JPS644298Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic circuit for generating a driving magnetic field for a DC motor.

In this type of magnetic circuit, in which an even number of pole pieces are combined radially, leaving a cylindrical space in the central shaft portion for accommodating the rotor, Alnico cast magnets have traditionally been widely used as the magnetic field source. However, although this permanent magnet has a high magnetic flux density, it is expensive, and from an economic point of view, it is preferable to use a ferrite magnet. However, ferrite magnets have a low residual magnetic flux density, and in order to obtain a magnetic field strength comparable to that of a magnetic circuit using alnico cast magnets, it is necessary to make major improvements to the magnetic circuit structure.

FIG. 1 shows one of the conventional magnetic circuits that meet this requirement. This magnetic circuit consists of a cylindrical frame 1 made of a non-magnetic material, an even number of pole pieces 2 made of laminated silicon steel plates, etc., arranged radially around the center axis with a cylindrical space 3 for accommodating the rotor. Permanent magnets 4 are arranged between adjacent pole pieces 2 so that the same magnetic poles face each other, and different magnetic poles are formed on the inner peripheral surface 5 of each pole piece 2. .

In this magnetic circuit, the permanent magnet 4 is sandwiched between the pole pieces 2, and the magnetic pole surface can be made wider compared to the size of the magnet, so it is possible to use an inexpensive ferrite magnet with high magnetic efficiency. In order to obtain a good magnetic field balance and a high degree of dimensional accuracy,
Since high dimensional accuracy is required for the pole piece 2 and the permanent magnet 4, and even higher assembly accuracy is also required, there is a problem in that the assembly work is significantly complicated.

That is, in this magnetic circuit, pole piece 2
Since the permanent magnet 4 and the permanent magnet 4 form one cylindrical body, if there is a dimensional error or assembly error in these, a gap may occur at the joining surface of the two or the roundness of the cylindrical body may deteriorate. , which disrupts the magnetic field balance generated in the cylindrical space 3 inside the cylinder. In addition, since high concentricity is required between the magnetic circuit and the rotor inserted therein, in the magnetic circuit described above, it is difficult to obtain sufficient dimensional accuracy. It is necessary to finish the inner circumferential surface 5 of the magnetic circuit, which further complicates the assembly work of the magnetic circuit.

In order to solve this problem, the present invention has an even number of pole pieces 2 arranged in a radial manner, leaving a cylindrical space 3 for accommodating the rotor in the central shaft part, so that each pole piece 2 has the same number of pole pieces 2 in the circumferential direction. A pair of annular permanent magnets 4', 4' forming a magnetic pole surface,
The pair of annular permanent magnets 4', 4' are sandwiched from both ends in the central axis direction so that the same magnetic pole surfaces face each other, and the magnetic efficiency is improved because the magnetic pole surfaces of each permanent magnet 4 can be made wide. Not only is it possible to use inexpensive ferrite magnets with high ferrite magnets, but also because the cylindrical space 3 is formed only with the pole pieces 2 without the permanent magnet 4 being sandwiched between the pole pieces 2, there is no possibility that the permanent magnet 4 will be slightly misaligned. Even if there is a problem, the magnetic field balance will not be adversely affected, and the permanent magnet 4 can be installed extremely easily.

Hereinafter, the magnetic circuit of the present invention will be explained in detail based on FIGS. 2 and 3.

Fig. 2 is a perspective view partially showing the overall structure of an example of a magnetic circuit embodying the present invention in cross section, and Fig. 3 shows the pole piece 2, annular permanent magnet 4', and yoke 6 of the same magnetic circuit. This is an exploded view showing the positional relationship, and shows a case where there are four pole pieces 2, that is, a four-pole magnetic circuit for a DC motor.

According to FIG. 2, inside the cylindrical frame 1 made of non-magnetic material such as aluminum die-cast,
Four pole pieces 2 made of laminated silicon steel plates, etc.
It is fixed to the cylindrical frame 1 by screwing or the like radially and axially symmetrically, leaving a cylindrical space 3 for accommodating the rotor at the central axis l portion.

The cylindrical frame 1 is not essential for configuring this magnetic circuit, and is simply a part of the pole piece 2.
It is used as a fixing means. Therefore, if the pole piece 2 is temporarily fixed with a jig or the like and then integrated with a resin or the like, the pole piece 2 can be fixed without using the cylindrical frame 1.

Although the number of pole pieces 2 is four in this embodiment, it may be an even number such as two or eight, and the structure is not limited to a laminated structure, but may also be an integral piece of magnetic material, and the shape can also be changed. It is not limited to the examples.

