JP2001339915A - Small dc motor and manufacturing method for the motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a welded structure and its welding method having consistent stiffness at all around and high productivity for connecting a rotor yoke and a shaft of a small DC motor, and thereby to materialize a small DC motor compact in size and characterized in welding having high reliability. SOLUTION: The motor comprises a rotor yoke 11 and a shaft 14 inserted in the center of the yoke. The shaft 14 is so arranged as to dispose its one end flush with the axial-direction end face of the rotor yoke 11 in the neighborhood of the shaft, and is fixed to the rotor yoke 11 by heat-welding the whole of the end face of the one end of the shaft 14. Also, by heat-welding the whole of the end face of the one end of the shaft 14 for fixing the rotor yoke 11, a spherical convex is weld-formed at the center of the end face of the one end of the shaft 14.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a small DC motor, and more particularly, to a structure and a method for welding and connecting a rotating body and a shaft thereof.

[0002]

2. Description of the Related Art When joining shafts in a general machine, a welding method is often used due to its strength and reliability. The welding rod is brought close to the boundary between the shaft and the mating member, and welding is performed so as to sew the entire circumference while causing arc discharge. Alternatively, when the required strength is low, several places around the shaft are welded and joined.

[0003] In recent years, even in a small DC motor, a shaft and a rotating body have been joined by welding. For example, the present applicant has disclosed an example in Japanese Patent Application Laid-Open No. Hei 8-23.
No. 7914. As shown in FIG. 6, a laser welding head 91 is used, and a motor core 92 and a shaft 93 are spot-welded by a laser beam 95 near a boundary 94 between them. In order to further determine the joining strength, the number of spot melting points is four or more.

As described above, when the welding method is applied to the shaft joining of a small DC motor, a conventional arc welding method is applied in a proportionally reduced manner, a laser beam is used instead of a welding rod, and the entire circumference of the shaft is used. Several places were welded and joined, or welded so as to sew all around. Since this method is a proportional reduction of the arc welding method, its technical problems and reliability are easy to predict.

However, this method involves joining several places along the entire circumference or welding so as to sew the entire circumference, so that a certain time is inevitable from the start to the completion of welding. Also, since one portion of the entire circumference of the shaft hardens first, the portion shrinks, and in order to prevent the occurrence of inclination due to the shrinkage, the laser beam is divided and radiated to several places at the same time, as shown in the above publication, And the power must be uniform. This requires delicate adjustments and therefore increases equipment costs and adjustment time.

[0006]

SUMMARY OF THE INVENTION Accordingly, the present invention relates to a method of joining a rotating body of a small DC motor and a shaft by joining several places around the entire shaft or welding the entire periphery. To solve the disadvantages, that is, it takes a certain amount of time from the start to the end of welding, increases the equipment cost and adjustment time, etc., and has a high productivity, uniform and strong joining technology over the entire circumference. provide. It is another object of the present invention to realize a compact and highly reliable small DC motor utilizing the characteristics of welding.

[0007]

In order to achieve the above object, a compact DC motor according to the present invention comprises a rotating body and a shaft inserted at the center of rotation, and one end of the shaft is arranged in an axial direction near the shaft of the rotating body. The shaft was disposed so as to be substantially flush with the end surface, and the rotating body at or near the one end surface of the shaft was fixed by heating and melting. Also, one end of the shaft is disposed so as to slightly protrude from an axial end face of the rotating body near the shaft, and the entire end face of the shaft is heated and melted and fixed to the rotating body, and the center of one end face of the shaft is fixed. A convex portion was melt-formed at the portion. Further, the innermost peripheral portion of the end face of the rotating body is heated and melted by arc discharge and fixed to the shaft.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention comprises: a) a rotating body and a shaft inserted at the center of rotation thereof, and b) one end of the shaft in the axial direction near the shaft of the rotating body. C) A small DC motor which is disposed so as to be substantially coplanar with, and c) heat-melts and fixes a rotating body at or near one end surface of the shaft.

First, the end face of the shaft and the rotating body are substantially on the same plane. Therefore, there is no protrusion of the shaft, and the heating and melting means can be arranged coaxially with the rotation center. And
The rotating body at or near one end surface of the shaft was heated and melted. Therefore, the shaft end face and the rotating body in the vicinity thereof can be melted and cooled uniformly over substantially the entire circumference at the same time, and a uniform and strong joining structure can be obtained. Further, only the vicinity of the shaft end face needs to be melted only once, and the time required for heat melting is shortened, thereby improving productivity. Here, “substantially the same plane” refers to a positional relationship where the rotating body at or near one end surface of the shaft can be fixed by heating and melting.

