JP7711528B2 - Stroke Sensor - Google Patents

Description

The present invention relates to a stroke sensor.

Conventionally, stroke sensors of this type are known, such as that 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 an object to be detected, and includes a spring that returns the detection shaft to the origin position after it has moved from the origin position, a magnet that changes the magnetic field as the detection shaft moves, and a magnetic detection element that detects the amount of movement of the detection shaft from the change in the magnetic field as the detection shaft moves, and is configured such that the magnet is embedded in a recess formed by hollowing out the end of the detection shaft, and the magnet is fixed by disposing an adhesive in the recess.

JP 2020-139838 A

However, in the case of the stroke sensor described in Patent Document 1, it is necessary to drill a hole in the detection shaft to provide the recess, and further, after the hole drilling, the magnet to be embedded in the recess is adhesively fixed in place, which increases the expense of manufacturing the stroke sensor and results in increased costs.
SUMMARY OF THE PRESENT DISCLOSURE In order to address the above-mentioned problems, an object of the present invention is to provide a stroke sensor that can achieve low costs.

The present invention provides a stroke sensor that detects the amount of movement of a detection shaft that moves from an origin position in response to a detected object, the stroke sensor comprising: a spring that returns the detection shaft to the origin position after it has moved from the origin position; a magnet that changes a magnetic field as the detection shaft moves; and a magnetic detection element that detects the amount of movement of the detection shaft from the change in the magnetic field as the detection shaft moves, the detection shaft having a large diameter portion, a middle diameter portion that is smaller in diameter than the large diameter portion, and a small diameter portion that is smaller in diameter than the middle diameter portion, the magnet is located between a magnet receiving portion provided in the middle diameter portion and a magnet holding member disposed in the small diameter portion, and a part of the magnet holding member is disposed in a groove provided on the outer circumferential surface of the small diameter portion. The present invention also provides a stroke sensor that detects the amount of movement of a detection shaft that moves from an origin position in response to a detected object, the stroke sensor comprising: a spring that returns the detection shaft to the origin position after it has moved from the origin position; a magnet that changes a magnetic field as the detection shaft moves; and a magnetic detection element that detects the amount of movement of the detection shaft from the change in the magnetic field as the detection shaft moves, the detection shaft having a large diameter portion, a middle diameter portion that is smaller in diameter than the large diameter portion, and a small diameter portion that is smaller in diameter than the middle diameter portion, the magnet being positioned between a magnet receiving portion provided in the middle diameter portion and a magnet holding member disposed on the small diameter portion, and the magnet holding member being a snap ring with two ends.

The present invention is also characterized in that the magnet is formed in an annular shape and has a through-hole through which the small diameter portion passes.

The present invention is also characterized in that the magnet has a first annular surface located on the magnet receiving portion side and a second annular surface located on the magnet holding member side.

The present invention is also characterized in that the outer shape of the magnet is larger than the outer shape of the central diameter portion and the magnet holding member.

The present invention is also characterized in that the distance between the magnet holding member and the magnet receiving portion is greater than the distance between the first annular surface and the second annular surface.

The present invention provides a stroke sensor that can achieve the intended purpose, has a simplified structure, and is low-cost.

FIG. 2 is a cross-sectional view of the stroke sensor according to the embodiment. FIG. 4 is a cross-sectional view of a detection shaft, a spring, and a magnet according to the embodiment. FIG. 4 is an enlarged cross-sectional view of a main portion of the detection shaft according to the embodiment. FIG. 4 is a cross-sectional view of first and third housings according to the embodiment. FIG. 4 is a cross-sectional view of a second housing according to the embodiment.

The following describes an embodiment of the present invention with reference to the attached drawings.

Refer to FIG. 1. The stroke sensor 1 according to this embodiment is a stroke sensor that detects the amount of movement S of the detection shaft 10 that moves from the origin position O in response to the object to be detected, and includes the detection shaft 10, a first housing 20, a second housing 30, a spring 40 that returns the detection shaft 10 to the origin position O after it has moved from the origin position O, a magnet 50 that changes the magnetic field as the detection shaft 10 moves, a magnetic detection element 60 that detects the amount of movement S of the detection shaft 10 from the change in the magnetic field as the detection shaft 10 moves, a third housing 70, and a sealing member 80.

