Stroke sensor

Abstract

To provide a stroke sensor which achieves cost reduction by simplifying its configuration.SOLUTION: A stroke sensor 1 for detecting a travel distance S of a detection shaft 10 which travels from an origin position O while following a detected object includes: a spring 40 for making the detection shaft 10 return to the origin position O after the travel from the origin position O; a magnet 50 for changing a magnetic field in accordance with the travel of the detection shaft 10; and a magnetic detection element 60 for detecting the travel distance S of the detection shaft 10 from the change of the magnetic field in accordance with the travel of the detection shaft 10. The detection shaft 10 includes a large diameter part 11, a middle diameter part 12, and a small diameter part 13. The magnet 50 is positioned between a magnet reception part 12a and a magnet holding member 16.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] Conventionally, as for this type of stroke sensor, for example, the one disclosed in Patent Document 1 is known. 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 the origin position following a detection object, and includes a spring that returns the detection shaft after moving from the origin position to the origin position, a magnet for changing 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 accompanying the movement of the detection shaft. The magnet was embedded in a recess formed by penetrating the end portion of the detection shaft, and the magnet was fixed by disposing an adhesive in the recess.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the case of the stroke sensor described in Patent Document 1, it is necessary to perform drilling on the detection shaft to provide the recess, and further, since the magnet embedded in the recess after the drilling is adhesively fixed with an adhesive, the cost for manufacturing the stroke sensor increases, resulting in a cost increase. Therefore, an object of the present invention is to provide a stroke sensor capable of achieving cost reduction in order to address the above-described problems.

Means for Solving the Problems

[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. The stroke sensor includes a spring that returns the detection shaft after moving from the origin position to the origin position, a magnet for changing 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 accompanying the movement of the detection shaft. The detection shaft has 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. , the magnet holding member is characterized in that a part thereof is disposed in a groove provided on the outer peripheral surface of the smaller-diameter portion. Further, 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, a spring that returns the detection shaft after moving from the origin position to the origin position, a magnet for changing a magnetic field as the detection shaft moves, and a magnetic detection element that detects the amount of movement of the detection shaft from a change in the magnetic field accompanying the movement of the detection shaft. The detection shaft has a larger-diameter portion, a middle-diameter portion having a smaller diameter than the larger-diameter portion, and a smaller-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 disposed in the smaller-diameter portion, and the magnet holding member is a retaining ring with an end.

[0006] Further, the present invention is characterized in that the magnet is formed in an annular shape and includes a through-hole through which the small-diameter portion passes.

[0007] Further, the present invention is characterized in that the magnet includes a first annular surface located on the magnet receiving portion side and a second annular surface located on the magnet holding member side.

[0008] Further, the present invention is characterized in that the outer shape of the magnet is larger than the outer shapes of the middle-diameter portion and the magnet holding member.

[0011] Further, the present invention is characterized in that the distance between the magnet holding member and the magnet receiving portion is larger than the distance between the first annular surface and the second annular surface.

Advantages of the Invention

[0012] According to the present invention, it is possible to provide a stroke sensor that can achieve a desired purpose, simplify the structure, and realize cost reduction.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Mode for Carrying Out the Invention

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

[0015] Referring to FIG. 1, the stroke sensor 1 according to the present embodiment is a stroke sensor that detects the movement amount S of a detection shaft 10 that moves from the origin position O following a detected object. The stroke sensor 1 includes a detection shaft 10, a first housing 20, a second housing 30, a spring 40 that returns the detection shaft 10 after moving from the origin position O to the origin position O, a magnet 50 for changing a magnetic field as the detection shaft 10 moves, a magnetic detection element 60 that detects the movement amount S of the detection shaft 10 from the change in the magnetic field accompanying the movement of the detection shaft 10, a third housing 70, and a sealing member 80.

[0016] Referring to FIGS. 2 and 3 together, the detection shaft 10 is a detection medium that is followed by the movement of the detected object. For example, it is connected to the detected object and an external force is transmitted, and it reciprocates in the axial direction to follow. The detection shaft 10 is preferably made of a non-magnetic material having a certain degree of rigidity, for example, austenitic stainless steel (Steel Use Stainless; SUS).