According to a second aspect of the present invention, there is provided a) a rotating body and a shaft inserted into the center of rotation of the rotating body, and b) one end of the shaft is slightly projected from an axial end face near the shaft of the rotating body. A small DC motor comprising: c) heating and melting the entire end face of one end of the shaft to be fixed to the rotating body; and d) melting and forming a convex portion at the center of the end face of one end of the shaft.

First, the shaft is fused and joined with the shaft slightly projecting from the rotating body. Therefore, the shaft end face can be melted while maintaining the fitting length between the two, so that the amount of fusion required for bonding can be secured while maintaining the inclination of the shaft with respect to the rotating body in a favorable manner, and accurate and strong bonding can be performed. Next, the shaft is melt-welded so as to have a shape protruding hemispherically from the rotating body. Therefore, it is convenient to dispose the member at a position close to and opposed to the spherical end face to restrict the axial movement of the rotating body. Here, 'slightly' means an amount sufficient to heat and melt the protruding portion to form a convex portion at the center of the end face, and to heat and melt the entire end face and fix it to the rotating body. Refers to the amount.

According to a third aspect of the present invention, a member for restricting the axial movement of the rotating body is disposed at a position close to and opposed to the convex portion formed at the center of the end face of one end of the shaft. It is a small DC motor as described. Usually, a movement restricting mechanism having a structure that comes into contact when acceleration due to an impact or the like is applied in a non-contact manner does not need to be as smooth as a thrust bearing that rotates while always in contact with a sliding surface. However, when the rotation radius of the contact point is large, sliding noise and wear occur. By forming the shaft end surface in a hemispherical shape in combination with the invention of claim 2, the contact point can be made closer to the center of rotation. Therefore, a movement restricting mechanism with less sliding noise and wear can be realized at low cost without additionally performing spherical processing or the like.

According to a fourth aspect of the present invention, there is provided the small DC motor according to the first or second aspect, wherein the means for heating and melting is an arc discharge. Since heat fusion bonding is performed by arc discharge, a relatively large area can be melted very easily with simple equipment as compared with an electron beam, a laser, or the like. Further, it is easy to uniformly melt the shaft end face, and the entire circumference can be uniformly and firmly joined.

According to a fifth aspect of the present invention, there is provided a) a rotating body and a shaft inserted at the center of rotation, and b) one end of the shaft is disposed so as to be substantially flush with the axial end face of the rotating body. And c) a small DC motor in which the vicinity of the shaft of the rotating body is heated and melted by arc discharge and fixed to the shaft.

An easily meltable convex portion such as a thin annular portion is formed on the innermost peripheral portion of the end face of the rotating body, and this portion is melted by arc discharge. This arc discharge can instantaneously melt the entire projecting portion without scanning like a laser beam. Then, since only the portion which is to be truly melt-bonded is melted, it can be melt-fixed with a small arc energy. by this,
A high-quality motor with minimal heat generation and minimal melting and alteration of the surroundings can be obtained.

According to a sixth aspect of the present invention, there is provided a small DC motor according to any one of the first, second and fifth aspects, comprising a rotating body and a shaft inserted into the center of rotation of the rotating body with an intermediate or close fit. It is a motor. First, the shaft to be inserted into the rotating body has an intermediate or close fit tolerance, so that, even if there is some non-uniformity when the welded part cools, the fitting part resists inclination and misalignment. have. Therefore, the inclination and displacement of the shaft with respect to the rotating body can be prevented, and a motor with high rotation accuracy can be obtained. Second, it can be handled and transferred with the shaft inserted into the rotating body. Therefore, the welding step and the insertion step can be separated, the degree of freedom of the process is increased, the cycle time of the equipment is shortened, and the productivity is improved.

According to a seventh aspect of the present invention, there is provided the small DC motor according to any one of the first, second, and fifth aspects, wherein a fitting length between the rotating body and the shaft is smaller than a shaft diameter.
In order to obtain an assembly having a small fitting inclination and a strong connection, it is generally considered that the fitting length is preferably, for example, 1.5 times or more the shaft diameter. However, when a flat shape is strongly required, the fitting length must be reduced to the shaft diameter or less, and it becomes difficult to maintain the inclination and strength. In such a case, by combining with the first or second aspect of the present invention, it is possible to obtain a motor that satisfies all of the flat shape, the inclination, and the strength.

According to the invention described in claim 8, the vicinity of the shaft of the rotating body and the shaft are made of an iron-based metal.
A small direct-current motor according to any one of claims 2 and 5. First, since the members to be welded are made of metals having properties similar to each other, welding is easy, and good welding quality can be maintained. When the rotating body is a rotor yoke of a small DC motor, it is generally made of a ferromagnetic ferrous metal. By employing a structure in which this is directly welded to the shaft, a simple and small motor can be obtained.
Further, when a flat motor is desired, the iron-based metal can be made thin because of its large longitudinal elasticity coefficient, and at the same time, it is possible to form a highly rigid rotating body with a small fitting length.

