Travel sensor and braking system and steering system of a vehicle using the same

Abstract

The present application has a technical problem of adjusting a magnetic field distribution without moving a position of a magnet. A stroke sensor (1) of the present application has a first magnet (2A), a second magnet (2B), and a first magnetic field detection sensor (3A) that detects a magnetic field intensity formed by the first and second magnets (2A, 2B). The first and second magnets (2A, 2B) are relatively movable in a first direction (X) with respect to the first magnetic field detection sensor (3A). The first magnet (2A) has a first surface (5A) opposite to the first magnetic field detection sensor (3A) in a second direction (Z), and the second magnet (2B) has a second surface (5B) opposite to the first magnetic field detection sensor (3A) in the second direction (Z). The first surface (5A) and the second surface (5B) have different polarities. A reference axis (RA) is formed by passing through a midpoint (MP) of a smallest interval (S) containing the first and second magnets (2A, 2B) in the first direction (X) and being parallel to the second direction (Z), and a position of the first direction (X) where a magnetic field intensity (Bz) of the second direction (Z) becomes zero is between the reference axis (RA) and the second magnet (2B).

Description

TECHNICAL FIELD

[0001] This application is based on Japanese Application No. 2021-143883 filed on September 3, 2021, and priority is claimed on the same. This application is hereby incorporated by reference in its entirety.

[0002] The present application relates to a stroke sensor and a brake system and a steering system of an automobile using the same. BACKGROUND

[0003] A stroke sensor having a magnetic field detecting sensor and a magnet relatively moving linearly with respect to the magnetic field detecting sensor is known. The magnet is connected to a measurement object and moves in conjunction with the object. The moving distance of the magnet is detected by detecting the change in the magnetic field intensity formed by the magnet with the magnetic field detecting sensor, whereby the moving distance of the object can be measured. A stroke sensor having a plurality of magnets separated from each other and a magnetic field detecting sensor opposed to the magnets is disclosed in Patent No. 5013146. SUMMARY

[0004] The plurality of magnets of the stroke sensor disclosed in Patent No. 5013146 have the same shape and size. Therefore, the magnetic field formed between the adjacent magnets becomes a sine wave, and the magnetic field intensity in the direction orthogonal to the pole face of the magnet becomes zero at the intermediate position of the adjacent magnets. However, in the case where, for example, the moving range of the magnet is restricted, or the setting position of the magnetic field detecting sensor is restricted, it can be difficult to obtain the necessary magnetic field intensity of the magnetic field detecting sensor in such a magnetic field distribution.

[0005] An object of the present application is to provide a stroke sensor which is not able to adjust the magnetic field distribution without moving the position of the magnet.

[0006] The stroke sensor of the present application has: a first magnet; a second magnet having a fixed interval distance from the first magnet in a first direction; a first magnetic field detecting sensor disposed apart from the first and second magnets in a second direction orthogonal to the first direction, detecting the magnetic field formed by the first and second magnets. The first and second magnets are relatively movable in the first direction with respect to the first magnetic field detecting sensor. The first magnet has a first face opposed to the first magnetic field detecting sensor in the second direction, and the second magnet has a second face opposed to the first magnetic field detecting sensor in the second direction, the polarities of the first face and the second face being different from each other. A reference axis is formed by including the midpoint of the minimum interval of the first and second magnets in the first direction and being parallel to the second direction. In one mode, the position of the first direction where the magnetic field intensity of the second direction becomes zero is between the reference axis and the second magnet. In another mode, the magnetic field formed by the first and second magnets is asymmetric with respect to the reference axis.

[0007] According to the present application, it is possible to provide a stroke sensor capable of adjusting a magnetic field distribution without moving a position of a magnet.

[0008] The above and other objects, features and advantages of the present application will become clear from the following detailed description of the application taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0009] Figure 1 is a conceptual diagram of a brake system of an automobile using a stroke sensor.

