Stroke Sensor

Abstract

To suppress a manufacturing cost.SOLUTION: There is provided a stroke sensor 100 including: a shaft 30 which moves in parallel to the direction of an axial line C1 of a cylindrical case 20; annular magnet 40 fixed to the outer periphery of the shaft 30; and a magnet sensor 14 for detecting a change in the magnetic field of the magnet 40. There is a first magnetic pole 41 in the outer peripheral part of the magnet 40, and there is a second magnet pole 42 with the reverse polarity to that of the first magnet 41 in the inner peripheral part of the magnet 40. The magnetic sensor 14 is arranged in a position which faces the outer peripheral surface 40a of the magnet 40.SELECTED DRAWING: Figure 5

Description

[Technical Field]

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

[0002] Conventionally, stroke sensors that magnetically detect the amount of movement of a shaft moving in the axial direction have been known. For example, the stroke sensor disclosed in Patent Document 1 detects the amount of movement of the shaft by detecting changes in the magnetic field generated by a magnet using a detection element. In this magnet, the north and south poles are aligned in the axial direction. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Publication 2020-139839 Summary of the Invention [Problem to be solved by the invention]

[0004] However, depending on the distance between the magnet and the detection element, there is a risk of false detection due to axial wobble caused by shaft rotation. In Patent Document 1, a D-shaped notch is provided in the shaft to prevent it from rotating. However, if a process to prevent rotation becomes necessary during the shaft manufacturing stage, this leads to an increase in manufacturing costs.

[0005] The purpose of this technology is to reduce manufacturing costs. [Means for solving the problem]

[0006] In order to achieve the above object, the stroke sensor of the present technology includes: a cylindrical case; Consisting of magnetic material,The device comprises a shaft that moves parallel to the axial direction of the case, an annular magnet fixed to the outer periphery of the shaft, and a detection member that detects changes in the magnetic field of the magnet, wherein the magnet has a first magnetic pole on its outer periphery and a second magnetic pole that is opposite in polarity to the first magnetic pole on its inner periphery, and the detection member is disposed in a position facing the outer periphery of the magnet. A shielding portion made of a magnetic material is provided on the outer side of the detection member in the radial direction of the shaft, and no magnetic material exists between the detection member and the magnet in the radial direction of the shaft. [Effects of the Invention]

[0007] According to this technology, it is possible to reduce manufacturing costs. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. [Figure 2] FIG. 2 is a vertical cross-sectional view of the stroke sensor. [Figure 3] FIG. 3 is a cross-sectional view taken along line AA in FIG. 2. [Figure 4] FIG. [Figure 5] FIG. 2 is a schematic diagram of a magnet viewed from a direction perpendicular to the axis. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present technology will be described with reference to the drawings.

[0010] FIG. 1 is a perspective view of a stroke sensor according to an embodiment of the present technology.

[0011] This stroke sensor 100 has a sensor cover 10 and a shaft 30. The shaft 30 moves back and forth in the Z direction (+Z direction, -Z direction) in response to the operation of the object to be detected. An example of the object to be detected is a shift pedal 15. The shift pedal 15 is a member that is operated to change the shift position of a motorcycle, for example. Note that the shift pedal 15 is not limited to motorcycles, and may be provided on three- or four-wheeled vehicles such as buggies. Furthermore, the object to be detected is not limited to the shift pedal 15. The sensor cover 10 includes a connector housing 11. An electric cord 16 extending from the connector housing 11 is electrically connected to a control unit (not shown) in the vehicle body.

[0012] Fig. 2 is a vertical cross-sectional view of the stroke sensor 100. Fig. 3 is a cross-sectional view taken along line AA in Fig. 2.

[0013] 2, the stroke sensor 100 has, as its main components, the sensor cover 10 and shaft 30 described above, as well as a case 20, a cap 33, a magnet 40, and a magnetic sensor 14. A cylindrical case 20 and a cap 33 are arranged inside the sensor cover 10. The case 20 is fixed to the sensor cover 10. The -Z side end of the case 20 and the cap 33 are fixed to each other by screwing or the like.

