JPH0242161B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a position detection device using a reed switch, and more particularly to a control rod position detection device incorporated into an electronic furnace control rod drive mechanism.

A reed switch is a type of detector that detects the position of a moving object in a non-contact manner, and there are detection devices that use the reed switch. A reed switch is a switch made of two magnetic leads mounted in a tube made of an insulator such as glass, and an example of its structure is shown in a vertical cross-sectional view in FIG. A reed switch 1 has two magnetic leads 2 sealed in a glass tube 3 with their free ends overlapping. This overlapping free end, which serves as a contact, is usually treated with a contact treatment such as vapor-depositing a precious metal to improve reliability, and in order to prevent deterioration of contact performance, a contact treatment is applied to the overlapped free end. Usually, it is filled with inert gas. When a magnet is brought close to the reed switch 1 and a magnetic field is applied in the axial direction of the reed, the reed 2 is magnetized, and a magnetic attraction force acts on the free end forming the contact, closing the contact. When the magnet is moved away to release the magnetic field, the contact opens due to the mechanical restoring force of the lead 2. Means for applying a magnetic field to the reed switch 1 include means for electrically forming a magnetic field by winding a coil, or means for bringing a permanent magnet close to each other.The former is used as a reed relay, and the latter is used as a push button switch as a proximity switch. It's being used.

FIG. 2 shows a conceptual configuration of a position detection device using a plurality of such reed switches. This figure shows an example in which the position of an object 4 is detected using nine reed switches 1. Reed switch 1 is object 4
are spaced apart, for example, at equal intervals along the direction of movement of the conductors 6, each of which is connected to a different pair of conductors 6. A permanent magnet 5 is attached to the object 4 and moves together with the object 4 in the axial direction of the reed switch 1. If the distance between each reed switch 1 and the moving path of the magnet 5 is adjusted and selected so that the reed switch 1 closes only when the magnet 5 comes close to each reed switch 1, the distance between the reed switch 1 and the moving path of the magnet 5 can be adjusted. As the reed switch 1 moves, the reed switch 1 operates sequentially. Therefore, by identifying through the conductor 6 which reed switch 1 is closed, the position of the object 4 can be determined discontinuously.

The above is the concept of a position detection device using a plurality of reed switches, but in order to actually use it as a detection device, it is necessary to have a specific structure of the detection device for holding the reed switch 1 and the conducting wire 6, etc. for it. Is required. The following matters are required for the structure of this detection device.

The first point is that it has a structure that can protect the reed switch 1. When the reed switch 1 is made of a glass tube or the like, the structure of the detection device needs to have strength not only to support the detection device itself but also to protect the reed switch 1 from unexpected disturbances.

The second point is that the conductor 6 and the connecting portion between the conductor 6 and the reed switch 1 have a structure that can sufficiently electrically insulate them from each other and from others. In order to increase the reliability of the detection device, the possibility of short circuits should be minimized.

The third point is not to shield magnetic force.
Although this is related to the selection of materials, it is natural since the reed switch 1 is used.

The fourth point is that it is relatively compact. Generally, it is undesirable for the detection device to become large. The position detection device needs to have a length sufficient to detect the position in the moving direction of the object, but it is better that the length in the direction perpendicular to the length, that is, the thickness, be thin. Even the thinnest commercially available reed switches have a diameter of about 3 mm. Therefore, it is naturally impossible to use a reed switch in a space narrower than this, but it is better that the thickness of the detection device be as thin as possible within a range that is wider than the diameter of the reed switch. Particularly in the case of a position detection device using a reed switch, it is necessary to consider the distance relationship with the magnet attached to the object. The distance between the magnet and the detection device is
Type of reed switch, sensitivity of reed switch,
It is understood that this depends on the strength and size of the magnet, the direction in which the magnet and reed switch face each other, etc., but in any case, it is limited to a relatively close range.
In other words, if this distance is too large, the reed switch will not operate at all, and if this distance is too small and the reed switches are too close together compared to the magnetic force of the magnet, each reed switch will not close. may become unidentifiable. Considering the accuracy of position detection, the tolerance for variations in the magnet's magnetic force, and the actual usage conditions, the positions where the position detection device can be installed are usually quite limited. The range of use is wider.

The fifth point is that the positioning of the reed switch is easy. Since the position of the reed switch is related to the performance of the detection device itself, it is desirable that the detection device has a structure that allows easy positioning of each reed switch during assembly.