According to a ninth aspect of the present invention, there is provided the small DC motor according to any one of the first, second, and fifth aspects, wherein the shaft diameter is approximately 2 mm or less. The invention disclosed herein is:
It is suitable for a very small rotating body having a shaft diameter of up to about 2 mm. Generally, heating and melting the entire shaft end face at once requires much more energy than partial heating such as spot welding. Therefore, excessive dissolution or alteration is likely to occur in the peripheral portion due to this energy. However, the energy required for a small rotor with a small shaft diameter is relatively small. In addition, a rotating body of this scale requires a relatively small coupling strength. In other words, if the shaft diameter is up to about 2 mm, it is easy to find a balance point in which the entire end face of the shaft is heated and melted at one time, and the necessary bonding strength is obtained without causing side effects such as melting or deterioration of the peripheral portion. It is.

According to a tenth aspect of the present invention, the rotator includes an eccentric weight and a rotor yoke for holding the eccentric weight, and the eccentric weight and the rotor yoke are welded and fixed in the same direction as the end face of one end of the shaft. A small direct-current motor according to any one of 2, 5 and 6. In some vibration generating motors, the rotor yoke and the eccentric weight must be joined in addition to the joint between the shaft and the rotor yoke. At this time, the productivity of the motor can be improved by unifying the two joining parts to the end faces in the same direction and unifying the joining method by heating and melting.

According to an eleventh aspect of the present invention, a) the rotator is an eccentric weight attached to a shaft protruding from the small DC motor, and b) the eccentric weight is a substantially circular cross section located on the outer peripheral side of the small DC motor. It has an arc-shaped weight portion and a connecting portion located on the end face side for connecting the weight portion and the shaft. C) The axial length of the weight portion is a length covering a part of the outer diameter of the small DC motor. The small direct-current motor according to any one of claims 1, 2, and 5, wherein the small direct-current motor has: d) a connecting portion and a shaft fixed to each other.

The connecting portion and the shaft are fused and fixed at their end surfaces. At this time, the fitting length between the connecting portion and the shaft and the thickness of the connecting portion around the shaft only need to be thick enough to maintain the strength of the eccentric weight itself. Therefore, unnecessary weight can be reduced in both the axial and radial directions, and the necessary amount of eccentricity can be maintained. Therefore, a light and compact motor can be obtained while generating large vibration.

The eccentric weight has a substantially arc-shaped weight section located on the outer peripheral side of the motor, and its axial length has a length covering a part of the outer diameter of the motor. To make the equipment thinner, it is desirable to make the whole vibration motor thinner, but to obtain the required vibration level and reduce the weight, the outer diameter of the eccentric weight must have a constant outer diameter regardless of the motor outer diameter . Therefore, the weight portion is disposed so as to cover a part of the outer diameter of the small-diameter motor, and the remaining portion of the outer diameter is used for attachment and holding to the device. With this configuration, it is possible to obtain a compact motor that can contribute to a reduction in the thickness of the device by making the main portion small in diameter while generating large vibration.

According to a twelfth aspect of the present invention, a) the rotating body and the shaft inserted into the center of rotation are b) one end of the shaft is substantially flush with or slightly protruding from the axial end face of the rotating body near the shaft. And c) heating and melting the entire end face of one end of the shaft and fixing the shaft to a rotating body.

In this way, the entire end face of one end of the shaft is melted and joined. Because it melts all around at the same time,
Uniform and strong bonding can be achieved. Since the shaft end face only needs to be heated and melted once, the time for heating and melting is shortened, and the productivity is improved.

A thirteenth aspect of the present invention is the method for manufacturing a small DC motor according to the twelfth aspect, wherein the means for heating and melting is an arc discharge. The arc welding method has been used widely in relatively large mechanical equipment, and can easily heat and melt a wide area with simple equipment. Therefore, it is suitable for instantaneously and uniformly melting the end face of the shaft, and by precisely controlling the arc energy to a low level, it becomes optimal for the method of the present invention. In addition, the equipment cost can be reduced as compared with laser welding, and a motor can be provided at a low price.

According to a fourteenth aspect of the present invention, there is provided a small direct-current motor according to the thirteenth aspect, wherein a convex portion is provided in advance at the center of one end surface of the shaft, and the convex portion is melted by arc discharge and fixed to a rotating body. This is a method for manufacturing a motor. The discharge electrode is placed close to the center of the shaft so that it faces the convex part, and the convex part is melted by arc discharge and fixed to the rotating body. A high quality motor can be obtained.

