Linear sensor

Abstract

To obtain a linear sensor that can easily detect the absolute position of a movable member. [Solution] This linear sensor comprises a movable member 1 that can move in a movable direction D1 and has a first detectable part 11 and a second detectable part 12 made of a magnetic material, a first magnetic sensor 2 provided opposite the first detectable part 11, a second magnetic sensor 3 provided opposite the second detectable part 12, and a position calculation unit 5. The first detectable part 11 has a plurality of first protrusions 111, and the second detectable part 12 has a plurality of second protrusions 121. The first magnetic sensor 2 outputs a first detection signal corresponding to the position of the plurality of first protrusions 111 relative to the first magnetic sensor 2 in the movable direction D1, and the second magnetic sensor 3 outputs a second detection signal corresponding to the position of the plurality of second protrusions 121 relative to the second magnetic sensor 3 in the movable direction D1. The position calculation unit 5 uses the first detection signal and the second detection signal to calculate the absolute position of the movable member 1 in the movable direction D1.

Description

Technical Field

[0001] This invention relates to a linear sensor.

Background Art

[0002] Conventionally, a linear sensor including a shaft member made of a magnetic material and moving axially, and a magnetic sensor provided facing the outer peripheral surface of the shaft member has been known. The shaft member has a plurality of convex portions arranged axially at preset intervals. The magnetic sensor detects the position of the shaft member in the axial direction by using the change in the magnetic flux density between the shaft member and the magnetic sensor (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the configuration of the linear sensor described in Patent Document 1, the magnetic flux density between the shaft member and the magnetic sensor changes periodically due to the axial movement of the shaft member. Therefore, there is a problem that the absolute position of the shaft member cannot be detected unless the period of the change in the magnetic flux density between the shaft member and the magnetic sensor is counted.

[0005] This invention has been made to solve the above-described problems, and an object thereof is to provide a linear sensor capable of easily detecting the absolute position of a movable member.

Means for Solving the Problems

[0006] The linear sensor according to this invention comprises a movable member having a first detectable part and a second detectable part made of a magnetic material, and being movable in a movable direction which is a preset direction; a first magnetic sensor provided opposite the first detectable part; a second magnetic sensor provided opposite the second detectable part; and a position calculation unit. The first detectable part has a plurality of first protrusions arranged in the movable direction at a first interval; the second detectable part has a plurality of second protrusions arranged in the movable direction at a second interval which is longer than the first interval; the first magnetic sensor outputs a first detection signal which is a signal corresponding to the position of the plurality of first protrusions relative to the first magnetic sensor in the movable direction; the second magnetic sensor outputs a second detection signal which is a signal corresponding to the position of the plurality of second protrusions relative to the second magnetic sensor in the movable direction; and the position calculation unit calculates the position of the movable member in the movable direction using the first detection signal and the second detection signal. In the linear sensor according to this invention, the shape of the movable member is formed in a cylindrical shape, each of the plurality of first protrusions is arranged over the entire area of ​​the first detected part in the circumferential direction of the movable member, and each of the plurality of second protrusions is arranged over the entire area of ​​the second detected part in the circumferential direction. In the linear sensor according to this invention, the movable member is made entirely of the same material. In the linear sensor according to this invention, when the length in the movable direction is set to a predetermined length, and the number of first protrusions included in the range of the measurement length of the plurality of first protrusions is n, the number of second protrusions included in the range of the measurement length of the plurality of second protrusions is n-1. [Effects of the Invention]

[0007] According to the linear sensor of this invention, the absolute position of a movable member can be easily detected. [Brief explanation of the drawing]

[0008] [Figure 1] This is a front view showing a linear sensor according to Embodiment 1. [Figure 2] Figure 1 is a block diagram showing the linear sensor. [Modes for carrying out the invention]

[0009] Embodiment 1. Figure 1 is a front view showing a linear sensor according to Embodiment 1. Figure 2 is a block diagram of the linear sensor in Figure 1. The linear sensor according to Embodiment 1 comprises a movable member 1, a first magnetic sensor 2, a second magnetic sensor 3, a magnetic sensor support 4, and a position calculation unit 5.

[0010] The movable member 1 is made of a magnetic material. The entire movable member 1 is made of the same material. The shape of the movable member 1 is formed as a long, elongated shape extending in one direction. Specifically, the shape of the movable member 1 is formed as a cylinder. Therefore, the movable member 1 is an axial member.

[0011] The movable member 1 is movable in a predetermined direction, which is the movable direction D1. The movable direction D1 coincides with the axial direction of the movable member 1. Therefore, the movable member 1 is movable in the axial direction.

[0012] The movable member 1 has a first detected part 11 and a second detected part 12. The first detected part 11 and the second detected part 12 are positioned offset from each other in the movable direction D1.

[0013] The first detected portion 11 has a plurality of first protrusions 111. The plurality of first protrusions 111 are arranged in the movable direction D1 at a predetermined interval B1. Each of the plurality of first protrusions 111 is formed over the entire area of ​​the first detected portion 11 in the circumferential direction D2 of the movable member 1. Each of the plurality of first protrusions 111 is formed by turning the movable member 1.

