Holding structure for non-evaporable getter member in airtight container

Abstract

To expose a portion in which getters are overlapped with each other in an airtight container as wide as possible, to increase a substantially surface area.SOLUTION: A holding structure comprises a getter holder 22 that holds a plurality of getters 10 in an overlapping state and is attached to a getter attachment part 18 of an airtight container. The holding structure comprises a spacer 23 made of wire mesh, which is inserted between two getters 10 adjacent to each other.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a holding structure for non-evaporable getter members in an airtight container that holds a plurality of non-evaporable getter members stacked on top of each other. [Background technology]

[0002] In airtight containers that require a high degree of vacuum, a non-evaporable getter material that adsorbs gas inside the container is sometimes incorporated. A known example of a device that uses this type of non-evaporable getter material is a diaphragm vacuum gauge.

[0003] The measurement principle of a diaphragm vacuum gauge is to compare the pressure to be measured applied to a pressure sensor with the pressure in a reference vacuum chamber. For this reason, the reference vacuum chamber of a diaphragm vacuum gauge must be a high vacuum. Diaphragm vacuum gauges that use pressure sensors with a minimum range of 10 Pa are required to maintain a vacuum on the order of 10-4 Pa for 10 years. In a diaphragm vacuum gauge, it is difficult to reduce the pressure in the reference vacuum chamber to zero because there are gas leak routes, such as (1) outgassing from components housed in the reference vacuum chamber and (2) leaks from the outside.

[0004] Conventionally, to create a high vacuum in the reference vacuum chamber, parts are cleaned as pre-processing and highly airtight packaging is implemented, but this does not prevent pressure buildup from the vacuum due to leaks in the reference vacuum chamber. Therefore, it is necessary to maintain a high vacuum by using a non-evaporable getter material as a chemical pump inside the reference vacuum chamber. The adsorption efficiency of a non-evaporable getter material increases the larger the open surface area in the reference vacuum chamber. For this reason, it is desirable to use multiple non-evaporable getter materials.

[0005] Devices using multiple non-evaporable getter members are described in, for example, Patent Document 1 and Patent Document 2. The non-evaporable getter members disclosed in these patent documents are formed in a disk shape and arranged along the inner wall surface of a cylindrical airtight container in the circumferential direction and the axial direction of the airtight container. In arranging multiple disk-shaped non-evaporable getter members in this manner, the non-evaporable getter members are stood upright so that the axial direction of the disks is oriented in the radial direction of the airtight container, and are held in place by a mesh. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 6095586 [Patent Document 2] Patent No. 6133821 Summary of the Invention [Problem to be solved by the invention]

[0007] In an airtight container such as that used in a diaphragm vacuum gauge, the space inside the container is narrow, so it is not possible to arrange disc-shaped non-evaporable getter members upright as described in Patent Document 1 and Patent Document 2. In order to assemble multiple non-evaporable getter members into a small airtight container, it is conceivable to install multiple non-evaporable getter members stacked in the thickness direction. However, when such a configuration is adopted, adjacent non-evaporable getter members overlap each other, and the area exposed to the inside of the airtight container at the overlapping portions becomes small, resulting in a problem that gas adsorption is impaired. Furthermore, since the getter mounting portion of the airtight container abuts against the end face of the non-evaporable getter that faces the getter mounting portion, the abutting end face of the non-evaporable getter is not exposed, which creates the problem that gas is not adsorbed on the end face of the non-evaporable getter.

[0008] The object of the present invention is to provide a holding structure for a non-evaporable getter member in an airtight container that can increase the effective surface area by exposing as much of what was previously dead space as possible within the airtight container, such as the area where non-evaporable getter members overlap, or the getter mounting portion of the airtight container and the end face of the non-evaporable getter facing this getter mounting portion. [Means for solving the problem]

[0009] In order to achieve this object, the holding structure for non-evaporable getter members in the airtight container of the present invention comprises a getter holder that holds multiple non-evaporable getter members stacked on top of each other and is attached to the getter mounting portion of the airtight container, and a spacer made of wire mesh inserted at least between two adjacent non-evaporable getter members, or between the getter mounting portion and the non-evaporable getter member facing the getter mounting portion.

