JP7357485B2 - Variable capacitor and NMR probe - Google Patents

Description

The present invention relates to a variable capacitor and an NMR probe including the same, and particularly to a bearing structure in a variable capacitor.

A nuclear magnetic resonance (NMR) measurement device has an NMR probe that includes a detection circuit. The detection circuit generally includes a detection coil, a tuning capacitor, and a matching capacitor. The tuning capacitor and the matching capacitor each include a variable capacitor. For example, an operating force is transmitted to each variable capacitor via an operating member. This changes the capacitance (capacitance). Specifically, the operating force is transmitted as linear movement or rotational movement of the operating member.

Variable capacitors generally include a bearing structure that holds the shaft and guides movement of the shaft. Ball bearings are well known as bearing structures. It follows a point contact system and requires lubricating oil for the rotation of the individual balls. At low temperatures, particularly at extremely low temperatures, the functionality of lubricating oils deteriorates or even ceases to function. Ball bearings are difficult to use at low temperatures. On the other hand, it is conceivable to use a bearing structure that includes a cylindrical member made of a resin (eg, fluororesin) having a small coefficient of friction. It follows the surface contact method. Generally, the linear expansion coefficient of resin is large, and it can be pointed out that such a bearing structure may not function properly in an environment where there is a large temperature change.

Note that the variable capacitor disclosed in Patent Document 1 has a bush that holds the shaft member so that it can move forward and backward. The bushing is an annular member into which the shaft member is inserted. Note that variable capacitors may be used in devices other than NMR measurement devices.

US Patent No. 9500726

It is desired to realize a bearing structure for a variable capacitor that can stably hold a moving shaft and smoothly guide the movement of the shaft under the environment in which the variable capacitor is used. For example, it is desired to realize a bearing structure that exhibits appropriate holding functions and appropriate guiding functions under cryogenic cooling.

An object of the present invention is to provide a bearing structure that can properly hold a shaft body and properly guide the movement of the shaft body in an environment where a variable capacitor is used. Alternatively, it is an object of the present invention to provide a bearing structure that can stably hold the shaft while the variable capacitor is in a cooled state and can smoothly guide the movement of the shaft.

The variable capacitor according to the embodiment includes a first member, a second member, and a bearing structure. The first member is a member having a cavity. The second member has a shaft body inserted into the cavity, and is a member that moves relative to the first member when changing the capacity. The bearing structure is a structure provided across the first member and the second member. Specifically, the bearing structure includes a plurality of linear contacts provided on one of the first member and the second member, and a plurality of linear contacts provided on the other member of the first member and the second member. a contact surface with which the linear contact contacts. Each linear contact extends along the direction of relative movement of the second member. The contact surface is an inner circumferential surface formed on the first member or an outer circumferential surface formed on the second member.

The above configuration employs a line contact method. According to the line contact method, it is generally easier to obtain a stable holding effect than the point contact method, and it is easier to reduce frictional resistance than the surface contact method. That is, according to the above configuration, since each linear contactor extends along the relative movement direction, and since the plurality of linear contacts are in contact with the contact surface around the shaft body, The holding of the other member by one member is stabilized, and the relative movement of the other member with respect to the one member is guided smoothly. Each wire contact may be constructed from a relatively flexible metal wire. One or both of the first member and the second member are configured as moving members.

There are several aspects of the bearing structure. In the first aspect, the first member is configured as a fixed member, the second member is configured as a movable member, the first member is provided with a plurality of linear contacts projecting inwardly, and the second member is provided with an outer side. A facing contact surface is provided. In a second aspect, the first member is configured as a fixed member, the second member is configured as a movable member, the first member is provided with an inwardly facing contact surface, and the second member includes a plurality of outwardly projecting lines. A shaped contact is provided. In a third aspect, the first member is configured as a movable member, the second member is configured as a fixed member, the first member is provided with a plurality of linear contacts projecting inwardly, and the second member is provided with an outer side. A facing contact surface is provided. In a fourth aspect, the first member is configured as a movable member, the second member is configured as a fixed member, the first member is provided with an inwardly facing contact surface, and the second member includes a plurality of outwardly projecting lines. A shaped contact is provided.

