Stroke Sensor

Abstract

To provide a stroke sensor reduced in cost by simplifying a structure.SOLUTION: A stroke sensor 1, which detects a movement amount of a detection shaft 10 moving from an origin position O by following a body to be detected and in which the detection shaft 10 is formed of a magnetic material, includes: a spring 40 that returns the detection shaft 10 which has moved from the origin position O to the origin position O; a magnet 51 that is arranged so as to be an immobile state and changes a magnetic field accompanying movement of a yoke portion 17 provided in the detection shaft 10(small diameter portion 13); and a magnetic detection element 52 that detects a movement amount S of the detection shaft 10 from the change in the magnetic field accompanying the movement of the yoke portion 17.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a stroke sensor. [Background technology]

[0002] A displacement sensor that detects the linear motion of a magnetic body is disclosed, for example, in Patent Document 1. The displacement sensor described in Patent Document 1 is composed of a number of divided coils wound around the outer periphery of a bobbin, and converts the amount of displacement of the movable body into an electrical quantity for differential detection. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 5-26602 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the configuration disclosed in Patent Document 1 has a problem in that the cost is high when applied to a stroke sensor that detects linear motion in one direction. SUMMARY OF THE INVENTION In order to address the above-mentioned problems, an object of the present invention is to provide a stroke sensor that can be simplified in structure and reduced in cost. [Means for solving the problem]

[0005] The present invention relates to a stroke sensor that detects the amount of movement of a detection shaft that moves from an origin position following a detected object and in which the detection shaft is made of a magnetic material, and that includes a spring that returns the detection shaft to the origin position after it has moved from the origin position. ,before The magnetic field is changed in accordance with the movement of the yoke portion provided on the detection shaft. and is arranged to be immobile.a magnet; and a magnetic detection element that detects the amount of movement of the detection shaft from a change in a magnetic field that accompanies movement of the yoke portion, the detection shaft having a large diameter portion and a small diameter portion that is smaller in diameter than the large diameter portion, the yoke portion being provided on the small diameter portion, and the yoke portion being configured by a recessed portion provided on an outer circumferential surface of the small diameter portion, The magnet and the magnetic detection element are arranged so as to overlap each other in a storage portion provided in a housing that supports the small diameter portion. It is characterized by:

[0008] In the invention, the magnetic detection element is disposed between the detection shaft and the magnet.

[0010] In the present invention, the spring is attached around the small diameter portion located between the large diameter portion and the yoke portion.

[0011] In the invention, the magnet and the magnetic detection element are arranged so as to overlap each other in the storage section with a portion of each being positioned in a through-hole provided in the substrate. [Effects of the Invention]

[0012] According to the present invention, it is possible to provide a stroke sensor that can achieve the intended purpose, has a simplified structure, and can achieve low costs. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 2 is a cross-sectional view of the stroke sensor according to the embodiment. [Figure 2] FIG. 3 is a cross-sectional view of the detection shaft according to the embodiment. [Figure 3] FIG. 3 is a cross-sectional view of a first housing according to the embodiment. [Figure 4] FIG. 4 is a cross-sectional view of a second housing according to the embodiment. [Figure 5] FIG. 10 is a cross-sectional view of a stroke sensor according to a modified example of the embodiment. [Figure 6] FIG. 10 is a diagram showing a part of the first housing, a magnet, a magnetic detection element, and a substrate according to another modification of the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

[0015] Referring to Figure 1, the stroke sensor 1 according to this embodiment detects the amount of movement S of the detection shaft 10, which moves from an origin position O in response to a detection object. The stroke sensor 1 includes the detection shaft 10 made of a magnetic material, 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 51 that changes the magnetic field in response to the movement of the detection shaft 10 (a recessed portion provided in the detection shaft 10, which will be described later), and a magnetic detection element 52 that detects the amount of movement S of the detection shaft 10 from the change in the magnetic field in response to the movement of the detection shaft 10 (the recessed portion).

[0016] See also Figure 2. The detection shaft 10 is a detection medium that follows the movement of the object to be detected, and is connected to the object to which an external force is transmitted, moving back and forth in the axial direction to follow the object. The detection shaft 10 is preferably made of a soft magnetic material with a certain degree of rigidity, such as ferritic stainless steel (SUS430).