[0010] In the present invention, in the holding structure for a non-evaporable getter member in the airtight container, the spacer may be formed in a U-shape that sandwiches one of the non-evaporable getter members from both sides in the stacking direction, which is the direction in which the multiple non-evaporable getter members overlap.

[0011] In the holding structure for non-evaporable getter members in the airtight container of the present invention, the spacer may be formed by bending a strip of wire mesh into a predetermined shape, and may have an insertion portion inserted between two adjacent non-evaporable getter members, end portions facing the end faces of the non-evaporable getter members, which are both ends in the stacking direction in which the multiple non-evaporable getter members overlap, and a connecting portion connecting the insertion portion to the end portions.

[0012] In the structure for holding a non-evaporable getter member in an airtight container according to the present invention, the getter holder may be formed of a metal plate having air vents.

[0013] In the holding structure for a non-evaporable getter member in the airtight container according to the present invention, the getter holder may be formed of a wire mesh. [Effects of the Invention]

[0014] According to the present invention, it is possible to provide a holding structure for a non-evaporable getter member in an airtight container, which can increase the effective surface area by exposing as much as possible of the area where non-evaporable getter members overlap, or the area between the getter mounting portion and the non-evaporable getter member facing the getter mounting portion, inside the airtight container. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a cross-sectional view showing the general configuration of a diaphragm vacuum gauge. [Figure 2] FIG. 2 is a perspective view showing the holding structure according to the first embodiment. [Figure 3] FIG. 3 is an exploded perspective view of the non-evaporable getter member and the getter holder. [Figure 4] FIG. 4 is a cross-sectional view of the main part. [Figure 5] FIG. 5 is a perspective view showing a procedure for combining the non-evaporable getter member and the spacer with the getter holder. [Figure 6] FIG. 6 is an enlarged cross-sectional view showing a spacer insertion portion. [Figure 7] FIG. 7 is a side view of a non-evaporable getter member and a spacer showing a modified example of the spacer. [Figure 8] FIG. 8 is a perspective view of a holding structure according to the second embodiment. [Figure 9] FIG. 9 is a side view of a non-evaporable getter member and a spacer according to the second embodiment. [Figure 10] FIG. 10 is a perspective view showing a modified example of the getter holder. [Figure 11] FIG. 11 is a perspective view showing a modified example of the getter holder. DETAILED DESCRIPTION OF THE INVENTION

[0016] (First embodiment) Hereinafter, one embodiment of a holding structure for a non-evaporable getter member in an airtight container according to the present invention will be described in detail with reference to FIGS. First, an airtight container to which the non-evaporable getter member holding structure according to the present invention is applied will be described. In this embodiment, an example will be described in which the airtight container is a housing for accommodating the pressure chip of a diaphragm vacuum gauge.

[0017] 1 includes a sensor chip 2, a housing 3, a pressure introduction tube 4, a sensor case 5, a heater 6, a heat insulator 7, a partition wall 8, a baffle 9, and a non-evaporable getter member 10. The sensor chip 2 is a sensor element that detects the pressure of the medium to be measured. The housing 3 corresponds to the "airtight container" of the present invention and houses the sensor chip 2. The pressure introduction pipe 4 connects, for example, the housing 3 to a space containing the medium to be measured so that the pressure of the medium to be measured is transmitted to the sensor chip 2. A plate-shaped baffle 9 is installed at the connection between the pressure introduction pipe 4 and the housing 3. The baffle 9 prevents the medium to be measured from directly hitting the sensor chip 2.

[0018] The sensor case 5 is a case that covers the housing 3. The heater 6 is provided so as to surround the outer peripheral surface of the sensor case 5. The heater 6 heats the sensor case 5 so that the temperature inside the sensor case 5 reaches a set temperature based on instructions from a control device (not shown). Here, the housing 3 and the sensor case 5 are formed, for example, in a cylindrical shape. The outer periphery of the heater 6 is further covered with a heat insulating material 7.

