Magnetic sensors and braking and steering systems that use magnetic sensors

Abstract

This invention provides a magnetic sensor that is cost-effective and highly sensitive. The magnetic sensor (1) of this invention comprises: a magnetic field detection element (2); and a plurality of magnets (3A-3C) arranged separately from each other in a first direction (X) and movable relative to the magnetic field detection element (2) in the first direction (X). The plurality of magnets (3A-3C) have a first surface (6A-6C) opposite to the magnetic field detection element (2), and the plurality of magnets (3A-3C) are magnetized such that the first surfaces (6A-6C) of two adjacent magnets (3A-3C) have different polarities in a second direction (Y) intersecting the first direction (X). The magnetic sensor (1) further comprises: at least one soft magnetic body (4A-4C) disposed on the first surface (6A-6C) of at least one magnet (3A-3C).

Description

Technical Field

[0001] This application is based on and claims priority to Japanese Application No. 2021-102503, filed on June 21, 2021. The entire contents of that application are incorporated herein by reference.

[0002] This invention relates to magnetic sensors and braking and steering systems using magnetic sensors, and more particularly to stroke sensors. Background Technology

[0003] A stroke sensor for measuring the displacement of a movable object in one direction is known. Japanese Patent No. 5013146 discloses a magnetic sensor in which multiple magnets are arranged separately from each other in one direction, and these magnets move relative to a magnetic detection element. By arranging the magnets separately, the detection accuracy can be improved compared to a magnetic sensor where adjacent magnetic pole faces are in contact with each other. Japanese Patent No. 6492193 discloses a stroke sensor with the same structure, where the surface of the magnet facing the magnetic field detection part is rounded and convex relative to the magnetic field detection part. Japanese Patent Application Publication No. 2013-238485 discloses an encoder with an elongated magnet. The surface of the magnet facing the magnetic sensor is provided as an elongated N pole, and the N pole of the magnet is covered by a yoke. On the surface of the yoke, the concave and convex shapes are arranged along the long side of the magnet. Summary of the Invention

[0004] Because magnets are expensive, it is desirable to minimize their size. Therefore, it is considered to round the end faces of the magnet disclosed in Japanese Patent No. 5013146, similar to the magnet disclosed in Japanese Patent No. 6492193. However, while this structure is effective in reducing the magnet's size, magnets are generally quite hard, so processing incurs costs. In encoders like those in Japanese Patent Application Publication No. 2013-238485, where the yoke has a concave-convex shape, the magnetic field is determined by the shape of the yoke. Therefore, it is difficult to ensure the amount of change in magnetic flux density, especially the difference between the maximum and minimum magnetic flux density, resulting in insufficient sensitivity.

[0005] The purpose of this invention is to provide a magnetic sensor that is cost-effective and highly sensitive.

[0006] The magnetic sensor of the present invention comprises: a magnetic field detection element; and a plurality of magnets arranged separately from each other in a first direction and movable relative to the magnetic field detection element in the first direction. The plurality of magnets have a first surface opposite to the magnetic field detection element, and the plurality of magnets are magnetized such that the first surfaces of two adjacent magnets in a second direction intersecting the first direction have different polarities from each other. The magnetic sensor further comprises: at least one soft magnetic body disposed on the first surface of at least one magnet.

[0007] According to the present invention, a magnetic sensor with low cost and high sensitivity can be provided.

[0008] The foregoing and other objects, features and advantages of this application will become apparent from the following detailed description with reference to the accompanying drawings illustrating this application. Attached Figure Description

[0009] Figure 1A This is a schematic structural diagram of the magnetic sensor according to the first embodiment of the present invention.

[0010] Figure 1B This is a schematic structural diagram of the magnetic sensor according to the second embodiment of the present invention.

[0011] Figure 1C This is a schematic structural diagram of the magnetic sensor according to the third embodiment of the present invention.

[0012] Figures 2A-2L This is a conceptual diagram illustrating various variations of soft magnetic materials.

[0013] Figure 3A This is a calculation example of magnetic flux density in Comparative Example 1.

[0014] Figure 3B This is a calculation example of the error in Comparison Example 1.

[0015] Figure 4A This is a calculation example of magnetic flux density in Comparative Example 2.

[0016] Figure 4B This is a calculation example of the error in Comparative Example 2.

[0017] Figure 5A This is an example of calculating magnetic flux density in Example 1.

