JP2023158253A - stroke sensor - Google Patents

Abstract

To provide a stroke sensor with a simplified structure and reduced cost.SOLUTION: A stroke sensor includes: a spring 40 that returns a detection shaft 10 to the home position O after it has moved from the home position O; a magnet 50 for changing the magnetic field as the detection shaft 10 moves; a magnetic detection element 60 that detects an amount of movement S of the detection shaft 10 from changes in the magnetic field accompanying the movement of the detection shaft 10: a third housing 70 as a case having a space 74 that accommodates a substrate 75 on which the magnetic detection element 60 is arranged; a first housing 20 housing the magnet 50; screws T that fix the substrate 75, third housing 70, and first housing 20: and a sealing member 80 filling the space 74.SELECTED DRAWING: Figure 1

Description

The present invention relates to a stroke sensor.

BACKGROUND ART Conventionally, this type of stroke sensor is known, for example, as disclosed in Patent Document 1. The stroke sensor described in Patent Document 1 is a stroke sensor that detects the amount of movement of a detection shaft that moves from an origin position following a detected object, and returns the detection shaft to the origin position after moving from the origin position. A spring for returning the sensor, a magnet for changing the magnetic field as the detection shaft moves, a magnetic detection element that detects the amount of movement of the detection shaft from changes in the magnetic field as the detection shaft moves, and a magnetic detection element are installed. The case is made of resin and has a space for accommodating a printed circuit board, and a housing that accommodates a magnet and a portion of the detection shaft inside. It is configured to be fixed with multiple screws. Furthermore, it is known to use a screw locking agent for the purpose of preventing the screws from loosening when screwing the case and the housing together (see, for example, Patent Document 2).

JP 2019-100779 Publication Japanese Patent Application Publication No. 2008-237143

By the way, when fixing the case and the housing with a plurality of screws as described above, it is assumed that the screw locking agent described in Patent Document 2 is used in order to improve the reliability of fixing the case and the housing. Since it is necessary to use a thread locking agent for each screw, the assembly work is complicated, and the cost for manufacturing the stroke sensor increases, resulting in an increase in cost.
Therefore, an object of the present invention is to provide a stroke sensor that can realize cost reduction in order to deal with the above-mentioned problems.

The present invention provides a stroke sensor that detects the amount of movement of a detection shaft that moves from an origin position following a detected object, including a spring that returns the detection shaft to the origin position after it has moved from the origin position; A magnet for changing a magnetic field as the detection shaft moves, a magnetic detection element for detecting the amount of movement of the detection shaft from a change in the magnetic field as the detection shaft moves, and the magnetic detection element are provided. a case having a space for accommodating a substrate, a housing for accommodating the magnet, a screw for fixing the substrate, the case, and the housing, and a sealing member filled in the space. Features.

Further, in the present invention, the detection shaft has a large-diameter portion and a small-diameter portion smaller in diameter than the large-diameter portion, and the magnet is formed in an annular shape, and the small-diameter portion penetrates through the magnet. It is characterized by comprising a section.

Further, the present invention is characterized in that the case is made of a resin material, and the housing is made of a non-magnetic metal material.

According to the present invention, it is possible to provide a stroke sensor that can achieve the intended purpose, simplify the structure, and realize cost reduction.

FIG. 2 is a sectional view of a stroke sensor according to the present embodiment. FIG. 3 is a sectional view of a detection shaft, a spring, and a magnet according to the same embodiment. FIG. 3 is an enlarged cross-sectional view of a main part of the detection shaft according to the same embodiment. FIG. 3 is a sectional view of the first and third housings according to the same embodiment. FIG. 5 is a plan view of the main parts of the stroke sensor when viewed from the direction of arrow A in FIG. 4; BB sectional view of FIG. 5. FIG. 3 is a sectional view of the second housing according to the same embodiment.

Embodiments of the present invention will be described below based on the accompanying drawings.

Please refer to FIG. The stroke sensor 1 according to the present embodiment is a stroke sensor that detects a movement amount S of a detection shaft 10 that moves from an origin position O following a detected object, and includes a detection shaft 10, a first housing 20, A second housing 30, a spring 40 for returning the detection shaft 10 to the origin position O after it has moved from the origin position O, a magnet 50 for changing the magnetic field as the detection shaft 10 moves, and the detection shaft 10 It includes a magnetic detection element 60 that detects the movement amount S of the detection shaft 10 from changes in the magnetic field accompanying the movement of the detection shaft 10, a third housing 70, and a sealing member 80.

