Travel sensor and brake system using the same

Abstract

A stroke sensor capable of improving the measurement accuracy of the orientation of a magnetic field. A stroke sensor (1) has: a magnetic field detecting element (2) that detects a magnetic field; a magnet (3) that generates the magnetic field detected by the magnetic field detecting element (2) and moves in a first direction relative to the magnetic field detecting element (2); and a first soft magnetic body (4A) whose relative position to the magnetic field detecting element (2) is fixed. The magnetic field detecting element (2) and the first soft magnetic body (4A) are apart from the magnet (3) in a second direction orthogonal to the first direction. The first soft magnetic body (4A) is located to the side of the magnetic field detecting element (2) in the first direction as viewed in the second direction. A direction orthogonal to the first and second directions is set as a third direction; a dimension of the first soft magnetic body (4A) in the first direction is set as L1; a dimension of the first soft magnetic body (4A) in the second direction is set as D1; and a dimension of the first soft magnetic body (4A) in the third direction is set as W1, and L1>D1 and L1>W1.

Description

TECHNICAL FIELD

[0001] The present application relates to a stroke sensor and a brake system using the same. BACKGROUND

[0002] Generally, a stroke sensor detects the orientation of a magnetic field, and detects the presence or absence of movement, and the movement distance, of an object as a measurement target. A stroke sensor disclosed in Patent Literature 1 has a magnetic field detecting element that detects a magnetic field, and a magnet that generates the magnetic field detected by the magnetic field detecting element and relatively moves with respect to the magnetic field detecting element. The stroke sensor disclosed in Patent Literature 1 has a soft magnetic body on both sides of the relative movement direction of the magnetic field detecting element. According to Patent Literature 1, by providing the soft magnetic body, the magnetic flux density can be increased, and the stroke can be increased.

[0003] PRIOR ART DOCUMENTS

[0004] PATENT LITERATURE

[0005] Patent Literature 1: Japanese Patent Application Publication No. 2014-95615 SUMMARY

[0006] PROBLEMS TO BE SOLVED BY THE INVENTION

[0007] In a stroke sensor, it is important to increase the magnetic flux density detected by the magnetic field detecting element, but it is also important to increase the measurement accuracy of the orientation of the magnetic field.

[0008] An object of the present application is to provide a stroke sensor capable of increasing the measurement accuracy of the orientation of the magnetic field.

[0009] MEANS FOR SOLVING THE PROBLEMS

[0010] The present application provides a stroke sensor including a magnetic field detecting element that detects a magnetic field, a magnet that generates the magnetic field detected by the magnetic field detecting element and relatively moves in a first direction with respect to the magnetic field detecting element, and a first soft magnetic body whose relative position with respect to the magnetic field detecting element is fixed. The magnetic field detecting element and the first soft magnetic body are apart from the magnet in a second direction orthogonal to the first direction. The first soft magnetic body is located on the side of the magnetic field detecting element in the first direction, as viewed in the second direction. When a direction orthogonal to the first and second directions is set as a third direction, a dimension of the first soft magnetic body in the first direction is set as LI, a dimension of the first soft magnetic body in the second direction is set as DI, and a dimension of the first soft magnetic body in the third direction is set as WI, LI > DI and LI > WI.

[0011] EFFECTS OF THE INVENTION

[0012] According to the present application, it is possible to provide a stroke sensor capable of increasing the measurement accuracy of the orientation of the magnetic field. BRIEF DESCRIPTION OF DRAWINGS

[0013] Figure 1 is a schematic diagram of a stroke sensor of the first embodiment of the present application.

[0014] Figure 2 is a conceptual diagram showing the structure of a magnet.

[0015] Figure 3 is a diagram explaining the concept of the angle θBof a magnetic flux line and the error θBerror.

[0016] Figure 4 is a conceptual diagram showing the relative position of a magnet and the orientation of a magnetic flux line.

[0017] Figure 5 is a graph showing the characteristics of the stroke sensors in Examples 1, 2, and Comparative Examples.

[0018] Figure 6 is an analysis example of the magnetic flux in the vicinity of a magnet and a magnetic field detection element.

[0019] Figure 7 is a graph showing the relationship between the configuration length T of a soft magnetic body and the error θerror.

[0020] Figure 8 is a graph showing the relationship between the dimensions D1, D2 of a soft magnetic body and the error θerror.

[0021] Figure 9 is a graph showing the relationship between the dimensions W1, W2 of a soft magnetic body and the error θerror.

[0022] Figure 10 is a graph showing the relationship between the separation distances G1, G2 of a soft magnetic body and the error θerror.

[0023] Figure 11 is a graph showing the relationship between the separation distances H1, H2 of the center of a soft magnetic body and the center of a magnetic induction portion of a magnetic field detection element and the error θerror.

[0024] Figure 12 is a schematic diagram of a stroke sensor of the second embodiment of the present application.