According to a fifteenth aspect of the present invention, a) the rotating body and the shaft inserted at the center of rotation are arranged such that b) one end of the shaft is substantially flush with the axial end face of the rotating body. , C) an annular portion protruding in the axial direction from the other portion of the end surface of the rotating body at the innermost peripheral portion of the end surface of the rotating body;
This is a method for manufacturing a small DC motor, in which an annular portion is heated and melted by arc discharge and fixed to a shaft.

A thin annular portion is projected from the innermost peripheral portion of the end face of the rotating body, and this portion is melted by arc discharge. The melt volume can be reduced, and the melt can be fixed with a small arc energy. This minimizes heat generation and minimizes dissolution and alteration of the surroundings.

The invention according to claim 16 is the method for manufacturing a small DC motor according to claim 13 or 15, wherein the earth electrode is connected to the rotating body. Sparks are occasionally generated at portions where the electrodes of the workpiece are in contact, but since no electrodes are connected to the shaft, no sparks are generated and no damage occurs. Therefore, a motor can be produced while maintaining good quality.

According to a seventeenth aspect of the present invention, the earth electrode is a pedestal made of a metal having good heat conductivity, and the earth electrode is brought into contact with the rotating body near the shaft of the rotating body.
3. A method for manufacturing a small DC motor according to (1). A metal electrode having good thermal conductivity is brought into contact with the rotating body near the shaft thereof. As a result, the current passing length of the rotating body itself is minimized to minimize Joule heat, and the generated heat is conducted and radiated at a position closest to the shaft. Therefore, it is possible to obtain a high-quality motor in which surrounding melting and alteration due to arc energy are minimized.

[0032]

Embodiments of the present invention will be described below with reference to the drawings.

Embodiment 1 FIG. 1 is a side sectional view showing the structure of a brushless outer rotor motor according to a first embodiment of the present invention. FIG. 2 is a structural diagram of the rotor,
(A) is a top view, (b) is a side sectional view, and (c) is a bottom view. FIG. 3 is a schematic view for explaining the welding process of the rotor.

The motor shown in FIG.
mm, which is a vibration motor mainly used as a silent notification vibration source of a mobile phone. In the figure, the motor includes a stator (non-rotating portion), a rotor (rotating portion), and a cover. The rotor 10 is mainly composed of a cup-shaped rotor yoke 11 (rotary body), and has a ring-shaped magnet 12 mounted inside. Further, an eccentric weight 13 is attached to the rotor yoke 11. And it rotates about the shaft 14 attached in the center.

The stator is mainly composed of a motor base 31,
A stator assembly 20 including a stator core 21, a wire processing member 22, and a winding 23 is attached.
Is attached to its center. The ends of the windings are connected to terminals 33 of the motor base. And metal 32
, The rotor shaft 14 is rotatably fitted. The outer periphery of the stator core 21 radially opposes the inner periphery of the magnet 12. The two axial positions are displaced from each other, thereby generating an axial magnetic attractive force to attract and hold the rotor 10 to the motor base 31 side. These are covered with a cover 34. The cover constitutes a movement restricting mechanism having a structure in which it is close to the tip of the shaft 14 at the center thereof and comes into contact when a force is applied to the rotor in a direction in which the rotor comes off.

A terminal 33 is exposed on the lower surface of the motor so that it can be reflow-connected to a substrate (not shown) of the device. The motor is connected to the board of the device (mobile phone) by soldering, and the winding is controlled through terminals 33 on the lower surface to rotate the rotor. Then, vibration is generated by the eccentric weight 13 attached to the rotor to vibrate the device.

Hereinafter, a rotor which is a main part of the present invention will be described.

FIG. 2 shows the structure of the rotor. Rotor 10
Comprises a rotor yoke 11, a magnet 12, an eccentric weight 13, and a shaft 14, and are assembled in a positional relationship as shown in the figure. Rotor yoke 11 is eccentric weight 1
3 and a magnetic material that forms a magnetic path together with the magnet 12. Therefore, the rotor yoke 11 is made of a strong and ferromagnetic iron-based metal. The thickness of the fastening portion with the shaft 14 is given a dimension smaller than the diameter of the shaft in order to obtain a flat shape. Since the shaft 14 is a component of the bearing, the shaft 14 is made of a ferrous metal such as SUS420 which has high hardness, is hard to rust, and is suitable for precision machining. The outer diameter in this example is as small as about 0.8 mm. The eccentric weight 13 needs to have a large specific gravity, but at the same time, it is required to have excellent ductility and weldability, so a copper-tungsten alloy is used. Then, the shaft and the rotor yoke, and the eccentric weight and the rotor yoke are fixed by welding.