See also Figures 2 and 3. The detection shaft 10 is a detection medium that is moved by the movement of the object to be detected, and is connected to the object to which an external force is transmitted, and moves back and forth in the axial direction to move forward and backward to move forward and backward to move forward and backward to move forward and backward to move forward and backward. The detection shaft 10 is preferably made of a non-magnetic material with a certain degree of rigidity, such as austenitic stainless steel (Steel Use Stainless; SUS).

The detection shaft 10 has a cylindrical large diameter section 11, a medium diameter section 12, and a small diameter section 13, which are different in diameter. In this embodiment, the small diameter section 13, the medium diameter section 12, and the large diameter section 11 are arranged in sequence from the direction of the first housing 20. In this case, the large diameter section 11 is composed of a large diameter section 11a, which has the largest diameter in the detection shaft 10, and a large diameter section 11b, which has a diameter slightly smaller than that of the large diameter section 11a. In addition, 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 the disk-shaped portion with the largest diameter in the detection shaft 10, and is disposed within the second housing 30 to support the second washer 17b. The large diameter portion 11b protrudes outward from a shaft hole in the second housing 30, which will be described later, and is connected to a detection object (not shown). In addition, an airtight member 14 is attached to the large diameter portion 11b.

The middle diameter portion 12 is a generally cylindrical portion with a smaller diameter than the large diameter portion 11. The middle diameter portion 12 is fitted with the second washer 17b, spring 40, first washer 17a, and retaining ring 15, which are positioned in order as they move away from the large diameter portion 11. In addition, the middle diameter portion 12 is provided with a stepped magnet receiving portion 12a adjacent to the small diameter portion 13, which receives the magnet 50.

The small diameter portion 13 is a generally cylindrical portion with a smaller diameter than the large diameter portion 11 (medium diameter portion 12), and is disposed within the first housing 20. The small diameter portion 13 has a generally circular end face 13a on the side opposite the medium diameter portion 12. The curved outer circumferential surface 13b of the small diameter portion 13 is provided with a groove portion 13c into which the inner edge portion of the magnet holding member 16, which will be described later, fits.

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

The retaining ring 15 may be a radially mounted retaining ring made of a non-magnetic material, and is held in place by a groove (not shown) provided in the middle diameter portion 12b. The retaining ring 15 supports a first washer 17a. In other words, 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 a snap ring (a radially attached snap 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 circumferential 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 that of the retaining ring 15 and smaller than the inner diameter of the cylindrical portion of the first housing 20, which will be described later.

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 smaller than the inner diameter of the thin cylindrical portion of the second housing 30, which will be described later. The first washer 17a and the second washer 17b are designed to withstand the 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 the same size.

Also refer to FIG. 4. The first housing 20 is configured to have a first washer support portion 21 that receives the first washer 17a, a recess 22, an attachment portion 23, and a female thread portion 24.

The first housing 20 is preferably made of a non-magnetic material such as aluminum or stainless steel, and is formed of a substantially cylindrical portion 20a and a non-cylindrical portion 20b in which part of the outer periphery is formed into a flat surface shape.

The first washer support portion 21 is an annular surface provided on the inside of the cylindrical portion 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 generally cup-shaped recess that supports the small diameter portion 13 of the detection shaft 10. The recess 22 has a first corresponding portion 22a that is provided to face (oppose) the end face 13a of the small diameter portion 13, and a shaft support portion 22b that is configured to be able to support the small diameter portion 13 (outer peripheral surface 13b).

The first corresponding portion 22a functions as a receiving portion that receives the end face 13a (small diameter portion 13) and has the 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 of compression of the spring 40 is reduced. This reduces the burden on the spring 40 and extends its life. In addition, the small diameter portion 13 is supported by the shaft support portion 22b, which improves the sliding of the detection stroke S along the axial direction of the detection shaft 10.

The mounting portion 23 is the flat surface provided on a portion of the outer periphery of the non-cylindrical portion 20b. This mounting portion 23 functions as a portion for mounting the third housing 70 using an appropriate fixing means.

The female thread portion 24 is provided on the inner surface of the cylindrical portion 20a and is used to connect the first housing 20 and the second housing 30.

See also FIG. 5. The second housing 30 is configured to have a hole portion 31 as a void that accommodates the large diameter portion 11 of the detection shaft 10, a shaft hole 32, a second washer support portion 33, and a male thread portion 34.

The second housing 30 is preferably made of a non-magnetic material such as aluminum or stainless steel, and is formed into a roughly cylindrical shape.