[0014] The second detection portion 12 has a plurality of second protrusions 121. The plurality of second protrusions 121 are arranged in the movable direction D1 at a predetermined interval B2. Each of the plurality of second protrusions 121 is formed over the entire area of ​​the second detection portion 12 in the circumferential direction D2 of the movable member 1. Each of the plurality of second protrusions 121 is formed by turning the movable member 1.

[0015] The length in the movable direction D1 is set to a preset length. The measurement length range A1 in the first detected unit 11 is the range in which the positions of multiple first protrusions 111 are detected by the first magnetic sensor 2. The measurement length range A2 in the second detected unit 12 is the range in which the positions of multiple second protrusions 121 are detected by the second magnetic sensor 3.

[0016] If the number of first protrusions 111 included in the measurement length range A1 of the multiple first protrusions 111 is n, then the number of second protrusions 121 included in the measurement length range A2 of the multiple second protrusions 121 is n-1.

[0017] Specifically, the measured length is 10.0 mm, the number of first protrusions 111 included in the measured length range A1 of the multiple first protrusions 111 is 10, and the number of second protrusions 121 included in the measured length range A2 of the multiple second protrusions 121 is 9.

[0018] Therefore, the first spacing B1 of the multiple first protrusions 111 arranged in the movable direction D1 is 1.0 mm, and the second spacing B2 of the multiple second protrusions 121 arranged in the movable direction D1 is 10 / 9 mm, which is approximately 1.11 mm.

[0019] The first magnetic sensor 2 is provided facing the outer circumferential surface of the first detection unit 11. The first magnetic sensor 2 outputs a first detection signal corresponding to the positions of the multiple first protrusions 111 in the movable direction D1 relative to the first magnetic sensor 2.

[0020] Examples of the first magnetic sensor 2 include a magnetoresistive element, a Hall sensor, and a coil-type sensor. The first magnetic sensor 2 outputs a first detection signal by using a change in magnetic resistance, a change in magnetic induction, or a change in magnetic flux density between the first magnetic sensor 2 and the first detection target portion 11.

[0021] The shape of each of the plurality of first protrusions 111 is formed such that when the movable member 1 moves in the movable direction D1, the waveform of the first detection signal becomes a sine wave shape.

[0022] The second magnetic sensor 3 is provided facing the outer peripheral surface of the second detection target portion 12. The second magnetic sensor 3 outputs a second detection signal corresponding to the positions of the plurality of second protrusions 121 with respect to the movable direction D1 with respect to the second magnetic sensor 3.

[0023] Examples of the second magnetic sensor 3 include a magnetoresistive element, a Hall sensor, and a coil-type sensor, similar to the first magnetic sensor 2. The second magnetic sensor 3 outputs a second detection signal by using a change in magnetic resistance, a change in magnetic induction, or a change in magnetic flux density between the second magnetic sensor 3 and the second detection target portion 12.

[0024] The shape of each of the plurality of second protrusions 121 is formed such that when the movable member 1 moves in the movable direction D1, the waveform of the second detection signal becomes a sine wave shape.

[0025] The magnetic sensor support portion 4 supports each of the first magnetic sensor 2 and the second magnetic sensor 3. An intermediate member (not shown) is provided between the magnetic sensor support portion 4 and the movable member 1, and the movable member 1 is movable in the movable direction D1 with respect to the magnetic sensor support portion 4. As a result, the movable member 1 is movable in the movable direction D1 with respect to the first magnetic sensor 2 and the second magnetic sensor 3.

[0026] The position calculation unit 5 receives the first detection signal output from the first magnetic sensor 2 and the second detection signal output from the second magnetic sensor 3. The position calculation unit 5 uses the first detection signal and the second detection signal to calculate the absolute position of the movable member 1 in the movable direction D1.

[0027] Next, the method for calculating the absolute position of the movable member 1 in the movable direction D1 by the position calculation unit 5 will be explained. The movable member 1 is movable in the movable direction D1 by a measured length of 10.0 mm relative to the first magnetic sensor 2 and the second magnetic sensor 3.

[0028] The difference between the first detection signal output from the first magnetic sensor 2 and the second detection signal output from the second magnetic sensor 3 is affected by a phase shift of one cycle as the movable member 1 moves by the measured length in the movable direction D1. Therefore, the position calculation unit 5 can calculate the absolute position of the movable member 1 in the movable direction D1 by calculating the difference between the first detection signal and the second detection signal.

