JPS6198142A - Small-sized motor - Google Patents

Abstract

PURPOSE:To center a rotor shaft in a high accuracy by associating a rotor shaft together with an exciting coil and a rotor in a case, and then securing one bearing of the rotor while centering with respect to the case. CONSTITUTION:A rotor 2 and a stator 3 of a small-sized motor 1 are associated in a cup-shaped case 4. This case 4 is formed at one end with a flat hole 5 and secured at the other end (bottom) to a mounting plate 6. The stator 3 of the associated state is inserted into the case, and a rotor shaft 21 is inserted into the central hole of the bearing 22. At this time, the rotor 2 of a permanent magnet secured to the shaft 21 is opposed to pole teeth in a stator core 9. The shaft 21 is inserted into the central hole 28 of a jig 26 in this state, and accurately centered by an internal positioning cone 29. Then, a case 18 is opposed to the hole 5 of the case 4, and the bearing 19 is engaged with the shaft 21. The jig 27 is opposed, and the shaft 21 is centered by a pair of positioning cones 29, 33.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to a small electric motor, and particularly to an improvement in the centering structure of its rotor shaft.

BACKGROUND OF THE INVENTION The rotor shaft of this type of small electric motor is supported by bearings at both ends of the rotor. These bearings are then supported by the bearing portion of the case.

Usually, the case is divided into a front case and a back case, and is formed by press working. Further, a stator core corresponding to the rotor is also mounted in a positioned state by the case portion.

However, in press-formed cases, the accuracy during molding is not sufficient, so cutting is required to center the bearing part of the case, and cutting is also required for the rotor positioning part of the case. Become. For this reason, machining of the case portion is complicated, and since cutting is performed for each case on the front and back sides, the machining accuracy is the same, but the center of the rotor axis appears to be off.

In addition, when this type of small electric motor is finally assembled, the centering of the rotor shaft may become inaccurate due to accumulated errors in the machining accuracy of the case and other parts.
Furthermore, the gap between the rotor and the stator core cannot be set as small as possible, which affects the rotational torque. In particular, in a rotor shaft having a relatively long rotor shaft and having a feed screw at its tip, the centering error of the rotor shaft becomes large at the tip of the feed screw. Therefore, the small electric motor having the above structure is no longer used for precision equipment such as floppy disk drives.

OBJECTS OF THE INVENTION AND SOLUTIONS THEREOF Therefore, an object of the present invention is to make it possible to ensure the centering accuracy of the rotor shaft in the final assembly process without depending on the accuracy of the assembly of the rotor shaft on the accuracy of other parts. It is.

Therefore, the present invention has been developed to center the rotor shaft with high precision by incorporating the rotor shaft together with the excitation coil and rotor into the case, and then fixing one bearing part of the rotor to the case while centering the rotor shaft. At the same time, the rotor axis can be set perpendicularly to the motor mounting plate. In this way, since the perpendicularity of the rotor shaft to the mounting plate and the centering of the rotor shaft are performed using a jig or the like in the final assembly process, cumulative errors in the case and other parts do not appear, resulting in a product of excellent quality. can be ensured without the need for cutting the case or the like.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of the present invention will be specifically explained below based on the embodiments shown in the drawings.

First, FIGS. 1 and 2 show the small electric tal of the present invention.
It represents the completed state of Yuu. A rotor 2 and a stator 3 of a small electric motor 1 are assembled inside a cup-shaped case 4. In addition to FIGS. 1 and 2, this case 4 includes
As shown in FIG. 3, it is, for example, a press-worked product, formed into a cup shape or a closed-end cylindrical shape, with a flat opening 5 formed on one end surface, and a flat opening 5 on the other end surface. That is, it is fixed to the mounting plate 6 at the bottom, and a small cylindrical bearing part 7 is integrally formed at the center position.

Further, the stator 3 is constituted by a plurality of, for example, four annular stator cores 9 and excitation coils 10, which are provided with a plurality of pole teeth 8 along the inner periphery.

These stator cores 9 have two excitation coils 1, for example.
They are applied to both sides of the bobbin 11 of No. 0 and assembled as shown in FIGS. 4 and 5. Note that a positioning projection 12 is formed on the side surface of the bobbin 11, and two positioning holes 13 are formed in the stator core 9 for each projection 12 in correspondence with this. The rotational angle positioning of the stator core 9 is determined by these fits.

