JPH07311213A - Sensor device - Google Patents

Abstract

PURPOSE:To provide a rotation-detecting sensor device, in which the components of a magnetic circuit rustproofed and the increase of the reluctance of the magnetic circuit by a rustproof film is prevented while obtaining a rustproof effect and an output therefrom is improved. CONSTITUTION:The nickel film of a magnetic substance is employed as a film 10 formed on the surfaces of a magnet 2 with the object of rust prevention, a core 3 and a yoke 6 housed in a case 1, thus preventing the increase of the reluctance of a magnetic circuit by the rustproof film, and improving an output from a sensor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotation detecting sensor device used for detecting the rotation speed of a wheel of an automobile or a crankshaft of an engine.

[0002]

2. Description of the Related Art A rotation sensor that detects the rotational speed of a rotating body and is currently in the mainstream is an electromagnetic power generation type sensor. This sensor faces a gear-shaped sensor rotor that rotates integrally with the object to be detected to cause magnetic flux coupling between the rotor and the rotor. Induces a voltage according to the rotation speed.

FIG. 3 shows a specific example of this type of sensor. In the figure, 1 is a non-magnetic case (housing), 2 is a magnet housed in the case, 3 is an iron core (pole piece), 4 is a bobbin, 5 is a coil wound around a bobbin 4, 6 is a yoke, and 7 is External resin for sealing the rear part of the case, 8 is a coil terminal, 9
Is an output line.

Sensor rotor SR combined with this sensor
Is a gear-shaped rotor in which peaks and valleys are alternately formed on the outer circumference, and is attached to an axle or the like of which rotation is to be detected and rotates integrally with the axle or the like. The rotation causes the size of the air gap g to change, so that the magnetic flux coupling between the iron core 3 and the sensor rotor SR changes in intensity, and the amount of magnetic flux flowing in the iron core 3 changes, causing the coil 5 to rotate at the rotational speed of the sensor rotor. A corresponding voltage is induced and this is taken out as an output.

In the conventional sensor of this type, the surfaces of the magnet 2, the iron core 3 and the yoke 6 constituting the magnetic circuit are plated with aluminum, zinc, tin or the like having a high anticorrosive effect for the purpose of preventing rust. .

[0006]

Aluminum, zinc, tin and the like are non-magnetic materials, and aluminum also has a large eddy current loss.

In the conventional sensor, this non-magnetic rust preventive coating is present in the middle of the magnetic circuit, which hinders improvement of the magnetic characteristics of the circuit.

Since there is a loss due to the magnetic resistance of the film and a loss due to the eddy current, the output voltage becomes smaller accordingly.
When it is said that the sensor size is limited, it may not be possible to secure performance and the like as desired.

An object of the present invention is to solve the problem of resistance increase due to the rust-preventive plating film and increase the sensor output.

[0010]

In order to solve the above problems, in the present invention, a rust preventive film provided on the surface of a magnetic circuit component is a nickel film.

When the nickel coating is provided on all magnetic circuit components for each component, or on at least one component, the nickel coating is collectively provided on the outer periphery of the assembly after the components are bonded and integrated. There are three possible cases.

[0012]

FIG. 4 (a) shows a combination of the magnet 2, the iron core 3, and the yoke 6 each having the rust preventive coating 10 in the used state. Now, when the anticorrosion coating 10 in the figure is a non-magnetic material,
The electrical equivalent circuit of the magnetic circuit in which the magnetic flux B flows as shown by the arrow is as shown in FIG. The resistor R5 in the figure is due to the air gap between the resistor R5 and the sensor rotor, and changes periodically as the sensor rotor rotates. Resistance R ₁ ~ R
_{No. 4} is due to the film, and the output V ₁ becomes small because this extra resistance is added.

On the other hand, if the film 10 is a magnetic substance,
This is as if there were substantially no resistors R ₁ -R ₄ in the circuit, and therefore the sensor output is increased according to the invention.

[0014]

EXAMPLE FIG. 1 (a) shows an example of the sensor device of the present invention. This rotation sensor is referred to as a pole piece built-in type, and the iron core 3 is enclosed in a non-magnetic case 1 as in FIG. 3, but the iron core 3 is hermetically sealed from the case 1. The present invention is also applied to a pole-piece protruding type sensor that is protruded to face the sensor rotor SR.

Reference numeral 2 is a magnet, 4 is a resin bobbin, 5 is a coil, 6 is a yoke, 7 is an external resin for sealing the rear part of the case, and 8
Is a coil terminal, and 9 is an output line.

This rotation sensor uses a nickel film as a rust preventive film 10 provided by plating on the surfaces of the magnet 2, the iron core 3 and the yoke 6, and other configurations except this point are the same as the conventional sensor of FIG. Is.

As shown in FIG. 1 (b), the anticorrosive coating 10 may be provided individually on each surface of the magnet 2, the iron core 3, and the yoke 6, or, as shown in FIG. 1, the iron core 3 and the yoke. When burying 6 in resin, it is necessary to prevent rust from iron core 3
2 (a), only the iron core 3 may be provided with the nickel anticorrosion coating 10 as shown in FIG. 2 (a). further,
As shown in FIG. 2 (b), three parts are adhered in advance to form an aggregate, and the rust preventive coating 1 is collectively formed on the surface of the aggregate.
You may make it the structure which provides 0. This structure is advantageous in terms of productivity because rust prevention of each part can be performed by a single plating treatment.

The output of the rotation sensor of the present invention thus constructed is improved by 5 to 10% as compared with the conventional product.

[0019]

As described above, according to the present invention,
While protecting the magnetic circuit components from rust while increasing the sensor output by eliminating the increase in magnetic resistance due to the protective coating, a wheel speed sensor for automobiles, where rust prevention treatment is indispensable for exposure to harsh environments, It is particularly effective when used as an engine rotation speed sensor.

[Brief description of drawings]

FIG. 1A is a cross-sectional view showing an example of a sensor of the present invention. FIG. 1B is an enlarged view showing a state in which a nickel anticorrosive coating is formed.

FIG. 2 is a view showing another example of the formation pattern of the nickel anticorrosion coating.

FIG. 3 is a sectional view of a conventional sensor.

FIG. 4A is an explanatory view of operation. FIG. 4B is an electrical equivalent circuit in the case where the coating film in FIG. 4A is a non-magnetic material.

[Explanation of symbols]

 1 Case 2 Magnet 3 Iron core 4 Bobbin 5 Coil 6 Yoke 7 External resin 8 Coil terminal 9 Output wire 10 Rust-proof coating SR Sensor rotor g Air gap

Claims (3)

[Claims] 1. A magnetic circuit component including a magnet is housed in a case, magnetic flux from the magnet is transmitted to a gear-shaped sensor rotor through an air gap, and the strength of magnetic flux coupling changes with the rotation of the sensor rotor. A sensor device for rotation detection that extracts an output signal according to the rotation speed of a sensor rotor, characterized in that a rust-proof coating of nickel is provided on the surface of each of the magnetic circuit components. 2. A sensor device in which the nickel anticorrosive coating is provided on at least one of magnetic circuit components. 3. A sensor device in which the nickel anticorrosive coating is provided on the surface of an assembly of magnetic circuit component parts that are adhesively fixed.