Referring to FIG. 3, rotor yoke 11 (rotary body)
The step of welding the shaft 14 and the shaft 14 will be described. The figure shows a state in which the two are welded by arc discharge, and depicts a state immediately before arc discharge is performed. The shaft 14 has a substantially cylindrical shape, and one end thereof is press-fitted and fixed to the rotor yoke 11 in advance. The end face is slightly projected from the end face of the rotor yoke 11. Further, the tip of the shaft 14 is formed in a conical shape with a convex central portion.

In this state, the support 71 for the rotor yoke 11
Place on. The cradle also serves as a ground terminal for arc welding. Since the welding is performed on the outer surface side of the rotor yoke 11, the receiving base 71 supports the inner surface side of the rotor yoke 11. Furthermore, it is configured to come into contact with the vicinity of the shaft on the inner peripheral side of the rotor yoke. At this time, the shaft 14
And a gap is provided between them so that they do not come into contact with each other. Although not shown, an air suction mechanism is further connected to the receiving base 71, so that the rotor yoke and the receiving base are securely brought into close contact with each other. If necessary, a cooling mechanism for cooling the pedestal itself is connected, so that even if welding is performed frequently, stable production can be achieved without overheating.

After the rotor yoke is mounted on the pedestal, the welding head 70 is lowered from above to approach the tip of the shaft. The discharge electrode 72 of the welding head has a conical tip and is concentric with the shaft 14. This discharge electrode 72 is a non-consumable electrode using tungsten or the like. Then, the electrode allows the tip of the gas nozzle 73 to be viewed from the center. The gas 74 to be ejected is an inert gas such as argon, and covers the periphery of the shaft tip, which is a welding base material, in an inert gas atmosphere. An apparatus of a type called TIG welding is constituted. In this state, arc discharge occurs, and the tip of the shaft melts instantaneously. Then, the melted base material is solidified while melting with the rotor yoke in the vicinity, and the joining is completed.

At this time, by controlling the concentricity of the shaft 14 and the discharge electrode 72, the shape of the shaft tip, the amount of protrusion of the shaft, the arc energy, and the like, the welding range between the shaft 14 and the rotor yoke 11 is made uniform with respect to the center of rotation. As a result, there is no inclination of the shaft due to the non-uniformity, and good fixation having uniform strength over the entire circumference is performed. Further, in order to form a convex spherical surface (convex portion) at the center of the end face at the tip of the shaft, the surface tension of the molten metal at the end face of the shaft is used. At this time, by controlling the above parameters more precisely, such as making the welding range between the shaft and the rotor yoke uniform and constant, slightly increasing the amount of protrusion of the shaft, and keeping the posture of the work to be welded horizontal. In addition, it is possible to obtain a favorable spherical shape in which the height and the misalignment of the sphere are kept within a certain range.

In this embodiment, the eccentric weight 13 is welded simultaneously with the shaft welding. FIG.
Is a state immediately before the eccentric weight 13 is welded. In this manner, the eccentric weights 13 are joined by the same welding method on the same surface as the shaft. The eccentric weight is made of tungsten or another metal having a high specific gravity. By using this as an alloy containing tungsten and copper, the melting temperature of the eccentric weight is reduced to about the melting temperature of iron, and welding is facilitated.

As described above, in the motor of this embodiment,
One end of the shaft 14 is disposed so as to be substantially flush with the axial end face of the rotor yoke 11, and the entire end face of one end of the shaft is heated and melted and fixed to the rotating body. Therefore, it is possible to simultaneously melt and cool the entire circumference of the shaft end face at the same time, so that a uniform and strong joining structure can be obtained. Since the shaft end face needs to be melted only once, the heating and melting time is shortened and the productivity is improved.

Further, in the motor of the present embodiment, the heat welding is performed by arc welding. It is suitable for instantaneously and uniformly melting the shaft end face, and by precisely controlling the arc energy to a low level, it is optimal for the method of the present invention. In addition, the equipment cost can be reduced as compared with laser welding, and a motor can be provided at a low price.

Further, in the motor of this embodiment, the shaft 14 is fusion-bonded with the shaft 14 slightly projecting from the rotor yoke 11. Therefore, since the shaft is mainly melted outside the fitting portion, it can be accurately and firmly joined without inclination. Further, the shafts are fusion-bonded so as to have a shape projecting hemispherically from the rotor yoke. Therefore, it is convenient to arrange the member at a position close to and opposing the spherical end face to restrict the axial movement of the rotating body.

Further, in the motor of the present embodiment, the rotor yoke 11 and the shaft 14 are welded after being inserted with an intermediate or close fit. This can prevent the shaft from being inclined or displaced from the rotor yoke. Also, it can be handled and transferred with the shaft inserted in the rotor yoke. Therefore, the welding step and the insertion step can be separated, and the productivity is improved.