[0017] The detection shaft 10 has a cylindrical large-diameter section 11, a medium-diameter section 12, and a small-diameter section 13, each having different diameters. In this embodiment, the small-diameter section 13, the large-diameter section 11, and the medium-diameter section 12 are arranged in this order from the direction of the first housing 20. An airtight member 14 is attached to the medium-diameter section 12 of the detection shaft 10. In FIG. 1, reference numerals 15a and 15b denote first and second washers attached to the detection shaft 10, and these first and second washers 15a and 15b are located on both ends of the spring 40. For example, as shown in FIG. 1, the first washer 15a is located on the right side of the spring 40, and the second washer 15b is located on the left side of the spring 40.

[0018] The large diameter portion 11 is a disk-shaped portion of the detection shaft 10 that has the largest diameter, and is disposed within the second housing 30 to support the second washer 15 b attached to the small diameter portion 13 .

[0019] The middle diameter portion 12 is a portion having a smaller diameter than the large diameter portion 11. The middle diameter portion 12 protrudes outward from a shaft hole (described later) of the second housing 30, and is connected to a detection object (not shown).

[0020] The small diameter portion 13 has a smaller diameter than the large diameter portion 11 (middle diameter portion 12). The small diameter portion 13, which has a smaller diameter than the large diameter portion 11, is fitted with a second washer 15b, a spring 40, and a first washer 15a, which are positioned in increasing order as the distance from the large diameter portion 11 increases. In FIG. 1 , reference numeral 16 denotes a retaining ring. This retaining ring 16 is a radially mounted retaining ring made of a non-magnetic material and is held in a groove (not shown) provided approximately in the middle of the small diameter portion 13. The retaining ring 16 supports the first washer 15a. In other words, in this example, the first washer 15a, the spring 40, and the second washer 15b are sandwiched between the retaining ring 16 and the large diameter portion 11.

[0021] The airtight member 14 can be an O-ring made of rubber, and is held in a groove provided in the central diameter portion 12. 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 to exhibit the airtight function.

[0022] The first washer 15a can be, for example, an O-shaped washer made of a non-magnetic material, and its diameter is larger than the inner diameter of the first housing 20 and the spring 40, but smaller than the inner diameter of the cylindrical portion of the first housing 20, which will be described later.

[0023] The second washer 15b can be, for example, an O-shaped washer made of a non-magnetic material, and its diameter is larger than the large diameter portion 11, the inner diameter of the second housing 30, and the spring 40, but smaller than the inner diameter of a cylindrical portion of the second housing 30, which will be described later. The first washer 15a and the second washer 15b are designed to withstand a thrust load when the detection shaft 10 moves and comes into contact with another member. In this case, the first washer 15a and the second washer 15b are the same size.

[0024] 1, a recessed portion 17 serving as a yoke portion is provided on the right side of small diameter portion 13. Recessed portion 17 is formed in a generally concave shape (a generally annular groove shape) and is provided on the outer peripheral surface of small diameter portion 13 in a portion directly below magnet 51 and magnetic detection element 52 in FIG. 1. In other words, FIG. 1 shows an example in which recessed portion 17 (i.e., the yoke portion formed by recessed portion 17) is provided around the entire outer peripheral surface of small diameter portion 13 in a portion directly below magnet 51 and magnetic detection element 52.

[0025] 3, the first housing 20 includes a first receiving portion 21 that receives the retaining ring 16, a shaft support portion 22, a first washer support portion 23, a storage portion 24, and a female thread portion 25.

[0026] The first housing 20 is preferably made of a non-magnetic material such as aluminum or stainless steel, and is formed by a substantially cylindrical portion 20a and a substantially flat portion 20b. Note that this first housing 20 corresponds to the housing in the claims described below.

[0027] The first receiving portion 21 is an annular surface provided on the inside of the cylindrical portion 20a, and is configured to be able to come into contact with the retaining ring 16, thereby limiting the movement amount S of the detection shaft 10. By limiting the movement amount S of the detection shaft 10, the amount by which the spring 40 is crushed is reduced. This reduces the burden on the spring 40 and extends its lifespan. The length from the origin position O to the first receiving portion 21 is configured to be shorter than the maximum deflection amount of the spring 40.