[0019] Furthermore, in the diaphragm vacuum gauge 1, a partition wall 8 is provided inside the housing 3. The partition wall 8 has a base plate 8a and a support plate 8b. The base plate 8a and support plate 8b separate the internal space of the housing 3 into a measured pressure chamber 11 and a reference vacuum chamber 12. The outer periphery of the support plate 8b is fixed to the housing 3, and supports the base plate 8a in a floating state within the internal space of the housing 3. The sensor chip 2 is fixed (bonded) to the base plate 8a on the side of the reference vacuum chamber 12. The base plate 8a is also formed with a pressure introducing hole 13 that introduces the pressure inside the measured pressure chamber 11 to a diaphragm (not shown) of the sensor chip 2.

[0020] The reference vacuum chamber 12 communicates with the inside of the sensor chip 2 and is sealed in a high vacuum state together with a capacitance chamber (not shown) inside the sensor chip 2. The reference vacuum chamber 12 is formed by a cylindrical body 14, one end of which is closed by a partition wall 8 and the sensor chip 2, and a cover 15 that closes the other end of the body 14. The body 14 and the cover 15 form part of the housing 3. An electrode lead pin 16 connected to the sensor chip 2 passes through the cover 15, and a non-evaporable getter member 10 is provided in the cover 15.

[0021] The pressure introduction pipe 4 is connected to the measurement pressure chamber 11 side of the housing 3. The pressure P of the measurement medium is introduced to the diaphragm of the sensor chip 2 via this pressure introduction pipe 4. The measurement medium introduced through the pressure introduction pipe 4 hits the plate surface of the baffle 9 described above, passes through the gap around the baffle 9, and flows into the measurement pressure chamber 11 of the housing 3.

[0022] The cover 15 of the housing is formed in a disk shape, as shown in Fig. 2. Three electrode lead pins 16 are attached to the cover 15 shown in Fig. 2, each via a hermetic seal 17. A getter mounting portion 18 is formed on the back surface 15a of the cover 15, which forms the wall surface of the reference vacuum chamber 12, so that the thickness of the cover 15 is partially thin, as shown in Fig. 3.

[0023] Two non-evaporable getter members 10 are attached to the getter attachment portion 18 in a state where they are held by a holding structure 21 . The non-evaporable getter member 10 (hereinafter simply referred to as getter 10) uses a chemically active metal film as an adsorbent to adsorb gas. The getter 10 according to this embodiment is formed in a disk shape. As shown in FIG. 2, these getters 10 are aligned in the thickness direction so as to be positioned on the same axis.

[0024] 3 and 4, the holding structure 21 includes a getter holder 22 made of a metal plate and a spacer 23 made of a mesh (wire netting) bent into a U-shape in side view. In Fig. 4, the mesh spacer 23 is simply depicted as a plate. The getter holder 22 is formed by bending a metal plate into a predetermined shape. Specifically, as shown in FIGS. 2 and 3 , the getter holder 22 has two legs 24, one end of which is welded to the getter mounting portion 18 and which extend through the reference vacuum chamber 12 toward the opposite side of the cover 15, and a connecting portion 25 that connects the other ends of the two legs 24. The connecting portion 25 has a connecting plate 25a that extends in the direction in which the two legs 24 are aligned and a pair of arms 25b that protrude from the connecting plate 25a, and is formed in a cross shape when viewed from a direction facing the back surface 15a of the cover 15. The tip ends 25c of the arms 25b extend in a direction perpendicular to the back surface 15a of the cover 15. A space 26 surrounded by the two tip ends 25c of the pair of arms 25b and the pair of legs 24 is large enough to accommodate a disk-shaped getter 10.

[0025] The spacer 23 is formed by folding a strip of mesh into a U-shape. The mesh is a plain-woven wire mesh, and for example, a mesh with a count of 200 mesh can be used. The thickness of a mesh with a count of 200 mesh is about 0.09 mm. The width of the strip-shaped mesh in the short direction is at least 1 / 2 of the outer diameter of the getter 10. The length of the mesh in the long direction is at least 2 / 3 of the outer diameter of the getter 10. The U-shape of the spacer 23 means that it sandwiches one getter 10 from both sides in the stacking direction, which is the direction in which two getters 10 overlap. This U-shaped spacer 23 is formed by a pair of flat plate portions 23a and a connecting portion 23b that connects one end of these flat plate portions 23a, and is used in a state in which the pair of flat plate portions 23a sandwich the disk-shaped getter 10 from both sides in the axial direction. The getter holder 22 holds an assembly formed by combining a spacer 23 and one getter 10 together with another getter 10 in a state where they overlap, and is attached to the getter attachment portion 18 in this state.