The sixth point is that it has sufficient environmental resistance. This includes, for example, heat resistance. Ordinary reed switches can be used satisfactorily in the temperature range from minus 2 to 30 degrees Celsius to plus 100 degrees Celsius. Although the ambient temperature around the detection device will of course vary depending on the conditions in which it is used, materials and structures for the detection device that are inferior in heat resistance to at least the reed switch itself are undesirable because they limit the range of use.

A position detection device using a reed switch is desired to have a structure that satisfies the above conditions.

An object of the present invention is to provide a position detection device using a reed switch that satisfies the above requirements, and furthermore, to provide a control rod position detection device incorporated in a narrow space of a nuclear reactor control rod drive mechanism. It is about providing.

The position detection device of the present invention detects the position of an object by arranging a plurality of reed switches in a row that are opened and closed by the magnetic field of a magnet attached to the object. A first type of insulating solid having a plurality of peripheral holes or grooves through which the reed switch conductor is inserted, and a plurality of second type insulating solids having a plurality of peripheral holes or grooves through which the reed switch conductor is inserted. The control rod position detection device of the present invention is characterized by being arranged in series and adjacent to each other in a protective tube made of a non-magnetic material, and the control rod position detection device of the present invention is connected to a control rod and driven by hydraulic pressure. A nuclear reactor control rod drive mechanism comprising a piston, a guide tube for the piston, and an outer tube around the guide tube,
A magnet is attached to the piston, a pressure tube is provided in the axial direction in the gap between the guide tube and the outer tube, and a center hole in which each of a plurality of reed switches is housed, and a plurality of peripheral holes through which conductive wires for each reed switch are inserted. Protection in which a plurality of first type insulating solids having holes or grooves and second type insulating solids having a plurality of peripheral holes or grooves through which the conductor for the reed switch is inserted are arranged in series adjacent to each other inside. The pipe is housed within the pressure-resistant pipe.

An embodiment of the position detection device of the present invention will be described with reference to FIGS. 3 to 6. Figure 3 shows its longitudinal section.
4, 5, and 6 show the AA cross section, the BB cross section, and the CC cross section of FIG. 3, respectively. A plurality of blocks of nonmagnetic insulating solids 7a, 7b, and 7c are stacked in series in a protective tube 9 made of a nonmagnetic material. A reed switch 1 is housed in the center hole of the insulating solid body 7a, and a conductive wire 6 is inserted into a hole 8 (this may be a groove) around the reed switch 1. The insulating solid body 7b has holes 8 through which the conductive wires 6 are inserted, one of which is wide enough to accommodate the connecting portion between the conductive wire 6 and the terminal of the reed switch. The insulating solid 7c has only holes through which the conductive wires 6 are inserted. These insulating solids 7a, 7b, 7c are stacked in a required number according to the number of reed switches 1. In addition, each reed switch 1 and conductor 6
The manner of connection with the terminal may be the same as shown in Figure 2,
It goes without saying that the object 4 with the magnet 5 shown in FIG. 2 whose movement position along the protection tube 9 is to be detected is arranged at a short distance outside the protection tube 9.

Various materials can be used as the insulating solid, for example ceramics can be used. Among ceramics, alumina has a high insulation resistance and excellent insulation properties, especially at high temperatures.It also has a small coefficient of thermal expansion, excellent thermal shock resistance, and high heat resistance. If such a material is used, a detection device with a small diameter and excellent heat resistance and strength can be obtained.

According to the structure of the detection device described above, the reed switch 1 is protected from external damaging effects, each conductor 6 and its connection with the reed switch 1 is sufficiently electrically insulated, and the reed switch 1 is protected from external damaging effects. The magnetic force is not shielded, the outer diameter of each insulating solid and the protection tube 9 can be made small, so the detection device can be made thin, and each reed switch 1 can be easily positioned by stacking the insulating solids 7a, 7b, and 7c. It is obvious that environmental resistance such as heat resistance can be imparted by selecting the materials of the insulating solid and the protection tube.