[0010] Figure 2A is a schematic configuration diagram of a stroke sensor of the first embodiment.

[0011] Figure 2B is a conceptual diagram of magnetic lines of force of the first embodiment.

[0012] Figure 3A is a schematic configuration diagram of a stroke sensor of Comparative Example 1.

[0013] Figure 3B is a conceptual diagram of magnetic lines of force of Comparative Example 1.

[0014] Figure 3C is a graph conceptually showing the magnetic field strength in the second direction in Comparative Example 1.

[0015] Figure 4 is a graph showing the relationship between the relative displacement of the magnet and the magnetic field strength in the second direction.

[0016] Figure 5A is a graph showing the relationship between the relative displacement of the magnet and the magnetic field strength in the second direction in Comparative Examples 1 and 2.

[0017] Figure 5B is a graph showing Figure 5A is an enlarged view showing the relationship between the relative displacement of the magnet from the initial position and the increment of the magnetic field strength from the initial position in Comparative Example 1.

[0018] Figure 5C is a graph showing the magnetic field strength detected by the first magnetic field detection sensor.

[0019] Figure 6A is a graph showing the relationship between the relative displacement of the magnet and the magnetic field strength in the second direction in Example 1.

[0020] Figure 6B is a graph showing Figure 6A is an enlarged view showing the relationship between the relative displacement of the magnet from the initial position and the increment of the magnetic field strength from the initial position in Example 1.

[0021] Figure 6Cis a graph showing the magnetic field strength detected by the first magnetic field detection sensor.

[0022] Figure 7A is a graph showing the relationship between the relative displacement of the magnet and the magnetic field strength in the second direction in Embodiments 2, 3.

[0023] Figure 7B is a graph showing Figure 7A is an enlarged view of the relationship between the relative displacement of the magnet from the initial position and the increment of the magnetic field strength from the initial position in Embodiments 2, 3.

[0024] Figure 8A is a graph showing the relationship between the relative displacement of the magnet and the magnetic field strength in the second direction in Embodiment 4.

[0025] Figure 8B is a graph showing Figure 8A is an enlarged view of the relationship between the relative displacement of the magnet from the initial position and the increment of the magnetic field strength from the initial position in Embodiments 2, 3.

[0026] Figure 9A is a graph showing the relationship between W1 / W2 and the minimum magnet moving amount.

[0027] Figure 9B is a graph showing the relationship between (W1+W2) / L and the minimum magnet moving amount.

[0028] Figure 10A is a schematic configuration view of a stroke sensor of a second embodiment.

[0029] Figure 10B is a conceptual view of a magnetic flux line of the stroke sensor of the second embodiment.

[0030] Figure 11A is a graph showing the relationship between the relative displacement of the magnet and the magnetic field strength in the second direction in Embodiments 5 to 8 and Comparative Examples 1, 3, 4.

[0031] Figure 11B is a graph showing Figure 11A is an enlarged view of the relationship between the relative displacement of the magnet from the initial position and the increment of the magnetic field strength from the initial position in Embodiments 2, 3.

[0032] Figure 12 is a conceptual view of a steering system of an automobile using the stroke sensor.

[0033] Explanation of Reference Numerals

[0034] 11, 1A, 101 stroke sensor

[0035] 2A first magnet

[0036] 2B second magnet

[0037] 3A first magnetic field detection sensor

[0038] 3B second magnetic field detection sensor

[0039] 4 support body

[0040] 11 brake system

[0041] 12 brake pedal

[0042] 21 steering system

[0043] Bz magnetic field strength in the second direction Z

[0044] RA reference axis

[0045] X first direction

[0046] Z second direction DETAILED DESCRIPTION

[0047] Hereinafter, several embodiments of the present application will be described with reference to the drawings. In the following description, the first direction refers to the direction in which the first magnet and the second magnet are arranged, and is sometimes referred to as the X direction. The second direction refers to the direction orthogonal to the first direction, or the direction orthogonal to the first face of the first magnet and the second face of the second magnet, and is sometimes referred to as the Z direction. The direction orthogonal to the first direction and the second direction is sometimes referred to as the third direction or the Y direction. In addition, as will be apparent from the following description, the second magnetic field detection sensor 3B is not an essential element in the present application, and can be omitted.