The above relative motion includes linear motion and rotational motion. If linear motion is employed, each linear contact is configured as a linear linear contact. In that case, the plurality of linear contacts are arranged around the central axis of the shaft. When rotational movement is employed, each linear contact is configured as a circular linear contact, in which case the plurality of linear contacts are arranged along the central axis of the shaft.

In embodiments, the first member is a fixed member and the second member is a movable member. The plurality of linear contacts are provided on the fixed member, and the contact surface is the outer peripheral surface of the shaft body. The relative movement direction is the direction of the central axis of the shaft. This configuration corresponds to the first aspect described above.

In embodiments, the bearing structure includes a wire with multiple loops. The plurality of linear contacts are a plurality of portions (linear portions) that contact the outer peripheral surface of the shaft body in a plurality of loops. According to this configuration, the arrangement and manufacturing of the plurality of linear contacts is facilitated.

In the embodiment, the number of loops included in the wire is 3 or more and 30 or less. If it is 3 or more, the central axis of the shaft body is stabilized. If the number of loops is too large, surface contact will approach and frictional resistance will increase, so it is desirable that the number of loops be 30 or less. When the shaft body is relatively thin, the number of loops may be set to 3 or more and 20 or less. It is desirable to adjust the number of loops so that a certain amount of space is created between adjacent loops. Further, it is desirable that the sizes of the plurality of gaps arranged in the circumferential direction are approximately the same.

In embodiments, the plurality of loops have a helical configuration wrapped around a toroidal core. According to this configuration, a plurality of linear members can be formed more easily. For example, multiple loops are formed by physically wrapping a single wire around a core in a helical manner. If the angle of inclination of the individual loops with respect to the central axis is small, the inclination angle can be ignored, ie, even in this case a stable holding effect and a smooth movement guiding effect can be obtained. The wire may be made of a relatively soft metal. According to the above configuration, while reducing the frictional resistance in the direction of movement, the frictional resistance in the direction perpendicular to the direction of movement is naturally increased. Moreover, it becomes easier to form a good contact state (including an electrical contact state) between the contact surface and the plurality of loops. In embodiments, the plurality of loops are independently wrapped around the toroidal core. According to this configuration, the action of each loop can be made more ideal.

In embodiments, the outer circumferential surface is coated with a coating that reduces frictional forces. In the embodiment, each linear contact is also coated with a coating that reduces frictional force. According to these configurations, sliding resistance can be reduced or an appropriate sliding resistance can be obtained.

In the embodiment, the fixed member has a fixed electrode, the shaft body has a conductive member electrically insulated from the fixed electrode, and the spatial relationship between the fixed electrode and the conductive member is changed by moving the movable member back and forth. This changes the capacitance. Specifically, the conductive member is a movable electrode that serves as a counter electrode to a fixed electrode. Alternatively, the fixed electrode includes a first fixed electrode and a second fixed electrode that are opposite to each other, and the conductive member is a member for changing the dielectric constant between the first fixed electrode and the second fixed electrode.

In an embodiment, the variable capacitor is used in a cooled state. The bearing structure described above does not necessarily require lubricating oil to support movement, and looseness is less likely to occur between the fixed member and the movable member in a cooled state.

