JPH10104249A - Wheel speed sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wheel speed sensor which can detect the turn of an object to be detected in an extremely good condition without being affected by a foreign magnetic body. SOLUTION: This sensor is provided with a magnetoelectric conversion element 4 which detects the turn of a rotor 2 based on changes of a bias magnetic field which is generated by a bias magnet 5 toward the rotor 2 in the vicinity of a wheel to make the intensity of the bias magnetic field which is applied on an object to be detected from the bias magnet 5 which is remote from the magnetoelectric conversion element 4 among the bias magnets 5 stronger than the intensity of the bias magnetic field which is applied on the rotor 2 from the bias magnet 5 which is near to the magnetoelectric conversion element 4 among the bias magnets 5. A magnetic body foreign matter adheres to the bias magnet 5 which is remote from the magnetoelectric conversion element 4 among the bias magnets 5 having the strong bias magnetic field.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wheel speed sensor for detecting the rotation of a wheel in a vehicle based on the output of a magnetoelectric transducer.

[0002]

2. Description of the Related Art Conventionally, a wheel speed sensor for detecting a wheel speed has been known. The wheel speed sensor includes a bias magnet that generates a bias magnetic field toward a rotor provided inside the wheel, and detects a change in the bias magnetic field by a magneto-electric conversion element to detect a wheel speed. doing.

[0003]

However, the wheel speed sensor is placed in an extremely bad environment near the wheel where magnetic foreign matter is likely to adhere. In such an environment, when a magnetic foreign matter adheres to the vicinity of the magnetoelectric conversion element, the magnetic flux density converges on the magnetic foreign matter, and the change in the bias magnetic field that changes with the rotation of the rotor decreases. As a result, there is a problem that the detection sensitivity of the magnetoelectric conversion element is reduced.

SUMMARY OF THE INVENTION In view of the foregoing, it is an object of the present invention to provide a wheel speed sensor capable of detecting a rotor movement extremely well.

[0005]

In order to achieve the above object, the following technical means are employed. According to the first aspect of the present invention, the rotation of the rotor (2) is detected based on a change in the bias magnet (5) that generates a bias magnetic field toward the rotor (2) near the wheel (1). A bias magnetic field (H2) applied to the rotor (2) from a side of the bias magnet (5) remote from the magnetoelectric conversion element (4); Wherein the bias magnetic field intensity (H1) applied to the rotor (2) from the side closer to the magnetoelectric conversion element (4) is larger than the bias magnetic field intensity (H1).

By the way, magnetic foreign matter is generated near the wheel (1) due to the winding of the magnetic foreign matter on the road by the wheel. In such a state, since the wheel speed sensor has the above-described configuration, a magnetic foreign matter can be attached to a side of the bias magnet (5) having a strong bias strength (H2) far from the magnetoelectric conversion element (4). . Therefore, the magnetic foreign matter can be effectively removed from the magnetoelectric conversion element (4), and as a result, the movement of the rotor (2) can be detected well.

Here, the wheel speed sensor is disposed near the wheel (1). In the vicinity of the wheel (1), it is necessary to dispose a brake and a suspension in addition to the wheel speed sensor as described above, so that the wheel speed sensor is required to be compact. In the inventions according to the second to fourth aspects, the bias magnet (5) is provided on one side of the surface passing through the magnetoelectric conversion element (4) among the surfaces parallel to the surface perpendicular to the axial direction of the rotor (2). The magnet (4) is arranged at a small distance from the magnetoelectric conversion element (4) in a direction parallel to the axial direction of the rotor (2), and the rotor (2) is arranged from the side of the bias magnet (5) far from the magnetoelectric conversion element (4). ) Is larger than the bias magnetic field intensity (H1) applied to the rotor (2) from the side closer to the magnetoelectric conversion element (4) of the bias magnet (5). It is characterized by.

According to this, the same effect as in the first aspect is obtained, and the bias magnet (5) is provided on the surface passing through the magnetoelectric conversion element (4) out of the surface parallel to the surface perpendicular to the axial direction of the rotor (2). The wheel speed sensor can be made compact by disposing it only on one side. The wheel speed sensors can be arranged vertically as in the third aspect of the invention or horizontally in the fourth aspect of the invention.

