydrogen gas”. However, according to the present invention, although there is a possibility that the erosion of hydrogen to the ceramic insulating layer and the metal foil covering the strain gauge may be prevented, the adhesive layer formed by the adhesive between the strain gauge and the strain generating body has a hydrogen layer. The problem of erosion cannot be solved. This problem also applies to the strain gauge described in Patent Document 2 that is thin-film coated with a material made of at least one selected from aluminum, gold, and zinc.

  The present invention has been made to solve such problems of the prior art, and an object thereof is to provide a load cell that can be used at a high pressure and in a corrosive atmosphere such as hydrogen.

  In order to achieve the above object, the present inventors have earnestly studied a load cell installed in a pressure vessel of a high pressure material strength test apparatus, and as a result, obtained the following knowledge.

  (A) Although the coating method after attaching the strain gauge has a certain effect on the corrosive gas immediately after the start of use, there is a problem that the strain gauge peels off after a certain period of time. For this reason, it is necessary to cover the portion where the strain gauge is attached with a housing to block the corrosive gas in the external environment (in the case of a high pressure material strength test apparatus, the environment in the pressure vessel).

  (B) However, simply shutting off the corrosive gas causes a pressure difference between the inside and the outside of the housing, making accurate measurement impossible. For this reason, it is important to synchronize the pressure inside the housing with the pressure change outside the housing.

  The present invention has been made on the basis of the above findings, and is summarized as a high-pressure load cell shown in the following (1) to (5) and a high-pressure material strength test apparatus shown in the following (6).

  (1) A high-pressure load cell used in a corrosive gas atmosphere, comprising a strain gauge and a housing that forms an internal sealed space and accommodates the strain gauge, and the internal seal is provided via a medium flow path. A high-pressure load cell characterized by synchronizing an internal pressure of the internal sealed space with an external pressure by injecting or discharging an inert medium into the space.

  (2) The above (1) further comprising an inert medium pressure adjusting means for adjusting an internal pressure of the internal sealed space by injecting or discharging an inert medium into the internal sealed space through a medium flow path. High pressure load cell.

  (3) The high-pressure load cell according to (1) or (2), further including signal extraction means for extracting an electric signal of the strain gauge from the internal sealed space to the outside.

  (4) The high pressure load cell according to any one of (1) to (3), wherein the inert medium is an electrical insulating oil.

  (5) The high pressure load cell according to any one of (1) to (4), wherein the housing is formed of a flanged tube, and the strain gauge is attached to an inner surface of the tube of the housing.

  (6) The high-pressure material strength test apparatus using the high-pressure load cell according to (5) above, wherein one of the flanges of the housing is attached to a guide in the pressure vessel of the high-pressure material strength test apparatus, and the other is the subject. A high-pressure material strength testing device attached to a support member.

  Since the load cell according to the present invention can be used for a long period of time in a high-pressure and corrosive gas atmosphere such as hydrogen, it is particularly installed in a high-pressure material strength test apparatus to grasp the stress state of the test piece. Useful for.

The figure which shows the example of the high voltage | pressure load cell which concerns on this invention (a) Longitudinal sectional view (b) Top view The figure which shows the example of the high-pressure material strength test apparatus based on this invention The figure which shows the other example of the high voltage | pressure material strength test apparatus which concerns on this invention Temporal change of pressure in pressure vessel and output of strain gauge in Example 1 of the present invention Temporal change of pressure in pressure vessel and output of strain gauge in Example 2 of the present invention Change with time of pressure in pressure vessel and output of strain gauge in Example 3 of the present invention Diagram showing an example of a conventional high-pressure material strength testing device

  FIG. 1 is a view showing an example of a high-pressure load cell according to the present invention, where (a) is a longitudinal sectional view, (b) is a top view (however, (a) a top view with the upper lid 5 removed). Each).

  As shown in FIG. 1, for example, the high-pressure load cell 10 according to the present invention includes strain gauges 1a, 1b, 1c, and 1d, a housing 3 that houses the strain gauges 1a, 1b, 1c, and 1d, and an internal sealed space 9. And a medium flow path 4 for injecting or discharging an inert medium. In the high-pressure load cell 10, an inert medium is injected into or discharged from the internal sealed space 9 through the medium flow path (medium flow pipe or the like) 4, thereby reducing the internal pressure of the internal sealed space 9. Synchronize with external pressure changes.

