JPH07243865A - Magnetic rotor for tachometer - Google Patents

Abstract

PURPOSE:To provide a magnetic rotor for a tachometer which continues to give a high output without any corrosion or magnetism reduction even under strict usage conditions. CONSTITUTION:A magnetic rotor for a magnetic tachometer which is a component of the ABS device of an automobile protects the outer-periphery surface and upper and lower surfaces of a ring magnet 2 by fixing the ring magnet 2 formed by Nd permanent magnet to a holder 1 which is manufactured by a corrosion-resistance metal plate, and further a weather resistant plastic seal member 3 is applied to the inner-periphery surface for sealing. In this manner, the ring magnet 2 is insulated from external air and corrosion can be completely prevented, thus obtaining a tachometer which can be used for a long time even if the easily rust-forming Nd permanent magnet is used.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to improvements in magnetic rotors for use in tachometers.

[0002]

2. Description of the Related Art For example, as a tachometer used for an ABS device of an automobile, a magnetic tachometer in which a ring-shaped magnet and a magnetic detection element are combined is used. As this ring magnet, an Nd-based permanent magnet that can obtain a high magnetic flux density is suitable, and it is generally manufactured by injection molding the magnet alloy powder using a plastic binder. Since the ring magnet must be held coaxially with the rotating shaft for measuring the number of rotations, but separated magnetically, it is fixed to a magnet holder made of a non-magnetic material and attached to the rotating shaft.

However, Nd-based magnets have a drawback in that they are easily rusted, and in applications where the operating environment is harsh, such as ABS devices, they rust in a short time, and demagnetization is so great that they are no longer useful. The marked changes in temperature and the sprinkling of salt on the road surface in winter make the usage conditions severe in this application. Conventionally, a thin plate made of a corrosion-resistant metal such as SUS304 is used for the magnet holder.
Also, as shown in FIG. 2, a structure in which the outer periphery and the upper and lower surfaces of the ring magnet (2) are protected by the case member (12) of the holder (1) has been adopted, but it was insufficient.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a tachometer magnetic rotor which continues to provide a high output without being corroded or demagnetized even under severe conditions of use.

[0005]

As shown in FIG. 3, a magnetic rotor according to the present invention is a ring magnet (2) in which an Nd-based permanent magnet is formed into a ring shape and the outer peripheral portion or the flat portion is magnetized to have multiple poles. ) Is fixed to a holder (1) made of a non-magnetic material, which is coaxial with the axis of rotation but is magnetically separated, and a ring magnet (2)
The outer peripheral surface and both upper and lower flat surfaces are covered with a corrosion-resistant metal plate case member (12), and the inner peripheral surface is covered with a weather-resistant plastic sealing material (3).

The holder (1) comprises a cylindrical fixing member (11) into which a rotary shaft is press-fitted, and a case member (12).

As is well known, the Nd-based permanent magnet is used by forming a powder obtained by rapidly cooling a molten metal of a magnet alloy by sintering or bonding. In this case, it is advantageous to use a bonded magnet by injection molding using a plastic binder, which is suitable for mass production and has a low cost. As the plastic binder, a commonly used epoxy resin may be used.

As the corrosion-resistant metal plate, the above-mentioned stainless steel plate (SUS304, SUS316, etc.) or titanium alloy plate is suitable.

The structure of the holder is not limited to the one having the integral structure as shown in FIG. 3, but as shown in FIG. 4, the fixing member (11) and the case member (12) are separately manufactured, and then the holder is manufactured. It may be a structure integrated by welding or adhesion.
In this case, as shown in FIG. 4, the fixing member (11) may be only a cylinder, or as shown in FIGS. 5 and 6, a wide or narrow flange extends from one end of the cylinder and the rest is a case member ( It may be in the form of 12). The welded portion (4) in FIGS. 4 and 6 does not need to extend over the entire circumference, and spot welding at several places is sufficient.

If a sealant having a high adhesiveness with the ring magnet is selected, it will not fall off under normal use conditions, but since it is a magnetic rotor to which vibration is strongly applied in addition to rotation, securing is secured. As described above, it is desirable to devise the cross-sectional shape near the inner circumference of the ring magnet of the case member (12). For example, as shown in FIGS. 5 and 6, the opening has a narrow width.

[0011]

[Function] By coating the outer circumference and upper and lower surfaces of the magnetic rotor of the magnetic rotor with corrosion-resistant metal plates, and further by covering the inner peripheral surface with the sealing material, the ring magnet is completely insulated from the outside, and oxygen, salt water, etc. A structure that prevents anything that causes corrosion from coming near is realized.

[0012]

The magnetic rotor of the present invention has a rust-prone N content.
Even if a d-system permanent magnet is used as a ring magnet, the ring magnet is sufficiently protected and corrosion can be prevented. Therefore, even if it is used for a long time under severe conditions, there is no fear of demagnetization and a high output can be obtained. You can use your own tachometer.

Therefore, the magnetic rotor of the present invention is an automatic A
When used as a BS device, it exhibits its significance best.

[Brief description of drawings]

FIG. 1 is a plan view showing a magnetic rotor of a conventional magnetic tachometer.

FIG. 2 is a vertical cross-sectional view of the magnetic rotor of FIG.

FIG. 3 is a vertical sectional view of a magnetic rotor of the present invention.

FIG. 4 is a vertical cross-sectional view showing another embodiment of the ring magnet holder of the magnetic rotor of the present invention.

FIG. 5 is a partial vertical cross-sectional view showing another embodiment of the magnetic rotor of the present invention.

FIG. 6 is a partial vertical cross-sectional view showing still another aspect of the magnetic rotor of the present invention.

[Explanation of symbols]

 1 Magnet Holder 11 Fixing Member 12 Case Member 2 Ring Magnet 3 Sealing Material 4 Welding Part

Claims (4)

[Claims] 1. A ring magnet, which is formed by molding an Nd-based permanent magnet into a ring shape and has a multi-pole magnetized outer peripheral portion or a flat surface portion, which is coaxial with the rotating shaft but is magnetically separated. In a magnetic rotor for a tachometer fixed to a holder made of magnetic material, the outer peripheral surface and both upper and lower flat surfaces of the ring magnet were covered with a corrosion-resistant metal plate, and the inner peripheral surface was covered with a weather-resistant plastic sealing material. A magnetic rotor characterized by that. 2. The magnetic rotor according to claim 1, wherein a stainless steel plate or a titanium alloy plate is used as the corrosion-resistant metal plate. 3. A sealing material for weather-resistant plastic,
The magnetic rotor according to claim 1, wherein a silicone adhesive, a urethane resin adhesive, or an epoxy resin is used and coating is applied. 4. A sealing material for weather-resistant plastic,
The magnetic rotor according to claim 1, wherein a silicone resin, a urethane resin, or a polyester resin is used and coating is performed by insert injection molding.