[0017] The detection shaft 10 has a large-diameter portion 11, a medium-diameter portion 12, and a small-diameter portion 13 with a cylindrical shape and different diameters. In this embodiment, it is composed of the small-diameter portion 13, the medium-diameter portion 12, and the large-diameter portion 11 in this order from the direction of the first housing 20. Also, in this case, the large-diameter portion 11 consists of a large-diameter portion 11a with the largest diameter in the detection shaft 10 and a large-diameter portion 11b with a slightly smaller diameter than the large-diameter portion 11a. In FIG. 1, 17a and 17b are the 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.

[0018] The large-diameter portion 11a is a disk-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 (to be described later) of the second housing 30 and is connected to a detected object (not shown). Also, an airtight member 14 is attached to the large-diameter portion 11b.

[0019] The medium-diameter portion 12 is a substantially cylindrical portion with 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 to the medium-diameter portion 12 so as to be positioned as the distance from the large-diameter portion 11 increases. Also, a magnet receiving portion 12a having a stepped shape for receiving the magnet 50 is provided at a position adjacent to the small-diameter portion 13 on the medium-diameter portion 12.

[0020] The small-diameter portion 13 is a substantially cylindrical portion with a smaller diameter than the large-diameter portion 11 (medium-diameter portion 12) and is disposed within the first housing 20. A substantially circular end face 13a is formed on the small-diameter portion 13 on the side opposite to the medium-diameter portion 12 side. Also, a groove portion 13c into which an inner edge portion (to be described later) of the magnet holding member 16 fits is provided on the curved outer peripheral surface 13b of the small-diameter portion 13.

[0021] The airtight member 14 can be an O-ring formed 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 maintaining the airtightness of the stroke sensor 1, and the groove is configured to satisfy the groove structure necessary for the airtight member 14 to exhibit its airtight function.

[0022] The retaining ring 15 can be a radially mounted retaining ring made of a non-magnetic material and is held by a groove (not shown) provided in the middle-diameter 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.

[0023] The magnet holding member 16 can be an end-shaped retaining ring (radially mounted retaining ring) made of a non-magnetic material and is configured to be able to hold the magnet 50. A part of the inner edge portion 16a of the magnet holding member 16 is disposed (held) in a groove portion 13c provided on the outer peripheral surface 13b. That is, this means that the magnet holding member 16 is disposed in the small-diameter portion 13.

[0024] 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 a cylindrical portion (to be described later) of the first housing 20.

[0025] The second washer 17b can be, for example, an O-shaped washer made of a non-magnetic material, and its diameter is larger than that of the large-diameter portion 11a and smaller than the inner diameter of a thin-walled cylindrical portion (to be described later) of the second housing 30. The first washer 17a and the second washer 17b are designed to withstand the thrust load when they contact another member due to the movement of the detection shaft 10. In this case, the first washer 17a and the second washer 17b are of the same size.

[0026] Refer to FIG. 4 together. The first housing 20 is configured to include a first washer support portion 21 for receiving the first washer 17a, a recess 22, a mounting portion 23, and a female screw portion 24.

[0027] 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 cylindrical portion 20a and a non-cylindrical portion 20b in which a part of the outer peripheral portion has a flat surface shape.

[0028] The first washer support portion 21 is an annular surface provided inside the cylindrical portion 20a, and supports the outer edge portion of the first washer 17a.

[0029] The recess 22 is provided inside the non-cylindrical portion 20b, and is formed as a substantially cup-shaped recess for supporting the reduced-diameter portion 13 of the detection shaft 10. The recess 22 has a first corresponding portion 22a provided so as to face the end surface 13a of the reduced-diameter portion 13, and a shaft support portion 22b configured to support the reduced-diameter portion 13 (outer peripheral surface 13b).

[0030] The first corresponding portion 22a functions as a receiving portion for receiving the end surface 13a (reduced-diameter portion 13), and has a function of restricting the movement amount S of the detection shaft 10. By restricting the movement amount S of the detection shaft 10, the amount by which the spring 40 is crushed becomes smaller. According to this, the burden on the spring 40 can be reduced, and the service life can be extended. Further, since the reduced-diameter portion 13 is supported by the shaft support portion 22b, the sliding along the axial direction of the detection shaft 10 for the detection stroke S is good.

[0031] The mounting portion 23 is the flat surface provided on a part of the outer peripheral portion of the non-cylindrical portion 20b. This mounting portion 23 functions as a portion for attaching the third housing 70 using appropriate fixing means.

[0032] The female screw portion 24 is provided on the inner peripheral surface of the cylindrical portion 20a, and is used for connecting the first housing 20 and the second housing 30.