[0028] The shaft support portion 22 is provided inside the flat plate portion 20b and is formed as a groove that supports the small diameter portion 13 of the detection shaft 10. The small diameter portion 13 is supported by the shaft support portion 22, thereby improving the sliding of the detection shaft 10 along the axial direction of the detection stroke S.

[0029] The first washer support portion 23 is an annular surface provided on the inside of the cylindrical portion 20a, and supports the outer edge portion of the first washer 15a. The first washer support portion 23 is formed at a position one step higher from the position where the first receiving portion 21 is formed toward the spring 40.

[0030] The storage section 24 is provided outside the flat plate section 20b. More specifically, the storage section 24 is provided so as to stand upright from the shaft support section 22. The storage section 24 accommodates a magnet 51, a magnetic detection element 52, and a substrate 53 having a through-hole 53a through which a magnet end portion (described later) of the magnet 51 penetrates.

[0031] The female thread portion 25 is provided on the outer peripheral surface of the thin-walled cylindrical portion 26 of the cylindrical portion 20 a and is used to connect the first housing 20 and the second housing 30 .

[0032] Also see Figure 4. 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.

[0033] The second housing 30 is preferably made of a non-magnetic material such as aluminum or stainless steel, and is formed in a substantially cylindrical shape.

[0034] 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. In addition, a second receiving portion 35 consisting of an annular surface that receives the large-diameter portion 11 is formed in the hole 31 at the boundary with the shaft hole 32. The second receiving portion 35 receives the large-diameter portion 11 and limits the movement amount S of the detection shaft 10. By limiting the movement amount S of the detection shaft 10, the amount by which the spring 40 is compressed is reduced. This reduces the burden on the spring 40 and extends its lifespan. The length from the origin position O to the second receiving portion 35 is configured to be shorter than the maximum deflection amount of the spring 40.

[0035] The shaft hole 32 is provided so as to communicate with the hole portion 31, and slidably supports the detection shaft 10 so as to lead it out to the outside.

[0036] 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 15b.

[0037] The male thread portion 34 is provided on the inner peripheral surface of the thin-walled cylindrical portion 30a of the second housing 30, facing 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.

[0038] The spring 40 is preferably made of a non-magnetic material such as stainless steel, and is configured as a cylindrical coil spring made of, for example, SUS304WPB.

[0039] The spring 40 is configured so that the small diameter portion 13 of the detection shaft 10 passes through the inside thereof, and is in contact with the first washer 15a and the second washer 15b at both ends thereof. In other words, the spring 40 is attached around the small diameter portion 13 located between the recessed portion 17 (first washer 15a) and the large diameter portion 11 (second washer 15b).

[0040] When the detection shaft 10, which is at the origin position O, moves in a manner such that it is pressed toward the first housing 20, the second washer 15b supported by the large diameter portion 11 presses the spring 40, and the first washer 15a supported by the first washer support portion 23 supports the spring 40, thereby compressing the spring 40 and allowing the spring 40 to move by a distance S until the retaining ring 16 hits the first receiving portion 21 of the first housing 20. Then, when the force pressing the detection shaft 10 is released, the spring force accumulated in the spring 40 returns the detection shaft 10 to the origin position O.

[0041] Furthermore, when the detection shaft 10, which is at the origin position O, moves so as to be pulled toward the second housing 30, the first washer 15a supported by the retaining ring 16 presses the spring 40, and the second washer 15b supported by the second washer support portion 33 supports the spring 40, thereby compressing the spring 40 and allowing the spring 40 to move an amount S until the first washer 18a supported by the retaining ring 16 hits the second receiving portion 35 of the second housing 30. Then, when the force pulling the detection shaft 10 is released, the spring force accumulated in the spring 40 returns the detection shaft 10 to the origin position O.