[0029] As described above, the linear sensor according to Embodiment 1 comprises a movable member 1, a first magnetic sensor 2, a second magnetic sensor 3, and a position calculation unit 5. The movable member 1 has a first detectable part 11 and a second detectable part 12 made of a magnetic material, and is movable in the movable direction D1. The first magnetic sensor 2 is provided opposite the first detectable part 11. The second magnetic sensor is provided opposite the second detectable part 12. The first detectable part 11 has a plurality of first protrusions 111 arranged in the movable direction D1 at a first interval B1. The second detectable part 12 has a plurality of second protrusions 121 arranged in the movable direction D1 at a second interval B2 which is longer than the first interval B1. The first magnetic sensor 2 outputs a first detection signal, which is a signal corresponding to the position of the plurality of first protrusions 111 relative to the first magnetic sensor 2 in the movable direction D1. The second magnetic sensor 3 outputs a second detection signal, which is a signal corresponding to the positions of multiple second protrusions 121 relative to the second magnetic sensor 3 in the direction of movement D1. The position calculation unit 5 uses the first detection signal and the second detection signal to calculate the position of the movable member 1 in the direction of movement D1. With this configuration, the absolute position of the movable member 1 can be easily detected.

[0030] Furthermore, in the linear sensor according to Embodiment 1, the shape of the movable member 1 is cylindrical. Each of the multiple first protrusions 111 is arranged over the entire area of ​​the first detected portion 11 in the circumferential direction D2. Each of the multiple second protrusions 121 is arranged over the entire area of ​​the second detected portion 12 in the circumferential direction D2. With this configuration, each of the multiple first protrusions 111 and the multiple second protrusions 121 can be easily manufactured by turning the movable member 1.

[0031] Furthermore, in the linear sensor according to Embodiment 1, the movable member 1 is made entirely of the same material. This configuration allows the movable member 1 to be easily manufactured.

[0032] Furthermore, in the linear sensor according to Embodiment 1, when the length in the movable direction D1 is set to a preset length, and the number of first protrusions 111 included in the measurement length range A1 is n, then the number of second protrusions 121 included in the measurement length range A2 is n-1. With this configuration, the absolute position of the movable member 1 in the movable direction D1 can be calculated by calculating the difference between the first detection signal and the second detection signal.

[0033] In the linear sensor according to Embodiment 1, the configuration of the linear sensor in which the movable member 1 is formed in a cylindrical shape has been described. However, the configuration is not limited to this. The linear sensor may also have a configuration in which the movable member 1 is formed in a shape other than a cylinder.

[0034] Furthermore, in the linear sensor according to Embodiment 1, a configuration was described in which the entire movable member 1 is made of the same material. However, the configuration is not limited to this. For example, a configuration in which only the first detected part 11 and the second detected part 12 are made of a magnetic material is also possible.

[0035] Furthermore, in the linear sensor according to Embodiment 1, a configuration of a linear sensor in which the first detected part 11 and the second detected part 12 are offset from each other in the movable direction D1 has been described. However, the configuration is not limited to this. For example, the linear sensor may have a configuration in which the first detected part 11 and the second detected part 12 are aligned with each other in the movable direction D1 and offset from each other in the circumferential direction D2.

[0036] Although a linear sensor according to preferred embodiment 1 has been described above, the linear sensor according to embodiment 1 is not limited to the linear sensor according to embodiment 1 described above. Various modifications and transformations can be made to the linear sensor according to embodiment 1 described above without departing from the scope of the claims. [Explanation of Symbols]

[0037] 1 Movable member, 2 First magnetic sensor, 3 Second magnetic sensor, 4 Magnetic sensor support part, 5 Position calculation part, 11 First detected part, 12 Second detected part, 111 First protrusion, 121 Second protrusion.

Claims

1. A movable member (1) having a first detectable part (11) and a second detectable part (12) made of a magnetic material, and being movable in a movable direction (D1) which is a preset direction, A first magnetic sensor (2) is provided opposite to the first detection unit (11), A second magnetic sensor (3) is provided opposite to the second detection unit (12), Position calculation unit (5), Equipped with, The first detected portion (11) has a plurality of first protrusions (111) arranged at first intervals in the movable direction (D1), The second detection unit (12) has a plurality of second protrusions (121) arranged in the movable direction (D1) at a second interval that is longer than the first interval, The first magnetic sensor (2) outputs a first detection signal which is a signal corresponding to the position of the plurality of first protrusions (111) relative to the first magnetic sensor (2) in the movable direction (D1), The second magnetic sensor (3) outputs a second detection signal which is a signal corresponding to the position of the plurality of second protrusions (121) relative to the second magnetic sensor (3) in the movable direction (D1). The position calculation unit (5) is a linear sensor that uses the first detection signal and the second detection signal to calculate the position of the movable member (1) in the movable direction (D1).

2. The shape of the movable member (1) is formed in a cylindrical shape. Each of the plurality of first protrusions (111) is arranged over the entire area of ​​the first detected portion (11) in the circumferential direction (D2) of the movable member (1), The linear sensor according to claim 1, wherein each of the plurality of second protrusions (121) is arranged over the entire area of ​​the second detection portion (12) in the circumferential direction (D2).

3. The linear sensor according to claim 1 or claim 2, wherein the movable member (1) is composed entirely of the same material.

4. The linear sensor according to claim 1 or claim 2, wherein the length in the movable direction (D1) is set in advance and the measured length is set, and the number of first protrusions (111) included in the range of the measured length among the plurality of first protrusions (111) is n, and the number of second protrusions (121) included in the range of the measured length among the plurality of second protrusions (121) is n-1.

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