JP2001165946A - Rotational speed detector and rotary shaft used for the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the manufacturing cost, improve the detection accuracy and reduce the size. SOLUTION: The detector detects rotational speed by magnetic field change that a rotation sensor 3 facing a shaft receives due to the rotation of a rotary shaft 1. A magnetic pattern 6 that causes magnetic field change on the circumferential surface of the rotary shaft 1 is formed directly. As a result of this, the material cost and machining cost can be reduced to without producing a magnetic field pattern ring and the like as additional parts. The rotary shaft 1 generally has highly accurate dimension and the magnetic pattern formed on the circumferential surface of the rotary shaft with high accuracy dimensions is easily distinguished. So the gap between the sensor and the rotary shaft (magnetic pattern) can be set small, and very weak magnetization can be detected. Accordingly, by increasing the number of magnetic poles of the magnetic pattern and pulse number per revolution, the lowering of detection accuracy in a low revolution number can be restricted. In the case of the same number of magnetic poles, the diameter can be reduced and thus, it is advantageous for making it small in size.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for detecting a rotational speed of a wheel or the like of an automobile and a rotary shaft used for the apparatus.

[0002]

2. Description of the Related Art A device for detecting the rotational speed of a wheel or the like of an automobile is generally provided with a function of generating a magnetic field variation corresponding to the rotational speed on its rotating shaft, and the magnetic field variation is detected by a sensor. is there. For example, Japanese Patent Application Laid-Open No. 2-102
271 (Publication 1) and JP-A-9-138240 (Publication 2).

In the technique described in the former publication 1, as shown in FIG. 2, a magnetic rotor 2 is mounted on a rotating shaft 1 and a sensor 3 comprising a magnet 3a and a Hall element 3b is opposed to the magnetic rotor 2. Provided by the sensor 3
Magnetic protrusions 2 on the peripheral surface of the magnetic rotor 2 due to rotation of the rotor 2
The rotation speed is detected by detecting a change in the magnetic field due to a.

In the technique disclosed in the latter publication 2, as shown in FIG. 3, a magnet rotor 5 is fitted on a rotating shaft 1 and a sensor 3 similar to the above is provided on the magnet rotor 5 so as to face the same. A magnetic pattern 5a in which N poles and S poles are alternately arranged is formed on the circumferential surface of the magnet rotor 5, and the sensor 3 detects the magnetic field generated by the magnetic pattern 5a accompanying the rotation of the magnet rotor 5. By detecting the change, the rotation speed is detected.

[0005]

SUMMARY OF THE INVENTION
In each of the conventional technologies, a magnetic rotor 2 or a magnet rotor 5 that generates a magnetic field change is provided on a rotating shaft 1. Since the magnetic rotor 2 and the like are separate components, an operation of attaching the magnetic rotor 2 and the like to the rotating shaft 1 and material and processing costs of the magnetic rotor 2 and the like are required. Further, since this kind of rotation speed detecting device is mounted in a narrow place, the size of the device is increased due to the presence of the magnetic rotor 2 and the like, and there is a limit in meeting the need for downsizing.

SUMMARY OF THE INVENTION It is an object of the present invention to reduce costs and reduce the size of the entire apparatus under the above-mentioned circumstances.

[0007]

In order to achieve the above object, according to the present invention, a magnetic pattern is formed directly on a rotating shaft. In this way, it is not necessary to manufacture the magnetic rotor or the like as a separate component, so that material costs and processing costs can be reduced, and cost can be reduced. In addition, the rotating shaft generally has high dimensional accuracy, and the gap between the sensor and the rotating shaft (magnetic pattern) can be set small, so that the sensor can detect even a small amount of magnetization. Therefore, by increasing the number of magnetic poles of the magnetic pattern, the number of pulses per rotation (information amount)
And a decrease in detection accuracy at a low rotation speed can be reduced. Also, when the number of magnetic poles is the same, the outer diameter of the rotating shaft (magnetic pattern) can be reduced, which is advantageous for miniaturization.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As a preferred embodiment of a rotational speed detecting device according to the present invention, a sensor is provided so as to face a rotating shaft.
In a device that detects the rotation speed by the change in the magnetic field received by the sensor due to the rotation of the rotation shaft, a configuration may be employed in which a magnetic pattern that causes the magnetic field change is formed directly on the peripheral surface of the rotation shaft.

Further, in the embodiment of the rotating shaft according to the present invention, a configuration in which a magnetic pattern for causing the above-mentioned magnetic field change is directly formed on a peripheral surface thereof may be adopted.

As the means for forming the magnetic pattern, various well-known means can be employed. For example, a method using a magnetized yoke or the like is employed. The magnetic pattern distribution is
Any may be used as long as a magnetic field change occurs, but in general,
It is assumed that N poles and S poles are provided alternately and periodically in the circumferential direction.

[0011]

FIG. 1 shows an embodiment of the present invention. In this embodiment, a peripheral surface of a rotating shaft (axle) 1, which is a shaft of a wheel, is provided with N
A magnetic pattern 6 in which poles and S poles are alternately arranged is formed. The number of the north pole and the south pole is appropriately determined in consideration of the diameter of the rotating shaft 1, the required detection accuracy, and the like.

The above-mentioned sensor 3 is provided to face the magnetic pattern 6 of the rotating shaft 1. The sensor 3 detects a change in the magnetic field due to the magnetic pattern 6 accompanying the rotation of the rotating shaft 1 and detects the number of rotations.

[0013]

As described above, according to the present invention, since the magnetic pattern is formed directly on the rotating shaft, the cost can be reduced, the detection accuracy can be improved, and the apparatus can be downsized.

[Brief description of the drawings]

FIG. 1 is a perspective view of a main part of an embodiment.

FIG. 2 is a sectional view of a main part of a conventional example.

FIG. 3 is a perspective view of a main part of a conventional example.

[Description of Signs] 1 Rotary axis 3 Sensor 6 Magnetic pattern

Claims (2)

[Claims] 1. A device for providing a sensor (3) opposite to a rotating shaft (1) and detecting a rotation speed of the rotating shaft (1) by a change in a magnetic field applied to the sensor (3). A rotation speed detecting device, wherein a magnetic pattern 6 for causing the magnetic field change is formed directly on the surface. 2. A rotating shaft 1 used in the rotating speed detecting device according to claim 1, wherein a magnetic pattern 6 for causing the magnetic field change is formed directly on a peripheral surface thereof. Axis of rotation.