[0014] The axis C1, which is the axial center of the shaft 30, is parallel to the Z direction. The axis C1 coincides with the axis of the case 20. The shaft 30 is disposed inside the case 20 and the cap 33 and is held by the case 20 and the cap 33. The shaft 30 is movable parallel to the axis C1 direction (Z direction) relative to the case 20 and the cap 33. The shaft 30 is also rotatable around the axis C1 relative to the case 20 and the cap 33. The shaft 30 is made of, for example, a magnetic material.

[0015] 2, an E-ring 36 is attached to the shaft 30, and an E-ring 37 is attached to the -Z side of the E-ring 36. The E-rings 36 and 37 are engaged in grooves formed in the shaft 30. The positions of the E-ring 36 and E-ring 37 in the direction of the axis C1 relative to the shaft 30 are fixed.

[0016] A first spring 25 is disposed around the shaft 30 inside the case 20. A second spring 35 is disposed around the shaft 30 inside the cap 33. The first spring 25 is disposed on the outer periphery of the first portion 30A of the shaft 30, and the second spring 35 is disposed on the outer periphery of the second portion 30B of the shaft 30. The +Z side end of the first spring 25 abuts against the E-ring 36 via the washer 23, and the -Z side end of the first spring 25 abuts against the E-ring 37 via the washer 24. That is, the first spring 25 is located between the washer 23 and the washer 24 in the direction of the axis C1. The washers 23 and 24 are movable in the direction of the axis C1 relative to the shaft 30.

[0017] The second spring 35 is disposed between the E-ring 37 and the bottom surface 33a of the cap 33. A washer that is movable relative to the shaft 30 in the direction of the axis C1 is interposed between the E-ring 37 and the second spring 35.

[0018] 2 shows the state in which the shaft 30 is in the neutral position. When the shaft 30 is at the origin (neutral position), both the first spring 25 and the second spring 35 are slightly compressed. The maximum amount of movement of the shaft 30 in the +Z direction is restricted by the shoulder 31 of the shaft 30 abutting against the abutment surface 21 of the case 20. The maximum amount of movement of the shaft 30 in the -Z direction is restricted by the shoulder 32 of the shaft 30 abutting against the bottom surface 33a of the cap 33.

[0019] 2 and 3, an annular magnet 40 is fixed to the outer peripheral surface 30Ca of the third portion 30C of the shaft 30. The magnet 40 is fixed to the third portion 30C by adhesive. However, the magnet 40 may be fixed by other methods, such as press-fitting or engagement with a claw.

[0020] A connector 12, a shielding yoke 13 (shielding portion), and a magnetic sensor 14 (detection member) are arranged in the connector accommodating portion 11. The shielding yoke 13 and the magnetic sensor 14 are held by the sensor cover 10 via the connector 12.

[0021] The magnetic sensor 14 is disposed opposite the outer peripheral surface 40a (FIG. 3) of the magnet 40 and detects changes in the magnetic field of the magnet 40. The magnetic sensor 14 is formed, for example, by a Hall element, and converts changes in the magnetic field, such as the direction and strength of the magnetic field, into an electrical signal for output. The terminals of the magnetic sensor 14 are electrically connected to the electrical cord 16 (FIG. 1).

[0022] The shielding yoke 13 is made of a magnetic material and is disposed outside the magnetic sensor 14 in the radial direction of the shaft 30. Therefore, the magnetic sensor 14 is located between the outer peripheral surface 40a of the magnet 40 and the shielding yoke 13.

[0023] FIG. 4 is a perspective view of magnet 40. Magnet 40 has a first magnetic pole 41 on its outer periphery and a second magnetic pole 42 on its inner periphery. That is, the outer periphery of magnet 40 is first magnetic pole 41, and the inner periphery of magnet 40 is second magnetic pole 42. Second magnetic pole 42 has the opposite polarity to the first magnetic pole; for example, first magnetic pole 41 is a north pole and second magnetic pole 42 is a south pole. Inner periphery surface 40b of magnet 40 engages with outer periphery surface 30Ca of third portion 30C of shaft 30. Note that magnet 40 may be formed integrally with shaft 30.

[0024] 5 is a schematic diagram of the magnet 40 viewed from a direction perpendicular to the axis C1, showing the distribution of magnetic flux vectors generated by the magnet 40.