Here, the two positioning holes 13 are selectively used depending on the rotational direction of the rotor 2.

The four lead wires 14 of the excitation coil 10 are connected to the notches 15 formed on the outer periphery of the stator core 9 and the bobbin 1.
The stator core 9 and the excitation coil 10 in the 0-combined state, which can be led out to one side along the notch 16 formed in the flange portion of the stator 3, constitute the stator 3 and are housed inside the case 4. ing. Also,
A draw-out port 24 is formed on the opening 5 side of the case 4 to correspond to the draw-out portion of the lead wire 14, and an arc-shaped presser body 25 is fitted in the 7 portion.

In this way, the lead wire 14 passes through the inside of the notch 15.16 and is pressed by the presser body 25, while the lead wire 14 passes through the inside of the cutout 15.
24 to the outside.

Further, a case 18 is applied as a flat member to the planar opening 5 and fixed after position adjustment. This flat plate-shaped case 18 has a flat joint surface 18a on the inner outer peripheral surface, holds a bearing 23 at the center bearing part 17, and has an outer peripheral part for guiding the lead wire 14. A drawer opening 20 is formed by a notch. The rotor shaft 21 of the rotor 2 forms a feed screw 21a on the output side and a conical recess 21b on the end face, and the bearing 2 is housed inside the bearing portion 7.17.
2.23, the rotor 2, which is made of a permanent magnet, for example, is rotatably supported at a position corresponding to the pole teeth 8 of the stator core 9. Of course, the gap between the outer periphery of the rotor 2 and the pole teeth 8 is set as narrow as possible in order to obtain high torque.

Function of the Invention Next, the function of the present invention will be explained together with the assembly order of the above-mentioned small electric motor 1.

First, the case 4 and the mounting plate 6 are assembled in the state shown in FIG. 3, fixed by appropriate means, and then placed on a suitable jig. In this state, the mounting is corrected so that the angle of the generatrix direction of the case 4 with respect to the plate 6 is exactly 90 degrees around the entire circumference. Of course, if the perpendicularity between the two is already ensured at the time of combination, such correction is not required.

Next, the stator cores 9 are applied to the two bobbins 11 from their respective sides, and the two bobbins 11 are assembled so that their pole teeth 8 are shifted at a constant angle. The stator 3 in such a combined state is inserted into the case 4 at a predetermined angle. After doing this, the rotor shaft 21 is inserted into the center hole of the bearing 22 with the washer and spring washer 1.
It is inserted with 9 interposed. At this time, the rotor shaft 21
The permanent magnet rotor 22 fixed to the stator core 9
It is located inside the pole tooth 8 and faces the pole tooth 8 thereof.

In this state, the rotor shaft 21 is moved as shown in FIG.
It is inserted into the center hole 28 of the jig 26 and has a conical recess 21b.
It fits into the internal positioning cone 29 and is accurately centered. At this time, the bearing part 7 fits inside the recess 30 of the jig 26 and is prevented from being deformed. In this way, the rotor shaft 21 is exactly 90 degrees to the upper surface of the jig 26, that is, the mounting plate 6, that is, it is in a vertical state.

After that, the case 1 is placed in the planar opening 5 of the case 4.
8 is applied by its joining surface 18a, and the bearing 19 at the center position is fitted into the rear end portion of the rotor shaft 21. Prior to this, a presser body 25 is applied to the outlet 24 of the lead wire 14. It's broken. In this way, when the flat case 18 is applied to the opening 5 of the case 4, the two are not yet fixed, and the gap formed between the rotor 2 and the pole teeth 8 is It is in a state where it can move in the radial direction within a range.

In this way, the almost assembled small electric motor 1 is fixed to the lower jig 26, and then the jig 27 is applied from above. This jig 27 has a positioning cone 3 which is biased by a spring 32 in the recess 31.
3 is provided.

The positioning cones 29 and 33 of the pair of jigs 26 and 27 are the circles 't (IE
When the groove 21b is sandwiched, the rotor shaft 21 is centered with high accuracy by the jigs 26 and 27, and is restrained in a state perpendicular to the mounting plate 6.