[0042] 3 may be, for example, a rare earth magnet (such as a magnet made of SmCo or NdFeB) formed in a rectangular column shape, and provides a magnetic field to the magnetic detection element 52. The magnet 51 changes the magnetic field in accordance with the movement of the recess 17 provided in the small diameter portion 13 (detection shaft 10) made of a soft magnetic material.

[0043] Depending on the manufacturing method, magnet 51 may be either a sintered magnet or a plastic magnet that is mixed with plastic and compressed or molded. While sintered magnets have a stronger magnetic force, plastic magnets have properties such as ease of mass production and high crack resistance, so the appropriate magnet can be selected depending on the conditions of use and design requirements.

[0044] The magnetic detection element 52 detects changes in the position or amount of movement of the object to be detected based on the direction and strength of the magnetic field, and is configured, for example, by a Hall element. The magnetic detection element 52 is disposed between the detection shaft 10 and the magnet 51. For example, the magnetic detection element 52 is joined to the magnet 51 using an appropriate fixing means such as an adhesive. In other words, the magnet 51 and the magnetic detection element 52 are disposed immobile so as to overlap each other in the storage portion 24 provided in the first housing 20.

[0045] The magnetic detection element 52 detects the amount of movement S of the detection shaft 10 from changes in the magnetic field that accompany the movement of the recessed portion 17 made of a soft magnetic material. That is, as the detection shaft 10, which is a soft magnetic material, moves, the direction and strength of the magnetic field that the magnet 51 applies to the magnetic detection element 52 changes, and the magnetic detection element 52 detects the result as the amount of movement S. This allows the stroke sensor 1 to detect the movement of the detection shaft 10 in a simple manner with a simplified structure.

[0046] 1, a through-hole 53a is formed in the approximate center of the substrate 53. In this case, the magnet 51 and the magnetic detection element 52 are disposed so as to overlap each other in the storage section 24, with a portion of the magnet 51 (for example, the magnet end 51a of the magnet 51 located on the magnetic detection element 52 side) located inside the through-hole 53a. In this case, the magnetic detection element 52 is conductively connected to one surface P1 of the substrate 53 located on the detection shaft 10 side by two lead wires 54 on both sides thereof.

[0047] Furthermore, power is supplied to the magnetic detection element 52 on the substrate 53 and electrical signals are output to the outside via an electrical cord (not shown) connected to the substrate 53. Note that a direct connector, coupler, or the like may be used instead of an electrical cord to supply power to the magnetic detection element 52 on the substrate 53 and output electrical signals to the outside.

[0048] For example, epoxy resin is used for the sealing member 60. The sealing member 60 is injected into the housing portion 24 and hardens to airtightly seal the magnet 51, the magnetic detection element 52, and the substrate 53.

[0049] As described above, this embodiment includes 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 51 that is disposed so as to be immobile and that changes its magnetic field in accordance with the movement of the yoke portion 17 provided on the small diameter portion 13 (detection shaft 10); and the magnetic detection element 52 that detects the amount of movement S of the detection shaft 10 from the change in the magnetic field in accordance with the movement of the yoke portion 17. Therefore, it is possible to detect the amount of displacement of the movable body (detection shaft) with a simple configuration using a single magnet and a single magnetic detection element, rather than a complex configuration in which multiple coils are wound around the outer periphery of a bobbin as in the conventional case. Therefore, the present invention can provide a stroke sensor that can be simplified in structure and reduced in cost.

[0050] In addition, in this embodiment, a recess 17 is provided as a yoke portion on the outer peripheral surface of the small diameter portion 13, which has the advantage that the magnetic flux passing through the recess 17 is concentrated, thereby increasing the change in the magnetic field and improving detection accuracy.

[0051] The present invention is not limited to the above-described embodiments and drawings, and modifications (including the omission of components) can be made as appropriate within the scope of the present invention.

[0052] For example, in the above-described embodiment, the first housing 20 and the second housing 30 are both formed of a non-magnetic material, but at least one of the first housing 20 and the second housing 30 may be formed of a resin material.