The NMR probe according to the embodiment includes a detection circuit and a transmission member. The detection circuit has a variable capacitor for tuning or matching, and is used in a cooled state. The transmission member is a member that transmits an external operating force to the variable capacitor when the capacitance of the variable capacitor is varied. The variable capacitor has a fixed member, a movable member, and a bearing structure. The fixing member has a cavity. The movable member is a member that has a shaft body that is inserted into a cavity, and that moves linearly in the direction of a central axis that the shaft body has in response to an operating force. The bearing structure is a structure provided across the fixed member and the movable member. Specifically, the bearing structure includes a plurality of linear contacts and a contact surface. A plurality of linear contacts are provided on the fixed member, and each linear contact extends along the direction of the central axis. The contact surface is a surface with which a plurality of linear contacts come into contact, and is the outer circumferential surface of the shaft body.

The above-mentioned variable capacitor follows a line contact method, and is capable of stably holding the capacitor in a cooled state while reducing frictional resistance when moving in the direction of the central axis.

According to the present invention, the shaft body can be properly held and the movement of the shaft body can be appropriately guided in an environment where a variable capacitor is used. Alternatively, according to the present invention, the shaft body can be stably held while the variable capacitor is in a cooled state, and the movement of the shaft body can be smoothly guided.

FIG. 1 is a schematic diagram showing a nuclear magnetic resonance (NMR) measurement device. FIG. 2 is a cross-sectional view of the variable capacitor according to the first embodiment. FIG. 2 is a perspective view of a variable capacitor according to a first embodiment. FIG. 2 is an exploded perspective view of the variable capacitor according to the first embodiment. FIG. 3 is a sectional view showing the cross section indicated by A in FIG. 2; It is a perspective view showing the upper part of a wire bearing. FIG. 7 is an exploded perspective view of a fixed part and a movable part according to a second embodiment. FIG. 3 is a diagram for explaining the operation of the variable capacitor according to the first embodiment. FIG. 7 is a diagram for explaining the operation of the variable capacitor according to the second embodiment. FIG. 7 is a diagram for explaining the operation of a variable capacitor according to a third embodiment. It is a sectional view showing a first modification. It is a sectional view showing a second modification.

Hereinafter, embodiments will be described based on the drawings.

FIG. 1 shows a configuration example of a nuclear magnetic resonance (NMR) measurement apparatus according to a first embodiment. This NMR measuring device is a device that measures NMR generated in a sample in order to analyze the sample. The illustrated NMR measurement apparatus includes a spectrometer 10, a static magnetic field generator 12, and an NMR probe 14. In addition to these, it has a vacuum pump 20 and a cooling device 22. Spectrometer 10 constitutes the main console. Specifically, the spectrometer 10 includes a transmitter, a receiver, a spectrum generator, and the like. The static magnetic field generator 12 generates a static magnetic field parallel to the z direction. The static magnetic field generator 12 includes, for example, a superconducting coil. In each figure, the first horizontal direction is the x direction, the second horizontal direction is the y direction, and the vertical direction is the z direction. The three directions are orthogonal to each other.

The NMR probe 14 includes an insertion section 16 and a base section 18 . The insertion portion 16 is a cylindrical portion inserted into the bore 12A of the static magnetic field generator 12. The upper end of the insertion section 16 is a probe head, and a detection circuit 26 is provided inside the probe head. The detection circuit 26 is a circuit that generates NMR in the sample in the sample tube 24 and detects the generated NMR. Typically, the detection circuit 26 includes a detection coil, a tuning capacitor, and a matching capacitor.

In the illustrated configuration example, for example, variable capacitor 28 is a tuning capacitor, and variable capacitor 30 is a matching capacitor. Three or more variable capacitors may be provided within the detection circuit 26. In the embodiment, the two variable capacitors 28, 30 have the same configuration. Their configurations may be different.

The base 18 is provided with a transmitting/receiving port, and a signal line is disposed between the transmitting/receiving port and the spectrometer 10. A vacuum pump 20 is connected to the base 18 via piping, and a cooling device 22 is connected to the base 18 via another piping. Due to the action of the vacuum pump 20, the inside of the NMR probe 14 (particularly the inside of the probe head) is evacuated. The cooling device 22 functions as a driving source and a cooling source for the refrigerant circulation system. Coolant exiting the cooling device 22 is routed through the base 18 to the probe head. A coolant cools the individual elements within the probe head. Coolant is then passed from the probe head through base 18 to cooling device 22 . Examples of the refrigerant include liquid helium and liquid nitrogen. The detection circuit 26 is maintained at a temperature of, for example, 100K or less, preferably 50K or less. These temperatures are exemplary only. The temperature of the detection circuit 26 may be set to room temperature.