[0018] Figure 5B This is an example of error calculation in Example 1.

[0019] Figure 6A This is an example of calculating magnetic flux density in Example 2.

[0020] Figure 6B This is an example of error calculation in Example 2.

[0021] Figure 7A , 7B This is a conceptual diagram illustrating the method for calculating errors.

[0022] Figure 8A This is an example of calculating magnetic flux density using the ratio b / a of the height b of the soft magnetic body to the height a of the magnet as a parameter.

[0023] Figure 8B This is an example of calculating the error using the ratio b / a of the height b of the soft magnetic body to the height a of the magnet as a parameter.

[0024] Figure 9A This is an example of calculating magnetic flux density using the width of the magnet as a parameter.

[0025] Figure 9B This is an example of calculating the error using the width of the magnet as a parameter.

[0026] Figure 10 This is a conceptual diagram of a car's braking system that uses a magnetic sensor as a travel sensor.

[0027] Figure 11 This is a conceptual diagram of a car's steering system that uses a magnetic sensor as a travel sensor.

[0028] Explanation of reference numerals in the attached figures

[0029] 1. Magnetic sensor

[0030] 2. Magnetic field detection element

[0031] 3A, 3B First magnet

[0032] 3C Second Magnet

[0033] 4A, 4B First soft magnetic body

[0034] 4C Second Soft Magnetic Material

[0035] Page 1 of 6A-6C

[0036] Pages 2 (7A-7C)

[0037] Page 3 of 8A-8C

[0038] 11 Braking System

[0039] 21 Steering System

[0040] X, first direction

[0041] Y 2nd direction Detailed Implementation

[0042] Hereinafter, several embodiments of the present invention will be described with reference to the accompanying drawings. In the following description, the first direction X is the direction in which the plurality of magnets move relative to the magnetic field detection element and the direction in which the plurality of magnets are arranged separately from each other. The second direction Y is the direction in which the plurality of magnets are magnetized, and it intersects the first direction X (orthogonal in this embodiment). Figure 1A This is a schematic structural diagram of the magnetic sensor 1 according to the first embodiment of the present invention.

[0043] The magnetic sensor 1 includes: a magnetic field detection element 2, multiple magnets 3A-3C, soft magnetic bodies 4A-4C disposed on each of the magnets 3A-3C, and a common magnetic yoke 5 connecting the magnets 3A-3C to each other. The multiple magnets 3A-3C, the multiple soft magnetic bodies 4A-4C, and the common magnetic yoke 5 are sealed with resin (not shown). The multiple magnets 3A-3C include two first magnets 3A and 3B and one second magnet 3C. The first and second magnets 3A-3C are generally cuboids, have the same dimensions, and are formed of a magnetic material such as neodymium. The first and second magnets 3A-3C are not limited to cuboids, but are preferably cylindrical or have a certain cross-sectional shape in the second direction Y. This reduces the manufacturing cost of the magnets 3A-3C.

[0044] Magnets 3A to 3C are separated from each other in the first direction X, and their relative positions are fixed. A second magnet 3C is located between the two first magnets 3A and 3B. The center C3 of the second magnet 3C in the first direction X is equidistant from the centers C1 and C2 of the two first magnets 3A and 3B in the first direction X. Therefore, the interval between the first magnet 3A and the second magnet 3C is equal to the interval between the first magnet 3B and the second magnet 3C. The common yoke 5 is made of a soft magnetic material such as NiFe, which increases the magnetic flux density around the magnets 3A to 3C and is used for positioning the first magnets 3A, 3B, and the second magnet 3C. The two first magnets 3A and 3B and the second magnet 3C move relative to the magnetic field detection element 2 in the first direction X. These magnets 3A to 3C can move between the position of the first magnet 3A relative to the magnetic field detection element 2 and the position of the first magnet 3B relative to the magnetic field detection element 2; the stroke S of the magnetic sensor 1 is determined by the distance between these two positions. In this embodiment, the magnetic field detection element 2 is fixed, while the first magnet 3A, 3B and the second magnet 3C are movable. Alternatively, the magnetic field detection element 2 can be movable, while the first magnet 3A, 3B and the second magnet 3C are fixed.