[0048] (First Embodiment)

[0049] Figure 1 A conceptual diagram of a brake system to which the stroke sensor 1 of the present embodiment is applied is shown. The brake system 11 has 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 caliper 18 connected to the master cylinder 15, a control circuit 16, a motor 17, and the stroke sensor 1. The stroke sensor 1 measures the depression amount of the brake pedal 12 and transmits it to the control circuit 16. The control circuit 16 controls the driving force of the motor 17 in accordance with the depression amount of the brake pedal 12, and the motor 17 assists the booster 14. The brake force input from the brake pedal 12 is amplified by the booster 14 assisted by the motor 17, and is transmitted to the caliper 18 via the master cylinder 15. The caliper 18 brakes a brake disc 19.

[0050] Figure 2AThe outline configuration of the stroke sensor 1 of the first embodiment is shown. The stroke sensor 1 has a first magnet 2A, a second magnet 2B, a first magnetic field detecting sensor 3A, and a second magnetic field detecting sensor 3B. As described later, the magnetic field formed by the first magnet 2A and the second magnet 2B is detected by the first magnetic field detecting sensor 3A and the second magnetic field detecting sensor 3B. The first magnet 2A and the second magnet 2B are supported by a support 4 composed of a soft magnetic body. The support 4 is a cantilever beam having one end fixed to the brake booster 14, and the first magnet 2A is fixed to the front end 4A thereof, and the second magnet 2B is fixed between the front end 4A and the base 4B. Thus, the interval distance of the first magnet 2A and the second magnet 2B in the first direction X is fixed. The first and second magnets 2A, 2B are movable in the first direction X in conjunction with the operation of the brake pedal 12, and the first and second magnetic field detecting sensors 3A, 3B are fixed to the frame (not shown) of the brake booster 14. As a result, the first and second magnets 2A, 2B are relatively movable in the first direction X with respect to the first and second magnetic field detecting sensors 3A, 3B.

[0051] The first magnet 2A and the second magnet 2B are formed of a magnetic material such as neodymium. The first magnet 2A and the second magnet 2B are substantially rectangular parallelepipeds, and the dimensions in the X direction, the Y direction, and the Z direction are not limited. The first magnet 2A has a first face 5A which is a magnetic pole face opposite to the first and second magnetic field detecting sensors 3A, 3B in the second direction Z. The second magnet 2B has a second face 5B which is a magnetic pole face opposite to the first and second magnetic field detecting sensors 3A, 3B in the second direction Z. The polarities of the first face 5A and the second face 5B are different from each other. In the present embodiment, the first face 5A of the first magnet 2A is an N pole, and the second face 5B of the second magnet 2B is an S pole, but the first face 5A of the first magnet 2A can be an S pole, and the second face 5B of the second magnet 2B can be an N pole.

[0052] In the following description, an axis passing through the midpoint MP of the smallest interval S including the first and second magnets 2A, 2B in the first direction X and parallel to the second direction Z is referred to as a reference axis RA when viewed from the third direction Y. The smallest interval S including the first and second magnets 2A, 2B means an interval having both ends at the portion 6A of the first magnet 2A farthest from the second magnet 2B in the first direction X and the portion 6B of the second magnet 2B farthest from the first magnet 2A in the first direction X.