[0026] To attach two getters 10 to the cover 15 using the getter holder 22, first, as shown in Figure 5(A), the getter holder 22 is held by, for example, a jig (not shown) so that the space 26 enclosed by the legs 24 of the getter holder 22 and the tip 25c of the arm 25b is open upward. Then, the first getter 10 is inserted into this space 26 from above, and this getter 10 is placed on the connecting part 25.

[0027] Next, the spacer 23 is combined with the second getter 10. In this operation, first, the outer peripheral surface of the getter 10 is placed over the longitudinal center of a strip-shaped mesh 27 (see FIG. 5(B)) that serves as the base material of the spacer 23. At this time, the getter 10 is positioned so that the axis C of the getter 10 is oriented in the longitudinal direction of the spacer 23. Next, as shown in FIG. 5(C), both longitudinal ends of the spacer 23 are bent toward the axial end faces 10a of the getter 10 and placed over them. By bending the mesh 27 in this manner, a spacer 23 that is U-shaped when viewed from the side is formed.

[0028] 5(D), another getter 10 combined with a U-shaped spacer 23 is placed on top of the first getter 10 in the getter holder 22. Thereafter, the getter holder 22 is removed from the jig and placed on the getter mounting portion 18 of the cover 15, and the legs 24 of the getter holder 22 are welded to the getter mounting portion 18. By welding the getter holder 22 to the cover 15 in this manner, the two getters 10 are held by the getter holder 22 and attached to the cover 15 with the spacers 23 made of wire mesh inserted between two adjacent getters 10 and between the getter mounting portion 18 and the getter 10 facing the getter mounting portion 18, as shown in FIG.

[0029] 6, by sandwiching the spacer 23 between the two getters 10, the wires 28 of the spacer 23 (mesh) come into point contact with the opposing end faces 10a, 10a of the pair of getters 10. A large number of gaps 29 are formed between the wires 28 of the spacer 23 (mesh). As a result, the end faces 10a of the getters 10 are widely exposed inside the housing 3. After the getter holder 22 is welded to the housing 3 of the diaphragm vacuum gauge 1, the inside is evacuated and sealed. The housing 3 is then loaded into a heating furnace (not shown) and heated to a temperature at which the getter 10 is activated. After cooling, the housing 3 is removed from the heating furnace and sent to the next assembly process. The activated getter 10 functions as an adsorption pump that maintains a high vacuum within the reference vacuum chamber 12.

[0030] In the holding structure 21 for a non-evaporable getter member in an airtight container configured in this manner, a mesh spacer 23 is inserted between two adjacent getters 10, so that the opposing end faces 10a, 10a of the pair of getters 10 are widely exposed within the housing 3 through gaps 29 between the mesh wires 28. Since the spacer 23 according to this embodiment is also inserted between the getter 10 and the cover 15, the end face 10a of the getter 10 facing the cover 15 is widely exposed within the housing 3 through gaps 29 between the mesh wires 28.

[0031] This makes it possible to provide a holding structure for a non-evaporable getter member in an airtight container that can increase the effective surface area by exposing as much as possible within the airtight container the areas where the non-evaporable getter members overlap and the area between the getter mounting portion and the non-evaporable getter facing the getter mounting portion. The mesh forming the spacer 23 in this embodiment has a mesh count of 200. Since this mesh has a thickness of about 0.09 mm, two getters 10 can be housed in the housing 3 without changing the size of the housing 3.

[0032] The surface area exposed inside the housing 3 of the getter 10 according to this embodiment was calculated, and the results shown in Table 1 were obtained. Table 1 lists data such as the ratio of the total surface area of ​​the ideal non-evaporable getter member to the total surface area of ​​the ideal non-evaporable getter member when getters with the same conditions such as surface area, adsorption limit amount, and allowable leak amount are used for an ideal non-evaporable getter member, a conventional non-evaporable getter member (prototype: before measures), and the getter 10 according to this embodiment (improvement: after measures). As shown in Table 1, compared to a conventional non-evaporable getter member that does not use a spacer 23, the getter 10 according to this embodiment has twice the surface area, twice the adsorption limit amount, and twice the allowable leakage amount.