[0045] The magnetic field detection element 2 includes a first magnetic field detection element 2X with a sensitivity axis along a first direction X; and a second magnetic field detection element 2Y with a sensitivity axis along a second direction Y. The first magnetic field detection element 2X and the second magnetic field detection element 2Y are not limited as long as they can detect magnetic fields; Hall elements, magnetoresistive elements such as TMR (Tunnel Magneto Resistance Effect) elements, etc., can be used. The first magnetic field detection element 2X detects the magnetic flux density Bx in the first direction X, and the second magnetic field detection element 2Y detects the magnetic flux density By in the second direction Y. Therefore, by calculating atan(By / Bx), the angle θ of the magnetic flux at the position of the magnetic field detection element 2 can be obtained. Since the relative positions of the first and second magnets 3A to 3C with the magnetic field detection element 2 in the first direction X are related to the angle θ, this relative position can be obtained based on the angle θ. By setting the second magnet 3C, the angle θ of the magnetic flux varies within the range of 0 to 360° within the stroke S, thus improving the accuracy of the magnetic sensor 1.

[0046] Two first magnets 3A and 3B and a second magnet 3C each have a first surface 6A to 6C opposite to the magnetic field detection element 2. The two first magnets 3A and 3B and the second magnet 3C are magnetized in the second direction Y. The first surfaces of two adjacent magnets are magnetized in a manner having different polarities. In this embodiment, the first surfaces 6A and 6B of the two first magnets 3A and 3B are N poles, and the first surface 6C of the second magnet 3C is an S pole; however, it is also possible that the first surfaces 6A and 6B of the two first magnets 3A and 3B are S poles, and the first surface 6C of the second magnet 3C is an N pole.

[0047] A first soft magnetic body 4A and 4B are respectively provided on the two first magnets 3A and 3B, and a second soft magnetic body 4C is provided on the second magnet 3C. The first soft magnetic bodies 4A and 4B and the second soft magnetic body 4C are made of soft magnetic materials such as NiFe, and function as magnetic yokes to prevent the diffusion of magnetic flux entering and leaving the first magnets 3A and 3B and the second magnet 3C. In other words, the first soft magnetic bodies 4A and 4B and the second soft magnetic bodies 4C guide the magnetic flux entering and leaving the first magnets 3A and 3B and the second magnet 3C, and essentially function as part of the first magnets 3A, 3B and the second magnet 3C. Since the direction of the magnetic flux is determined by the shape of the soft magnetic bodies 4A to 4C, the first magnets 3A and 3B and the second magnet 3C can have simple shapes, which can reduce manufacturing costs.

[0048] The first and second soft magnetic bodies 4A to 4C each have: a curved second surface 7A to 7C opposite to the magnetic field detection element 2; and a third surface 8A to 8C in contact with the first surface 6A to 6C of the first and second magnets 3A to 3C. The height a (Y-direction dimension) of the first and second magnets 3A to 3C is equal to each other, and the height b (Y-direction dimension) of the first and second soft magnetic bodies 4A to 4C is also equal to each other. As will be described later, the ratio b / a of the height b of the first and second soft magnetic bodies 4A to 4C to the height a of the first and second magnets 3A to 3C is preferably 1 or less (but not 0), more preferably 0.5 or less (but not 0).

[0049] The first and second soft magnetic bodies 4A-4C are manufactured in a different manner, adjusting their position while being held by a clamp, and magnetically adsorbed onto the first surfaces 6A-6C of the first and second magnets 3A-3C. Subsequently, by resin injection molding, the first and second soft magnetic bodies 4A-4C are firmly fixed to the first and second magnets 3A-3C. Therefore, it is unnecessary to use adhesives to mount the first and second soft magnetic bodies 4A-4C onto the first and second magnets 3A-3C. The first and second soft magnetic bodies 4A-4C are only provided on the first surfaces 6A-6C of the first and second magnets 3A-3C. That is, the first and second soft magnetic bodies 4A-4C do not need to be shaped like caps covering the first surfaces 6A-6C and sides 9 of the first and second magnets 3A-3C. As a result, the dimensional accuracy of the first and second soft magnetic bodies 4A to 4C can be improved, and the fabrication of the first and second soft magnetic bodies 4A to 4C and the installation of them onto the first and second magnets 3A to 3C become much easier.