  As means for adjusting the internal pressure of the internal sealed space 9 by injecting or discharging the inert medium into the internal sealed space 9 via the medium flow path 4 (hereinafter referred to as “inert medium pressure adjusting means”). For example, a part of the corrosive gas supply pipe 17 having the same pressure as the external pressure is bypassed and connected to a valve containing a diaphragm or the like to detect expansion / contraction of the diaphragm or the like, and the medium flow path 4 is inactivated. A configuration in which the medium pressure is controlled to the same pressure as the external pressure may be employed.

  In the example shown in FIG. 1, wirings 2a, 2b, 2c, and 2d are connected to the strain gauges 1a, 1b, 1c, and 1d, and these wirings 2a, 2b, 2c, and 2d are connected to wiring extracting means (for high voltage use). A ground (e.g.) 8 is connected to a computer (not shown) disposed outside the housing 3 and an electric signal from the strain gauge is transmitted to the computer. In this manner, the strain of the housing 3 is detected from the change in the resistance value in the strain gauge. That is, in this example, the housing 3 in the present invention is a frame body that covers the strain gauges 1a, 1b, 1c, and 1d and a strain generating body.

  In the above description, the case where the electrical signal from the strain gauge is transmitted to the computer using a wire, that is, the wiring 2a, 2b, 2c, 2d and the wiring take-out means 8 has been described. The transmission of the electrical signal may be performed by wireless communication between a transmitter provided in the housing and a receiver provided outside the housing. In the present specification, means for transmitting an electric signal from a strain gauge to a computer regardless of wired or wireless is referred to as signal extraction means.

  In manufacturing the high-pressure load cell 10 according to the present invention, for example, the strain gauges 1a, 1b, 1c, and 1d are attached to the inner surface of the housing 3 with an adhesive, and the wirings 2a, 2b, 2c, and 2d are attached. Is coated with resin. Thereafter, for example, the wires 2a, 2b, 2c, and 2d are connected to the wire take-out means 8, the lower lid 6 is attached, and the upper lid 5 is also attached to seal the inside of the housing 3. A seal with the upper lid 5 and the upper lid 6 can be secured by an O-ring 7 attached to the body portion 3a of the housing 3.

  The inert medium may be a rare gas such as helium or argon, a gas such as nitrogen gas, or a liquid having insulating properties and nonflammability. Among them, it is preferable to use an electrical insulating oil that is easy to handle and easy to adjust pressure. The inactive medium is injected by first exhausting the inside sealed space 9 of the housing 3 through the medium flow path 4 by a vacuum pump or the like and then introducing the inert medium through the medium flow path 4 by a switching valve. It can be carried out.

  Since the housing 3 is exposed to a corrosive environment at a high pressure, a material having high strength and corrosion resistance (particularly resistance to hydrogen) is preferable. For example, stainless steel, high Ni-based alloy, or the like can be adopted.

  The shape of the housing 3 is not particularly limited, but it is preferable to use a flanged tube (see FIG. 1 and the like) that has high strength, high corrosion resistance, and can be easily attached to various test apparatuses. The location where the strain gauges 1a, 1b, 1c, and 1d are attached is a location isolated from the external environment, and is not particularly limited as long as the strain at the required location can be measured. For example, a case where the strain gauge is attached to the conventional high-pressure material strength test apparatus 110 shown in FIG. 7 will be described as an example. A strain gauge may be attached to an arbitrary portion of the pull rod 140 in the pressure vessel 120 and the periphery thereof may be covered with a housing. Is possible. However, when the housing and the pull rod are fixed, it is difficult to accurately measure the stress applied to the subject. Therefore, the embodiment shown in FIG. 3 can be adopted.

  In the example shown in FIG. 3, first, strain gauges 1 a, 1 b, 1 c, 1 d are attached to arbitrary positions of the pull rod 140 with the pull rod 140 in the pressure vessel (not shown) being inserted into the through hole of the lower housing 3 c. After the attachment, the lower housing 3c and the upper housing 3d are joined using a bolt or the like at a position covering the strain gauges 1a, 1b, 1c, and 1d. An internal sealed space 9 is formed in the housing 3 by the sealing material 155 attached to the contact surfaces of the pull rod 140, the upper housing 3d, and the lower housing 3c.

  The wires 2a, 2b, 2c, and 2d connected to the strain gauges 1a, 1b, 1c, and 1d are connected to a computer (not shown) disposed outside the housing 3 through the wire take-out means 8. The strain of the housing 3 is detected from the change in the resistance value in the strain gauge. Also in this example, the inert medium pressure adjusting means (not shown) injects or discharges the inert medium into the inner sealed space 9 of the housing 3 through the medium flow path (medium flow pipe or the like) 4 so that the internal sealing is performed. The internal pressure of the space 9 is synchronized with the pressure change outside the housing 3.