[0025] Figure 13 is a graph showing the characteristics of the stroke sensors in the second embodiment and Comparative Examples.

[0026] Figure 14 is a schematic diagram of a stroke sensor involved in the reference mode.

[0027] Figure 15 is a graph showing the characteristics of the stroke sensors in the reference mode and Comparative Examples.

[0028] Figure 16 This is a schematic diagram of the stroke sensor according to the third embodiment of the present invention.

[0029] Figure 17 This is a schematic diagram of the braking system according to the fourth embodiment of the present invention.

[0030] Explanation of reference numerals in the attached figures

[0031] 1...stroke sensor

[0032] 2...Magnetic field detection element

[0033] 3...Magnet

[0034] 4A... First soft magnetic body

[0035] 4B...Second soft magnetic body

[0036] 11……Braking System

[0037] 12……Brake pedal

[0038] 13……Modible components

[0039] 44…concave Detailed Implementation

[0040] Hereinafter, embodiments of the stroke sensor of the present invention and the braking system using the stroke sensor will be described with reference to the accompanying drawings. In the following description, the direction in which the magnet 3 moves relative to the magnetic field detection element 2 is referred to as the first direction X, the direction orthogonal to the first direction X and in which the magnetic field detection element 2, the first soft magnetic body 4A, and the second soft magnetic body 4B move away from the magnet 3 is referred to as the second direction Z, and the direction orthogonal to the first direction X and the second direction Z is referred to as the third direction Y.

[0041] (First Implementation)

[0042] Figure 1 A schematic diagram of the stroke sensor 1 according to the first embodiment of the present invention is shown. Figure 1 (a) shows a perspective view of the stroke sensor 1. Figure 1 (b) shows a side view of the travel sensor 1 as viewed from a third party towards the Y direction. Figure 1Fig. 2 is a plan view showing the stroke sensor 1 as viewed from the second direction Z. The stroke sensor 1 has a magnetic field detecting element 2 that detects a magnetic field and a magnet 3 that generates the magnetic field detected by the magnetic field detecting element 2. The magnet 3 is attached to a movable member 13 that is movable in the first direction X and moves in the first direction X together with the movable member 13. The magnetic field detecting element 2 is attached to a fixed member (not shown). Therefore, the magnet 3 relatively moves in the first direction X with respect to the magnetic field detecting element 2. The magnet 3 can also be attached to the fixed member and the magnetic field detecting element 2 can be attached to the movable member 13.

[0043] The magnetic field detecting element 2 has a first element (not shown) that detects a magnetic flux density Bx in the first direction X and a second element (not shown) that detects a magnetic flux density Bz in the second direction Z. The kind of the elements is not limited and, in addition to a Hall element, a magnetoresistance effect element such as an AMR element, a TMR element, etc. can be used. An operation section (not shown) of the stroke sensor 1 calculates an angle of a resultant magnetic field (vector sum of Bx and Bz) based on the magnetic flux densities detected by the first and second elements. Since the magnetic field distribution around the magnet 3 is previously found, the relative displacement of the magnet 3, i.e., the amount of movement of the movable member 13 in the first direction X can be detected based on the orientation of the resultant magnetic field.

[0044] The magnet 3 is formed of a magnetic material such as neodymium. The magnet 3 is magnetized in the first direction X. Figure 2 Fig. 3 shows a structure example of the magnet 3. The shape of the magnet 3 of the present embodiment is as shown in Figure 1 Fig. 2 (a), Figure 2 Fig. 2 (a) is a circular cylinder having a central axis C parallel to the first direction X. The movable member 13 is a cylindrical or rod-shaped member whose central axis C coincides with the central axis C of the magnet 3. The movable member 13 is inserted into a central hole 31 of the magnet 3 and the magnet 3 is fixed to the movable member 13 at a prescribed position of the movable member 13 by an appropriate means such as an adhesive, a screw, etc. As shown in Figure 2 Fig. 2 (b), the shape of the magnet 3 can also be a circular cylinder having a central axis C parallel to the first direction X. In this case, the magnet 3 is fixed to the end portion of the movable member 13 by an appropriate means such as an adhesive, a screw, etc. As shown in Figure 2 Fig. 2 (c), the magnet 3 can also be attached to the surface of a portion of the movable member 13 in the circumferential direction. In this case, it is preferable that the movable member 13 has a rectangular cross section and the magnet 3 is a rectangular parallelepiped. The magnetic flux distribution generated around the magnet 3 does not change when the magnet 3 of a circular cylinder or a circular cylinder shape rotates around the central axis C. Therefore, in the case where the movable member 13 can rotate around the central axis C, Figure 2 the structures shown in Figs. 2 (a) and (b) are advantageous. On the other hand, in the case where the rotation of the movable member 13 around the central axis C is limited, it is also possible to select Figure 2the structure shown in (c) of FIG. 1.