In the motor of this embodiment, the shaft fitting length of the rotor yoke is smaller than the shaft diameter. If there is a strong demand for a flat shape, such a choice must be made, but by adopting the joining method described above, it is possible to obtain a motor that satisfies the flat shape, inclination, and strength. it can.

In the motor of this embodiment, the rotor yoke 11 and the shaft 14 are made of an iron-based metal.
Since the metals have properties similar to each other, welding is easy, and a simple and small motor can be obtained.

Further, in the motor of this embodiment, the eccentric weight 13 and the rotor yoke 11 are fixed by welding from the same direction as the end face of one end of the shaft 14. By unifying the two joining parts to the end faces in the same direction and unifying to the heating and melting joining method, the equipment can be shared and the work transfer time can be reduced.

In the motor of the present embodiment, the end face of one end of the shaft 14 is provided with a projection at the center thereof in advance. The arc is always stably directed toward the center of the shaft end face, and a high-quality motor uniformly joined can be obtained.

In the motor of this embodiment, the ground electrode is a pedestal made of a metal having good heat conductivity, and is brought into contact with the rotating body near the shaft of the rotor yoke. As a result, the current passing length of the rotor yoke itself is minimized to minimize the Joule heat, and the generated heat is conducted and radiated at a position closest to the shaft. Therefore, it is possible to obtain a high-quality motor in which surrounding melting and alteration due to arc energy are minimized.

The shaft diameter of the motor of this embodiment is φ0.8
mm. It was necessary to join it vertically to a plate-like surface thinner than the shaft diameter with high precision and with high strength. Because this motor is extremely small, the air gap between the rotor and stator is small,
Moreover, it is necessary to withstand a shock of 10,000 G or more while having a heavy weight. In such a case, the conventional option has been only a method of joining the entire circumference of the shaft by sewing with a laser beam. The present invention provides a balance point that, when the shaft diameter is up to about 2 mm, the entire end face of the shaft is heated and melted at one time, and the necessary joining strength is secured without causing side effects such as melting and alteration of the peripheral portion. He has found that it is possible to obtain it, and based on this knowledge, has made numerous inventions.

(Embodiment 2) FIGS. 4A and 4B are sectional views of a rotor of a brushless outer rotor motor according to a second embodiment of the present invention. FIG. 4A shows a state before arc welding and FIG. 4B shows a state after arc welding. . Since this rotor is a partial modification of the rotor of the first embodiment, illustration and description of parts that have not been changed are omitted.

In FIG. 4A, the rotor yoke 41 has an annular portion 4 protruding in the axial direction at the innermost peripheral portion of its end face.
1a is formed. A shaft 44 is inserted into the center of the rotor yoke, and one end of the shaft is disposed so as to be substantially flush with the axial end surface of the rotor yoke except for the annular portion.

The annular portion 41a is fixed by heating and melting by arc discharge. At this time, for example, the discharge electrode 82 is not a spire as shown in the figure. After welding, the shape is as shown in FIG. As described above, the annular portion 41a of the rotor yoke is mainly melted and solidly dissolved with the shaft.

As described above, in this embodiment, the thin annular portion 41a which is easily melted is provided on the innermost peripheral portion of the end surface of the rotor yoke.
Are formed to protrude, and this portion is melted by arc discharge. The arc discharge can instantaneously melt the entire projection without scanning like a laser beam. Then, since only the portion which is to be truly melt-bonded is melted, it can be melt-fixed with a small arc energy. Therefore, a high-quality motor can be obtained in which heat generation is minimized and surrounding melting and deterioration are minimized. It is a thin shaft that is suitable for the annular fusion welding. For stable production, the diameter is more preferably about φ1.5 mm or less.

(Embodiment 3) FIG. 5 is a side view showing the appearance of a cylindrical vibration motor according to a third embodiment of the present invention. This motor is also used mainly as a silent notification vibration source of a mobile phone. The motor is mounted with its shaft parallel to the housing of the device, and is powered and rotated through a terminal 51 extending from the lower end in the axial direction. An eccentric weight is attached to the output shaft, and the rotation gives vibration to the device.

As shown in FIG.
(Rotating body) is a weight portion 53 on the outer peripheral side of the motor 50.
a and the connecting portion 53b on the end face side. The connecting portion 53b and the shaft 54 are welded and fixed at the end faces. This embodiment also uses arc discharge for fixing. This shaft diameter is 0.8 mm. Shaft end face 54
“a” is disposed at a position that is substantially flush with the end face of the connecting portion 53b and is slightly concave. In the case of this embodiment, the eccentric weight 53 is a copper tungsten alloy and
Melting point higher than 4. Therefore, it is effective to cause an arc discharge to the connecting portion 53b to melt it. Therefore, the shaft is arranged slightly concave, and the shape and position of the discharge electrode are also adjusted so that arc discharge occurs near the shaft insertion hole at the innermost periphery of the connecting portion 53b.