[0053] In the above-described embodiment, the recess 17 provided in the small diameter portion 13 serves as a yoke portion. However, as a modification of this embodiment, a protrusion 18 functioning as a yoke portion may be provided in the small diameter portion 13 instead of the recess 17, as shown in Fig. 6. In this case, the small diameter portion 13 is composed of a first small diameter portion 13a that forms its main portion, and a second small diameter portion 13b that is provided at a position corresponding to the magnet 51 and the magnetic detection element 52, and the diameter of the second small diameter portion 13b is formed slightly smaller than the diameter of the first small diameter portion 13a. The second small diameter portion 13b corresponds to the small diameter portion in the claims described below.

[0054] The protrusion 18 is formed as a convex shape (annular convex portion) protruding outward from the second small diameter portion 13b, and is provided on the outer circumferential surface of the second small diameter portion 13b directly below the magnet 51 and the magnetic detection element 52. Note that FIG. 6 shows an example in which the protrusion 18 is provided on the entire outer circumferential surface of the second small diameter portion 13b directly below the magnet 51 and the magnetic detection element 52. By providing the protrusion 18 as a yoke portion on the outer circumferential surface of the second small diameter portion 13b in this manner, it is possible to achieve low costs, as in the above-described embodiment. Furthermore, the concentration of magnetic flux passing through the protrusion 18 has the advantage of increasing the change in the magnetic field and improving detection accuracy. The shape of the recess 17 is not limited to a concave shape, and any other shape, such as a V-shape or a U-shape, can be used. Similarly, the shape of the protrusion 18 is not limited to a convex shape, and any other shape, such as a hemispherical shape, can be used.

[0055] Furthermore, in the above-described embodiment, the magnet 51 and the magnetic detection element 52 are arranged so as to overlap in the storage section 24 with the magnet end 51a located inside the through-hole 53a, but as another modification of this embodiment, as shown in Fig. 7, the magnet 51 and the magnetic detection element 52 may be arranged so as to overlap in the storage section 24 with the magnetic detection element 52 located inside the through-hole 53a. In this case, the magnetic detection element 52 is electrically connected to the other surface P2 of the substrate 53 located opposite to the one surface P1 by two lead wires 54 on both sides of the magnetic detection element 52.

[0056] In the above description, in order to facilitate understanding of the present invention, descriptions of well-known technical matters have been omitted as appropriate. [Explanation of symbols]

[0057] 1 Stroke sensor 10 Detection shaft 11 Large diameter section 12 Central 13 Small diameter 13a First diameter small part 13b Second small diameter part (small diameter part) 14 Airtight materials 15a First washer 15b Second washer 16 Retaining ring 17 Recessed part (yoke part) 18 Protrusion (yoke part) 20 First Housing (Housing) 21 First Receptacle 22 Shaft support part 24 Storage section 30 Second Housing 31 Hole 35 Second Receptacle 40 Spring 51 Magnet 52 Magnetic detection element 53 Circuit Board 53a Through hole section 60 Sealing member O Origin position S Travel amount

Claims

1. 1. A stroke sensor that detects the amount of movement of a detection shaft that moves from an origin position following a detection object, and the detection shaft is made of a magnetic material, a spring that returns the detection shaft to the original position after it has moved from the original position; a magnet that changes its magnetic field in accordance with the movement of a yoke portion provided on the detection shaft and is disposed so as to be stationary; a magnetic detection element that detects the amount of movement of the detection shaft from a change in a magnetic field that accompanies the movement of the yoke portion, the detection shaft has a large diameter portion and a small diameter portion having a diameter smaller than that of the large diameter portion, The yoke portion is provided on the small diameter portion, the yoke portion is configured by a recessed portion provided on an outer peripheral surface of the small diameter portion, The stroke sensor is characterized in that the magnet and the magnetic detection element are arranged so as to overlap each other in a storage portion provided in a housing that supports the small diameter portion.

2. 2. The stroke sensor according to claim 1, wherein the magnetic detection element is disposed between the detection shaft and the magnet.

3. A stroke sensor as described in claim 1 or claim 2, characterized in that the spring is attached around the small diameter portion located between the large diameter portion and the yoke portion.

4. A stroke sensor as described in claim 1, characterized in that the magnet and the magnetic detection element are arranged so as to overlap in the storage section, with a part of the magnet or the magnetic detection element being positioned in a through hole section provided in the substrate.

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