[0045] A first soft magnetic body 4A and a second soft magnetic body 4B are provided on both sides in the first direction X of the magnetic field detection element 2. More specifically, the first soft magnetic body 4A is located on the side of the magnetic field detection element 2 in the first direction X as viewed from the second direction Z, and the second soft magnetic body 4B is located on the side of the magnetic field detection element 2 in the first direction X as viewed from the second direction Z, that is, on the opposite side of the magnetic field detection element 2 from the first soft magnetic body 4A. The relative positions of the first soft magnetic body 4A and the second soft magnetic body 4B with respect to the magnetic field detection element 2 are fixed. The first soft magnetic body 4A and the second soft magnetic body 4B are rectangular parallelepipeds, the edges of which are parallel to any one of the first direction X, the second direction Z, and the third direction Y. The first soft magnetic body 4A and the second soft magnetic body 4B are formed of a soft magnetic body such as a general steel material. The first soft magnetic body 4A and the second soft magnetic body 4B are preferably formed of the same material. The magnetic field detection element 2, the first soft magnetic body 4A, and the second soft magnetic body 4B are apart from the magnet 3 in the second direction Z. The first soft magnetic body 4A and the second soft magnetic body 4B are apart from the magnetic field detection element 2 in the first direction X. The first soft magnetic body 4A and the second soft magnetic body 4B are mirror-symmetrical with respect to a plane that passes through the center 21 of the magnetic induction portion of the magnetic field detection element 2 and is parallel to the second direction Z and the third direction Y. With respect to the center 21 of the magnetic induction portion of the magnetic field detection element 2, in the case of a Hall element, it refers to the center of a semiconductor thin film (InSb thin film, GaAs thin film, or the like) that constitutes the Hall element, in the case of an AMR element, it refers to the center of a ferromagnetic metal thin film that constitutes the AMR element, and in the case of a TMR element or a GMR element, it refers to the center of a free layer.

[0046] Here, the definitions of the dimensions used in the following description are described (also refer to Figure 1 (b) of FIG. 1.

[0047] L1: dimension (length) in the first direction X of the first soft magnetic body 4A

[0048] D1: dimension (thickness) in the second direction Z of the first soft magnetic body 4A

[0049] W1: dimension (width) in the third direction Y of the first soft magnetic body 4A

[0050] L2: dimension (length) in the first direction X of the second soft magnetic body 4B

[0051] D2: dimension (thickness) in the second direction Z of the second soft magnetic body 4B

[0052] W2: dimension (width) in the third direction Y of the second soft magnetic body 4B

[0053] G1: distance in the first direction X from the magnetic field detection element 2 to the first soft magnetic body 4A

[0054] G2: distance in the first direction X from the magnetic field detection element 2 to the second soft magnetic body 4B

[0055] H1: interval in the second direction Z between the center 41 of the first soft magnetic body 4A and the center 21 of the magnetic induction portion of the magnetic field detection element 2 (positive in the direction in which the first soft magnetic body 4A and the magnetic field detection element 2 are away from the magnet 3, and negative in the direction in which they are close to the magnet 3)

[0056] H2: interval in the second direction Z between the center 42 of the second soft magnetic body 4B and the center 21 of the magnetic induction portion of the magnetic field detection element 2 (positive in the direction in which the second soft magnetic body 4B and the magnetic field detection element 2 are away from the magnet 3, and negative in the direction in which they are close to the magnet 3)

[0057] S: range in which the center (center of gravity) 31 of the magnet 3 is relatively movable with respect to the center 21 of the magnetic induction portion of the magnetic field detection element 2, or maximum value of the distance by which it is relatively movable (also referred to as stroke)

[0058] S1: distance by which the magnet 3 is relatively movable from the reference position R to the side of the first soft magnetic body 4A

[0059] S2: distance by which the magnet 3 is relatively movable from the reference position R to the side of the second soft magnetic body 4B

[0060] T: length of the smallest interval in the first direction X that contains the first soft magnetic body 4A and the second soft magnetic body 4B (also referred to as soft magnetic body arrangement length)

[0061] T1: length of the smallest interval in the first direction X that contains the first soft magnetic body 4A and the reference position

[0062] T2: length of the smallest interval in the first direction X that contains the second soft magnetic body 4B and the reference position

[0063] The magnet 3 is relatively moved with respect to the magnetic field detection element 2 with the reference position R as the center. The reference position R is the relative position of the magnet 3 with respect to the magnetic field detection element 2 (hereinafter, sometimes referred to as the relative position of the magnet 3), which is the position in the first direction X at which the center 31 of the magnet 3 coincides with the center 21 of the magnetic induction portion of the magnetic field detection element 2.

