JP2577500B2 - DC motor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a DC motor having a frame (yoke) with an open side surface.

(Prior art) As a motor (DC motor) conventionally used for electric razors and other small electric products, for example,
FIG. 5 and FIG.

This motor has an oval-shaped frame 1 having a bottomed cylindrical shape (cup shape) and a cross-sectional shape as shown in FIG. 4, and magnets 2 and 3 fixed to the arc-shaped inner surfaces 1a and 1b of the frame 1. The frame 1 includes a lid 4 for closing an open end, and a rotor 5 rotatably disposed in the frame 1. This rotor 5
Is rotatably held by the bottom wall 1c of the frame 1 and the lid 4.

The motor has a commutator 6 provided on the rotor 5 and a brush 7 held on the lid 3 and in elastic contact with the commutator 6. The frame 1 is made of a magnetic conductive material, and a magnetic path between the magnets 2 and 3 is formed on the flat side walls 1d and 1d of the frame 1.

It is desirable that the motor used in such a small electric appliance is as small as possible and has a large torque.

However, when a magnetic path is formed in the flat side walls 1d, 1d, magnetic poles are also formed in portions of the flat side walls 1d, 1d facing the rotor 5, and the magnetic force generated by the magnetic poles prevents the rotor 5 from rotating. Act on. As a result, the magnetic force of the magnets 2 and 3 cannot be effectively used for generating the torque of the motor.

Further, since the cup-shaped frame 1 has a small diameter and a small working space, it is not easy to insert and fix the magnets 2 and 3 in the frame 1, and it takes time to assemble the rotor 5 and the brush 7. There was a problem.

Therefore, the portions of the flat side walls 1d, 1d are opened, and the flat side walls 1d, 1d are opened.
A DC motor has been put to practical use to improve the torque of the motor by preventing the generation of magnetic force in the part 1d, and to make the frame composed of a plate bent in a U-shape to facilitate the assembly work and reduce the size. ing.

FIGS. 6 and 7 show such a DC motor.

In FIGS. 6 and 7, reference numeral 10 denotes a frame, which is a U-shaped plate 11 formed by bending a flat plate made of a magnetic conductive material into a U-shape, and free of the U-shaped plate 11. It is formed from an end plate 12 made of a magnetic conductive material and fixing the end.

The U-shaped plate 11 includes opposing walls 11a and 11b and an opposing wall 1
It is formed in a U-shape from a continuous wall 11c between 1a and 11b. Magnets 13 and 14 are fixed to the opposing surfaces of the opposing walls 11a and 11b, and a rotor 15 disposed between the magnets 13 and 14 is provided.
Is rotatably held by the end plate 12 and the connecting wall 11c, and the connecting wall 11c
Brushes 16, 16 held by the rotor 15 are commutators 17 of the rotor 15.
I am in contact with

By the way, in such a DC electric motor, since both side ends are open, the magnetic path is formed on the opposing walls 11a, 11b, the end plate 12, and the continuous wall 11c.

(Problems to be Solved by the Invention) However, since the U-shaped plate 11 is made of a thin iron plate from the viewpoint of easiness of processing, its cross-sectional area serving as a magnetic path is small,
For this reason, the magnetic resistance of the magnetic path was large, and the torque could not be increased. Further, since the hole 5b for holding the shaft 5a of the rotor 5 is formed in the end plate 12, the cross-sectional area of the end plate 12 serving as a magnetic path is smaller than the cross-sectional area of the opposing walls 11a and 11b. For this reason, magnetic saturation occurs in the end plate 12, and there is a problem that torque is reduced and high torque cannot be obtained.

Also, since the U-shaped plate 11 is made of a thin iron plate,
There is also a problem that the U-shaped plate 11 is easily deformed, and it is difficult to obtain an assembly accuracy.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a DC motor that can obtain high torque, can easily assemble, and can be manufactured at low cost. To provide.