[0009] In the invention according to claim 5,
When the bias magnet (5) has a rectangular parallelepiped shape, the bias magnetic field intensity (H2) applied to the rotor (2) from the side of the bias magnet (5) far from the magnetoelectric conversion element (4) is determined by the bias magnet (5). It is characterized in that it is magnetized so that it becomes larger than the bias magnetic field intensity (H1) applied to the rotor (2) from the side closer to the magnetoelectric conversion element (4) in (5), and specifically has a rectangular parallelepiped shape. The same effect as in claim 2 can be obtained by making the magnetization manner as described above in a compact shape.

According to the invention described in claim 6, the bias magnet (5) is fixed to the mold member (6), and the same effect as in claim 2 is obtained. Specifically, a bias magnet (5) having a shape as described in claim 7 or 8 is fixed to the mold member (6). That is, in the invention described in claim 7, the shape of the bias magnet (5) is a rectangular parallelepiped. Then, magnetization is performed in the same manner as in claim 5. Thereby, the same effect as that of the second aspect can be obtained.

Further, according to the invention described in claim 8, the shape of the bias magnet (5) is changed.
Of the bias magnetic field (H2) applied to the rotor (2) from the side farther from the magnetoelectric conversion element (4), and the rotor (2) from the side closer to the magnetoelectric conversion element (4) in the bias magnet (5). ) Applied to the bias magnetic field (H
The shape is larger than 1), and the same effect as in claim 2 can be obtained.

According to the ninth aspect of the present invention, the recess (3d) is formed in the housing (3) in the vicinity of the bias magnet (5) far from the magnetoelectric conversion element (4), so that the bias magnet is formed. The magnetic foreign matter adhering to the portion of (5) where the magnetic field strength is strong can be held by the recess (3d). For this reason, the magnetic foreign matter can be more effectively eliminated from the magnetoelectric conversion element (4).

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION

(First Embodiment) FIG. 1A is an arrangement diagram of a wheel speed sensor. FIG. 1B is an enlarged view of FIG.
As shown in FIGS. 1 (a) and 1 (b), the wheel speed sensors are respectively disposed in the vicinity of a gear-shaped rotor 2 provided inside each wheel 1 of a vehicle having four wheels. Specifically, the wheel speed sensors are arranged at a minute interval from the outer peripheral surface of the rotor 2.

FIG. 2 is an enlarged view of the vicinity of the wheel speed sensor in FIG. As shown in FIG. 2A, the wheel speed sensor includes a housing 3 having a magnetically sensitive surface 3a, and a magnetoresistive element (hereinafter, referred to as MRE) 4 serving as a magnetoelectric conversion element.
Is provided with a sensing unit. This is to detect the rotation of the wheel 1 by the sensing unit sensing the magnetic field change of the bias magnet 5 accompanying the rotation of the wheel 1.

In the above configuration, the housing 3 is formed of a non-magnetic metal, for example, a resin. MRE4 is a ferromagnetic magnetoresistive thin film element, for example, Ni-Co, Ni-Fe
And the like. In this embodiment, a vertical arrangement in which the longitudinal direction of the housing 3 is perpendicular to the axial direction of the rotor 2 is adopted. This MR
E4 is incorporated in a substrate such as a Si substrate formed in a circuit board, and a signal processing circuit for amplifying a signal from the MRE 4 and binarizing the signal is formed on the circuit board. The circuit board is mounted on a lead frame 7, and the circuit board and the lead frame 7 are molded by a mold resin (mold member) 6. However, a part of the lead frame 7 is exposed from the mold resin 6 as a terminal 7a for making an electrical connection with the outside.

The circuit board, the mold resin 6 and the lead frame 7 are provided so as to extend in the longitudinal direction of the housing 3, and the terminal 7 a is connected to an electronic control unit (not shown) via a wire harness 8 attached to the housing 3. The ECU is connected to, for example, an ECU for an ABS control device, and performs ABS control based on a signal generated by the wheel speed sensor.

The bias magnet 5 has a substantially rectangular parallelepiped shape.
The bias magnet 5 is fixed to a housing 6a formed on one side of a mold resin 6 including a circuit board.
The housing 6a is formed such that the center of the bias magnet 5 is offset from the MRE 4 by a predetermined distance. In the conventional wheel speed sensor, the bias magnet 5
Has a cylindrical shape, so that the entire wheel speed sensor is large. However, in the present embodiment, the size of the entire wheel speed sensor is also compact because the size of the bias magnet 5 is reduced to a rectangular parallelepiped. . For this reason, it is particularly effective to dispose the brakes and suspensions in the vicinity of the wheel 1 where there is little space, for example, because it is necessary to dispose the brakes and suspensions.