As shown in FIGS. 2 and 3, the assembly of pole pieces 2 combined radially extends from both ends of the assembly in the direction of the central axis l to annular permanent magnets 4', 4' within the cylindrical frame 1. It's sandwiched in between. The annular permanent magnets 4', 4' fixed to the pole piece 2 with adhesive or the like are magnetized into four parts in the circumferential direction corresponding to the pole piece 2, and the magnetic pole structure is similar to that of the pole piece 2. Each pole piece 2 is sandwiched between magnetic pole faces of the same polarity, and the polarity of the magnetic pole faces that sandwich the pole piece 2 is changed for each pole piece 2.

The individual annular permanent magnets 4', 4' magnetized separately in the circumferential direction are attached to annular yokes 6, 6 that are fixed to the magnetic pole surface on the opposite pole piece side of each annular permanent magnet 4', 4' with adhesive or the like. are coupled to form a magnetic path on the anti-pole piece side. York 6,
Similarly to the annular permanent magnets 4', 4', the magnets 6 are located inside the cylindrical frame 1, and have their central axes aligned with the central axis l of the assembly of pole pieces 2.

In this embodiment, the individual annular permanent magnets 4', 4' located on the same end side are annular permanent magnets made of one piece, in order to facilitate the production and assembly of the annular permanent magnets 4', 4'. The magnet material used is magnetized into four parts in the circumferential direction according to the number of poles of the magnetic circuit, but the invention is not limited to this. It may also be a ring-shaped combination of 3).

In the magnetic circuit with the above configuration, pole piece 2
A rotor driving magnetic field is generated in the inner cylindrical space 3, and it not only has the original function as a magnetic circuit for a DC motor, but also aligns the magnetic pole surface of the annular permanent magnet 4' with the central axis l of the assembly of pole pieces 2. Since the magnetic pole surface can be made wider than the scale of the magnet by contacting both end faces in the direction, it is possible to effectively utilize the ability of the annular permanent magnet 4', and as a result, the annular permanent magnet 4' is inexpensive. Even when a ferrite magnet is used, it is possible to obtain a magnetic field strength comparable to that of a magnetic circuit using an Alnico cast magnet. In particular, if a rare earth magnet is used as the annular permanent magnet 4', not only a high magnetic field can be obtained, but also an extremely small and lightweight magnetic circuit can be obtained.

In addition, in the magnetic circuit having the above configuration, there is nothing intervening between the pole pieces 2, and the circumferential mounting position of the pole piece 2 can be determined only by the pole piece 2, so that the annular permanent magnet 4 ′
Pole piece 2 due to dimensional errors of other parts such as
The mounting position of the pole piece 2 is not affected, and it is possible to assemble the magnetic circuit with extremely high precision and easily just by centering the pole piece 2.

That is, regarding the annular permanent magnet 4' and the yoke 6, since their dimensional errors do not affect the assembly accuracy of the pole piece 2, strict dimensional accuracy and assembly accuracy are not required, and the assembly work can be simplified. It is possible to achieve this.

In particular, when an annular permanent magnet 4' is used as an annular magnet made of an integral piece that is divided and magnetized in the circumferential direction according to the required number of poles, as shown in the embodiment,
Not only is it not necessary to attach permanent magnets to each pole piece 2, but there is no positional deviation between the permanent magnets on the same end, which improves the efficiency of assembly work and equalizes the magnetic field balance. It is extremely effective.

As is clear from the above explanation, the magnetic circuit of the present invention not only enables the use of ferrite magnets, but also solves problems such as imbalance in the generated magnetic field and assembly. The inefficiency is solved as much as possible, and the cost of the magnetic circuit can be reduced in terms of both the permanent magnets used and the efficiency of assembling them, and this has a great effect on reducing the manufacturing cost of DC motors.

[Brief explanation of the drawing]

Figure 1 is a partially cutaway perspective view of a conventional magnetic circuit structure in which ferrite magnets can be used.
The figure is a partially cutaway perspective view of the structure of an example of a magnetic circuit embodying the present invention, and FIG. 3 is an exploded view showing the main structure of the magnetic circuit of FIG. 2. In the figure, 1: cylindrical frame, 2: pole piece,
3: cylindrical space, 4': annular permanent magnet, 5: inner peripheral surface of pole piece 2, 6: yoke, l: central axis.

Claims (1)

[Scope of utility model registration request] An even number of pole pieces 2 radially combined leaving a cylindrical space 3 for accommodating the rotor in the central shaft portion are each connected to a pair of annular permanent magnets that form the same number of magnetic pole faces as the pole pieces 2 in the circumferential direction. 4',
At 4', the pair of annular permanent magnets 4', 4' are sandwiched from both ends in the direction of the central axis so that the same magnetic pole faces face each other, and the annular permanent magnets 4' on the same end side are reversed. A magnetic circuit for a DC motor, characterized in that the magnetic circuit is connected at a yoke 6 to form a magnetic path on the pole piece side.