(Means for Solving the Problems) A pair of divided frames of the same shape and the same size formed in a U-shape by die molding are combined to form four side walls having a square side surface and open sides. A frame is formed, and magnets are respectively fixed to opposing surfaces of two opposing walls of the frame, and a support shaft of a rotor disposed between the magnets is rotatable on the other two opposing walls. And the thickness of the wall holding the support shaft of the rotor is set to be thicker than the thickness of the wall to which the magnet is fixed.

(Operation) According to the present invention, since the divided frame is formed by molding with the above configuration, the thickness can be arbitrarily set, and therefore, the magnetic path area can be increased. In addition, dimensional accuracy can be easily obtained because of the molding. Further, since the U-shaped divided frames are assembled together, the assembling work is also easy.

(Embodiment) An embodiment of the present invention will be described below with reference to FIG. 1 and FIG.

FIG. 1 is a sectional view of a state in which a DC motor according to the present invention is assembled, and FIG. 2 is an exploded perspective view of the DC motor shown in FIG.

This DC motor has a rectangular frame 20 that opens to the side.
And magnets 30, 30 attached to the frame 20,
A rotor 40 disposed between the magnets 30, 30;
And a rotor shaft (supporting shaft) 41 provided integrally therewith.
As shown in FIG. 3, the magnet 30 has an arc-shaped cross section.

Further, the DC motor includes bearings 50 and 50 that rotatably support the rotor shaft 41 on the frame 20, a commutator 42 provided integrally with the rotor shaft 41, and a brush 43 attached to the frame 20 and elastically contacting the commutator 42. Having.

The above-described frame 20 has a pair of divided frames 21 and 21 formed of the same shape and the same size from a magnetic conductive material such as iron.
Having. This divided frame 21 is formed by sintering or precision casting. Here, in the case of sintering,
After the iron powder is press-molded in a mold, the press-formed product is fired to form the final divided frame 21.
In the case of precision casting, molten iron is injected into a cavity in a mold and cooled to form a final divided frame 21.

The divided frame 21 is formed in a U-shape from an intermediate wall (wall body) 21a and opposing walls 22b, 22b provided at both ends of the intermediate wall 21a at right angles in the same direction.

An arc-shaped surface 22 concentric with the rotor 40 is formed on a portion of the intermediate wall 21a facing the rotor 40, and the arc-shaped surface 22 is formed when the divided frame 21 is molded as described above. The outer peripheral surface of the magnet 30 is bonded and fixed to the arc-shaped surface 22. This bonding can be performed with the divided frames 21 and 21 separated.

As shown in FIG. 2, semi-cylindrical recesses 23 and 24 having large and small diameters are formed coaxially on the end surface 22c of each opposed wall 22b, and the recesses 23 sandwich the recesses 23. Positioned positioning hole
25 and a positioning protrusion 26 are formed. The recess 23 has a smaller diameter than the recess 24 and is located on the magnet 30 side. The area of the end face 22c is the intermediate wall 2
The thickness of the opposing wall 21b is formed to be larger than the thickness of the intermediate wall 21a so as to be the same as the cross-sectional area of 1a. The thickness can be set arbitrarily since the divided frame 21 is formed by molding.

Then, the end faces 21c, 21c of both opposing walls 21b, 21b of one divided frame 21 are connected to both opposing walls 21b, 21b of the other divided frame 21.
Of the one end face 21c to be fitted is fitted into the positioning hole 25 of the other end face 21c to be fitted. This allows the frame to be opened to the side with a substantially square side shape
20 is formed, and the end wall (wall body) 27 of the frame 20 is formed by the combined opposing walls 21b, 21b.

Moreover, the end faces 21 of the opposing walls 21b, 21b
Arc-shaped surfaces 21d, 21d are formed on the surface opposite to c, 21c, and the outer wall 27a of the end wall 27 formed by the opposed walls 21b, 21b is formed in an oval shape.

Also, by combining the divided frames 21, 21, the shaft insertion hole 28 is formed by the concave portion 23 of one divided frame and the concave portion 23 of the other divided frame 21.