The hole 31 is an annular groove provided on the inside of 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 to communicate with the hole portion 31 and slidably supports the detection shaft 10 for external extension.

The second washer support portion 33 is an annular surface provided around the outer periphery 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, which faces the shaft hole 32, and is used to connect the first housing 20 and the second housing 30. When connecting the first housing 20 and the second housing 30, a reinforcing adhesive (e.g., a sealant) may be used to prevent the threads from loosening, if necessary.

In addition, in FIG. 5, 35 is a second corresponding portion provided to correspond (face) to the large diameter portion 11, and this second corresponding portion 35 is an annular surface provided at the boundary between the hole portion 31 and the shaft hole 32. The second corresponding portion 35 functions as a receiving portion that receives 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 that the spring 40 is crushed is reduced. This reduces the burden on the spring 40 and extends its life.

The spring 40 is preferably made of a non-magnetic material such as stainless steel as shown in Figures 1 and 2, and is configured as a cylindrical coil spring made of, for example, SUS304WPB.

The spring 40 is configured to pass through the center diameter portion 12 of the detection shaft 10 on the inside, and is in contact with the first washer 17a and the second washer 17b at both ends. In other words, the spring 40 is attached around the center diameter portion 12 located between the first washer 17a and the second washer 17b.

When the detection shaft 10, which is at the origin position O, moves in a manner such that it is pushed toward 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 portion 21 supports the spring 40, so that the spring 40 is crushed and can move a distance S until the end face 13a (small diameter portion 13) hits the first corresponding portion 25. Then, when the force pushing the detection shaft 10 is gone, the spring force accumulated in the spring 40 returns it to the origin position O.

When the detection shaft 10 at the origin position O moves so as to be pulled in toward the second housing 30, the first washer 17a supported by the retaining ring 15 presses the spring 40, and the second washer 17b supported by the second washer support portion 33 supports the spring 40, so that the spring 40 is crushed and can move by the movement amount S until the large diameter portion 11 hits the second corresponding portion 35. Then, when the force pulling the detection shaft 10 disappears, the spring force accumulated in the spring 40 returns it to the origin position O.

The magnet 50 can be, for example, a rare earth magnet (e.g., a magnet made of a material such as SmCo or NdFeB) formed in an annular (ring-shaped) shape, and is located directly below the magnetic detection element 60 in FIG. 1.

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

The magnet 50 provides a magnetic field to the magnetic detection element 60, and as the magnet 50 moves with the detection shaft 10, it changes the direction and strength of the magnetic field it provides to the magnetic detection element 60, which the magnetic detection element 60 detects as a movement amount S. The magnet 50 may be either a sintered magnet or a plastic magnet that is mixed with plastic and compressed or molded, depending on the manufacturing method. While sintered magnets have a stronger magnetic force, plastic magnets have characteristics such as ease of mass production and high resistance to cracking, so the magnet can be selected appropriately depending on the usage conditions and design requirements.

The magnetic detection element 60 detects changes in the position and amount of movement of the object to be detected 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 caused by the movement of the object to be detected into an electrical signal and outputs it to the outside.

The third housing 70 is made of a resin material as shown in Figs. 1 and 4, and is fixed to the mounting portion 23 of the first housing 20 using an appropriate fixing means. The third housing 70 has a storage portion 71 formed with a cross-sectional shape that is approximately concave. Inside the storage portion 71, a substrate 71a is disposed so as to be approximately parallel to the axial direction of the detection shaft 10.

The substrate 71a may be a printed circuit board made of glass epoxy or the like, and the magnetic detection element 60 is mounted (disposed) on one side of the substrate 71a that faces the magnet 50. The magnetic detection element 60 provided on the substrate 71a is supplied with power and an electrical signal is output to the outside via an electrical cord (not shown) connected to the substrate 71a. Note that a direct connector or coupler may be used instead of an electrical cord to supply power to the magnetic detection element 60 and output an electrical signal to the outside.

The sealing member 80 is made of, for example, epoxy resin. The sealing member 80 is injected into the storage section 71 and hardens to airtightly seal the magnetic detection element 60 and the substrate 71a.