  Although not shown, the lower housing is fixed to the pressure vessel lid 150 with a bolt or the like so that the housing 3 does not vibrate in synchronization with the pull rod 140. In the example illustrated in FIG. 3, the example in which the housing is divided into two at the boundary between the cylindrical portion and the flange portion has been described, but there is no particular limitation on the number of divisions and the direction of division.

  However, also in this example, it is necessary to correct the output value of the load cell according to the deterioration of the sealing material 155 with the passage of time due to the influence of the frictional resistance of the sealing material 155. Therefore, the embodiment shown in FIG. 1 described above, that is, the embodiment in which the strain gauges 1a, 1b, 1c, and 1d are attached to the inner surface of the housing 3 formed of a flanged tube having the body portion 3a and the flange 3b. preferable. Hereinafter, an example in which the high-pressure load cell of the example shown in FIG. 1 is attached to a high-pressure material strength test apparatus will be described.

  FIG. 2 is a schematic view showing a high-pressure material strength test apparatus according to the present invention. As shown in FIG. 2, the high-pressure material strength test apparatus 20 according to the present invention includes a pressure vessel 12 that accommodates the subject 11, a support member (chuck) 13 that supports one end of the subject 11, and the subject 11. A pull rod 14 that supports the other end and applies tensile or compressive stress to the subject 11, a load loading means (not shown) that controls the movement of the pull rod 14, and a through hole 15 a for inserting the pull rod 14 are provided. This is an apparatus having a pressure vessel lid 15 and a corrosive gas supply pipe 17 for supplying a corrosive gas into the pressure vessel 12. In this apparatus, the support member 13 is attached to the guide 18 via the load cell 10, and the guide 18 is fixed to the pressure vessel lid.

  In this apparatus, one of the flanges of the housing of the load cell 10 (upper flange in the example shown in the figure) is attached to the guide 18 in the pressure vessel 12 of the high-pressure material strength test apparatus, and the other flange (example shown in the figure). Then, the lower flange) is attached to the support member 13 of the subject 11. Then, after connecting the support member (chuck) 13, the subject 11, and the pull rod 14, these are fixed to the guide 18, and then the pressure vessel 12 is put on the pressure vessel lid 15 and the bolt is tightened to press the pressure. The inside of the container 12 is sealed to the state shown in FIG. Thereafter, the inside of the pressure vessel 12 is depressurized through the corrosive gas supply pipe 17, the valve is switched, hydrogen gas or other corrosive gas is introduced into the pressure vessel 12 from the corrosive gas supply pipe 17, and the vessel is brought to a desired test pressure. Fatigue tests and other material tests are conducted while increasing the internal pressure and maintaining this state.

  At this time, in synchronism with the pressure reduction in the pressure vessel 12, the internal pressure of the inner sealed space of the housing is reduced, the corrosive gas is introduced into the pressure vessel 12, and the internal pressure ( That is, when the external pressure of the internal sealed space is increased, the internal pressure of the internal sealed space is increased in synchronization with the internal pressure of the pressure vessel 12. Thereafter, a fatigue test and other material tests are performed in a state where the internal and external pressures of the internal sealed space are maintained at the same pressure. Sealing properties between the pressure vessel 12 and the pressure vessel lid 15 and between the pressure vessel lid 15 and the pull rod 14 are ensured by O-rings 15b, 15c and 15d as sealing members, respectively. However, the method for ensuring the sealing property is not particularly limited, and a method using bellows or the like may be employed.

  In order to confirm the operational effects of the high-pressure load cell of the present invention, various load cells were placed in a test container maintained in a hydrogen gas atmosphere of 60 MPa, and changes over time in the housing internal pressure and the load cell gauge value were investigated.

  In Example 1 of the present invention, a strain gauge having a thickness of 0.026 mm was attached to the inner surface of a housing made of a flanged tube having the shape shown in FIG. 1 with an adhesive, and the strain gauge and wiring were coated with a resin. During the test, hydrogen gas is injected into the test container, and argon gas is injected into the housing to adjust the internal pressure of the housing so that it is synchronized with the external pressure (hydrogen gas pressure in the test container). Both were raised to 60 MPa, and the output of the gauge value was investigated for 30 minutes. The result is shown in FIG.

  In Example 2 of the present invention, a strain gauge having a thickness of 0.026 mm was attached to the inner surface of a housing made of a flanged tube having the shape shown in FIG. 1 with an adhesive, and the strain gauge and wiring were coated with a resin. During the test, hydrogen gas is injected into the test container, and electrical insulating oil (Galden (registered trademark) HT) is injected into the housing to synchronize with the external pressure (hydrogen gas pressure in the test container). The internal pressure was adjusted, both the external pressure and the internal pressure were increased to 60 MPa, and the output of the gauge value was investigated for 970 minutes. The result is shown in FIG.