As shown in FIG. 2B, the housing 3 is provided with a fixing portion 3c provided with a hole 3b, and the housing 3 is fixed to a vehicle via a bolt (not shown) through the hole 3b. ing. FIG. 3 is an explanatory diagram showing the magnetic field strength of the wheel speed sensor configured as described above. The bias magnet 5 is magnetized so that the magnetic field strength increases as the distance from the MRE 4 increases. As shown in FIG. 3, the relationship between the magnetic field strength H1 on the side closer to the MRE 4 and the magnetic field strength H2 on the far side of the bias magnet 5 satisfies H1 <H2 as shown in FIG.

Because of this relationship, the wheel 1
Is rotated, and a magnetic foreign substance such as iron powder is present, the magnetic foreign substance adheres to the bias magnet 5 on the side far from the MRE 4. Therefore, there is almost no magnetic foreign matter in the portion of the magneto-sensitive surface 3a where the MRE 4 is arranged.
Further, even if the magnetic foreign matter adheres to the magneto-sensitive surface 3a on the MRE 4, the rotation of the MRE 4 is detected in a weak magnetic field. MRE4 blown out or in bias magnet 5
Move to the far side from. For this reason, M
The effect on RE4 can be eliminated.

As a result, the magnetic field of the bias magnet 5 changes satisfactorily with the rotation of the wheel 1 on the MRE 4 without being affected by the magnetic foreign matter. Therefore, the MRE 4 can detect the rotation of the wheel 1 satisfactorily. As described above, the present invention is effective in a wheel speed sensor which is disposed in a bad environment near the wheel 1 where many magnetic foreign substances are present. (Second Embodiment) FIG. 4 is an enlarged explanatory view of a wheel speed sensor according to the present embodiment. Since the basic configuration of the wheel speed sensor is the same as that of the first embodiment, only different points will be described. The difference from the wheel speed sensor according to the first embodiment is that the shape of the housing 3 is changed as shown in FIG. Specifically, a recess 3d is provided in the housing 3 near the bias magnet 5 farther from the MRE 4 to reduce the distance between the bias magnet 5 and the outside of the housing 3.

The magnetic field strength of the bias magnet 5 is the same as that of the first embodiment. The magnetic field strength H2 of the bias magnet 5 farther from the MRE 4 is stronger than the magnetic field strength H1 of the closer magnet. Has become. Further, the intensity of the magnetic field generated by the bias magnet 5 is stronger in the two-dot chain line portion shown in FIG. Thus, the recess 3d is provided, and the bias magnet 5 and the housing 3 are provided.
Since the distance to the outside is reduced, it is possible to more effectively adhere the magnetic foreign matter. That is, since the magnetic foreign matter adheres in the region where the magnetic field intensity is maximum, the magnetic foreign matter can be further effectively removed from the MRE 4 by adopting the shape as in the present embodiment. (Third Embodiment) FIGS. 5A and 5B are enlarged explanatory views of a wheel speed sensor according to the present embodiment. Since the basic configuration of the wheel speed sensor is the same as that of the first embodiment, only different points will be described.

The difference from the wheel speed sensor of the first embodiment is that the wheel speed sensor is
And the magnetic sensing surface 3e facing the rotor 2 is formed by changing the shape of the bias magnet 5, and the magnetic field direction of the bias magnet 5 is changed. Specifically, the housing 3 of the wheel speed sensor
Are arranged horizontally with the longitudinal direction being parallel to the axial direction of the rotor 2.

Further, as shown in FIG.
Is formed as a plane parallel to the axial direction of the rotor 2,
As shown in FIG. 6, the bias magnet 5 is magnetized so that the relationship between the magnetic field strength H1 near the MRE 4 and the magnetic field strength H2 far from the MRE 4 satisfies H1 <H2. Because of such a relationship, the magnetic foreign matter adheres to the side of the bias magnet 5 far from the MRE 4, and the same effect as in the first embodiment can be obtained. (Fourth Embodiment) FIG. 7 is an enlarged explanatory view of a wheel speed sensor according to the present embodiment. Note that the basic configuration of this wheel speed sensor is the same as that of the second embodiment, and therefore only the differences will be described.