[0053] The first and second magnetic field detection sensors 3A, 3B are arranged apart from the first and second magnets 2A, 2B in the second direction Z, and detect the magnetic field formed by the first and second magnets 2A, 2B. The first and second magnetic field detection sensors 3A, 3B are supported by a common support 7. The first and second magnets 2A, 2B are shared by the first and second magnetic field detection sensors 3A, 3B. The first magnetic field detection sensor 3A detects the relative displacement of the first and second magnets 2A, 2B in the first direction X (hereinafter, sometimes simply referred to as the relative displacement of the magnets) corresponding to the depression amount of the brake pedal 12. The first magnetic field detection sensor 3A detects the relative displacement of the magnets in a range from a state where the brake pedal 12 is not depressed (depression amount is zero) to a state where it is depressed to the maximum extent. The first magnetic field detection sensor 3A normally detects the relative displacement of the first and second magnets 2A, 2B over several tens of mm.

[0054] The first magnetic field detection sensor 3A has an element that detects the magnetic field intensity Bx in the first direction X, and an element that detects the magnetic field intensity Bz in the second direction Z. The type 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, or the like can be used. An arithmetic unit (not shown) of the stroke sensor 1 calculates the angle of the resultant magnetic field (vector sum of Bx and Bz) from the magnetic field intensities detected by these elements. Since the magnetic field distribution around the first and second magnets 2A, 2B is obtained in advance, the relative displacement of the magnets, that is, the depression amount of the brake pedal 12 can be detected from the angle of the resultant magnetic field.

[0055] The second magnetic field detection sensor 3B detects the magnetic field intensity Bz in the second direction Z in the magnetic field formed by the first and second magnets 2A, 2B. The initial relative position of the second magnetic field detection sensor 3B with respect to the first and second magnets 2A, 2B in the first direction X is between the reference axis RA and the second magnet 2B. The magnetic field intensity Bz in the second direction Z detected by the second magnetic field detection sensor 3B changes in accordance with the relative displacement of the magnets, that is, the depression amount of the brake pedal 12. The second magnetic field detection sensor 3B is used, for example, for detection of the depression of the brake pedal 12 at the time of vehicle start, control of the timing of turning on the brake light, and the like. Therefore, it is sufficient for the second magnetic field detection sensor 3B to detect the relative displacement of the magnets to the extent of several mm, and this range becomes the operating range of the second magnetic field detection sensor 3B. When the detected magnetic field intensity Bz in the second direction Z reaches a prescribed magnitude, the second magnetic field detection sensor 3B transmits a signal indicating this to a control unit (not shown) of the vehicle. The second magnetic field detection sensor 3B mounts only an element that detects the magnetic field intensity Bz in the second direction Z, and as the element, in addition to a Hall element, a magnetoresistance effect element such as an AMR element, a TMR element, or the like can be used.

[0056] Figure 3A The outline structure of the stroke sensor 101 of Comparative Example 1 is shown.Figure 3B A portion of the magnetic force lines of the stroke sensor 101 of Comparative Example 1 is conceptually shown by broken lines. The first magnet 2A and the second magnet 2B are identical in shape and size. Therefore, the size Wl of the first magnet 2A in the first direction X is equal to the size W2 of the second magnet 2B in the first direction X. In Comparative Example 1, Wl = W2 = 5.5 mm. The height Hl of the first magnet 2A (size in the second direction Z) and the height H2 of the second magnet 2B (size in the second direction Z) are 5 mm, and the depth (size in the third direction Y) of the first magnet 2A and the second magnet 2B is 7 mm. As shown in FIG. 6, the first magnet 2A and the second magnet 2B are symmetric about the reference axis RA, and therefore the magnetic field distribution (shape of the magnetic flux) formed by the first magnet 2A and the second magnet 2B also becomes symmetric about the reference axis RA. As a result, the position in the first direction X at which the magnetic field strength Bz in the second direction Z is zero overlaps the reference axis RA. Figure 3B As shown in FIG. 6, the first magnet 2A and the second magnet 2B are symmetric about the reference axis RA, and therefore the magnetic field distribution (shape of the magnetic flux) formed by the first magnet 2A and the second magnet 2B also becomes symmetric about the reference axis RA. As a result, the position in the first direction X at which the magnetic field strength Bz in the second direction Z is zero overlaps the reference axis RA.

