JPS6341830Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to an improvement of a small DC motor using a permanent magnet as a field pole.

In small DC motors that use permanent magnets as field poles, the magnetic flux density in the gap between the field poles and the rotor can be increased by making the opposing area of the field poles facing the rotor as large as possible. However, in motors manufactured for special applications where the radial dimensions of the motor are limited, it is difficult to obtain sufficient magnetic flux with the permanent magnet field poles.

The applicant proposed the motor shown in FIG. 1 as a solution to the above problem.

That is, 1 is a rotor, 2 is a shaft, and 3 is a commutator, and one plate-shaped magnet 4 whose magnetic pole is oriented in the axial direction of the rotor is arranged near the end of the rotor in the axial direction. , the plate-shaped magnet has a magnetic pole plate surface,
One end side of each plate-shaped magnetically permeable body 5, 6 is brought into contact with the plate-shaped magnetically permeable body 5, 6, and the other end side of the magnetically permeable body 5, 6 is opposed to the circumferential surface of the rotor 1 with a required gap therebetween.

According to the above configuration, it has been revealed that the field poles can be adapted to the limitations of the radial dimension of the motor, and that the magnetic flux density can be improved by appropriately determining the thickness of the plate magnet. However, even if the thickness of the plate magnet is doubled, the magnetic flux does not double, and the problem is that the rate of increase is small.

The structure shown in FIG. 2 is a structure in which two magnets 4 are stacked, and the graph in FIG. 3 shows the BH curve thereof. In the figure, B represents the magnetic flux density, H represents the magnetic field strength, and Ha represents the magnetic field strength of one magnet.

As shown in the graph above, in the case of one magnet
Compared to the BH curve (shown by the solid line), when we look at the BH curve for two magnets (shown by the dotted line), even if the operating point changes from point a to point a', the magnetic flux density remains constant. The rate of increase from Ba to Ba' is extremely small.

This idea was made in order to solve the above problem, and in particular, the magnet that serves as the excitation source is placed near the end of the rotor in the axial direction, and the magnetic flux generated on the magnetic pole surface is transmitted through a magnetically permeable material. An object of the present invention is to provide a small DC motor in which the magnetic flux density can be increased approximately in proportion to the number of magnets used in the small DC motor in which the magnetic flux is guided to a portion facing the circumferential surface of the rotor through the magnets. It is something.

In the small DC motor according to this invention, a plurality of plate-shaped magnets with magnetic pole faces facing in the axial direction of the rotor are arranged near the outer end of the rotor in the axial direction, and each of the magnets is spaced apart from each other. On the NS magnetic pole face of
It is characterized by a structure in which magnetically permeable bodies are placed in contact with each other to collect the magnetic flux generated on the magnetic pole faces and guide it to a portion facing the circumferential surface of the rotor.

Hereinafter, this invention will be explained in detail based on drawings showing various embodiments thereof.

In Fig. 4, 1 is a rotor, 2 is a shaft, and 3 is a commutator, and near the outer end of the rotor 1 in the axial direction, there are two magnetic poles whose magnetic pole faces are oriented in the axial direction of the rotor. Plate magnets 4, 4 are arranged at intervals, and magnetically permeable materials 5a, 5a and 5a are respectively arranged on the NS magnetic pole surfaces of the magnets 4, 4.
One end side of 5b, 6a, 6b is brought into contact with the other end side, and the same polarity is overlapped with each other and positioned on the circumferential surface of the rotor.

As described above, according to the configuration in which the two magnets are independent and the magnetic flux generated on the magnetic pole surface of each magnet is collected and guided to the opposing portion of the circumferential surface of the rotor,
Since each magnet operates with a magnetic flux density Ba (see FIG. 3), the magnetic flux density in the air gap between the rotor and the magnetically permeable body is increased to approximately twice said magnetic flux density Ba.
Therefore, according to the above configuration, even when the radial dimension of the motor is limited, a high-performance compact DC motor can be obtained using inexpensive ferrite magnets.

The one shown in FIG. 5 is another embodiment of this invention, in which a thick magnetically permeable body 5 is commonly brought into contact with the same magnetic pole surface where two magnets 4, 4 face each other. According to this configuration, since the number of magnetically permeable bodies is reduced, the structure can be simplified accordingly. Further, a bearing (not shown) is provided on the thick magnetically permeable body 5, and after the shaft 2 of the rotor 1 is supported by this, the two-piece holed magnet 3 shown in FIG. 5A is arranged, By arranging the fork-shaped magnetically permeable body 5a shown in FIG. 5B, a structure that can be easily assembled automatically can be obtained.

The one shown in FIG. 6 is another embodiment of this invention, in which two magnets 4, 4 are provided on each side of the rotor, four magnetically permeable bodies 5a, 5b,
The structure is such that the magnetic flux is collected at 6a and 6b and guided to a portion facing the circumferential surface of the rotor. According to this configuration, the magnetic flux density Ba can be increased approximately four times.

As described above, according to this invention, a plurality of plate-shaped magnets are arranged separately and independently at the outer end of the rotor in the axial direction, and the magnetic flux generated on the magnetic pole surface of each magnet is transparent. Since the magnetic flux is collected on the opposing peripheral surface of the rotor via the magnetic material, the magnetic flux density in the air gap between the rotor and the magnetically permeable material facing the rotor increases approximately in proportion to the number of magnetic fluxes used. Therefore, a high-performance compact DC motor can be obtained using inexpensive ferrite magnets.

[Brief explanation of the drawing]

Figure 1 is a side view of a small DC motor related to this invention, Figure 2 is a side view of an improved motor, Figure 3 is a graph of the BH curve, and Figures 4 to 6 are implementations of this invention. FIG. 5A is a side view of a small DC motor showing an example, FIG. 5A is a perspective view of a magnet, and FIG. 5B is a perspective view of a magnetically permeable body. 1...Rotor, 2...Shaft, 3...Commutator, 4...
...Plate magnet, 5, 6, 5a, 5b, 6a, 6b...
...Magnetically permeable material.

Claims (1)

[Scope of utility model registration request] Near the outer end of the rotor in the axial direction, a plurality of plate-shaped magnets with magnetic pole faces facing in the axial direction of the rotor are arranged separately and independently, and the NS of each plate-shaped magnet is
A small DC motor characterized in that a magnetically permeable body is brought into contact with each of the magnetic pole faces for collecting magnetic flux generated on the magnetic pole faces and guiding it to a portion facing the circumferential surface of the rotor.