[0064] In the present embodiment, LI = L2 = 17 mm, DI = D2 = 1 mm, WI = W2 = 5 mm, LI > DI, LI > WI, and L2 > D2, L2 > W2 are established. That is, the first soft magnetic body 4A and the second soft magnetic body 4B have an elongated shape in the first direction X. As for the relationship between DI and WI, DI < WI, and preferably DI < WI. Likewise, as for the relationship between D2 and W2, D2 < W2, and preferably D2 < W2. That is, the first soft magnetic body 4A and the second soft magnetic body 4B have a flat shape in the second direction Z. The reference position R is located at the center of the stroke S, SI = S2 = S / 2. In addition, S = T, and SI = TI, S2 = T2. That is, when the center 31 of the magnet 3 is located at one end of the stroke S, the center 31 of the magnet 3 and the outer side end portion of the first soft magnetic body 4A coincide in the first direction X, and when the center 31 of the magnet 3 is located at the other end of the stroke S, the center 31 of the magnet 3 and the outer side end portion of the second soft magnetic body 4B coincide in the first direction X.

[0065] By providing such a first soft magnetic body 4A and a second soft magnetic body 4B, it is possible to correct the orientation of the magnetic flux generated by the magnet 3, and thus it is possible to measure the orientation of the magnetic field with higher accuracy. Here, reference is made to FIG. 6. Figure 3 The orientation of the magnetic field and the measurement error thereof will be described. Figure 3 The upper diagram of FIG. 6 shows the magnet 3 in the reference position R (indicated by a solid line) and the magnet 3 at both ends of the stroke S (indicated by a broken line). The arrows schematically indicate the orientation of the magnetic flux. Figure 3 The middle diagram of FIG. 6 shows the relationship between the relative position of the magnet 3 and the angle of the magnetic flux line (magnetic force line) at the center 21 of the magnetic induction portion of the magnetic field detection element 2. The angle is indicated as 0 degrees at the 9 o'clock position of the clock hand, and as positive for counterclockwise rotation. Figure 3 As shown in FIG. 6, the 9 o'clock position of the clock hand is defined as 0 degrees, and counterclockwise rotation is defined as positive.

[0066] As described above, the stroke sensor 1 detects the amount of movement of the magnet 3 in the first direction X based on the angle of the magnetic flux line, that is, the angle of the resultant magnetic field (vector sum of Bx and Bz) detected by the magnetic field detection element 2. Therefore, in order to detect the amount of movement in the first direction X with higher accuracy, it is desirable that the linearity between the relative position of the magnet 3 and the angle of the magnetic flux line at the center 21 of the magnetic induction portion of the magnetic field detection element 2 be high. Figure 3linearly low, the accuracy is reduced in a region where the angle of the magnetic flux line changes little. Moreover, if the linearity is reduced, the angle of the magnetic flux line becomes the same value at a plurality of relative positions, and the measurement itself becomes difficult. Here, the relationship between the relative position of the magnet 3 and the angle θB of the magnetic flux line at the center 21 of the magnetic induction portion of the magnetic field detection element 2 is linearly approximated by the least square method between the minimum value θB1 and the maximum value θB2 of the actual angle of the magnetic flux line. When the difference between the actual angle θB of the magnetic flux line and the angle θBo of the magnetic flux line on the linearly approximated line is set as ΔθB = θB - θBo, the error θBerror is found as ΔθB / (θB2 - θB1). Figure 3 The lower graph shows the relationship between the relative position of the magnet 3 and the error θBerror. In the present embodiment, the error θBerror thus found can be reduced. Hereinafter, the present embodiment is further described by way of examples and comparative examples.

[0067] In the stroke sensor 1 of Example 1, the magnet 3 is relatively moved within a range of 23 mm on both sides of the reference position R. In the following description, the relative displacement of the magnet 3 is set to 0 at the reference position R; negative on the left side of the reference position R; and positive on the right side of the reference position R. Figure 4 The (a) to (d) of FIG. 6 conceptually show the orientation of the magnetic flux line when the magnet 3 is located at several relative positions (-23 mm, -16 mm, -8 mm, 0 mm) with respect to the reference position R. Figure 5 The (a) of FIG. 7 shows the relationship between the relative position of the magnet 3 and the angle θB of the magnetic flux line at the center 21 of the magnetic induction portion of the magnetic field detection element 2, Figure 5 The (b) of FIG. 7 shows the relationship between the relative position of the magnet 3 and the error θBerror. The solid line is Example 1, and the dashed line is a comparative example in which the first soft magnetic body 4A and the second soft magnetic body 4B are removed from Example 1. In Example 1, the linearity of the relative position of the magnet 3 and the angle θB of the magnetic flux line is high, and a substantially linear coordinate graph can be obtained. In contrast, in the comparative example, the error θerror is large particularly at the relative position B (-16 mm). Referring to the coordinate graph corresponding to the relative position B, it is found that the angle θB of the magnetic flux line is not linearly changed with the relative position, and the error θerror is large. Figure 4 As is clear from the (b) of FIG. 7, in the comparative example, the magnetic flux line is slowly bent in the counterclockwise direction (change in θB), which is the cause of the error θerror. In contrast, in Example 1, the magnetic flux line is smoothly bent, and the change in θB can well follow the change in the relative position.