In fixing the eccentric weight 53 by welding, it is necessary to prevent the heat from welding from affecting the motor. To this end, rather than seeking uniformity over the entire circumference, the various parameters described in the first embodiment are controlled with a primary focus on how to reduce the heating energy while securing the required strength. The structure, type, amount, etc. of the cradle and the inert gas are controlled with a focus on how to effectively radiate heat. As for the eccentric weight, it is considered that the annular portion described in the second embodiment is provided on the innermost peripheral portion of the connecting portion 53b. Furthermore, on the motor side,
For example, various heat measures such as using bearing oil having high heat resistance are taken.

As described above, in this embodiment, since the end face side of the shaft 54 or the connecting portion 53b is melted and firmly joined, the fitting length between the connecting portion 53b and the shaft 54 and the peripheral portion of the connecting portion 53b around the shaft are formed. The thickness of the eccentric weight should be sufficient to maintain the strength of the eccentric weight itself. Therefore, unnecessary weight can be reduced in both the axial and radial directions, and the necessary amount of eccentricity can be maintained. Therefore, a light, compact and large vibration motor can be obtained. In the conventional fixing method by caulking, a wall thickness and an axial length are required near the shaft to withstand breaking by caulking. This portion not only includes the weight in the canceling direction or invalid as the eccentricity, but also becomes a hindrance factor in reducing the size of the vibration motor.

In this embodiment, the eccentric weight 53
Has a weight portion 53a located on the outer peripheral side of the motor 50 and having a substantially arc-shaped cross section, and its axial length has a length covering a part of the outer diameter of the motor. To make the device thinner, it is desirable to make the vibration motor thinner as a whole. However, in order to obtain a lightweight and large vibration, the outer diameter of the eccentric weight needs to have a constant outer diameter regardless of the motor outer diameter. For example, the outer diameter of the motor of the embodiment is 4 mm or less, but the outer diameter of the eccentric weight is 6 m.
m is preferable. Therefore, the weight portion 53a is arranged on the outer diameter side of the small-diameter motor 50 so as to cover a part of the axial length thereof, and the remaining axial length portion of the motor is mounted and held on the device. In the embodiment, approximately one third to one fifth of the motor length is used for the weight portion. Then, the weight portion is joined to the shaft by a thin connecting portion whose axial length near the shaft is less than twice the shaft diameter. The combination of the eccentric weight having such a shape and the thin motor makes it possible to realize a lightweight, large-vibration, thin housing. However, in order to firmly join the eccentric weight to the shaft with good productivity, the end face welding of the present invention is required. The technology is extremely effective.

On the equipment side where this motor is mounted, it is necessary to secure a rotation space of about φ6 mm only for the eccentric weight part, but the other main parts of the motor are made thin, so that the housing can be made thin. In addition, the length in the axial direction is reduced, so that a compact device can be obtained.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various applications and developments can be made within the scope of the present invention. The rotating body is not limited to the above embodiment. For example, laminated cores used for commutator motors, rotor cores and magnets for stepping motors, rotors for coreless commutator motors,
It can also be applied to pulleys, gears and actuators attached to the motor shaft. Further, the material of the portion near the shaft of the rotating body is preferably metal, but is not limited thereto. Even if they do not form a solid solution with each other, the object can be achieved by the anchor effect in which the molten shaft base material enters the mating member.

[0065]

As described above, according to the present invention, in joining a rotating body and a shaft of a small DC motor,
Disadvantages of the method of joining several places around the entire circumference of the shaft or welding so as to sew the entire circumference, that is, it takes a certain amount of time from the start to the end of welding, increases equipment costs and adjustment time, etc. Settled, uniform over the entire circumference,
A strong, highly productive welded joint structure and method can be provided. This makes it possible to realize a compact and highly reliable small DC motor utilizing the characteristics of welding.

[Brief description of the drawings]

FIG. 1 is a side sectional view showing a structure of a brushless outer rotor motor according to a first embodiment of the present invention.

FIG. 2A is a top view of the rotor of the brushless outer rotor motor according to the first embodiment of the present invention; FIG.

FIG. 3 is a schematic diagram illustrating a rotor welding process of the brushless outer rotor motor according to the first embodiment of the present invention.

FIG. 4A is a cross-sectional view of a rotor yoke and a shaft according to a second embodiment of the present invention before arc welding. FIG. 4B is a cross-sectional view after the arc welding.

FIG. 5A is an external top view of a cylindrical vibration motor according to a third embodiment of the present invention, and FIG.