[0057] In the first magnetic field detection sensor 3A, in order to ensure the reliability of the measurement, it is necessary to apply a magnetic field having a strength of a certain threshold value or more. Conversely, the first magnetic field detection sensor 3A needs to ensure the magnetic field strength necessary for the operation in the entire operating range with respect to the given magnetic field distribution. As a countermeasure in the case where the necessary magnetic field strength cannot be ensured, there can be an increase in the sensitivity of the element, a correction of the arrangement position of the first magnetic field detection sensor 3A, a correction of the magnetic field distribution, and the like. An increase in the sensitivity of the element generally has a large impact on the cost, and is sometimes impractical. A correction of the arrangement position of the first magnetic field detection sensor 3A is also sometimes difficult due to constraints on the layout. In order to correct the magnetic field distribution, it is considered to correct the position of at least one of the first magnet 2A and the second magnet 2B. However, the first magnet 2A and the second magnet 2B are surrounded by the frame 8, and it is sometimes difficult to avoid interference with the frame 8 and correct the position of the first magnet 2A or the second magnet 2B.

[0058] In the present embodiment, the size Wl of the first magnet 2A in the first direction X is larger than the size W2 of the second magnet 2B in the first direction X. Figure 2B A portion of the magnetic force lines of the stroke sensor 1 of the present embodiment is conceptually shown by broken lines. Compared to Comparative Example 1, the magnetic flux is displaced as a whole toward the second magnet 2B, and the position in the first direction X at which the magnetic field strength Bz in the second direction Z becomes zero is between the reference axis RA and the second magnet 2B. In other words, the magnetic field formed by the first and second magnets 2A, 2B is not symmetric about the reference axis RA. Therefore, without changing the positions of the first magnet 2A and the second magnet 2B (without changing the length L of the minimum interval S), it is possible to correct the magnetic field distribution.

[0059] On the other hand, for the second magnetic field detecting sensor 3B, since it is used for the above-described use, it is necessary to detect the depression of the brake pedal 12 with as small a depression amount as possible. As described above, the second magnetic field detecting sensor 3B outputs a signal when the magnetic field strength Bz in the second direction Z detected exceeds a prescribed threshold value. Therefore, it is important to make the relative displacement of the magnets when the magnetic field strength Bz in the second direction Z reaches the prescribed threshold value as small as possible.

[0060] Figure 4 The relationship between the relative displacement of the magnets and the magnetic field strength Bz in the second direction Z is schematically shown. In the initial position, the brake pedal 12 is not depressed. As the brake pedal 12 is deeply depressed (as the relative displacement of the magnets increases), in order for the second magnetic field detecting sensor 3B to rapidly operate for the increase of the magnetic field strength Bz in the second direction Z, it is important that the amount of movement of the first and second magnets 2A, 2B when the magnetic field strength Bz in the second direction Z reaches the prescribed threshold value (hereinafter referred to as the minimum magnet movement amount Tmin) be as small as possible. For this reason, it is important that the change in the magnetic field strength Bz in the second direction Z with respect to the relative displacement of the magnets be large within the operating range of the second magnetic field detecting sensor 3B. That is, it is effective to position the second magnetic field detecting sensor 3B close to the reference axis RA. This is because, as shown in FIG. 6, in Comparative Example 1, the magnetic field strength Bz in the second direction Z becomes zero at the reference axis RA, and therefore the rate of change ΔBz becomes large as the position in the first direction X becomes closer to the reference axis RA. Further, the minimum magnet movement amount Tmin of each of the examples and comparative examples described below is shown summarized in Table 1. Figure 3C