[0033] Refer to FIG. 5 together. The second housing 30 is configured to have 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 portion 33, and a male screw portion 34.

[0034] 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.

[0035] The hole 31 is an annular groove portion provided inside the second housing 30, and its opening width is larger than the opening width of the shaft hole 32.

[0036] The shaft hole 32 is provided so as to be continuous with the hole 31, slidably supports the detection shaft 10, and takes it out to the outside.

[0037] The second washer support portion 33 is an annular surface provided around the outer periphery of the hole 31 and supports the outer edge portion of the second washer 17b.

[0038] The male screw portion 34 is provided on the outer peripheral surface of the thin-walled cylindrical portion 30a of the second housing 30 in a direction opposite to the shaft hole 32 and is used to connect the first housing 20 and the second housing 30. In the connection, anti-loosening of the screw may be performed with a reinforcing adhesive (for example, a sealant) as necessary.

[0039] Also, in FIG. 5, 35 is a second corresponding portion provided so as to correspond (oppose) to the large-diameter portion 11. This second corresponding portion 35 is an annular surface provided at the boundary portion between the hole 31 and the shaft hole 32. The second corresponding portion 35 functions as a receiving portion for receiving 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 crushed becomes smaller. According to this, the burden on the spring 40 can be reduced and its service life can be extended.

[0040] The spring 40 is preferably made of a non-magnetic material such as stainless steel as shown in FIGS. 1 and 2, and is composed of, for example, a cylindrical coil spring made of SUS304WPB.

[0041] The spring 40 is configured to pass through the middle 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 thereof. That is, the spring 40 is mounted around the middle diameter portion 12 located between the first washer 17a and the second washer 17b.

[0042] When the detection shaft 10 at the origin position O moves so as to be pushed into the direction of the first housing 20, the second washer 17b supported by the large diameter portion 11 presses 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 by the amount of movement 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 disappears, the spring 40 is returned to the origin position O by the spring force accumulated in the spring 40.

[0043] Also, when the detection shaft 10 at the origin position O moves so as to be pulled into the direction of 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 amount of movement 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 40 is returned to the origin position O by the spring force accumulated in the spring 40.

[0044] The magnet 50 can be, for example, a rare earth magnet formed in an annular shape (ring shape) (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. 1.

[0045] The magnet 50 is positioned between the magnet receiving portion 12a and the magnet holding member 16 so as to surround the reduced-diameter portion 13, and includes a through portion 51 through which the reduced-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). Also, the outer shape of the magnet 50 here is larger than the outer shapes of the middle-diameter portion 12 and the magnet holding member 16.

[0046] And the magnet 50 provides a magnetic field to the magnetic detection element 60. By moving the magnet 50 together with the detection shaft 10, the direction and strength of the magnetic field applied to the magnetic detection element 60 are changed, and as a result, the magnetic detection element 60 detects it as the movement amount S. Note that the magnet 50 may be any of a sintered magnet, a plastic magnet compressed or molded by mixing with plastic, etc. depending on the manufacturing method. While the sintered magnet has a stronger magnetic force, the plastic magnet has characteristics such as high mass productivity and crack resistance, so it may be appropriately selected according to the usage conditions and design requirements.

[0047] The magnetic detection element 60 is for detecting changes in the position and movement amount 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 the change in the magnetic field accompanying the movement of the object to be detected into an electrical signal and outputs it to the outside.

[0048] The third housing 70 is formed of a resin material as shown in FIGS. 1 and 4, and is fixed to the attachment portion 23 of the first housing 20 using appropriate fixing means. The third housing 70 includes a storage portion 71 formed in a substantially concave cross-sectional shape. Inside the storage portion 71, a substrate 71a is disposed so as to be substantially parallel to the axial direction of the detection shaft 10.

[0049] The substrate 71a can be a printed circuit board made of glass epoxy or the like, and the magnetic detection element 60 is mounted (disposed) on one surface of the substrate 71a on the magnet 50 side. Power supply to the magnetic detection element 60 provided on the substrate 71a and output of an electrical signal to the outside are performed by an electrical cord (not shown) connected to the substrate 71a. Note that power supply to the magnetic detection element 60 and output of an electrical signal to the outside may be performed using a direct connector, a coupler, or the like instead of the electrical cord.

[0050] The sealing member 80 is made of, for example, an epoxy resin or the like. The sealing member 80 is injected into the storage portion 71 and cured to hermetically seal the magnetic detection element 60 and the substrate 71a.