Then, the end of the rotor shaft 41 is inserted into the shaft insertion hole 28, and this end is rotatably held by the bearings 50, 50 engaged with the shaft insertion hole 28. Moreover, the two opposing walls 21b, 21b
Is fixed by a cap 51 fitted to the outer peripheral surface of the end wall 27.

 Next, the operation of such a configuration will be described.

According to such a configuration, the rotor 40 is disposed between the U-shaped divided frames 21 and 21 having the same shape and the same size, and both ends of the rotor 40 are simply sandwiched between the divided frames 21 and 21. By doing so, the rotor 40 is assembled to the frame 20.

In this assembly, the magnet 30 is adhered to the arc-shaped surface 22 of the intermediate wall 21a in a state where the divided frames 21 and 21 are separated, and the brush 43 is divided as shown in FIG. Since it is sufficient to attach the DC motor to the frames 21, 21, the assembling work of the DC motor is simplified, and the DC motor can be manufactured at low cost. In addition, divided frames 21 and 2
Since 1 is a mold, it is easy to obtain dimensional accuracy, and therefore it is easy to obtain assembly accuracy.

Further, in this DC motor, since the both ends of the frame 20 are open, the magnetic path of the magnet 30 is formed by the intermediate walls 21a and 21a.
a and the opposing walls 21b, 21b, 21b, 21b (end wall 27). However, since the intermediate wall 21a and the opposing wall 21b are thick, the magnetic resistance of the magnetic path is small. The torque can be increased. Furthermore, a shaft insertion hole is formed in the end wall 27.
28, the area of the magnetic path is reduced by that much, but the thickness of the opposing wall 21b forming the end wall 27 is made larger than the thickness of the intermediate wall 21a, and the sectional area of the intermediate wall 21a is reduced. End face of opposing wall 21b
Since the area of 21c is the same, it is possible to prevent magnetic saturation at the end wall 27, so that a decrease in torque due to magnetic saturation is prevented and a high torque can be obtained.

In the above-described embodiment, the divided frame 21 is divided in the horizontal direction as shown in FIG. 1, but is not limited thereto, and may be divided in the vertical direction.

(Effects of the Invention) According to the present invention, since the divided frame is formed by molding, the thickness can be set arbitrarily to increase the magnetic path area, and furthermore, the thickness of the end wall can be reduced to an intermediate value. Since the wall is made thicker than the wall, magnetic saturation at the end wall can be prevented, and high torque can be obtained. In addition, since the divided frame is formed by molding, it is easy to increase the assembly accuracy, and the assembling operation is simple, so that it can be manufactured at low cost.

[Brief description of the drawings]

FIG. 1 is a sectional view of a DC motor showing one embodiment of the present invention, FIG. 2 is an exploded perspective view of the DC motor shown in FIG. 1 with the brushes omitted, and FIG. 3 is a DC motor shown in FIG. FIG. 4 is a half sectional view showing a conventional DC motor, FIG. 5 is a transverse sectional view of a DC motor shown in FIG. 4, and FIG. 6 is a DC showing another conventional example. FIG. 7 is a cross-sectional view of the DC motor shown in FIG. 20… Frame 21… Divided frame 21a… Intermediate wall (wall) 21b… Opposed wall 21c… End face 27… End wall (wall) 30… Magnet 40… Rotor 41… Rotor shaft ( Support shaft)

Claims (1)

(57) [Claims] 1. A pair of divided frames of the same shape and the same size, which are formed in a U-shape by molding, are combined to form a frame composed of four walls having a square side surface and open sides. Then, magnets are respectively fixed to the opposing surfaces of the two opposing walls of the frame, and the supporting shaft of the rotor disposed between the magnets is rotatably held by the other two opposing walls, A DC motor, wherein a thickness of a wall holding a support shaft of the rotor is set to be thicker than a thickness of a wall to which a magnet is fixed.