Please also refer to FIGS. 2 and 3. The detection shaft 10 is a detection medium that is followed by the movement of the object to be detected. For example, the detection shaft 10 is connected to the object to be detected, an external force is transmitted thereto, and the detection shaft 10 reciprocates in the axial direction to follow the object. The detection shaft 10 is preferably made of a non-magnetic material having some degree of rigidity, such as austenitic stainless steel (Steel Use Stainless; SUS).

The detection shaft 10 has a large diameter part 11, a middle diameter part 12, and a small diameter part 13 that are cylindrical and have different diameters. In this embodiment, the small diameter part 13, the middle diameter part 12 are , and a large diameter portion 11. Further, in this case, the large diameter portion 11 includes a large diameter portion 11a having the largest diameter in the detection shaft 10, and a large diameter portion 11b having a slightly smaller diameter than the large diameter portion 11a. In FIG. 1, 17a and 17b are first and second washers attached to the detection shaft 10, and these first and second washers 17a and 17b are located on both ends of the spring 40. For example, as shown in FIG. 1, the first washer 17a is located on the left side of the spring 40, and the second washer 17b is located on the right side of the spring 40.

The large-diameter portion 11a is a disc-shaped portion with the largest diameter in the detection shaft 10, is disposed within the second housing 30, and supports the second washer 17b. The large diameter portion 11b protrudes outward from a shaft hole, which will be described later, of the second housing 30, and is connected to an object to be detected (not shown). Further, an airtight member 14 is attached to the large diameter portion 11b.

The middle diameter portion 12 is a substantially cylindrical portion having a smaller diameter than the large diameter portion 11 . The second washer 17b, the spring 40, the first washer 17a, and the retaining ring 15 are assembled in the diametric center 12 so that they are located farther away from the larger diameter portion 11. Further, a magnet receiving portion 12 a having a stepped shape and receiving the magnet 50 is provided in the diameter portion 12 at a position adjacent to the small diameter portion 13 .

The small diameter portion 13 is a substantially cylindrical portion having a smaller diameter than the large diameter portion 11 (the middle diameter portion 12), and is disposed within the first housing 20. A substantially circular end surface 13a is formed in the small diameter portion 13 on the side opposite to the middle diameter portion 12 side. Further, the curved outer circumferential surface 13b of the small diameter portion 13 is provided with a groove portion 13c into which an inner edge portion of the magnet holding member 16, which will be described later, is fitted.

The airtight member 14 can be an O-ring made of rubber, and is held by a groove provided in the large diameter portion 11b. The airtight member 14 is provided for the purpose of keeping the stroke sensor 1 airtight, and the groove is configured to satisfy the groove structure necessary for the airtight member 14 to perform the airtight function. .

The retaining ring 15 can be a radially attached retaining ring made of a non-magnetic material, and is held by a groove (not shown) provided in the radial middle portion 12b. The retaining ring 15 supports the first washer 17a. That is, in this example, the first washer 17a, the spring 40, and the second washer 17b are sandwiched between the retaining ring 15 and the large diameter portion 11.

The magnet holding member 16 can be an end-shaped retaining ring (a radial retaining ring) made of a non-magnetic material, and is configured to be able to hold the magnet 50. The inner edge 16a of the magnet holding member 16 is disposed (held) in a groove 13c provided in the outer peripheral surface 13b. In other words, this means that the magnet holding member 16 is disposed in the small diameter portion 13.

The first washer 17a can be, for example, an O-shaped washer made of a non-magnetic material, and its diameter is larger than the retaining ring 15 and smaller than the inner diameter of the cylindrical portion of the first housing 20, which will be described later. be done.

The second washer 17b can be, for example, an O-shaped washer made of a non-magnetic material, and its diameter is larger than the large-diameter portion 11a and larger than the inner diameter of a thin-walled cylindrical portion of the second housing 30, which will be described later. Comprised of small size. The first washer 17a and the second washer 17b are designed to withstand thrust load when the detection shaft 10 moves and comes into contact with another member. In this case, the first washer 17a and the second washer 17b are of the same size.

Please also refer to FIGS. 4 to 6. The first housing 20 includes a first washer support portion 21 for receiving the first washer 17a, a recess 22, a cavity 23, a threaded portion 24, and a female screw portion 25. .