[0050] Two first soft magnetic bodies 4A and 4B are configured to be axially symmetrical or mirror-symmetrical about axis P, which is parallel to the second direction Y and equidistant from the two first magnets 3A and 3B. In this embodiment, axis P is set to coincide with the center C3 of the second magnet 3C and the center of the second soft magnetic body 4C. Furthermore, the second soft magnetic body 4C itself is also axially symmetrical or mirror-symmetrical about axis P. Through these symmetries, the magnetic flux entering and exiting each soft magnetic layer 4A-4C is axially symmetrical or mirror-symmetrical about axis P. As a result, the magnetic flux around the first and second magnets 3A-3C is axially symmetrical or mirror-symmetrical about the second magnet 3C and the second soft magnetic body 4C, thus improving the linearity of the magnetic sensor 1.

[0051] In this embodiment, the interval between the second surfaces 7A and 7B and the third surfaces 8A and 8B in the second direction Y of the first soft magnetic bodies 4A and 4B gradually decreases towards the two first soft magnetic bodies 4A and 4B. As an example, the shapes of the first soft magnetic bodies 4A and 4B are either quarter-elliptical shapes obtained by dividing an ellipse into four parts along its major and minor axes, or shapes obtained by dividing the portion surrounded by the chords and arcs of an ellipse into two parts by a straight line passing through the center of the arc and orthogonal to the arc. Furthermore, the interval between the second surface 7C and the third surface 8C in the second direction Y of the second soft magnetic body 4C is largest at the center of the second soft magnetic body 4C in the first direction X, gradually decreasing from the center towards both ends in the first direction X, and is zero at both ends in the first direction X. As an example, the shape of the second soft magnetic body 4C is either a semi-elliptical shape obtained by dividing an ellipse into two parts along its major axis, or a shape surrounded by the chords and arcs of an ellipse. The two ends of the soft magnetic bodies 4A to 4C in the first direction X are the same as the two ends of the magnets 3A to 3C in the first direction X.

[0052] The first soft magnetic bodies 4A and 4B, and the second soft magnetic body 4C can also have the same shape and size. For example, as Figure 1B As shown in the second embodiment, the first soft magnetic materials 4A and 4B can also be combined with... Figure 1A The second soft magnetic material 4C shown has the same shape. In this case, since only one type of soft magnetic material 4A to 4C needs to be manufactured, the manufacturing process is simple.

[0053] The first and second soft magnetic materials 4A to 4C are not limited to a quarter-elliptical or semi-elliptical shape, and can be formed into various shapes. Figures 2A-2L The diagram shows the various shapes that the first and second soft magnetic materials 4A to 4C can form. Figures 2A-2L The figures are from and Figures 1A-1C In the following description, magnets 3A to 3C are referred to as magnet 3, and soft magnetic bodies 4A to 4C are referred to as soft magnetic bodies 4, etc., when viewed from the same direction. Figure 2A , 2B Then with Figure 1A Similarly, in the second soft magnetic body 4C shown, the spacing between the second surface 7 and the third surface 8 in the second direction Y is largest at the center of the soft magnetic body 4 in the first direction X, and gradually decreases from the center towards the two ends in the first direction X, reaching 0 at the two ends in the first direction X. However, Figure 2A The two ends of the soft magnetic body 4 shown extend from the first surface 6 of the magnet 3 along the first direction X. Figure 2B The two ends of the soft magnetic body 4 shown are located inside the first surface 6 of the magnet 3.

[0054] exist Figure 2C The image shows a rectangular soft magnetic body 4 with the first surface 6 as its long side. Figure 2D shown in the Figure 2C The rectangle shown has hexagonal soft magnetic bodies 4 with chamfered upper corners on both sides. Figure 2E The image shows a soft magnetic body 4, which is an isosceles triangle with the third face 8 as its base. Figure 2F The image shows a trapezoidal soft magnetic body 4 with surface 3 (8) as the long side and surface 2 (7) as the short side. Figure 2G The image shows a trapezoidal soft magnetic body 4 with surface 3 (8) as the short side and surface 2 (7) as the long side. Figure 2H The image shows a soft magnetic body 4, which is a pentagon with the third face 8 as one side. Figure 2I The image shows a soft magnetic body 4, which is a hexagon with the third face 8 as one side. Figure 2J The diagram shows a heptagonal soft magnetic body 4 with the third face 8 as one side. In these examples, in a cross-section including the first direction X and the second direction Y, the soft magnetic body 4 is a polygon that does not extend along the first direction X to the outside of the side that overlaps with the first face 6 of the magnet 3. This prevents the magnetic flux entering and leaving the magnet 3 from diffusing within the soft magnetic body 4.