[0068] Figure 6 An analysis example of the magnetic flux in the vicinity of the magnet 3 and the magnetic field detection element 2 is shown. Figure 6 The (a) of FIG. 8 is Example 1, and although not shown, the second soft magnetic body 4B is also provided. Figure 6(b) is a comparative example. The position corresponding to the first soft magnetic body 4A is indicated by a quadrangle. The relative position of the magnet 3 and the magnetic flux density (absolute value) are shown in (c). The magnetic flux density becomes large when the magnet 3 is located near the reference position R. In the comparative example, the magnetic flux becomes a substantially sinusoidal wave, in contrast to which, in Embodiment 1, a part of the magnetic flux is drawn in by the first soft magnetic body 4A and is sucked in. Thereby, it is considered that the magnetic flux rotates substantially counterclockwise in the vicinity of the magnetic field detection element 2. Figure 4 (b) of FIG. 6. In the comparative example, the magnetic flux becomes a substantially sinusoidal wave, in contrast to which, in Embodiment 1, a part of the magnetic flux is drawn in by the first soft magnetic body 4A and is sucked in. Thereby, it is considered that the magnetic flux rotates substantially counterclockwise in the vicinity of the magnetic field detection element 2.

[0069] Figure 5 (c) of FIG. 6 shows the relationship between the relative position of the magnet 3 and the magnetic flux density (absolute value). The magnetic flux density becomes large when the magnet 3 is located near the reference position R. With respect to the magnetic flux density, in the vicinity of the reference position R, Embodiment 1 is slightly larger than the comparative example, but at a position away from the reference position R, the comparative example is slightly larger than Embodiment 1, and there is no large difference. It is understood that the first and second soft magnetic bodies 4A, 4B have little effect of increasing the magnetic flux density, and mainly function to reduce the error θBerror.

[0070] As described above, in the present embodiment, the first soft magnetic body 4A and the second soft magnetic body 4B have an elongated shape in the first direction X. In the comparative example, the first soft magnetic body 4A and the second soft magnetic body 4B have a circular shape. In the comparative example, the first soft magnetic body 4A and the second soft magnetic body 4B have a circular shape. Figure 5 In (a) and (b) of FIG. 6, Embodiment 2 is also indicated by a broken line. In Embodiment 2, the dimensions of the first soft magnetic body 4A and the second soft magnetic body 4B are LI = L2 = 5.5 mm, DI = D2 = 1 mm, WI = W2 = 5 mm, LI > DI, LI > WI, and L2 > D2, L2 > W2 are satisfied. As described above, in the comparative example, the first soft magnetic body 4A and the second soft magnetic body 4B have a circular shape, and the dimensions are L = 5.5 mm, D = 1 mm, and W = 5 mm, L > D, L > W are satisfied. Figure 5 In (a) and (b) of FIG. 6, Embodiment 2 is also indicated by a broken line. In Embodiment 2, the dimensions of the first soft magnetic body 4A and the second soft magnetic body 4B are LI = L2 = 5.5 mm, DI = D2 = 1 mm, WI = W2 = 5 mm, LI > DI, LI > WI, and L2 > D2, L2 > W2 are satisfied. As described above, in the comparative example, the first soft magnetic body 4A and the second soft magnetic body 4B have a circular shape, and the dimensions are L = 5.5 mm, D = 1 mm, and W = 5 mm, L > D, L > W are satisfied. Figure 5 In (c) of FIG. 6, with respect to the range of the position of the magnet 3 at which the magnetic flux density of 50 mT or more can be obtained, it is A in Embodiment 1, and it is B in Embodiment 2, and Embodiment 2 can ensure a larger stroke than Embodiment 1. It is considered that substantially the same effect as Embodiment 2 can be obtained in a range where 1 < LI / WI ≤ 1.2, 1 < L2 / W2 ≤ 1.2 are satisfied. In addition, it is considered that substantially the same effect as Embodiment 1 can be obtained in a range where 3 ≤ LI / WI ≤ 4, 3 ≤ L2 / W2 ≤ 4 are satisfied. In (c) of FIG. 6, with respect to the range of the position of the magnet 3 at which the magnetic flux density of 50 mT or more can be obtained, it is A in Embodiment 1, and it is B in Embodiment 2, and Embodiment 2 can ensure a larger stroke than Embodiment 1. It is considered that substantially the same effect as Embodiment 2 can be obtained in a range where 1 < LI / WI ≤ 1.2, 1 < L2 / W2 ≤ 1.2 are satisfied. In addition, it is considered that substantially the same effect as Embodiment 1 can be obtained in a range where 3 ≤ LI / WI ≤ 4, 3 ≤ L2 / W2 ≤ 4 are satisfied.