As described above, this embodiment includes a spring 40 that returns the detection shaft 10 to the origin position O after it has moved from the origin position O, a magnet 50 that changes the magnetic field as the detection shaft 10 moves, and a magnetic detection element 60 that detects the amount of movement S of the detection shaft 10 from the change in the magnetic field as the detection shaft 10 moves. The detection shaft 10 has a large diameter portion 11, a medium diameter portion 12, and a small diameter portion 13, and the magnet 50 is located between the magnet receiving portion 12a provided in the medium diameter portion 12 and the magnet holding member 16 arranged in the small diameter portion 13.

Therefore, it is no longer necessary to perform the conventional complicated work of drilling holes in the detection shaft and then gluing and fixing the magnet embedded in the recess after the drilling process. Instead, the magnet 50 can be placed between the magnet receiving portion 12a and the magnet holding member 16 by simply passing the small diameter portion 13 through the through portion 51 of the magnet 50 and fitting the magnet holding member 16 to the outer circumferential surface 13b. This reduces the cost of manufacturing the stroke sensor, making it possible to provide a stroke sensor that can achieve low costs.

In addition, in this embodiment, the magnet holding member 16 has an inner edge 16a, which is a part of the magnet holding member 16, disposed in a groove 13c provided on the outer circumferential surface 13b of the small diameter portion 13, thereby enabling the magnet 50 to be held in a simple configuration.

The present invention is not limited to the above-described embodiments and drawings. Modifications (including the deletion of components) can be made as appropriate without departing from the spirit of the present invention.

For example, in the above embodiment, both the first housing 20 and the second housing 30 are made of a non-magnetic material, but at least one of the first housing 20 and the second housing 30 may be made of a resin material.

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

In the above explanation, explanations of well-known technical matters have been omitted as appropriate to facilitate understanding of the present invention.

1 stroke sensor 10 detection shaft 11a, 11b large diameter portion 12 medium diameter portion 12a magnet receiving portion 13 small diameter portion 13a end face 13b outer circumferential surface 13c groove portion 16 magnet holding member 16a inner edge portion 17a first washer 17b second washer 20 first housing 22 recess 22a first corresponding portion 22b shaft support portion 30 second housing 31 hole portion 35 second corresponding portion receiving portion 40 spring 50 magnet 51 through portion 52 first annular surface 53 second annular surface 60 magnetic detection element 70 third housing 71 storage portion 71a substrate 80 sealing member O origin position S movement amount

Claims (6)

In a stroke sensor that detects the amount of movement of a detection shaft that moves from an origin position to follow a detection object,
a spring that returns the detection shaft to the original position after the detection shaft has moved from the original position;
a magnet for changing a magnetic field in accordance with the movement of the detection shaft;
a magnetic detection element that detects the amount of movement of the detection shaft from a change in a magnetic field caused by the movement of the detection shaft,
the detection shaft has a large diameter portion, a middle diameter portion having a smaller diameter than the large diameter portion, and a small diameter portion having a smaller diameter than the middle diameter portion,
The magnet is located between a magnet receiving portion provided in the middle diameter portion and a magnet holding member provided in the small diameter portion ,
The stroke sensor is characterized in that a portion of the magnet holding member is disposed in a groove provided on an outer circumferential surface of the small diameter portion . In a stroke sensor that detects the amount of movement of a detection shaft that moves from an origin position to follow a detection object,
a spring that returns the detection shaft to the original position after the detection shaft has moved from the original position;
a magnet for changing a magnetic field in accordance with the movement of the detection shaft;
a magnetic detection element that detects the amount of movement of the detection shaft from a change in a magnetic field caused by the movement of the detection shaft,
the detection shaft has a large diameter portion, a middle diameter portion having a smaller diameter than the large diameter portion, and a small diameter portion having a smaller diameter than the middle diameter portion,
The magnet is located between a magnet receiving portion provided in the middle diameter portion and a magnet holding member provided in the small diameter portion,
The stroke sensor is characterized in that the magnet holding member is a snap ring having two ends . 3. The stroke sensor according to claim 1 , wherein the magnet is formed in an annular shape and has a through-portion through which the small diameter portion passes . 4. The stroke sensor according to claim 3 , wherein the magnet has a first annular surface located on the magnet receiving portion side and a second annular surface located on the magnet holding member side . 5. The stroke sensor according to claim 1 , wherein an outer shape of the magnet is larger than outer shapes of the central diameter portion and the magnet holding member . 5. The stroke sensor according to claim 4 , wherein a distance between the magnet holding member and the magnet receiving portion is greater than a distance between the first annular surface and the second annular surface .