[0061] In Comparative Example 1, in order to position the second magnetic field detecting sensor 3B close to the reference axis RA, a method of moving the second magnetic field detecting sensor 3B toward one side of the reference axis RA (first method), a method of moving the second magnet 2B to the right side (second method), and a method of moving the first magnet 2A to the right side (third method) can be employed. However, sometimes the first method and the second method are difficult in layout. Figure 3A Figure 5A A relationship between the relative displacement of the magnets and the magnetic field strength Bz in the second direction Z when only the first magnet 2A is moved 1 mm to the right side is shown (Comparative Example 2) in Comparative Example 1 in which the third method is employed. Figure 5B A relationship between the relative displacement of the magnets from the initial position (=0) and the increase ΔBz of the magnetic field strength Bz from the initial position in the vicinity of the operating range of the second magnetic field detecting sensor 3B is shown. In Comparative Example 2, the magnetic field distribution can be corrected so as to position the second magnetic field detecting sensor 3B close to the reference axis RA. In Figure 5B In this case, the two curves almost overlap, but the minimum magnet movement amount Tmin becomes slightly smaller in Comparative Example 2 than in Comparative Example 1. On the other hand, Figure 5C ​​The magnetic field strength detected by the first magnetic field detection sensor 3A (vector sum of the magnetic field strengths Bz in the first direction X and the second direction Z) is shown in the vicinity of the operating range of the first magnetic field detection sensor 3A. A region in which the reference of the necessary magnetic field strength cannot be ensured is generated in the vicinity of the right end of the operating range. Thus, in the case where the first magnet 2A is moved to the right side alone, even if the minimum magnet moving amount Tmin can be reduced, it can not be possible to ensure the operation of the first magnetic field detection sensor 3A.

[0062] Figure 6A The relationship between the relative displacement of the magnet and the magnetic field strength Bz in the second direction Z when W1 = 8 mm and W2 = 3.5 mm in the first embodiment (Example 1) is shown. Figure 6B The relationship between the relative displacement of the magnet from the initial position and the increment ΔBz of the magnetic field strength Bz from the initial position in the vicinity of the operating range of the second magnetic field detection sensor 3B in Figure 6A The relationship between the relative displacement of the magnet from the initial position and the increment ΔBz of the magnetic field strength Bz from the initial position in the vicinity of the operating range of the second magnetic field detection sensor 3B in Figure 6C The magnetic field strength detected by the first magnetic field detection sensor 3A (vector sum of the magnetic field strengths Bz in the first direction X and the second direction Z) is shown in the operating range of the first magnetic field detection sensor 3A. The necessary magnetic field strength is ensured in the entire range of the moving range. In Example 1, the change in the magnetic field strength Bz in the second direction Z is greater and the minimum magnet moving amount Tmin is smaller than in Comparative Example 1. From the above, by setting W1 > W2, it is possible to ensure the necessary magnetic field strength of the first magnetic field detection sensor 3A and reduce the minimum magnet moving amount Tmin.

[0063] Figure 7A The relationship between the relative displacement of the magnet and the magnetic field strength Bz in the second direction Z is shown for the case where W1 is increased alone (Example 2) and the case where W2 is reduced alone (Example 3) with respect to Comparative Example 1. Figure 7B The relationship between the relative displacement of the magnet from the initial position and the increment ΔBz of the magnetic field strength Bz from the initial position in the vicinity of the operating range of the second magnetic field detection sensor 3B in Figure 7A The relationship between the relative displacement of the magnet from the initial position and the increment ΔBz of the magnetic field strength Bz from the initial position in the vicinity of the operating range of the second magnetic field detection sensor 3B in Figure 8A The relationship between the relative displacement of the magnet and the magnetic field strength Bz in the second direction Z is shown for the case where W2 is further reduced from Example 2 and set to W2 = 2 mm (Example 4).Figure 8B is a close-up view showing the vicinity of the operating range of the second magnetic field detection sensor 3B in Figure 8A , showing the relationship between the relative displacement of the magnets from the initial position and the increment ΔBz of the magnetic field strength Bz. Embodiment 4 is more effective than Comparative Example 1, but since W2 is too small, the magnetic field itself becomes weak, and thus it is not preferable that W2 be less than 2 mm.