[0025] Because the outer periphery of the magnet 40 is magnetized as a north pole and the inner periphery of the magnet 40 is magnetized as a south pole, the magnetic flux vector V generated by the magnet 40 exits the first magnetic pole 41 and enters the second magnetic pole 42. In other words, magnetic field lines are formed that exit mainly from the outer periphery 40a of the magnet 40 and head mainly toward the inner periphery 40b. The magnetic flux vector V is the same when viewed from any direction perpendicular to the axis C1. In other words, the magnet 40 is magnetized so that, assuming that the position of the shaft 30 in the direction of the axis C1 is the same, the magnetic flux vector V generated by the magnet 40 is constant at all positions in the circumferential direction around the axis C1. The magnetic flux vector V exiting from the outer periphery 40a includes a magnetic flux vector V1 that is parallel to the radial direction of the shaft 30.

[0026] Here, the shielding yoke 13 functions to shield the external magnetic field and thereby suppress its influence on the magnetic sensor 14. In addition, the magnetic flux vector V that reaches the shielding yoke 13 passes through the inside of the shielding yoke 13 and returns to the radially inner side of the shaft 30 via both ends of the shielding yoke 13, thereby increasing the magnetic flux density that gathers at the magnetic sensor 14. For these reasons, the shielding yoke 13 contributes to improving the detection accuracy of the magnetic sensor 14.

[0027] When the magnet 40 moves in the direction of the axis C1, the direction and magnitude of the magnetic flux passing through the magnetic sensor 14 change. For example, when the shift pedal 15 is pushed in the R1 direction (FIG. 1), the magnet 40 moves in the -Z direction together with the shaft 30. When the shaft 30 moves in the -Z direction from the origin, the E-ring 36 pushes the washer 23 in the -Z direction (FIG. 2). Meanwhile, the position of the washer 24 is restricted by the cap 33 and does not change, so the first spring 25 is further compressed. At the same time, the second spring 35 is pushed in the -Z direction by the E-ring 37 and is further compressed.

[0028] When magnet 40 moves in the -Z direction, and the change in the magnetic field detected by magnetic sensor 14 indicates that shaft 30 has moved a certain amount in the -Z direction from the origin, a control unit (not shown) in the vehicle body controls the shifter to downshift one step from the current shift position. After that, when the driver releases his / her foot from shift pedal 15, the urging force from springs 25 and 35 returns shaft 30 to the origin.

[0029] On the other hand, when the shift pedal 15 is pushed up in the R2 direction (FIG. 1), the magnet 40 moves in the +Z direction together with the shaft 30. When the shaft 30 moves in the +Z direction from the origin, the E-ring 37 pushes the washer 24 in the +Z direction. Meanwhile, the position of the washer 23 is restricted by the case 20 and does not change, so the first spring 25 is further compressed. At the same time, the compression state of the second spring 35 is relaxed by the amount that the E-ring 37 has moved.

[0030] When magnet 40 moves in the +Z direction, and the change in the magnetic field detected by magnetic sensor 14 indicates that shaft 30 has moved a certain amount in the +Z direction from the origin, a control unit in the vehicle body controls the shifter to shift up one position from the current shift position. After that, when the driver releases his / her foot from shift pedal 15, shaft 30 returns to the origin due to the biasing force of first spring 25. Note that the correspondence between the operating direction of shift pedal 15 and shifting up / down may be reversed from that illustrated.

[0031] According to this embodiment, an annular magnet 40 is fixed to the outer periphery of the shaft 30. The magnet 40 is magnetized so that a first magnetic pole 41 is located on its outer periphery and a second magnetic pole 42 is located on its inner periphery. The magnetic sensor 14 is positioned facing the outer periphery 40a of the magnet 40. Fixing the magnet 40 to the outer periphery of the shaft 30 facilitates a design that reduces the distance between the magnet 40 and the magnetic sensor 14. If a configuration in which magnetic flux vectors enter and exit from the end face of the magnet in the axial direction of the shaft were adopted, as in Patent Document 1, the magnetic flux density would decrease significantly with increasing radial distance from the axis. Therefore, the magnetic sensor must be positioned as close to the magnet as possible. However, design constraints make it difficult to position the magnetic sensor close to the magnet. In contrast, in this embodiment, by bringing the magnet 40 and the magnetic sensor 14 closer to each other, it is easy to increase the magnetic flux density passing through the magnetic sensor 14.