[0071] In order to further reduce the error θerror, it is preferable to make the ratio of the stroke S to the soft magnetic body arrangement length T as close to 1 as possible (as an example, 0.95 ≤ T / S ≤ 1.05). In Figure 7 In FIG. 6, the relationship between the soft magnetic body arrangement length T and the error θerror when the stroke S is set to be fixed (46 mm) is shown. If the soft magnetic body arrangement length T is larger than the stroke S, the magnetic flux lines are absorbed by the first and second soft magnetic bodies 4A and 4B outside the range of the stroke S, and the orientation of the magnetic flux lines is disordered. On the contrary, if the soft magnetic body arrangement length T is smaller than the stroke S, the first and second soft magnetic bodies 4A and 4B draw the magnetic flux near the end portions of the stroke S, and the effect of changing the direction of the magnetic flux cannot be obtained. The error θerror is minimized when the stroke S and the soft magnetic body arrangement length T are equal. The error θerror becomes 2% or less when the soft magnetic body arrangement length T is 32 mm or more and 69 mm or less, i.e., 0.69 ≤ T / S ≤ 1.5. The error θerror becomes 1% or less when the soft magnetic body arrangement length T is 40 mm or more and 56 mm or less, i.e., 0.89 ≤ T / S ≤ 1.22.

[0072] Figure 8 The relationship between the sizes Dl, D2 of the first and second soft magnetic bodies 4A, 4B and the error θerror is shown. The error θerror becomes 2% or less when 0.56 mm ≤ Dl ≤ 3 mm and 0.56 mm ≤ D2 ≤ 3 mm. The error θerror becomes 1% or less when 0.81 mm ≤ Dl ≤ 2.39 mm and 0.81 mm ≤ D2 ≤ 2.39 mm.

[0073] Figure 9 The relationship between the sizes Wl, W2 of the first and second soft magnetic bodies 4A, 4B and the error θerror is shown. The error θerror becomes 2% or less when 2.51 mm ≤ Wl ≤ 10 mm and 2.51 mm ≤ W2 ≤ 10 mm. The error θerror becomes 1% or less when 3.53 mm ≤ Wl ≤ 10 mm and 3.53 mm ≤ W2 ≤ 10 mm.

[0074] Figure 10 The relationship between the distances Gl, G2 from the magnetic field detection element 2 to the first and second soft magnetic bodies 4A, 4B and the error θerror is shown. The error θerror becomes 2% or less when 4.1 mm ≤ Gl ≤ 7.6 mm and 4.1 mm ≤ G2 ≤ 7.6 mm. The error θerror becomes 1% or less when 5.1 mm ≤ Gl ≤ 6.7 mm and 5.1 mm ≤ G2 ≤ 6.7 mm.

[0075] Figure 11The diagram illustrates the relationship between the intervals H1 and H2 along the second direction Z between the centers 42 of the first and second soft magnetic bodies 4A and 4B and the center 21 of the magnetic induction section of the magnetic field detection element 2, and the error θerror. When -3.5mm ≤ H1 ≤ 1.0mm and -3.5mm ≤ H2 ≤ 1.0mm, the error θerror becomes less than 1%. Preferably, along the second direction Z, the center 21 of the magnetic induction section of the magnetic field detection element 2 overlaps with the first and second soft magnetic bodies 4A and 4B.

[0076] (Second Implementation)

[0077] Figure 12 A schematic diagram of the stroke sensor 1 according to the second embodiment of the present invention is shown. The differences from the first embodiment will be explained below. Structures and effects omitted from the description are the same as in the first embodiment. In this embodiment, the length L1 of the first soft magnetic body 4A in the first direction X is smaller than the length L2 of the second soft magnetic body 4B in the first direction X (L1 < L2), and is S1 = T1. Figure 13 In (a), the relationship between the relative position of magnet 3 and the error θBerror is shown when T1 = 17 mm (L1 = 11 mm). Figure 13 In (b), the relationship between the relative position of magnet 3 and the error θBerror is shown when T1 = 12 mm (L1 = 6 mm). Figure 13 In (c), the relationship between the relative position of magnet 3 and the error θBerror is shown when T1 = 0 mm (L1 = 0 mm). In all cases, T2 = 23 mm (L2 = 17 mm). Embodiments and comparative examples are also shown in the figures. The error θBerror is... Figure 13 In (a), the calculation is performed within the range of magnet position from -17mm to +23mm. Figure 13 In (b), the calculation is performed within the range of magnet position from -12mm to +23mm. Figure 13 In (c), the calculations are performed within the range of magnet position from 0 mm to +23 mm. Compared to Example 1, Examples 3-1 to 3-3 show a reduction in the linearity of angle θB and the error θBerror, but compared to the comparative example, the linearity of angle θB and the error θBerror are improved. This embodiment is effective when the stroke S is limited.