The first housing 20 is made of a non-magnetic metal material such as aluminum or stainless steel, and includes a substantially cylindrical cylindrical portion 20a and a non-cylindrical portion 20b whose outer periphery is partially formed into a flat surface shape. has been done. Note that the first housing 20 corresponds to a housing described in the claims described below.

The first washer support part 21 is an annular surface provided inside the cylindrical part 20a, and supports the outer edge portion of the first washer 17a.

The recess 22 is provided inside the non-cylindrical portion 20b and is formed as a substantially cup-shaped recess that supports the small diameter portion 13 of the detection shaft 10. The recessed portion 22 includes a first corresponding portion 22a provided to correspond to (oppose) the end surface 13a of the small diameter portion 13, and a shaft support portion 22b configured to be able to support the small diameter portion 13 (outer peripheral surface 13b). has.

The first corresponding portion 22a functions as a receiving portion for receiving the end surface 13a (small diameter portion 13), and has a function of limiting the amount of movement S of the detection shaft 10. By limiting the amount of movement S of the detection shaft 10, the amount by which the spring 40 is crushed becomes smaller. According to this, the load on the spring 40 can be reduced and its life can be extended. Further, since the small diameter portion 13 is supported by the shaft support portion 22b, the sliding movement of the detection stroke S along the axial direction of the detection shaft 10 becomes favorable.

The cavity 23 is provided so as to be continuous with the recess 22 . Further, the cavity portion 23 provided in the first housing 20 here is configured as a portion that accommodates the small diameter portion 13, the magnet holding member 16, the magnet 50, and the like. The threaded portion 24 is provided on a flat surface 26 provided on a part of the outer circumference of the non-cylindrical portion 20b. This threaded portion 24 functions as a portion for fastening and fixing the third housing 70 and a substrate to be described later using screws T. That is, the screw T here is a fixing component for fixing the threaded part 24 (first housing 20), the third housing 70, and the board.

The female threaded portion 25 is provided on the inner peripheral surface of the cylindrical portion 20a and is used to connect the first housing 20 and the second housing 30.

Also refer to FIG. 7. The second housing 30 has a hole 31 as a cavity for accommodating the large diameter portion 11 of the detection shaft 10, a shaft hole 32, a second washer support 33, and a male screw portion 34. configured. The second housing 30 is preferably made of a non-magnetic material such as aluminum or stainless steel, and is formed into a substantially cylindrical shape.

The hole 31 is an annular groove provided inside the second housing 30, and its opening width is larger than the opening width of the shaft hole 32. The shaft hole 32 is provided so as to be continuous with the hole portion 31, and slidably supports the detection shaft 10 and takes it out to the outside. The second washer support portion 33 is an annular surface provided around the outside of the hole portion 31, and supports the outer edge portion of the second washer 17b.

The male threaded portion 34 is provided on the outer peripheral surface of the thin cylindrical portion 30a of the second housing 30 in a direction facing the shaft hole 32, and is used to connect the first housing 20 and the second housing 30. . During the connection, a reinforcing adhesive (eg, Sealock agent) or the like may be used to prevent the screws from loosening, if necessary.

Further, in FIG. 7, 35 is a second corresponding portion provided to correspond to (oppose) the large diameter portion 11, and this second corresponding portion 35 is a boundary portion between the hole portion 31 and the shaft hole 32. It is an annular surface provided on the The second corresponding portion 35 functions as a receiving portion for receiving the large diameter portion 11, and limits the amount of movement S of the detection shaft 10. By limiting the amount of movement S of the detection shaft 10, the amount by which the spring 40 is crushed becomes smaller. According to this, the load on the spring 40 can be reduced and its life can be extended.

As shown in FIGS. 1 and 2, the spring 40 is preferably made of a non-magnetic material such as stainless steel, and is constituted by a cylindrical coil spring made of SUS304WPB, for example.

The spring 40 is configured to pass through the radial middle portion 12 of the detection shaft 10 inside, and is in contact with the first washer 17a and the second washer 17b at both ends thereof. That is, the spring 40 is installed around the radial center 12 located between the first washer 17a and the second washer 17b.

When the spring 40 moves so that the detection shaft 10 at the origin position O is pushed in the direction of the first housing 20, the second washer 17b supported by the large diameter portion 11 pushes the spring 40 and The first washer 17a supported by the first washer support part 21 supports the spring 40, so that the spring 40 is crushed and the end face 13a (small diameter part 13) moves until it hits the first corresponding part 22a. It can be moved by an amount S. Then, when the force that pushes the detection shaft 10 is removed, the spring force accumulated in the spring 40 returns it to the original position O.