The different points from the wheel speed sensor according to the second embodiment are that the wheel speed sensor
And the magnetic sensing surface 3e facing the rotor 2 is formed by changing the shape of the bias magnet 5, and the magnetic field direction of the bias magnet 5 is changed. Specifically, the magneto-sensitive surface 3e is formed similarly to the third embodiment, and the bias magnet 5 is magnetized similarly to the third embodiment.

With such a configuration, since the concave portion 3d is provided as in the wheel speed sensor in the second embodiment, the magnetic foreign matter can be further effectively removed from the MRE 4. (Other Embodiments) In the first and second embodiments, the magnetic field strength H1 closer to the bias magnet 5 than the MRE 4 is.
The relationship of H1 <H2 in the magnetic field strength H2 on the far side is satisfied by changing the magnetization of the bias magnet 5, but is not limited to this. For example, as shown in FIG. The above relationship may be satisfied from the shape of the magnet 5. Also, in the third and fourth embodiments, the above-described relationship may be satisfied from the shape of the bias magnet 5 as shown in FIG. 8B.

In the first to fourth embodiments, MRE4
The structure is such that the bias magnet 5 is not provided on a surface perpendicular to or parallel to the axial direction of the rotor 2 passing therethrough, in order to more reliably remove magnetic foreign matter from near the MRE 4. Even if a part of the bias magnet 5 is applied to the surface, the magnetic foreign matter can be eliminated. Further, in the second and fourth embodiments, the recess 3d is provided to widen the area so that the magnetic foreign matter is more effectively attached. However, the present invention is not limited to this.
A similar effect can be obtained if the shape is such that the distance between the bias magnet 5 and the outside of the housing 3 is reduced.

Although the wheel speed sensor is arranged at the position shown in FIG. 1, it is not limited to the position shown here. For example, the wheel speed sensor may be located at any angle of 360 degrees on the outer periphery of the rotor 2.

[Brief description of the drawings]

FIG. 1 is a layout view of a wheel speed sensor according to an embodiment of the present invention.

FIG. 2A is an explanatory diagram in which the vicinity of a wheel speed sensor in FIG. 1 is enlarged, and FIG. 2B is a side view of FIG.

FIG. 3 is an explanatory diagram of a magnetic field intensity of a bias magnet 5 in FIG.

FIG. 4 is an explanatory diagram of a wheel speed sensor according to a second embodiment.

FIG. 5 is an explanatory diagram of a wheel speed sensor according to a third embodiment.

6 is an explanatory diagram of the magnetic field strength of the bias magnet 5 in FIG.

FIG. 7 is an explanatory diagram of a wheel speed sensor according to a fourth embodiment.

FIG. 8 is an explanatory diagram of a bias magnet 5 according to another embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Wheel, 2 ... Rotor, 3 ... Housing, 3a, 3e ...
Magnetic sensing surface, 4 ... Magnetic resistance element (MRE), 5 ... Bias magnet.

Claims (10)