Two rods 32, 34 are provided for transmitting operating forces to the two variable capacitors 28, 30. Knobs 36, 38 are provided at their lower ends. Each rod 32, 34 functions as an operating member when viewed from the variable capacitors 28, 30. That is, when the knobs 36 and 38 are rotated, the resulting operating force is transmitted to the variable capacitors 28 and 30 via the rods 32 and 34. Each rod 32, 34 is provided with a motion conversion mechanism (not shown). The motion conversion mechanism is a mechanism that converts rotational motion into linear motion.

When varying the capacitance of each variable capacitor 28, 30, a linear motion force is applied to each variable capacitor 28, 30 via each rod 32, 34. Rotation of the rods 32, 34 can be done manually or mechanically. Two variable capacitors 28, 30 are fixed to structures within the probe. The structure also functions as a heat conducting member to cool the two variable capacitors 28,30. In the following, the variable capacitor 28 will be representative of the two variable capacitors 28 and 30, and its structure will be explained in detail.

FIG. 2 shows an xz cross section of the variable capacitor 28. The variable capacitor 28 has a fixed part 40 as a fixed member and a movable part 42 as a movable member. Further, the variable capacitor 28 has a bearing structure 49 provided over or across the fixed part 40 and the movable part 42 . The inside of the fixing part 40 is hollow.

The fixed part 40 is fixed to the structure 60. Structure 60 also functions as a heat conductive member for cooling variable capacitor 28. The structure 60 is made of copper or phosphor bronze, for example. The fixing part 40 has a cylindrical body 43. The main body of the cylindrical body 43 is an insulating tube 44. The insulating tube 44 is made of transparent sapphire glass, for example. The insulating tube 44 has an outer circumferential surface and an inner circumferential surface, and a fixed electrode 46 as an electrode layer is formed at one end (the upper end in the figure) of the outer circumferential surface. The fixed electrode 46 has an annular shape and is a thin film.

A coating layer 47 is formed on the other end (lower end in the figure) of the outer peripheral surface of the insulating tube 44 . The covering layer 47 has an annular shape and is also a thin film. The fixed electrode 46 and the covering layer 47 are configured as, for example, a silver plating layer.

The fixing part 40 has a cylindrical holder 48. The holder 48 is made of phosphor bronze, for example. Specifically, the holder 48 consists of a main body 48A and an upper end 48B. The lower end of the cylindrical body 43 is inserted into the upper end 48B. Specifically, the upper end portion 48B is configured as a thin wall portion, and the main body 48A is configured as a thick wall portion. A step surface is formed between them, and the lower end surface of the cylindrical body 43 abuts against the step surface. The upper end portion 48B and the covering layer 47 are interconnected by soldering or the like. The main body 48A and the structure 60 are also interconnected by soldering or the like, if necessary.

A bearing structure 49 is arranged inside the main body 48A. A bearing structure 49 is secured to the body 48A, which in embodiments includes a wire bearing. Details of the bearing structure 49 will be explained later.

The movable part 42 has a movable shaft 52 as a shaft body, and a movable electrode 54 provided at the tip of the movable shaft 52. The movable shaft 52 and the movable electrode 54 are made of a conductive member, for example, made of phosphor bronze. The surfaces of the movable shaft 52 and the movable electrode 54 are coated. For example, a gold vapor deposited layer is formed on their surfaces. The movable electrode 54 constitutes a cylindrical enlarged portion, and its outer diameter is slightly smaller than the inner diameter of the insulating tube 44 . The fixed electrode 46 and the movable electrode 54 are opposite electrodes, and the capacitance between them changes depending on the position of the movable electrode 54 in the z direction.