[0051] As described above, in the present embodiment, the spring 40 that returns the detection shaft 10 after moving from the origin position O to the origin position O, the magnet 50 for changing the magnetic field as the detection shaft 10 moves, and the magnetic detection for detecting the movement amount S of the detection shaft 10 from the change in the magnetic field accompanying the movement of the detection shaft 10 are provided. 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 a magnet receiving portion 12a provided in the medium-diameter portion 12 and a magnet holding member 16 disposed in the small-diameter portion 13.

[0052] Therefore, it is not necessary to perform complicated operations such as drilling holes in the detection shaft as in the prior art or adhesively fixing a magnet embedded in the recess with an adhesive after the hole drilling. The small-diameter portion 13 is passed through the through-hole 51 of the magnet 50, and the magnet 50 can be disposed between the magnet receiving portion 12a and the magnet holding member 16 by a simple operation of fitting the magnet holding member 16 to the outer peripheral surface 13b. Thus, it is possible to provide a stroke sensor that can reduce the cost for manufacturing the stroke sensor and achieve cost reduction.

[0053] Also, in the present embodiment, the magnet holding member 16 can hold the magnet 50 with a simple configuration by disposing an inner edge portion 16a, which is a part of the magnet holding member 16, in a groove portion 13c provided on the outer peripheral surface 13b of the small-diameter portion 13.

[0054] The present invention is not limited by the above-described embodiments and drawings. Within the scope of not changing the gist of the present invention, modifications (including deletion of components) can be appropriately made.

[0055] For example, in the above-described embodiment, both the first housing 20 and the second housing 30 were 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.

[0056] Also, the magnet 50 only needs to be disposed between the magnet holding member 16 and the magnet receiving portion 12a. If necessary, the distance between the magnet holding member 16 and the magnet receiving portion 12a may be made larger than the distance between the first annular surface 52 and the second annular surface 53.

[0057] In the above description, for the sake of easy understanding of the present invention, the description of known technical matters has been appropriately omitted.

Description of Reference Numerals

[0058] 1 Stroke sensor 10 Detection shaft 11a, 11b Large-diameter portions 12 Medium-diameter portion 12a Magnet receiving portion 13 Small-diameter portion 13a End face 13b Outer peripheral 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 Axial support portion 30 Second housing 31 Hole portion 35 Second corresponding portion receiving portion 40 Spring 50 Magnet 51 Through-hole 52 First annular surface 53 Second annular surface 60 Magnetic detection element 70 Third housing 71 Storage part 71a Substrate 80 Sealing member O Origin position S Movement amount

Claims

1. In a stroke sensor that detects the amount of movement of a detection shaft that moves from an origin position following a detected object, a spring that returns the detection shaft after moving from the origin position to the origin position; a magnet for changing a 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 the magnetic field accompanying the movement of the detection shaft, and the detection shaft has a large-diameter portion, a medium-diameter portion smaller in diameter than the large-diameter portion, and a small-diameter portion smaller in diameter than the medium-diameter portion, the magnet is located between a magnet receiving portion provided in the medium-diameter portion and a magnet holding member disposed in the small-diameter portion, the magnet holding member is characterized in that a part thereof is disposed in a groove provided on the outer peripheral surface of the small-diameter portion.

2. In a stroke sensor that detects the amount of movement of a detection shaft that moves from an origin position following a detected object, a spring that returns the detection shaft after moving from the origin position to the origin position; a magnet for changing a 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 the magnetic field accompanying the movement of the detection shaft, and the detection shaft has a large-diameter portion, a medium-diameter portion smaller in diameter than the large-diameter portion, and a small-diameter portion smaller in diameter than the medium-diameter portion, the magnet is located between a magnet receiving portion provided in the medium-diameter portion and a magnet holding member disposed in the small-diameter portion, the magnet holding member is a retaining ring with an end, and is characterized by a stroke sensor.

3. The stroke sensor according to claim 1 or claim 2, wherein the magnet is formed in an annular shape and includes a through portion through which the small-diameter portion passes.

4. The stroke sensor according to claim 3, wherein the magnet includes 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 any one of claims 1 to 4, wherein the outer shape of the magnet is larger than the outer shapes of the medium-diameter portion and the magnet holding member.

6. The stroke sensor according to claim 4, wherein the distance between the magnet holding member and the magnet receiving portion is larger than the distance between the first annular surface and the second annular surface.

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