[0055] exist Figure 2K and Figure 2L The diagram shows a soft magnetic body 4, a right-angled triangle with the first face 6 as one side. These soft magnetic bodies 4 are asymmetrical about their respective central axes; therefore, they are not preferably used as the second soft magnetic body 4C, but can be used as the first soft magnetic bodies 4A and 4B. Figure 2K The soft magnetic material 4 shown is capable of interacting with Figure 1A The first soft magnetic material 4A is replaced. Figure 2L The soft magnetic material 4 shown is capable of interacting with Figure 1A The first soft magnetic body 4B is replaced. The right-angle vertex coincides with the outer end of the first face 6.

[0056] exist Figure 1C In the third embodiment shown, the second magnet 3C is omitted, and the polarity of the first magnet 3B is opposite to that of the first magnet 3B in the first and second embodiments (the first surface 6A of the first magnet 3A is the N pole, and the first surface 6B of the first magnet 3B is the S pole). In this case, the relative positions of the first magnets 3A and 3B and the magnetic field detection element 2 in the first direction X can also be determined according to the above principle. Because the second magnet 3C is omitted, the range of θ variation within the stroke S is 0 to 180°, which is disadvantageous from the viewpoint of the accuracy of the magnetic sensor 1. However, since the second magnet 3C is not provided, the cost of the magnetic sensor 1 can be reduced or miniaturized. (Illustrations omitted, but...) Figure 1B In the second embodiment shown, the second magnet 3C can also be omitted.

[0057] Next, the magnetic flux density distribution was determined using the aforementioned embodiments and comparative examples. A summary is shown in Table 1. The rectangular area R in the table represents the calculation area. In Comparative Example 1, the height of the first and second magnets 3A-3C is 4 mm, and the first surfaces 6A-6C are flat. In Comparative Example 2, the height of the first and second magnets 3A-3C is 4 mm, and the first surfaces 6A-6C are curved. In Example 1, the height of the first and second magnets 3A-3C is 3 mm, and approximately semi-elliptical soft magnetic bodies 4A-4C with a thickness of 1 mm are disposed on them. In Example 2, the height of the first and second magnets 3A-3C is 3 mm, approximately quarter-elliptical soft magnetic bodies 4A and 4B with a thickness of 1 mm are disposed on the first magnets 3A and 3B, and approximately semi-elliptical soft magnetic bodies 4C with a thickness of 1 mm are disposed on the second magnet 3C. Figures 3A-6B In this paper, the magnetic flux density and error of Comparative Examples 1 and 2, and Examples 1 and 2 are shown as functions of position in the first direction X. The gap G is the distance from the top of the magnet, and the magnetic flux density and error were calculated for multiple gaps G. The temperature condition was set to room temperature. For gaps G = 5.06 mm and 6.06 mm, the magnetic flux density and error were also calculated at a temperature of 150°C for both the magnet and the soft magnetic material. 150°C is, for example, an assumed temperature for high-temperature environments such as automotive applications. The error was calculated as described below. Figure 7A As shown, the relationship between the position in the first direction X and the output of magnetic sensor 1 is determined. A linear approximation is made using the least squares method between the minimum and maximum values ​​of the actual output, V1 and V2. The difference between the actual output V and the output Vo on the linear approximation line is denoted as ΔV = V - V0. Figure 7B As shown, the error is calculated as ΔV / (V2-V1).

[0058] Table 1

[0059]

[0060] The maximum magnetic flux density of Examples 1 and 2 is approximately the same, slightly greater than that of Comparative Example 1, and about 8% greater than that of Comparative Example 2. The minimum magnetic flux density of Example 1 is slightly greater than that of Example 2, and the minimum magnetic flux density of Example 2 is approximately the same as that of Comparative Example 1. The minimum magnetic flux density of Example 1 is about 11% greater than that of Comparative Example 2. The maximum magnetic flux density is sometimes limited by the guaranteed detection range of the magnetic sensor 1, and it is not necessarily better to be larger. When the minimum magnetic flux density is large, the sensitivity of the magnetic sensor 1 is improved. Regarding the error, Comparative Example 2 has the smallest error, and Examples 1 and 2 are smaller than Comparative Example 1. Furthermore, the error of Example 2 is smaller than that of Example 1. Therefore, it is preferable that the shape of the first soft magnetic bodies 4A and 4B is a 1 / 4 elliptical shape. In addition, regarding the volume of magnets 3A to 3C, Examples 1 and 2 are reduced by 25% compared to Comparative Example 1 and by 20% compared to Comparative Example 2. Since the cost of soft magnetic bodies 4A to 4C is lower than the cost of magnets 3A to 3C, in terms of total cost, Examples 1 and 2 are also smaller than Comparative Examples 1 and 2. Furthermore, at 150°C, the magnetic flux density decreased compared to room temperature, and the error was the same as that at room temperature, with no significant difference between Comparative Examples 1 and 2, and Examples 1 and 2.