Reference numeral 62 indicates the movement of the movable shaft 52 back and forth. When the movable electrode 54 is pulled down to the lowest level, the upper end level of the movable electrode 54 is lower than the lower end level of the fixed electrode 46, and the capacitance is minimized. On the other hand, when the movable electrode 54 is pulled up to the highest level, the fixed electrode 46 and the movable electrode 54 completely overlap when viewed from the horizontal direction, and the capacitance is maximized. In the first embodiment, a first signal line is connected to the fixed electrode 46, and a second signal line is connected to the holder 48. The holder 48 and the movable electrode 54 are in a conductive relationship.

A screw structure 56 is formed at the lower end of the movable shaft 52. The movable shaft 52 is connected to the rod 32 using the screw structure 56. The movable shaft 52 is integrated with the rod 32, and when the rod 32 is advanced (raised), the movable shaft 52 moves forward, and when the rod 32 is retreated (lowered), the movable shaft 52 retreats. The movable shaft 52 is electrically connected to the holder 48.

In FIG. 2, the length (size in the z direction) of the movable portion 42 is, for example, within a range of 50 to 60 mm. The length of the insulating tube 44 is, for example, within a range of 30 to 45 mm. The length of the fixed electrode 46 is, for example, within a range of 5 to 15 mm. The length of the movable electrode 54 is, for example, within a range of 5 to 15 mm. The length of the wire bearing 50 is, for example, within a range of 10 to 15 mm. The outer diameter of the insulating tube 44 is, for example, within a range of 3 to 8 mm. Its wall thickness is in the range of 0.3 to 1 mm. The outer diameter of the movable shaft 52 is, for example, within a range of 1.5 to 2.5 mm. The variable range of capacitance is, for example, 0.5 to 30 pF. All of those numerical values are merely examples.

FIG. 3 is a perspective view of the variable capacitor. As already explained, the variable capacitor is composed of the fixed part 40 and the movable part 42.

FIG. 4 is an exploded perspective view of the variable capacitor. As already explained, the movable part 42 is composed of the movable shaft 52 and the movable electrode 54.

The fixing part 40 has a cylindrical body 43 and a holder 48. A sheath 68 functioning as a spacer is provided inside the holder 48. Inside the sheath 68, a wire bearing 50, which is a main part of the bearing structure, is fixedly installed. The sheath 68 is made of, for example, a conductive member. The wire bearing 50 includes a cylindrical or annular core 64 and a wire 66 wound around the core 64. The wire 66 is made of a conductive material, for example a copper wire. Its cross section is circular. The core 64 is made of, for example, an insulating member. If it is constructed of an electrically conductive material, the core 64 or the wire 66 is treated so that at least electrical insulation is provided between the core 64 and the wire 66.

In an embodiment, the entire surface of the wire 66 is coated with a coating that reduces frictional resistance. The surface layer formed by coating is, for example, a gold vapor deposited layer. The diameter of the wire 66 is, for example, in the range of 0.15 to 0.3 mm.

Examples of the installation mode of the wire 66 include a first mode and a second mode. In a first embodiment, the wire 66 is constituted by a plurality of coils 67 as mutually separated pieces of wire. The plurality of coils 67 are evenly wound around the core 64 in the circumferential direction. In that case, the plurality of coils 67 are arranged radially outward from the central axis of the movable shaft 52. It is desirable that the plurality of gaps generated in the plurality of coils 67 be approximately uniform. In the plurality of coils 67, a plurality of portions that contact the surface of the movable shaft 52 function as a plurality of linear contacts. The plurality of linear contacts are means for stably holding the movable shaft and guiding the smooth movement of the movable shaft.