[0064] In Figure 9A , the relationship between W1 / W2 and the minimum magnet movement amount Tmin in each of the above cases is shown, and in Figure 9B , the relationship between (W1+W2) / L and the minimum magnet movement amount Tmin in each of the above cases is shown. W1 / W2 is preferably 1.4 or more and 2.7 or less, more preferably 1.6 or more and 2.3 or less. (W1+W2) / L is preferably 0.27 or more and 0.46 or less, more preferably 0.32 or more and 0.42 or less.

[0065]

Table 1

[0066]

[0067] (Second Embodiment)

[0068] Figure 10A The schematic structure of the stroke sensor 1A of the second embodiment is shown. Figure 10B A portion of the magnetic lines of force of the present embodiment in the stroke sensor 1A is shown conceptually in a broken line. The second face 5B of the second magnet 2B protrudes more toward the first and second magnetic field detection sensors 3A, 3B in the second direction Z than the first face 5A of the first magnet 2A. Unlike the first embodiment, the magnetic flux as a whole does not displace toward the second magnet 2B. However, due to the positional relationship in the second direction Z between the first face 5A of the first magnet 2A and the second face 5B of the second magnet 2B, the magnetic field formed by the first and second magnets 2A, 2B is asymmetric with respect to the reference axis RA, and the position in the first direction X at which the magnetic field strength Bz in the second direction Z becomes zero moves between the reference axis RA and the second magnet 2B. In other words, by not moving the second magnet 2B to the right in Figure 3A , the same effect as the movement is obtained. Thus, the present embodiment also exhibits the same effect as the first embodiment.

[0069] Figure 11A The relationship between the relative displacement of the magnets and the magnetic field strength Bz in the second direction Z with respect to various combinations of the height H1 of the first magnet 2A and the height H2 of the second magnet 2B is shown (Embodiment 5, Comparative Examples 1, 3). Figure 11B The following is shown: Figure 11Athe vicinity of the operating range of the second magnetic field detection sensor 3B in the embodiment 5 and comparative examples 1 and 3. Since the setting surfaces of the first magnet 2A and the second magnet 2B are on the horizontal plane, Hl and H2 indicate the positional relationship of the first surface 5A of the first magnet 2A and the second surface 5B of the second magnet 2B in the second direction Z. By setting Hl < H2, the same effect as the first embodiment is exerted.

[0070] [Table 2]

[0071] H1 H2 Minimum magnet movement amount Tmin (mm) Comparative Example 1 5 5 2.55 Comparative Example 3 5 4 3.17 Example 5 5 6 2.13

[0072] The present embodiment can also be combined with the first embodiment. In this case, the size Wl of the first magnet 2A in the first direction X is larger than the size W2 of the second magnet 2B in the first direction X, and the second surface 5B of the second magnet 2B protrudes more toward the first magnetic field detection sensor 3A in the second direction Z than the first surface 5A of the first magnet 2A.

[0073] The present application has been described with respect to several embodiments, but the present application is not limited to these embodiments. For example, the stroke sensor 1, 1A of the present application can be applied to a steering system of an automobile. In the case of applying to the steering system of the automobile, the second magnetic field detection sensor 3B can be omitted. Figure 12 In the embodiment 5, a steering system 21 of an automobile using the stroke sensor 1 is shown. 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 is engaged with a rack 26 of a link 25, and converts the rotational motion of the steering shaft 23 into the linear motion of the link 25 in the vehicle left-right direction. The link 25 is connected to a wheel (not shown) of a front wheel. By the linear motion of the link 25, the direction of the wheel is changed. The first magnet 2A and the second magnet 2B of the stroke sensor 1 are fixed to a mounting member 28 mounted to the link 25, and the first magnetic field detection sensor 3A is fixed to a vehicle body 27. The stroke sensor 1 detects the position of the link 25 in the vehicle left-right direction. In addition, in the stroke sensor 1, 1A applied to the steering system 21 of the automobile, the second magnetic field detection sensor 3B is omitted.