Next, a control rod position detecting device in which the position detecting device having the above structure is incorporated into a control rod drive mechanism of a boiling water reactor will be explained with reference to FIGS. 7 and 8. FIG. 7 shows a longitudinal sectional view of a control rod drive mechanism 11 using an electric motor used in a boiling water reactor, and FIG. 8 shows a DD cross section of FIG. 7. A control rod drive mechanism 11 is installed in a housing 19 at the bottom of a pressure vessel 10 of a boiling water reactor. The control rod drive mechanism 11 controls the reaction of the nuclear reactor by vertically moving a control rod 12 connected to its upper end and containing a neutron absorbing material. In this control rod drive mechanism 11, the vertical movement of the control rods 12 is normally adjusted by an electric motor M via a transmission screw, but in a scram system, all the control rods in the reactor are simultaneously inserted into the reactor core at high speed. During operation, high pressure water is sent into the control rod drive mechanism via the scram piping 13. Then, the pressure inside the control rod drive mechanism 11 and the reactor pressure vessel 1
The hollow piston 14 moves upward due to the difference in pressure inside the piston, and the control rod 12 connected thereto is inserted into the reactor core at high speed.

A permanent magnet 15 is incorporated in the hollow piston 14, and a pressure-resistant tube 17 is provided in the axial direction in the gap between the guide tube 20 and the outer tube 16 for the hollow piston 14, and a third pressure tube 17 is provided inside the tube.
A position detection device 18 having a configuration similar to that described in FIGS. 6 through 6 is housed. Thereby, the axial position of the hollow piston 14 and, in turn, the control rod 12 can be detected. In this control rod position detection device, the position detection device 18 is
The outer diameter is limited to several millimeters. Detection device 18 having the above-described structure according to the present invention
are very advantageous for use in such confined spaces, and also in view of the relatively severe temperature conditions and considerable strength requirements for use in control rod drive mechanisms. Furthermore, the presence of the pressure tube 17 protects the control rod position detection device 18 from high pressure within the control rod drive mechanism.

According to the present invention, it is suitable for protecting each reed switch in a position detection device using a plurality of reed switches, electrically insulating each conductive wire and its connection part, positioning the reed switch, and for use in a very narrow space. The thinness of the detection device can be easily ensured with a simple structure, and a pressure-resistant control rod position detection device that is suitable for the narrow space in the control rod drive device of a nuclear reactor can be obtained. .

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of a reed switch, FIG. 2 is a conceptual configuration diagram of a position detection device using a plurality of reed switches, and FIG. 3 is a longitudinal sectional view of an embodiment of a position detection device according to the present invention. Figures 4, 5 and 6
The figures are the AA cross section, BB cross section and CC cross section of Figure 3, respectively.
A cross-sectional view, FIG. 7 is a vertical cross-sectional view of a control rod drive mechanism incorporating a control rod position detection device according to the present invention,
FIG. 8 is a diagram showing the DD cross section of FIG. 7. 1...Reed switch, 4...Object, 5...Magnet, 6...Conducting wire, 7a, 7b, 7c...Insulating solid, 9...Protection tube, 10...Reactor pressure vessel, 1
1... Control rod drive mechanism, 12... Control rod, 14...
...Hollow cylinder, 15...Magnet, 16...Outer tube, 17...Pressure tube, 18...Position detection device, 20...Guide tube.

Claims (1)

[Scope of Claims] 1. A position detection device that detects the position of an object by arranging a plurality of reed switches in a row that are opened and closed by the magnetic field of a magnet attached to an object, including a center hole in which each reed switch is housed and each reed. A first type insulating solid having a plurality of peripheral holes or grooves through which the lead switch conductor is inserted, and a plurality of second type insulating solids having a plurality of peripheral holes or grooves through which the reed switch conductor is inserted. A position detection device characterized by being arranged in series and adjacent to each other in a protective tube made of a magnetic material. 2. In a reactor control rod drive mechanism comprising a piston connected to a control rod and driven by hydraulic pressure, a guide tube of the piston, and an outer tube around the guide tube, a magnet is attached to the piston, and a magnet is attached to the guide tube. A first type insulating solid having a pressure-resistant tube installed in the axial direction in the gap with the outer tube, and having a central hole in which each of a plurality of reed switches is housed, and a plurality of peripheral holes or grooves through which conductive wires for each reed switch are inserted. Further, a protection tube in which a plurality of second type insulating solids having a plurality of peripheral holes or grooves through which the conductor wire for the reed switch is inserted is arranged in series and in contact with each other is housed in the pressure-resistant tube. Characteristic control rod position detection device.