In the second embodiment, the wire 66 is physically constituted by one wire. By spirally winding the wire around the core 64, a plurality of coils are constructed. However, the plurality of coils 67 are not separated from each other and are connected. The angle of inclination of each coil with respect to the central axis is small, and the coils perform approximately the same function as a plurality of coils 67 separated from each other, i.e. a portion of them is connected to a plurality of linear contacts as above. functions as According to the second aspect, the wire bearing 50 can be easily manufactured, that is, the wire 66 can be easily arranged.

As already explained, the bearing structure includes the wire bearing 50 provided on the fixed member side and the outer peripheral surface of the movable shaft 52 provided on the movable member side. The arrangement of both may be exchanged. For example, a wire bearing may be provided on the movable member, and the wire bearing may be brought into contact with the inner peripheral surface of the fixed member. The shaft body may be configured as a fixed member, and the hollow body into which the shaft body is inserted may be a movable member.

FIG. 5 shows a cross section indicated by A in FIG. The movable shaft 52 has an outer circumferential surface 72 . The holder 48 has a cavity, a sheath 68 is disposed in the cavity, and a wire bearing 50 is provided inside the sheath 68. A wire 66 is wound around the wire bearing 50 and consists of a plurality of coils. Each coil is roughly divided into an outer portion and an inner portion, and the outer portion is fixed in contact with the inner peripheral surface of the sheath 68. The inner portion of each coil contacts the outer surface of the movable shaft 52 as a linear contact.

Each linear contact extends in a direction parallel to the central axis, that is, in the z direction. A plurality of linear contacts are provided to surround the movable shaft 52, and since they are in contact with the outer peripheral surface of the movable shaft, the movable shaft 52 is stably held. Furthermore, the movable shaft 52 can be smoothly moved linearly. FIG. 6 shows the upper end portion 50A of the wire bearing 50. Specifically, in FIG. 6, the upper end portion 64A of the core and the upper end portion 67A of each coil are visible.

FIG. 7 is an exploded perspective view of the variable capacitor according to the second embodiment. The variable capacitor according to the second embodiment basically has the same configuration as the variable capacitor according to the first embodiment, but the configuration of the electrode portion is different. In the second embodiment, the same reference numerals are given to the elements that have already been explained, and the explanation thereof will be omitted.

Specifically, in FIG. 7, the variable capacitor is composed of a fixed part 40A and a movable part 42A. In the fixed portion 40A, an electrode pair consisting of two electrodes 76 and 78 provided apart from each other in the direction of the central axis is provided at the end of the insulating tube. The movable portion 42A includes a movable shaft 80 and a conductor 54A. The movable shaft 80 is composed of a conductive portion 84 and an insulating portion 82, and a conductor 54A is attached to the insulating portion 82. The conductor 54A has the same form as the movable electrode shown in FIG. 2 and the like. The conductor 54A is electrically floating.

In the second embodiment, the capacitance is changed by moving the movable shaft 80 back and forth to change the spatial relationship of the conductor 54A with respect to the electrode pair 74. For example, when the movable shaft 80 is moved backward, the capacity decreases, and when the movable shaft 80 is moved forward, the capacity is increased. Capacity is maximized when the conductor 54A is delivered across or completely overlapping the two electrodes 76, 78. In the second embodiment, two signal lines are connected to the two electrodes 76 and 78.

According to the second embodiment, the variable range of capacitance is lower than that of the first embodiment, making fine adjustment of capacitance easier. For example, its capacitance is between 0.4 and 2.7 pF. Note that a dielectric may be provided instead of the conductor 54A.

FIG. 8 shows the operation of the variable capacitor 86 according to the first embodiment. A first signal line 88 is connected to the fixed electrode 46, and a second signal line 90 is connected to the holder 48. Reference numeral 92 indicates an equivalent circuit. As shown by reference numeral 93, the capacitance of the capacitor changes due to the vertical movement of the movable part. Line 88a corresponds to the first signal line 88, and line 90a corresponds to the second signal line 90.

