JPS6237421Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a field pole of a DC machine, particularly a field pole made of a permanent magnet.

The field structure of a DC motor (used for example to start an internal combustion engine) with field poles of this type is the first
As shown in the figure. 1 is a field structure consisting of a cylindrical yoke 2 generally made of a mild steel member and a field pole 3 made of a permanent magnet (a ferrite magnet is generally used);
It is fixed with adhesive to the inner peripheral surface of. The armature is not shown to simplify the drawing.

When a current flows in the direction shown in the armature conductor 4,
The interaction between this armature current and the magnetic flux generated by the field poles 3 causes the armature to rotate in the direction of the arrow 5. At the same time, magnetic flux 6 due to armature reaction
This causes a demagnetizing effect on one end of the field pole, resulting in the disadvantage that the magnetizing magnetic field of the permanent magnet is demagnetized.

This idea was made in order to eliminate the drawbacks of the conventional device as described above.A groove extending approximately in the direction of rotation of the armature is provided on the arc-shaped magnetic pole face of the field pole facing the armature. By fitting a strip member made of a magnetically permeable material with higher magnetic permeability than the permanent magnet into the groove, the magnetic flux caused by the armature reaction described above is bypassed through the strip member, thereby reducing the demagnetizing effect due to demagnetizing flux. The purpose of the present invention is to provide a field pole for a DC machine that has the following characteristics.

This invention will be explained below with reference to FIGS. 2 and 3. Note that the same parts as those in FIG. 1 are given the same reference numerals. According to this invention, the arc-shaped magnetic pole face 34 of radius R facing the armature of the field pole 3 made of a permanent magnet is provided with a radius R+ larger than the radius R.
A concave groove 35 of ΔR is formed, and a strip member 7 made of a material having higher magnetic permeability than the permanent magnet is fitted therein.

In this way, when the armature is energized and an armature current flows, a magnetic flux is generated due to the armature reaction indicated by the reference numeral 6 in FIG. The magnet is prevented from being demagnetized. The number of strip members 7 (therefore, the number of grooves 35) and the cross-sectional area of the strip members 7 are determined in relation to the coercive force of the permanent magnet, and if set at the limit value that will not cause demagnetization of the permanent magnet, then A sufficient anti-demagnetization function can be obtained without reducing the magnetomotive force too much.

The magnetic flux 6 due to armature reaction is efficiently transferred to the strip member 7.
As shown in FIG. 2, a concave groove 35 is formed over the entire length of the magnetic pole arc from one end 32 to the other end 33 of the field pole 3, and the strip member 7 is fitted over the entire length of this concave groove. It is preferable to do so. As mentioned above, ferrite magnets are generally used as permanent magnets, but the strip member 7 can be made of mild steel, which has a higher magnetic permeability than ferrite magnets. This idea can also be applied to the field poles of generators. The strip member 7 can be fixed to the groove 35 with adhesive.

As described above, according to this invention, a concave groove extending approximately in the rotational direction of the armature is provided on the arc-shaped magnetic pole face facing the armature of a field pole made of a permanent magnet, and the permanent magnet is placed in the concave groove. Since the strip member made of a magnetically permeable material with high magnetic permeability is fitted, most of the magnetic flux due to the armature reaction passes through the strip member, and the demagnetizing effect caused by this magnetic flux is eliminated, resulting in the effect of being obtained at a low cost.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view of the field structure of a DC motor with conventional field poles, Fig. 2 is a front view of the field pole according to this invention, and Fig. 3 is a sectional view taken along the line - in Fig. 2. It is. In the figure, 3 is a field pole, 34 is a magnetic pole surface, 35 is a groove, and 7 is a strip member.

Claims (1)

[Scope of claims for utility model registration] 1. In the field pole of a DC machine made of permanent magnets,
A concave groove extending substantially in the direction of rotation of the armature is provided on the arc-shaped magnetic pole face facing the armature, and a strip member made of a magnetically permeable material having higher magnetic permeability than the permanent magnet is fitted into the groove. The field pole of a DC machine. 2. The field pole of a DC machine according to claim 1, wherein the permanent magnet is a ferrite magnet and the magnetically permeable material is mild steel. 3 The groove extends the entire length of the magnetic pole arc,
A field pole for a DC machine according to claim 1 or 2, wherein a magnetically permeable material is fitted over the entire length of the groove.