[Claims] 1. A gear-shaped rotor (2) which is provided near a wheel (1), rotates with the rotation of the wheel (1), and is arranged to face the rotor (2). A bias magnet (5) for generating a bias magnetic field; and a magnetoelectric conversion element (4) for detecting rotation of the rotor (2) based on a change in the bias magnetic field. The bias magnetic field intensity (H2) applied to the rotor (2) from a side farther from the conversion element (4) is changed from the side of the bias magnet (5) closer to the magnetoelectric conversion element (4). ), Which is larger than the bias magnetic field intensity (H1) applied to the wheel speed sensor. 2. A wheel-shaped rotor (2) which is provided near a wheel (1) and which rotates with the rotation of the wheel (1). A bias magnet (5) for generating a bias magnetic field, a magnetoelectric conversion element (4) for detecting rotation of the rotor (2) based on a change in the bias magnetic field, and a signal transmitted from the magnetoelectric conversion element (4). A circuit board, the bias magnet (5) is provided only on one side of the circuit board, and the center of the bias magnet (5) and the magnetoelectric conversion element (4) are offset and arranged at a predetermined distance from each other; The bias magnetic field intensity (H2) applied to the rotor (2) from a side of the bias magnet (5) far from the magnetoelectric conversion element (4) is determined by the magnetoelectric conversion element of the bias magnet (5). Close from (4) Wheel speed sensors, characterized in that is larger than the bias field intensity applied from the side to the rotor (2) (H1). 3. A housing (3) including the magnetoelectric conversion element (4) and the bias magnet (5), and having a magneto-sensitive surface (3a) facing the rotor (2). The wheel speed sensor according to claim 2, wherein the wiring board extends in a longitudinal direction of the housing (3), and the wiring board is disposed perpendicular to an axial direction of the rotor (2). 4. A housing (3) including the magnetoelectric conversion element (4) and the bias magnet (5) and having a magneto-sensitive surface (3e) facing the rotor (2), wherein the circuit board is 3. The wheel speed sensor according to claim 2, wherein the circuit board extends in a longitudinal direction of the housing, and the circuit board is arranged in parallel with an axial direction of the rotor. 5. A rotor provided in the vicinity of a wheel (1) and arranged so as to face a gear-shaped rotor (2) rotating with the rotation of the wheel (1), and facing the rotor (2). A bias magnet (5) having a substantially rectangular parallelepiped shape for generating a bias magnetic field, a magnetoelectric conversion element (4) for detecting rotation of a rotor (2) based on a change in the bias magnetic field, and a magnetoelectric conversion element (4). A circuit board that transmits the signal of the bias magnet (5), the bias magnet (5) is provided only on one side of the circuit board, and a surface of the bias magnet (5) facing the rotor (2), The rotor (2) from a side of the bias magnet (5) far from the magnetoelectric conversion element (4).
Is larger than the bias magnetic field intensity (H1) applied to the rotor (2) from the side of the bias magnet (5) closer to the magnetoelectric conversion element (4). A wheel speed sensor characterized in that the wheel speed sensor is magnetized. 6. A gear-shaped rotor (2) provided near the wheel (1) and rotating with the rotation of the wheel (1), facing the rotor (2). A bias magnet (5) for generating a bias magnetic field, a magnetoelectric conversion element (4) for detecting rotation of the rotor (2) based on a change in the bias magnetic field, and a signal transmitted from the magnetoelectric conversion element (4). A circuit board, wherein the magneto-electric conversion element (4) and the circuit board are integrally formed by being included in a mold member (6); and the bias magnet (5) is formed by the magneto-electric conversion of the mold member (6). A housing part (6a) formed on one side of a plane perpendicular to the axial direction of the rotor (2) passing through the element (4)
The bias magnetic field strength (H2) applied to the rotor (2) from the side of the bias magnet (5) far from the magnetoelectric conversion element (4) is determined by the bias magnet (5). A wheel speed sensor characterized in that the bias magnetic field intensity (H1) applied to the rotor (2) from a side closer to the magnetoelectric conversion element (4) is larger than the bias magnetic field intensity (H1). 7. The bias magnet (5) has a substantially rectangular parallelepiped shape having a constant thickness in the bias magnetic field direction, and is far from the magnetoelectric conversion element (4) of the bias magnet (5). The bias magnetic field intensity (H2) applied to the rotor (2) from the side closer to the bias magnetic field applied to the rotor (2) from the side closer to the magnetoelectric conversion element (4) of the bias magnet (5). The wheel speed sensor according to claim 6, wherein the magnetization is magnetized so as to be greater than the strength (H1). 8. The thickness of the bias magnet (5) in the direction of the bias magnetic field is such that the side of the bias magnet (5) that is farther from the magnetoelectric conversion element (4) has the thickness of the bias magnet (5). The wheel speed sensor according to claim 6, wherein the wheel speed sensor is formed so as to be thicker than a side closer to the magnetoelectric conversion element (4). 9. Built-in bias magnet (5) and magneto-electric conversion element (4), having magneto-sensitive surfaces (3a, 3e) between magneto-electric conversion element (4) and rotor (2). A housing (3), wherein the housing (3) has a concave portion (3d) for holding a magnetic foreign matter in the vicinity of the bias magnet (5) far from the magnetoelectric conversion element (4). The wheel speed sensor according to any one of claims 6 to 8. 10. A bias magnetic field which is provided near a wheel (1) and is arranged to face a rotor (2) moving with the rotation of the wheel (1), and applies a bias magnetic field toward the rotor (2). A bias magnet (5) generated, a magnetoelectric conversion element (4) for detecting rotation of the rotor (2) based on a change in the bias magnetic field, and the bias magnet (5) and the magnetoelectric conversion element (4). Built-in, said magneto-electric conversion element (4) and said rotor (2)
A housing (3) having a magneto-sensitive surface (3a, 3e) between the housing and the housing (3), wherein the housing (3) is a magnetic material near the bias magnet (5) far from the magnetoelectric conversion element (4). A wheel speed sensor having a concave portion (3d) for holding a foreign object.