[0061] Next, in Figure 1A In the first embodiment shown, the total height of the first magnet 3A and the first soft magnetic body 4A, the total height of the first magnet 3B and the first soft magnetic body 4B, and the total height of the second magnet 3C and the second soft magnetic body 4C are each set to 4 mm. The magnetic flux density and error are obtained by changing the ratio of the height b of the first and second soft magnetic bodies 4A-4C to the height a of the first and second magnets 3A-3C. Figure 8B As shown, the error increases sharply when the ratio b / a exceeds 1. Therefore, b / a is preferably below 1. Figure 8A As shown, when the ratio b / a exceeds 0.5, the maximum magnetic flux density exceeds 100 mT, which may exceed the guaranteed detection range of magnetic sensor 1. Therefore, it is more preferable for b / a to be below 0.5.

[0062] Next, in Figure 1B In the second embodiment shown, the magnetic flux density and error were obtained by changing the width D1 (dimension in the first direction X) of the first and second soft magnetic bodies 4A-4C. Since the width D2 (dimension in the first direction X) of the first and second magnets 3A-3C is 6.5 mm, the first and second soft magnetic bodies 4A-4C with a width D1 of 6.5 mm correspond to... Figure 1B The first and second soft magnetic bodies 4A to 4C, with a width D1 greater than 6.5 mm, correspond to... Figure 2A The first and second soft magnetic bodies 4A to 4C, with a width D1 less than 6.5 mm, correspond to... Figure 2B When the width D1 is greater than 6.5mm ( Figure 2A This allows for maintaining the minimum magnetic flux density and reducing the maximum magnetic flux density. Therefore, it is easy to keep the magnetic flux density within the guaranteed detection range of magnetic sensor 1. When the width D1 is less than 6.5 mm ( Figure 2B This reduces errors. Furthermore, reducing the volume of the soft magnetic material lowers costs.

[0063] Several embodiments have been described above, but the present invention is not limited to these embodiments. The magnetic sensor 1 of the present invention may have at least one soft magnetic body 4A-4C disposed on the first surface 6A-6C of at least one magnet 3A-3C. For example, it is also possible to provide a first and a second soft magnetic body 4A, 4B on the first magnets 3A, 3B, and for the second magnet 3C, the portion corresponding to the third soft magnetic body 4C is also made of magnetic body.

[0064] Magnetic sensor 1, as a travel sensor, can be used for various applications. Figure 10 The diagram shows a braking system 11 of an automobile that uses a magnetic sensor 1 as a travel sensor. The braking system 11 includes: a brake pedal 12; a booster 14 connected to the brake pedal 12 via a connecting member 13; a master cylinder 15 connected to the booster 14; a hydraulic control circuit 16 connected to the master cylinder 15; and a caliper 17 connected to the hydraulic control circuit 16. A reservoir 18 is connected to the master cylinder 15. The first magnets 3A and 3B and the second magnet 3C of the magnetic sensor 1 are fixed to the booster 14, and the magnetic field detection element 2 is fixed to the vehicle body (not shown). The braking force input from the brake pedal 12 is amplified by the booster 14 and transmitted to the hydraulic control circuit 16. The amount of brake pedal 12 depressed, detected by the magnetic sensor 1, is also transmitted to the hydraulic control circuit 16. The hydraulic control circuit 16 supplies brake fluid to the caliper 17 according to the amount of brake pedal 12 depressed. The caliper 17 brakes the brake disc 19.