FIG. 6 is a diagram showing welding of a rotating body to a shaft in a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Rotor 11, 41 Rotor yoke (rotating body) 41a Annular part 12 Magnet 13 Eccentric weight 14, 44, 54 Shaft 20 Stator assembly 21 Stator core 22 Wire processing member 23 Winding 31 Motor base 32 Metal 33 Terminal 34 Cover (Movement restriction) Part of mechanism) 50 Cylindrical vibration motor 53 Eccentric weight (rotating body) 53a Weight part 53b Connecting part 70 Welding head 71 Receiver 72, 82 Discharge electrode 73 Gas nozzle 74 Inert gas

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor: Fukuoka Road 1006, Kazuma, Kazuma, Osaka, Japan Matsushita Electric Industrial Co., Ltd. (72) Inventor: Akihito Fukuda 1006, Kazuma, Kadoma, Osaka, Japan Matsushita Electric Industrial Co., Ltd. (72) Inventor Hideo Kobayashi 1006 Kadoma, Kazuma, Osaka Prefecture F-term in Matsushita Electric Industrial Co., Ltd. BB07 BB14 BB17 PP02 PP07 PP24 QQ02 SS05 SS16 SS19 5H621 BB07 GA01 GA04 GB08 JK17

Claims (17)

[Claims] A rotating body and a shaft inserted at the center of rotation of the rotating body, wherein one end of the shaft is disposed so as to be substantially flush with an axial end face of the rotating body near the shaft; A small DC motor, which is obtained by heating and melting and fixing the rotating body at or near one end face. 2. A rotator and a shaft inserted at the center of rotation of the rotator, one end of the shaft being disposed so as to slightly protrude from an axial end face of the rotator near the shaft, and one end of the shaft being provided. A small DC motor, wherein the entire end face is heated and melted and fixed to the rotating body, and a convex portion is formed by melting at the center of one end face of the shaft. 3. The small DC motor according to claim 2, wherein a member for restricting the axial movement of the rotating body is disposed at a position close to and opposed to the convex portion formed at the center of the end face of one end of the shaft. 4. The means for heating and melting is arc discharge.
The small DC motor according to claim 1. 5. A rotating body and a shaft inserted at the center of rotation of the rotating body, one end of the shaft is disposed so as to be substantially flush with an axial end face of the rotating body, and a portion near the shaft of the rotating body. A small DC motor which is heated and melted by arc discharge and fixed to the shaft. 6. The small DC motor according to claim 1, further comprising a rotating body and a shaft inserted into the center of rotation of the rotating body with an intermediate fit or an interference fit. 7. The small DC motor according to claim 1, wherein a fitting length between the rotating body and the shaft is smaller than a shaft diameter. 8. The small DC motor according to claim 1, wherein a portion near the shaft of the rotating body and the shaft are made of an iron-based metal. 9. The small DC motor according to claim 1, wherein the shaft diameter is approximately 2 mm or less. 10. The rotating body according to claim 1, wherein the rotator includes an eccentric weight and a rotor yoke for holding the eccentric weight, and the eccentric weight and the rotor yoke are welded and fixed in the same direction as the end face of one end of the shaft. The small DC motor according to any one of the above. 11. A rotating body is an eccentric weight attached to a shaft protruding from a small DC motor, wherein the eccentric weight is located on an outer peripheral side of the small DC motor and has a substantially arc-shaped cross section and is located on an end face side. And a connecting portion for connecting the weight portion and the shaft, and an axial length of the weight portion has a length covering a part of an outer diameter of the small DC motor. 6. The small DC motor according to claim 1, wherein the DC motor is fixed to a shaft. 12. A rotator and a shaft inserted at the center of rotation of the rotator are arranged such that one end of the shaft is substantially flush with or slightly protrudes from an axial end surface of the rotator near the shaft. A method for manufacturing a small DC motor, wherein the rotating body at or near one end of a shaft is heated and melted and fixed. 13. The method according to claim 12, wherein the means for heating and melting is arc discharge. 14. The method for manufacturing a small DC motor according to claim 13, wherein a convex portion is previously provided at the center of one end surface of the shaft, and the convex portion is melted by arc discharge and fixed to a rotating body. 15. A rotator and a shaft inserted into the center of rotation of the rotator are disposed such that one end of the shaft is substantially flush with an axial end face of the rotator, and an innermost end face of the rotator. A method of manufacturing a small direct-current motor, wherein an annular portion protruding in the axial direction from the other portion of the end surface of the rotating body is formed in the peripheral portion, and the annular portion is heated and melted by arc discharge and fixed to the shaft. . 16. The method according to claim 13, wherein the ground electrode is connected to a rotating body. 17. The method for manufacturing a small DC motor according to claim 13, wherein the ground electrode is a pedestal made of a metal having good heat conductivity, and is brought into contact with the rotating body near the shaft of the rotating body. .