[0078] Figure 14 A schematic diagram of the travel sensor 1 in the reference configuration is shown. The reference configuration is the same as in the second embodiment, where L1 < L2, but differs from the second embodiment in that S1 = S2. In other words, in the first embodiment, only the length L1 in the first direction X of the first soft magnetic body 4A is changed. Figure 15In (a) of FIG. 9, the relationship between Tl and the angle ΘB of the magnetic flux line at the center 21 of the magnetic induction portion of the magnetic field detection element 2 is shown, and in (b) of FIG. 9, the relationship between Tl and the error ΘBerror is shown, and in (c) of FIG. 9, the relationship between Tl and the magnetic flux density (absolute value) is shown. Tl = 0 corresponds to the case where the first soft magnetic body 4A is not present. As Tl decreases, the linearity of the angle ΘB and the error ΘBerror decrease. As Tl decreases, the magnetic flux density increases, but there is no large difference due to Tl. The effect of improving the linearity of the angle ΘB and the error ΘBerror is smaller than in the second embodiment. Figure 15 Figure 15 In (c) of FIG. 9, the relationship between Tl and the magnetic flux density (absolute value) is shown. Tl = 0 corresponds to the case where the first soft magnetic body 4A is not present. As Tl decreases, the linearity of the angle ΘB and the error ΘBerror decrease. As Tl decreases, the magnetic flux density increases, but there is no large difference due to Tl. The effect of improving the linearity of the angle ΘB and the error ΘBerror is smaller than in the second embodiment.

[0079] (Third Embodiment)

[0080] Figure 16 (a) of FIG. 10 shows a plan view of the stroke sensor 1 of the third embodiment of the present application. The first soft magnetic body 4A and the second soft magnetic body 4B have two faces 43 facing the third direction Y and facing each other, and the two faces 43 have recessed portions 44. The stroke sensor 1 is manufactured by insert molding. Figure 16 (b) of FIG. 10 shows the first soft magnetic body 4A and the second soft magnetic body 4B in which the recessed portions 44 are not provided. Resin 45 is provided around the first soft magnetic body 4A, the second soft magnetic body 4B, and the magnetic field detection element 2. The range in which the resin 45 is provided is limited by a mold (not shown). The first soft magnetic body 4A and the second soft magnetic body 4B are positioned inside the mold, and therefore first to third jigs 46A to 46C are provided on each of the three faces of the first and second soft magnetic bodies 4A, 4B. Figure 16 (c) of FIG. 10 shows the first soft magnetic body 4A and the second soft magnetic body 4B in which the recessed portions 44 are provided, and is the same as (b) of FIG. 10. The first to second jigs 46A to 46B are provided to the recessed portions 44. By the three faces of the recessed portions 44 abutting against the first to second jigs 46A to 46B, positioning in the X direction and the Y direction is possible. As a result, the third jig 46C becomes unnecessary, and the degree of freedom of the interval in the X direction between the first soft magnetic body 4A and the second soft magnetic body 4B and the magnetic field detection element 2 increases. As shown in (d) of FIG. 10, instead of the recessed portions 44, protruding portions 47 can be provided. In this case, by providing the first and second jigs 48A, 48B in a manner surrounding the protruding portions, the same effect is obtained. Figure 16 Figure 16 (d) of FIG. 10 shows the first soft magnetic body 4A and the second soft magnetic body 4B in which the recessed portions 44 are provided, and is the same as (c) of FIG. 10. The first to second jigs 46A to 46B are provided to the recessed portions 44. By the three faces of the recessed portions 44 abutting against the first to second jigs 46A to 46B, positioning in the X direction and the Y direction is possible. As a result, the third jig 46C becomes unnecessary, and the degree of freedom of the interval in the X direction between the first soft magnetic body 4A and the second soft magnetic body 4B and the magnetic field detection element 2 increases. As shown in (d) of FIG. 10, instead of the recessed portions 44, protruding portions 47 can be provided. In this case, by providing the first and second jigs 48A, 48B in a manner surrounding the protruding portions, the same effect is obtained.

[0081] (Fourth Embodiment)

[0082] The above-described stroke sensor 1 can be used in the brake system 11, for example. Figure 17 ​​A conceptual diagram of a brake system 11 is shown. The brake system 11 has the stroke sensor 1, a brake pedal 12, and a movable member 13 which moves in a first direction X in conjunction with the brake pedal 12. The brake pedal 12 is turned counterclockwise about a first fulcrum 14 by the operation of a driver. Thereby, a hydraulic circuit which is linked to the brake pedal 12 is operated. The movable member 13 is linked to a second fulcrum 15 which is distal from the first fulcrum 14 of the brake pedal 12, and the turning motion of the brake pedal 12 is converted into a linear motion parallel to the first direction X by a guide mechanism which is not shown. One end of a spring 16 is installed at an end portion of the movable member 13 which is opposite to the second fulcrum 15, and the other end of the spring 16 is installed on a vehicle. The brake pedal 12 is held at a prescribed position by the force of the spring 16 at a non-operation time, and is turned against the force of the spring 16 at an operation time. The magnet 3 is held on the movable member 13, and the magnetic field detecting element 2 and the first and second soft magnetic bodies 4A, 4B are held on the vehicle.