  In Example 3 of the present invention, a strain gauge having a thickness of 0.012 mm was attached to the inner surface of a housing made of a flanged tube having the shape shown in FIG. 1 with an adhesive, and the strain gauge and wiring were coated with a resin. During the test, hydrogen gas is injected into the test container, and electrical insulating oil (Galden (registered trademark) HT) is injected into the housing to synchronize with the external pressure (hydrogen gas pressure in the test container). The internal pressure was adjusted, both the external pressure and the internal pressure were increased to 60 MPa, and the output of the gauge value was investigated for 970 minutes. The result is shown in FIG.

  In Comparative Example 1, a strain gauge having a thickness of 0.026 mm was attached to the inner surface of a housing made of a flanged tube having the shape shown in FIG. 1 with an adhesive, and the strain gauge and wiring were coated with a resin. However, since the upper lid was not attached, the internal sealed space was not formed and the same atmosphere as in the test container was exposed. During the test, when hydrogen gas was injected into the test container, the gauge value fluctuated by 100 με or more immediately after the start of hydrogen gas injection, and the test was stopped before reaching 60 MPa.

  As shown in FIG. 4, in Example 1 of the present invention, even after 30 minutes have elapsed since the start of the test, the gauge value has decreased only by about 20 με, and if it is under a pressure lower than 60 MPa, it is at a sufficiently usable level. there were.

  As shown in FIG. 5, in Example 2 of the present invention, the initial gauge value was 79.1 με, but even after 970 minutes had elapsed since the start of the test, the gauge value decreased only by 6.1 με, and 60 MPa It was also found that it can be used sufficiently even under a high pressure higher than that.

  As shown in FIG. 6, in the present invention example 3 in which the thickness of the strain gauge is reduced, the initial gauge value is 13.3 με, which is significantly lower than that of the present invention example 2, and is even better. Results were obtained. In addition, even after 970 minutes had passed since the start of the test, the gauge value decreased only 10.1 με, and it was found that the gauge value can be sufficiently used even under a high pressure of 60 MPa or more.

  Since the load cell according to the present invention can be used for a long period of time under a high pressure and in a corrosive atmosphere such as hydrogen, it is particularly installed in a high pressure material strength test apparatus to accurately grasp the stress state of the test piece. Useful for.

1a, 1b, 1c, 1d: strain gauges 2a, 2b, 2c, 2d: wiring 3: housing 3a: body portion 3b: flange 3c: lower housing 3d: upper housing 4: medium flow path 5: upper lid 6: lower lid 7: O-ring 8: Wiring extraction means 9: Internal sealed space 10: High-pressure load cell 11 according to the present invention: Subject 12: Pressure vessel 13: Support member (chuck)
14: Pull rod 15: Pressure vessel lid 15a: Through holes 15b, 15c, 15d: O-ring 17: Corrosive gas supply pipe 18: Guide 20: High-pressure material strength test apparatus 110 according to the present invention 110: Conventional high-pressure material strength test apparatus 120: pressure vessel 130: support member 131: guide 140: pull rod 150, 150a: pressure vessel lid 151: through-holes 152, 153, 154, 155: O-ring 160: subject 170: corrosive gas supply pipe

Claims (6)

A high-pressure load cell used in a corrosive gas atmosphere,
Strain gauges,
A housing that forms an internal sealed space and accommodates the strain gauge,
A high-pressure load cell characterized by synchronizing an internal pressure of the internal sealed space with an external pressure by injecting or discharging an inert medium into the internal sealed space through a medium flow path.   The apparatus further comprises an inert medium pressure adjusting means for adjusting an internal pressure of the internal sealed space by injecting or discharging an inert medium into the internal sealed space through a medium flow path. The high pressure load cell according to 1.   The high pressure load cell according to claim 1, further comprising a signal extraction unit that extracts an electric signal of the strain gauge from the internal sealed space to the outside.   The high-pressure load cell according to any one of claims 1 to 3, wherein the inert medium is an electrical insulating oil.   5. The high-pressure load cell according to claim 1, wherein the housing is formed of a flanged tube, and the strain gauge is attached to an inner surface of the tube of the housing.   6. A high-pressure material strength test apparatus using the high-pressure load cell according to claim 5, wherein one of the flanges of the housing is attached to a guide in a pressure vessel of the high-pressure material strength test apparatus, and the other is attached to a support member of a subject. A high-pressure material strength testing apparatus characterized by

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