FIG. 9 shows the operation of the variable capacitor 94 according to the second embodiment. A first signal line 96 is connected to the electrode 76, and a second signal line 98 is connected to the electrode 78. Reference numeral 100 indicates an equivalent circuit. As shown by numerals 101a and 101b, the capacitance of two capacitor elements connected in series changes in conjunction with the vertical movement of the movable part. Line 96a corresponds to the first signal line, and line 98a corresponds to the second signal line. The line 102a corresponds to an electrically floating conductor.

FIG. 10 shows the configuration and operation of the variable capacitor 104 according to the third embodiment. A semi-cylindrical electrode 108 is provided on one end of the insulating tube, and a semi-cylindrical electrode 110 is provided on the other end. A first signal line 122 is connected to the electrode 108, and a second signal line 114 is connected to the electrode 110. The movable part includes a movable electrode. The third signal line 116 is electrically connected to the movable electrode via the wire bearing and the movable shaft. Reference numeral 118 indicates an equivalent circuit. As shown by reference numerals 119a and 119b, the capacitances of the two capacitor elements change in conjunction with each other due to the vertical movement of the movable part. Line 112a corresponds to a first signal line, and line 114a corresponds to a second signal line. Line 116a corresponds to the third signal line.

FIG. 11 shows a first modification. The movable part has a movable shaft 124. The fixed part includes a holder 120 and a bearing 122. The bearing 122 holds the movable shaft 124 and guides its rotational movement. The bearing consists of a cylindrical main body 126 and an annular projection row 128 provided on the inner peripheral surface of the main body. The annular projection row 128 is composed of a plurality of annular projections 130 arranged in the direction of the central axis C. The apex portion 132 of each annular projection 130 functions as a linear contact having a ring shape. Each vertex portion 132 is in contact with the outer peripheral surface 134 of the movable shaft 124. A bearing structure is configured by the plurality of annular protrusions 130 and the outer circumferential surface in contact with them.

Since the movable shaft is held by the plurality of annular protrusions 130, its holding state is stabilized. Furthermore, since each annular protrusion 130 has an annular shape, the frictional resistance generated during rotational movement of the movable shaft 124 can be reduced. In the first modification, a configuration is adopted in which the capacity changes with rotation of the movable shaft.

FIG. 12 shows a second modification. A wire bearing 144 is fixed to the movable shaft 140. The wire bearing 144 has a core 146 and a plurality of coils 150 wound around the core 146 , and the outer portion of each coil is in contact with the inner peripheral surface of the holder 142 . That is, each outer portion functions as a linear contact. When adopting the second modification, it is desirable to lengthen the holder 142 in the direction of the central axis or to increase the length of the wire bearing in the direction of the central axis. In the first modification and the second modification, it is also desirable to coat two members that are in contact with each other.

According to each of the above embodiments, the movable shaft can be properly held and the movement of the movable shaft can be appropriately guided in an environment where the variable capacitor is used. In particular, the movable shaft can be stably held in a cooled state and the movement of the movable shaft can be smoothly guided.

10 Spectrometer, 12 Static magnetic field generator, 14 NMR probe, 26 Detection circuit, 28, 30 Variable capacitor, 40 Fixed part (fixed member), 42 Movable part (movable member), 46 Fixed electrode, 49 Bearing structure, 50 Wire bearing, 52 movable shaft, 54 movable electrode, 64 core, 66 wire, 67 loop.