Further, when the spring 40 moves so that the detection shaft 10 at the origin position O is pulled in the direction of the second housing 30, the first washer 17a supported by the retaining ring 15 pushes the spring 40, and The second washer 17b supported by the second washer support part 33 supports the spring 40, so that the spring 40 is crushed and the large diameter part 11 moves by the amount S until it hits the second corresponding part 35. can only be moved. Then, when the force to pull the detection shaft 10 is removed, the spring force accumulated in the spring 40 returns it to the original position O.

The magnet 50 can be, for example, a ring-shaped rare earth magnet (for example, a magnet made of a material such as SmCo or NdFeB), and is located directly below the magnetic detection element 60 in FIG.

The magnet 50 is located between the magnet receiving part 12a and the magnet holding member 16 so as to surround the small diameter part 13, and has a through part 51 through which the small diameter part 13 passes and a second part located on the side of the magnet receiving part 12a. It includes one annular surface 52 and a second annular surface 53 located on the magnet holding member 16 side (see FIG. 3). Further, the outer shape of the magnet 50 here is larger than the outer shape of the radial portion 12 and the magnet holding member 16.

The magnet 50 housed in the first housing 20 provides a magnetic field to the magnetic detection element 60, and as the magnet 50 moves together with the detection shaft 10, the direction and strength of the magnetic field applied to the magnetic detection element 60 can be changed. As a result, the magnetic detection element 60 detects the amount of movement S. The magnet 50 may be a sintered magnet or a plastic magnet mixed with plastic and compressed or molded depending on the manufacturing method. While sintered magnets have stronger magnetic force, plastic magnets have characteristics such as better mass productivity and higher cracking resistance, so they may be selected as appropriate depending on usage conditions and design requirements.

The magnetic detection element 60 is for detecting changes in the position and amount of movement of the detected object based on the direction and strength of the magnetic field, and is composed of, for example, a Hall element. The magnetic detection element 60 converts changes in the magnetic field due to movement of a detected object into an electrical signal and outputs the electrical signal to the outside.

The third housing 70 is, for example, a resin case made of a resin material. As shown in FIGS. 4 to 6, the third housing 70 includes a contact portion 71 that contacts the flat surface 26 of the non-cylindrical portion 20b (first housing 20), and a portion that rises from the outer peripheral portion of the contact portion 71. A substantially frame-shaped peripheral wall portion 72 provided so as to cover the substrate, an open portion 73 provided to face the contact portion 71, and an area surrounded by the contact portion 71 and the peripheral wall portion 72, which will be described later. It has a space part 74 that accommodates.

The contact portion 71 is formed into a substantially flat plate shape and includes a substrate receiving portion 71a for receiving a peripheral portion of the substrate, and a first screw hole 71b through which the threaded portion T1 of the screw T can pass. The board receiving portion 71 a is provided at the boundary between the contact portion 71 and the peripheral wall portion 72 and at the edge of the contact portion 71 . For example, a plurality of first screw holes 71b are formed in the board receiving portion 71a. Specifically, the first screw holes 71b are provided at two diagonally located locations near the four corners of the board receiving portion 71a. Further, in this case, a substrate 75 is disposed in the space 74 along the axial direction of the detection shaft 10 .

A printed circuit board made of glass epoxy or the like can be used as the substrate 75, and the magnetic detection element 60 is mounted (arranged) on one surface P of the substrate 75 that is on the magnet 50 side (the substrate receiving part 71a side). . The substrate 75 is provided with second screw holes 75a through which the screw portions T1 can pass, respectively, at positions corresponding to the plurality of first screw holes 71b described above. Here, an example of attaching the substrate 75 and the third housing 70 to the threaded portion 24 will be described. Installation is performed using screws T. First, the third housing 70, the board 75, and the first housing 20 are positioned so that both the first screw hole 71b and the second screw hole 75a overlap the threaded part 24. Then, the threaded portion T1 is passed through (inserted) through the second threaded hole 75a and the first threaded hole 71b in this order, and the threaded portion T1 that has passed through the first threaded hole 71b is screwed into the threaded portion 24. At this point, the screw fixation of the board 75 and the third housing 70 to the threaded portion 24 is completed.

Furthermore, power is supplied to the magnetic detection element 60 provided on the substrate 75 and electrical signals are outputted to the outside using an electric cord 90 connected to the substrate 75, for example. Note that a direct connector, coupler, or the like may be used instead of the electric cord 90.