[0074] Several preferred embodiments of the present application have been shown and described in detail, but it should be understood that various changes and modifications can be made without departing from the spirit or scope of the appended claims.

Claims

1. A stroke sensor, comprising: First magnet; The second magnet has a fixed spacing distance from the first magnet in the first direction; A first magnetic field detection sensor is configured separately from the first and second magnets in a second direction orthogonal to the first direction, and detects the magnetic field formed by the first and second magnets. The first and second magnets are capable of moving relative to the first magnetic field detection sensor along the first direction. The first magnet has a first surface opposite to the first magnetic field detection sensor in the second direction, and the second magnet has a second surface opposite to the first magnetic field detection sensor in the second direction, wherein the polarities of the first surface and the second surface are different. The position of the first direction, where the magnetic field strength in the second direction becomes zero, is located between the reference axis and the second magnet. The reference axis passes through the midpoint of the smallest interval in the first direction that includes both the first and second magnets, and is parallel to the second direction. It includes: a second magnetic field detection sensor that detects the magnetic field strength in the second direction of the magnetic field formed by the first and second magnets. The initial position of the second magnetic field detection sensor is between the reference axis and the second magnet.

2. A stroke sensor, comprising: First magnet; The second magnet has a fixed spacing distance from the first magnet in the first direction; A first magnetic field detection sensor is configured separately from the first and second magnets in a second direction orthogonal to the first direction, and detects the magnetic field formed by the first and second magnets. The first and second magnets are capable of moving relative to the first magnetic field detection sensor along the first direction. The first magnet has a first surface opposite to the first magnetic field detection sensor in the second direction, and the second magnet has a second surface opposite to the first magnetic field detection sensor in the second direction, wherein the polarities of the first surface and the second surface are different. The magnetic field formed by the first and second magnets is asymmetrical about a reference axis, which passes through the midpoint of the smallest interval containing the first and second magnets in the first direction and is parallel to the second direction. It includes: a second magnetic field detection sensor that detects the magnetic field strength in the second direction of the magnetic field formed by the first and second magnets. The initial position of the second magnetic field detection sensor is between the reference axis and the second magnet.

3. The stroke sensor according to claim 1 or 2, wherein, The dimension W1 of the first magnet in the first direction is larger than the dimension W2 of the second magnet in the first direction.

4. The stroke sensor according to claim 3, wherein, W1 / W2 is greater than 1.4 and less than 2.

7.

5. The stroke sensor according to claim 3, wherein, W1 / W2 is greater than 1.6 and less than 2.

3.

6. The stroke sensor according to claim 4 or 5, wherein, When the length of the minimum interval in the first direction is set to L, (W1+W2) / L is above 0.27 and below 0.

46.

7. The stroke sensor according to claim 4 or 5, wherein, When the length of the minimum interval in the first direction is set to L, (W1+W2) / L is above 0.32 and below 0.

42.

8. The stroke sensor according to claim 1 or 2, wherein, The second face of the second magnet protrudes further toward the first magnetic field detection sensor in the second direction than the first face of the first magnet.

9. The stroke sensor according to claim 1 or 2, wherein, The dimension of the first magnet in the first direction is larger than the dimension of the second magnet in the first direction, and the second face of the second magnet protrudes more toward the first magnetic field detection sensor in the second direction than the first face of the first magnet.

10. The stroke sensor according to claim 1 or 2, wherein, It has: a support body that supports the first magnet and the second magnet, and is made of a soft magnetic material.

11. A braking system for an automobile, comprising a stroke sensor according to any one of claims 1 to 10.

12. A steering system for an automobile, comprising a travel sensor according to any one of claims 1 to 10.

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