[0032] Furthermore, because the magnet 40 has a north pole on its outer periphery and a south pole on its inner periphery, many magnetic flux vectors V radiate outward from the outer periphery 40a. This also makes it easy to increase the number of magnetic flux vectors passing through the magnetic sensor 14. Moreover, when the position of the shaft 30 in the direction of the axis C1 is the same, the magnetic flux vector V is substantially constant at all positions in the circumferential direction around the axis C1. Therefore, even if the shaft 30 rotates, the change in the magnetic field detected by the magnetic sensor 14 is small. Therefore, with regard to the magnetic field detected by the magnetic sensor 14, the change in the magnetic field caused by the rotation of the shaft 30 is extremely small compared to the change in the magnetic field caused by the movement of the magnet 40 in the direction of the axis C1.

[0033] In this way, many magnetic flux vectors pass through the magnetic sensor 14, and the magnetic flux vector V is substantially constant at all positions in the circumferential direction. Therefore, even if the shaft 30 rotates and causes rotational wobble, the effect on detection accuracy is small, and the risk of erroneous detection is low. Therefore, there is no need to restrict the rotation of the shaft 30, and the process of preventing rotation of the shaft 30 can be eliminated. This allows for reduced manufacturing costs.

[0034] In particular, the magnetic flux generated by magnet 40 includes magnetic flux (magnetic flux vector V1) in a direction parallel to the radial direction of shaft 30 at outer peripheral surface 40a of magnet 40, thereby increasing the magnetic flux density gathering at magnetic sensor 14. In particular, magnetic flux vector V (including magnetic flux vector V1) that reaches shielding yoke 13 returns to shaft 30 via shielding yoke 13, effectively increasing the magnetic flux density gathering at magnetic sensor 14. This makes it possible to improve detection accuracy.

[0035] Furthermore, since the shaft 30 is made of a magnetic material, the shaft 30 functions as a yoke for the magnet 40, increasing the magnetic flux density and improving detection accuracy. However, it is not essential that the shaft 30 be made of a magnetic material.

[0036] In addition, a shielding yoke 13 made of a magnetic material is provided outside the magnetic sensor 14 in the radial direction of the shaft 30. This suppresses the influence of external magnetism and increases the magnetic flux density concentrated in the magnetic sensor 14, thereby improving detection accuracy.

[0037] Furthermore, in the radial direction of the shaft 30, no magnetic material or magnetic member exists between the magnetic sensor 14 and the magnet 40. This increases the magnetic flux density concentrated at the magnetic sensor 14, thereby improving detection accuracy.

[0038] Furthermore, since the shaft 30 moves in response to the operation of the shift pedal 15, the stroke sensor 100 can be used to detect the shift operation.

[0039] The first magnetic pole 41 may be an S pole, and the second magnetic pole 42 may be an N pole.

[0040] The present technology has been described above in detail based on preferred embodiments thereof, but the present technology is not limited to these specific embodiments, and various forms within the scope of the gist of the present technology are also included in the present technology. [Explanation of symbols]

[0041] 14 magnetic sensor, 20 case, 30 shaft, 40 magnet, 41 first magnetic pole, 42 second magnetic pole, 100 stroke sensor

Claims

1. A cylindrical case and a shaft made of a magnetic material and moving parallel to the axial direction of the case; an annular magnet fixed to the outer periphery of the shaft; a detection member for detecting a change in the magnetic field of the magnet, a first magnetic pole on the outer periphery of the magnet and a second magnetic pole of opposite polarity to the first magnetic pole on the inner periphery of the magnet; the detection member is disposed at a position facing the outer circumferential surface of the magnet, a shielding portion made of a magnetic material is provided on the outer side of the detection member in the radial direction of the shaft, A stroke sensor in which no magnetic material exists between the detection member and the magnet in the radial direction of the shaft.

2. The stroke sensor according to claim 1 , wherein the shaft moves in response to operation of a shift pedal.

Images