Claims (13)

a first member having a cavity;
a second member having a shaft body inserted into the cavity and moving relative to the first member when changing the capacity;
a bearing structure provided across the first member and the second member;
including;
The bearing structure is
A wire provided on one of the first member and the second member and having a plurality of loops;
a contact surface provided on the other of the first member and the second member;
including;
A plurality of portions that contact the contact surface in the plurality of loops function as a plurality of linear contacts,
Each of the linear contacts extends along the relative movement direction of the second member,
The relative movement direction is a direction of a central axis of the shaft body,
The contact surface is an inner circumferential surface formed on the first member or an outer circumferential surface formed on the second member,
A variable capacitor characterized by: The variable capacitor according to claim 1,
The first member is a fixed member,
the second member is a movable member;
The plurality of linear contacts are provided on the fixed member,
The contact surface is an outer peripheral surface of the shaft body,
A variable capacitor characterized by: The variable capacitor according to claim 1,
the wire is a metal wire;
A variable capacitor characterized by: The variable capacitor according to claim 1,
The number of loops included in the wire is 3 or more and 30 or less,
A variable capacitor characterized by: a first member having a cavity;
a second member having a shaft body inserted into the cavity and moving relative to the first member when changing the capacity;
a bearing structure provided across the first member and the second member;
including;
The bearing structure is
A wire provided on one of the first member and the second member and having a plurality of loops;
a contact surface provided on the other of the first member and the second member;
including;
A plurality of portions that contact the contact surface in the plurality of loops function as a plurality of linear contacts,
Each of the linear contacts extends along the relative movement direction of the second member,
The contact surface is an inner circumferential surface formed on the first member or an outer circumferential surface formed on the second member,
The plurality of loops have a spiral shape wound around an annular core,
A variable capacitor characterized by: a first member having a cavity;
a second member having a shaft body inserted into the cavity and moving relative to the first member when changing the capacity;
a bearing structure provided across the first member and the second member;
including;
The bearing structure is
A wire provided on one of the first member and the second member and having a plurality of loops;
a contact surface provided on the other of the first member and the second member;
including;
A plurality of portions that contact the contact surface in the plurality of loops function as a plurality of linear contacts,
Each of the linear contacts extends along the relative movement direction of the second member,
The contact surface is an inner circumferential surface formed on the first member or an outer circumferential surface formed on the second member,
The plurality of loops are wound around the annular core independently of each other,
A variable capacitor characterized by: The variable capacitor according to claim 1,
The contact surface is coated with a coating that reduces frictional force.
A variable capacitor characterized by: The variable capacitor according to claim 1,
Each of the linear contacts is coated with a coating that reduces frictional force.
A variable capacitor characterized by: The variable capacitor according to claim 2,
The fixed member has a fixed electrode,
The shaft body has a conductive member electrically insulated from the fixed electrode,
The spatial relationship between the fixed electrode and the conductive member changes due to the forward and backward movement of the movable member, thereby changing the capacitance.
A variable capacitor characterized by: The variable capacitor according to claim 9,
The conductive member is a movable electrode that serves as a counter electrode to the fixed electrode.
A variable capacitor characterized by: The variable capacitor according to claim 9,
The fixed electrode includes a first fixed electrode and a second fixed electrode in a counter electrode relationship,
The conductive member is a member for changing the dielectric constant between the first fixed electrode and the second fixed electrode,
A variable capacitor characterized by: The variable capacitor according to claim 1,
The variable capacitor is a tuning capacitor or matching capacitor used in a cooled state in an NMR probe.
A variable capacitor characterized by: a detection circuit having a variable capacitor for tuning or matching and used in a cooled state;
a transmission member that transmits an external operating force to the variable capacitor when the capacitance of the variable capacitor is varied;
including;
The variable capacitor is
a fixing member having a cavity;
a movable member that has a shaft inserted into the cavity and that moves linearly in the direction of a central axis of the shaft due to the operating force;
a bearing structure provided across the fixed member and the movable member;
including;
The bearing structure is
A wire provided on the fixing member and having a plurality of loops;
an outer peripheral surface of the shaft;
including;
A plurality of portions extending along the direction of the central axis in the plurality of loops function as a plurality of linear contacts,
the plurality of linear contacts contact the outer peripheral surface;
An NMR probe characterized by:

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