During this centering process, the contact surface 18a of the flat case 18 moves with respect to the end surface of the opening 5, allowing the centering operation. After centering and positioning is done in this way,
The case 18 is fixed to the opening 5 of the case 4 by suitable means, such as adhesive or plasma welding means.

After such an assembly process, the rotor shaft 21 is set perpendicular to the mounting plate 6 with high precision,
Moreover, it is not dependent on the precision of each part, and is accurately centered.

Modifications of the Invention In the above embodiment, the outer diameter of the opening 5 of the case 4 is set to be approximately equal to the outer diameter of the flat case 18. However, as shown in FIG. may be set small, or a stepped portion may be formed with an adjustment range left inside the case 18.

In addition, when the means for fixing the case 4 and the case 18 is adhesive, the case 4 and the case 18 are
It is preferable to form notches 34 at predetermined intervals on the outer circumferential surface of 8 as shown in FIG.

Further, in the above embodiment, the case 4 is cup-shaped and the flat case 18 is flat as its name suggests, but this case 18 is symmetrical with the case 4 in a cup shape as shown in FIG. It can also be configured.

Furthermore, in the embodiment shown in FIG. 6, conical depressions 21b are formed on both end faces of the rotor shaft 21, corresponding to the positioning cones 29.33, but if a positioning circle tflEE recess 37 is formed in the jig 26, , those conical recesses 21b can be omitted. Further, in the embodiment shown in FIG. 6, the centering of the rotor shaft 21 is performed at both ends, but if the rotor shaft 21 protrudes long on its output side, that is, on the feed screw 21a side, As shown in the figure, centering of the rotor shaft 21 becomes possible by applying a fixed ■ block 35 at a position close to the bearing 22 and applying a movable V block 36 from the opposite side.

In this way, centering on one side of the rotor shaft 21 is effective for a type of rotor shaft 21 in which the rear end portion does not protrude to the outside.

Further, in the above embodiment, the rotor shaft 21 is made to protrude on the side of the mounting plate 6 as an example, and that is the output side. It may also protrude on the bearing 23 side.

Effect of the invention The present invention provides the following unique effects.

First, even if there is an error in the perpendicularity and centering of the rotor axis with respect to the mounting plate during the assembly process, it will be corrected in the centering direction during the subsequent mutual fixing process of the case and the member on the joint surface side. As a result, verticality and centering can be ensured with high precision, resulting in a finished product with high mechanical precision even when the rotor axis is long, making it suitable for applications requiring high precision such as floppy disk drives. can also be used.

Furthermore, since assembly can be performed with such high precision, the gap between the rotor and the stator can be set as small as possible, thereby increasing the output torque.
- Furthermore, in the final assembly stage, the machining accuracy of each part is absorbed and does not appear as an accumulated error, so parts such as the case can be constructed from press-formed products, and therefore cutting is not required. Productivity of parts is improved, and strict quality control for each part can be omitted.

[Brief explanation of the drawing]

Fig. 1 is a side view of the small electric motor of the present invention, Fig. 2 is a vertical sectional view thereof, Fig. 3 is a vertical sectional view showing the relationship between the case and the mounting plate, Fig. 4 is a side view of the excitation coil, Fig. 5 is a front view of the stator, Fig. 6 is a vertical cross-sectional view when assembling the small electric motor of the present invention, Fig. 7 is a cross-sectional view of a part of the fixed part of the case, and Fig. 8 is a cross-sectional view of the fixed part of the case. FIG. 9 is a sectional view of another embodiment in a different case, and FIG. 1O is a sectional view of a part of the 46 jig during assembly and adjustment. 1. Small electric motor, 2. Rotor, 3. Stake, 4
...Case, 5.Opening, 6.Mounting plate, 7.17
...Bearing part, 18...Case, 18a...Joint surface, 1
9.22.23...Bearing, 21...Rotor shaft.

Claims (1)

[Claims] In a small electric motor having a rotor shaft supported by a bearing on a mounting plate side and a bearing on the opposite side of the mounting plate, a bearing part on the side opposite to the output side of the rotor shaft among the bearing parts supporting both the bearings. Forming a flat joint surface on a member that is integral with the
This joint surface is applied to the planar opening of the cup-shaped case, so that the above-mentioned member can be moved in the radial direction when assembling the electric motor, and the above-mentioned rotor axis can be adjusted so as to be perpendicular to the above-mentioned mounting plate. A small electric motor featuring