The sealing member 80 is made of, for example, epoxy resin. The sealing member 80 is injected (filled) into the space 74 after the above-mentioned screw fixation and is hardened, thereby airtightly sealing the magnetic detection element 60, the substrate 75, and the screw T. Note that in FIG. 6, illustration of the sealing member 80 is omitted. Moreover, in FIG. 5, 100 indicates a grommet. The grommet 100 is made of a known elastic material such as nitrile rubber, and is attached so as to fit into a convex fitting portion 72a provided on the peripheral wall portion 72. Grommet 100 is formed with an insertion hole (not shown) through which electrical cord 90 is passed. The grommet 100 has a concave portion corresponding to a fitting portion 72a provided in the peripheral wall portion 72, and is fitted into the peripheral wall portion 72 using these uneven shapes. The fitting mechanism between the grommet 100 and the peripheral wall 72 allows easy positioning of the grommet 100 with respect to the peripheral wall 72.

As described above, in this embodiment, the spring 40 that returns the detection shaft 10 to the origin position O after it has moved from the origin position O, the magnet 50 that changes the magnetic field as the detection shaft 10 moves, and the detection A third case as a case having a magnetic detection element 60 that detects the movement amount S of the detection shaft 10 from a change in the magnetic field accompanying the movement of the shaft 10, and a space 74 that accommodates a substrate 75 on which the magnetic detection element 60 is disposed. housing 70, the first housing 20 housing the magnet 50, the screw T fixing the substrate 75, the third housing 70, and the first housing 20, and the sealing member 80 filled in the space 74. It is equipped with the following.

Therefore, when fixing the third housing 70 and the first housing 20 (to the board 75) with screws, it is no longer necessary to perform the complicated work of using a screw locking agent as in the past. By filling the space 74 with the sealing member 80 after fixing the screws in order to keep T in an immobile state, the assembly work is facilitated and the fixation of the third housing 70 and the first housing 20 (with the substrate 75) is reliable. Therefore, it is possible to provide a stroke sensor that can realize cost reduction while improving performance.

The present invention is not limited to the above embodiments and drawings. It is possible to make changes (including deletion of constituent elements) as appropriate without changing the gist of the present invention.

For example, in the embodiment described above, the third housing 70 was formed of a resin material and the first housing 20 was formed of a non-magnetic metal material, but the third housing 70 and the first housing 20 Both may be formed of a resin material or a non-magnetic metal material, or the first housing 20 may be formed of a resin material and the third housing 70 may be formed of a non-magnetic metal material.

Further, the magnet 50 only needs to be disposed between the magnet holding member 16 and the magnet receiving part 12a, and if necessary, the distance between the magnet holding member 16 and the magnet receiving part 12a may be adjusted to the first annular surface. 52 and the second annular surface 53.

In addition, in the above description, in order to facilitate understanding of the present invention, description of known technical matters has been omitted as appropriate.

1 Stroke sensor 10 Detection shaft 11 Large diameter portion 12 Middle diameter portion 13 Small diameter portion 16 Magnet holding member 20 First housing (housing)
20a Cylindrical portion 20b Non-cylindrical portion 24 Screwing portion 26 Flat surface 30 Second housing 40 Spring 50 Magnet 51 Penetrating portion 60 Magnetic detection element 70 Third housing (case)
71 Contact part 72 Peripheral wall part 73 Open part 74 Space part 75 Substrate 80 Sealing member O Origin position S Travel amount T Screw

Claims (3)

In a stroke sensor that detects the amount of movement of a detection shaft that moves from its origin position following a detected object,
a spring that returns the detection shaft to the original position after being moved from the original position;
a magnet for changing the magnetic field as the detection shaft moves;
a magnetic detection element that detects the amount of movement of the detection shaft from a change in a magnetic field accompanying movement of the detection shaft;
a case having a space for accommodating a substrate on which the magnetic detection element is disposed;
a housing containing the magnet;
a screw for fixing the board, the case, and the housing;
A stroke sensor comprising: a sealing member that fills the space. The detection shaft has a large diameter portion and a small diameter portion smaller in diameter than the large diameter portion,
The stroke sensor according to claim 1, wherein the magnet is formed in an annular shape and includes a through portion through which the small diameter portion passes. 3. The stroke sensor according to claim 1, wherein the case is made of a resin material, and the housing is made of a non-magnetic metal material.

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