[0033] [Table 1]

[0034] The spacer 23 according to this embodiment is formed in a U-shape in side view, sandwiching one getter 10 from both sides in the stacking direction, which is the direction in which two getters 10 overlap. Therefore, a part of the spacer 23 is disposed on the side of the getter 10, so that the presence or absence of the spacer 23 can be easily determined visually.

[0035] (Modification of spacer when there are two non-evaporable getter members) The spacer can be formed in an S-shape when viewed from the side, as shown in Fig. 7. In Fig. 7, the same or equivalent members as those described with reference to Figs. 1 to 6 are designated by the same reference numerals, and detailed description thereof will be omitted where appropriate. 7 is formed by bending a single strip-shaped plain woven wire mesh into an S-shape in side view. More specifically, this spacer 31 has an insertion portion 31a inserted between two getters 10, first and second end portions 31b, 31c facing end faces 10a of getters 10 which are opposite ends in the stacking direction in which the two getters 10 overlap, a first connecting portion 31d connecting one end of insertion portion 31a to first end portion 31b, and a second connecting portion 31e connecting the other end of insertion portion 31a to second end portion 31c.

[0036] Even when the spacer 31 is formed in an S-shape in side view as shown in this embodiment, it is possible to provide a getter holding structure in an airtight container that can expose as much of the overlapping portion of the getters 10 as possible inside the airtight container, thereby increasing the effective surface area. In particular, according to this embodiment, the spacer 23 is inserted also between the connecting portion 25 of the getter holder 22 and the getter 10, so that the end face 10a of the getter 10 facing the connecting portion 25 is exposed inside the housing 3 through the gaps 29 between the mesh wires 28, making it possible to further increase the effective surface area of ​​this end face 10a.

[0037] (Second embodiment) The holding structure for non-evaporable getter members in the airtight container according to the present invention can hold three non-evaporable getter members, as shown in Figure 8 and Figures 9(A) and (B). In Figures 8 and 9(A) and (B), members that are the same as or equivalent to those described in Figures 1 to 6 are given the same reference numerals, and detailed description will be omitted where appropriate. Figure 9(A) is a side view of the getter and spacer when one mesh is used, and Figure 9(B) is a side view of the getter and spacer when three meshes that are U-shaped when viewed from the side are used.

[0038] The getter holder 22 shown in FIG. 8 has legs 24 that are longer than those of the getter holder 22 shown in the first embodiment so that it can hold three getters 10 stacked in the axial direction. 9(A) is formed by bending a strip-shaped plain weave mesh so as to contact the end faces 10a of all the getters 10. More specifically, the spacer 32 according to this embodiment has a first insert portion 32a and a second insert portion 32b inserted between two adjacent getters 10, first and second end portions 32c, 32d facing the end faces 10a, 10a of the getters 10, which are both ends in the stacking direction in which the three getters 10 are stacked, a first connecting portion 32e connecting one end of the first insert portion 32a to the first end 32c, a second connecting portion 32f connecting the other end of the first insert portion 32a to one end of the second insert portion 32b, and a third connecting portion 32g connecting the other end of the second insert portion 32b to the second end 32d.

[0039] 9(B) is configured using the spacer 23 that is U-shaped in side view, which was used when the first embodiment was adopted. That is, a spacer 23 that is U-shaped in side view is combined with each of the three getters 10. In this case, a large space is formed between the lowest getter 10 and the central getter 10, and between the highest getter 10 and the central getter 10, because two layers of flat plate portions 23a of the spacer 23 overlap each other.

[0040] As shown in Figures 9(A) and 9(B), by using three getters 10 in combination with spacers 32 or spacers 33, the number of getters 10 increases and the actual surface area of ​​the getters 10 increases due to contact of the getters 10 with the mesh wires 28, thereby further improving the adsorption efficiency.