[0065] exist Figure 11 The diagram shows a car steering system 21 that uses a magnetic sensor 1 as a travel sensor. In the steering system 21, one end of a steering shaft 23 is connected to a steering wheel 22, and a pinion 24 is provided at the other end of the steering shaft 23. The pinion 24 engages with the rack 26 of a lever 25, converting the rotational motion of the steering shaft 23 into linear motion of the lever 25 in the left-right direction of the vehicle. The lever 25 is connected to the front wheels (not shown). The direction of the wheels is changed by the linear motion of the lever 25. The first magnets 3A and 3B and the second magnet 3C of the magnetic sensor 1 are fixed to a mounting member 28 mounted on the lever 25, and the magnetic field detection element 2 is fixed to the vehicle body 27. The magnetic sensor 1 detects the left-right position of the lever 25.

[0066] Several preferred embodiments of the present invention have been shown and described in detail, but it should be understood that various changes and modifications can be made without exceeding the spirit or scope of the appended claims.

Claims

1. A magnetic sensor, wherein, there are: a magnetic field detecting element; and a plurality of magnets arranged apart from each other in a first direction, relatively moving in the first direction with respect to the magnetic field detecting element, the plurality of magnets have a first surface opposite to the magnetic field detecting element, the plurality of magnets are magnetized in a manner that the first surfaces of two magnets adjacent to each other in a second direction intersecting the first direction have different polarities from each other, the magnetic sensor further has: at least one soft magnetic body provided on the first surface of at least one of the magnets, the at least one soft magnetic body is axisymmetric about an axis parallel to the second direction and passing through the center of the soft magnetic body, the at least one soft magnetic body has: a second surface opposite to the magnetic field detecting element, which is curved; and a third surface in contact with the first surface of the magnet, the interval of the second surface and the third surface in the second direction is largest at a central portion of the soft magnetic body in the first direction, and gradually decreases from the central portion toward both end portions in the first direction.

2. The magnetic sensor according to claim 1, wherein, the at least one soft magnetic body is provided only on the first surface.

3. The magnetic sensor according to claim 1, wherein, the both end portions of the at least one soft magnetic body protrude from the first surface of the magnet in the first direction.

4. The magnetic sensor according to claim 1, wherein, the both end portions of the at least one soft magnetic body are located inside the first surface of the magnet.

5. The magnetic sensor according to claim 1, wherein, the ratio of the height of the soft magnetic body to the height of the magnet is 1 or less.

6. The magnetic sensor according to claim 1, wherein, the ratio of the height of the soft magnetic body to the height of the magnet is 0.5 or less.

7. The magnetic sensor according to claim 1, wherein, the magnet has a certain cross-sectional shape in the second direction.

8. A magnetic sensor, wherein, there are: a magnetic field detecting element; and a plurality of magnets arranged apart from each other in a first direction, relatively moving in the first direction with respect to the magnetic field detecting element, the plurality of magnets have a first surface opposite to the magnetic field detecting element, the plurality of magnets are magnetized in a manner that the first surfaces of two magnets adjacent to each other in a second direction intersecting the first direction have different polarities from each other, the magnetic sensor further has: at least one soft magnetic body provided on the first surface of at least one of the magnets, the plurality of magnets have two first magnets, and the at least one soft magnetic body has two first soft magnetic bodies, one of the first soft magnetic bodies being provided on each of the two first magnets, the two first soft magnetic bodies have: a second surface opposite to the magnetic field detecting element, which is curved; and a third surface in contact with the first surface, the interval of the second surface and the third surface in the second direction gradually decreases toward between the two first soft magnetic bodies.

9. The magnetic sensor according to claim 8, wherein, The two first soft magnetic bodies are axisymmetric with respect to an axis parallel to the second direction and passing through the center of the second soft magnetic body.

10. The magnetic sensor according to claim 8, wherein The plurality of magnets has a second magnet between the two first magnets, and the at least one soft magnetic body has a second soft magnetic body, the second soft magnetic body being provided to the second magnet, The second soft magnetic body is axisymmetric with respect to an axis parallel to the second direction and passing through the center of the second soft magnetic body.

11. The magnetic sensor according to claim 8, wherein The ratio of the height of the soft magnetic body to the height of the magnet is 1 or less.

12. The magnetic sensor according to claim 8, wherein The ratio of the height of the soft magnetic body to the height of the magnet is 0.5 or less.

13. The magnetic sensor according to claim 8, wherein The magnet has a certain cross-sectional shape in the second direction.

14. The magnetic sensor according to any one of claims 1 to 13, wherein The magnetic sensor is a stroke sensor.

15. A brake system of an automobile, wherein The stroke sensor according to claim 14 is provided.

16. A steering system of an automobile, wherein The stroke sensor according to claim 14 is provided.

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