Claims

1. A stroke sensor, wherein there are: a magnetic field detecting element that detects a magnetic field; a magnet that generates the magnetic field detected by the magnetic field detecting element and relatively moves in a first direction with respect to the magnetic field detecting element; and a first soft magnetic body whose relative position with respect to the magnetic field detecting element is fixed, the stroke sensor detects an amount of relative movement of the magnet in the first direction with respect to the magnetic field detecting element based on an orientation of the magnetic field, the magnetic field detecting element and the first soft magnetic body are apart from the magnet in a second direction orthogonal to the first direction, the first soft magnetic body is located aside of the magnetic field detecting element in the first direction as viewed from the second direction, a direction orthogonal to the first and second directions is set as a third direction; a dimension of the first soft magnetic body in the first direction is set as LI; a dimension of the first soft magnetic body in the second direction is set as DI; and a dimension of the first soft magnetic body in the third direction is set as Wl, LI > DI and LI > Wl.

2. The stroke sensor according to claim 1, wherein the magnetic field detecting element has a first element that detects a magnetic flux density in the first direction and a second element that detects a magnetic flux density in the second direction, the stroke sensor further has an arithmetic unit that calculates an angle of a resultant magnetic field of a magnetic field in the first direction and a magnetic field in the second direction based on the magnetic flux density in the first direction detected by the first element and the magnetic flux density in the second direction detected by the second element.

3. The stroke sensor according to claim 1 or 2, wherein the first soft magnetic body is apart from the magnetic field detecting element in the first direction.

4. The stroke sensor according to claim 3, wherein the first soft magnetic body is apart from the magnetic field detecting element by 4.1 mm or more and 7.6 mm or less.

5. The stroke sensor according to claim 1 or 2, wherein 0.56 mm ≤ DI ≤ 3 mm.

6. The stroke sensor according to claim 1 or 2, wherein 2.51 mm ≤ Wl ≤ 10 mm.

7. The stroke sensor according to claim 1 or 2, wherein with a direction in which the first soft magnetic body and the magnetic field detecting element are apart from the magnet being positive and a direction in which they approach the magnet being negative, a separation between a center of the first soft magnetic body and a center of a magnetic induction portion of the magnetic field detecting element in the second direction is -3.5 mm or more and +1.0 mm or less.

8. The stroke sensor according to claim 7, wherein the center of the magnetic induction portion of the magnetic field detecting element overlaps the first soft magnetic body in the second direction.

9. The stroke sensor according to claim 1 or 2, wherein there is a second soft magnetic body whose relative position with respect to the magnetic field detecting element is fixed and which is located on an opposite side of the magnetic field detecting element from the first soft magnetic body, a dimension of the second soft magnetic body in the first direction is set as L2; a dimension of the second soft magnetic body in the second direction is set as D2; and a dimension of the second soft magnetic body in the third direction is set as W2, L2 > D2 and L2 > W2. a dimension of the second soft magnetic body in the second direction is set to D2; and a dimension of the second soft magnetic body in the third direction is set to W2, L2 > D2 and L2 > W2.

10. The stroke sensor according to claim 9, wherein the first soft magnetic body and the second soft magnetic body are mirror-symmetric about a plane that passes through a center of a magnetic induction portion of the magnetic field detection element and is parallel to the second direction and the third direction.

11. The stroke sensor according to claim 10, wherein a maximum value of a distance of the magnet that can be relatively moved is set to S; and a length of a minimum interval in the first direction that includes the first soft magnetic body and the second soft magnetic body is set to T, 0.69 < T / S < 1.

5.

12. The stroke sensor according to claim 11, wherein 0.89 < T / S < 1.

22.

13. The stroke sensor according to claim 9, wherein L1 < L2.

14. The stroke sensor according to claim 1 or 2, wherein a shape of the magnet is a cylindrical shape or a circular cylindrical shape having a central axis parallel to the first direction.

15. The stroke sensor according to claim 1 or 2, wherein the first soft magnetic body has two faces that face the third direction and are opposite to each other, the two faces having a recess or a protrusion.

16. A brake system, wherein there are: the stroke sensor according to any one of claims 1 to 15, a brake pedal, and a movable member that moves in the first direction in conjunction with the brake pedal, the magnet is held to the movable member.

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