[0041] (Third embodiment) The getter holder can be configured as shown in Figures 10 and 11. In Figures 10 and 11, members that are the same as or equivalent to those described with reference to Figures 1 to 6 are given the same reference numerals, and detailed description thereof will be omitted as appropriate. The getter holder 41 shown in Fig. 10 is formed of a metal plate having a plurality of ventilation holes 42. More specifically, the ventilation holes 42 consisting of a plurality of through holes are formed in the connecting portion 25 of the getter holder 41 shown in Fig. 10. The connecting portion 25 having the ventilation holes 42 formed therein has a smaller area of ​​the portion that comes into contact with the getter 10 than the connecting portion 25 having no ventilation holes 42 formed therein. Therefore, by adopting this embodiment, it is possible to further increase the substantial surface area of ​​the portion of the getter 10 that is exposed inside the housing 3.

[0042] 11 is formed of a mesh similar to the mesh that forms the spacer 23. This getter holder 43 has a pair of legs 24 and a connecting portion 25, similar to the getter holder 22 when the first embodiment is adopted. By using the getter holder 43 made of mesh to hold the getter 10, there is no part that comes into surface contact with the getter 10. As a result, the surface area of ​​the part of the getter 10 that is exposed inside the housing 3 can be further increased. [Explanation of symbols]

[0043] 1...diaphragm vacuum gauge, 3...housing (airtight container), 10...non-evaporable getter member, 10a...end surface, 18...getter mounting portion, 21...holding structure, 22, 41, 43...getter holder, 23, 31, 32, 33...spacer, 25...connecting portion, 31a...insertion portion, 31b...first end, 31c...second end, 31d...first connecting portion, 31e...second connecting portion, 32a...first insertion portion, 32b...second insertion portion, 32c...first end, 32d...second end, 32e...first connecting portion, 32f...second connecting portion, 32g...third connecting portion, 42...vent hole.

Claims

1. a getter holder that holds a plurality of non-evaporable getter members for absorbing gas, each formed as a member having a pair of end faces on the front and back, stacked in a thickness direction with the end faces facing each other, and is attached to a getter attachment portion of the airtight container; a spacer made of a wire mesh inserted at least between two adjacent non-evaporable getter members or between the getter mounting portion and the non-evaporable getter member facing the getter mounting portion in order to increase an adsorption limit of the gas adsorbed onto the non-evaporable getter member, The spacer is configured to connect one of the non-evaporable getter members to the plurality of non-evaporable getter members.

2. A holding structure for a non-evaporable getter member in an airtight container, the holding structure being formed in a U-shape so as to sandwich the non-evaporable getter member from both sides in a stacking direction, which is a direction in which the non-evaporable getter member overlaps.

2. In the holding structure for a non-evaporable getter member in the airtight container according to claim 1, The spacer is A single strip of wire mesh is bent into a predetermined shape, and two adjacent non-evaporation type The insertion portion inserted between the getter members and the plurality of non-evaporable getter members overlap each other. end portions opposite to the end faces of the non-evaporable getter member, which are both ends in the stacking direction, The airtight container has a connecting portion that connects the insertion portion and the end portion. A holding structure for a non-evaporable getter member.

3. A method for storing a non-evaporable getter member in an airtight container according to any one of claims 1 to 2. In the supporting structure, The getter holder is formed of a metal plate having ventilation holes. A structure for holding a non-evaporable getter member in an airtight container.

4. A method for storing a non-evaporable getter member in an airtight container according to any one of claims 1 and 2. In the supporting structure, The getter holder is formed of a wire mesh. A holding structure for a non-evaporable getter member.

5. A method for storing a non-evaporable getter member in an airtight container according to any one of claims 1 to 4. In the supporting structure, The airtight container is a holding structure that is a housing that accommodates a sensor element that detects the pressure of a medium to be measured.

6. In the holding structure for a non-evaporable getter member in the airtight container according to claim 5, A holding structure in which the housing is separated into at least a measured pressure chamber and a reference vacuum chamber, and the non-evaporable getter member is provided in the reference vacuum chamber.

7. The holding structure for a non-evaporable getter member in the airtight container according to claim 6, The reference vacuum chamber is formed by at least a cylindrical body and a cover, and the end surface of the non-evaporable getter member is a holding structure that faces the cover.

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