JP2001112212A - Compact motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a thrust catch structure for supporting a shaft in a thrust direction, and to suppress impact sound being generated by the tip of the shaft. SOLUTION: In the compact motor, a recessed part 20 is formed at the center of a case lid 5, a support part is formed on the bottom surface of the recessed part, an elastic thrust plate 4 for supporting a shaft end part in a thrust direction is placed, and a sliding bearing 3 is used as a bearing in a radial direction for forcing into the recessed part 20. The thrust plate 4 is held between the support part where the periphery of the thrust plate 4 is formed on the bottom surface of the recessed part and the forced-in sliding bearing 3 for fixing so that a closed gap 21 is formed, thus effectively absorbing impact being generated when the tip of the shaft collides with the thrust plate 4 by the elasticity of the thrust plate 4 and the closed gap 21 operating as an elastic layer when a load fluctuates.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a small motor, and more particularly, to a small motor which suppresses an impact sound generated when a shaft tip collides with a thrust receiving structure at the time of a load change such as a reverse rotation or a load off.

[0002]

2. Description of the Related Art A small motor with a worm speed reducer has been known for driving an auto air conditioner or a power window device for an electric component of a vehicle. In this technology, a worm is connected to a shaft of a motor, a worm wheel meshing with the worm is provided, and a load is connected to an output shaft of the worm wheel for driving.

When such a small motor with a worm speed reducer rotates for driving a load, a reaction corresponding to the rotation direction of the motor, that is, the rotation direction of the worm wheel, causes the motor shaft to move back and forth in the axial direction. In a direction, slightly forward or backward. In this state,
When the motor power is turned off, the magnet provided in the case of this type of motor attracts the core of the rotor, and a force acts to return to a predetermined position in the axial direction, so that the motor shaft moves in the opposite direction. Alternatively, such movement in the opposite direction also occurs when the rotation direction of the motor is reversed. At this time, the tip of the shaft collides with a thrust receiving structure provided on the case or the case lid or the like, and an impact sound is generated.

Conventionally, in order to suppress such an impact,
A technique of arranging an elastic plate which receives a thrust force of a rotating shaft is known (see Japanese Utility Model Laid-Open No. 58-31756). 9 and 10 exemplify such a thrust receiving structure. FIG. 9 shows the entire structure of a conventional small motor in a right half section, and shows a thrust receiving structure at a shaft end in the drawings. Are shown in FIG. In these figures, the illustration of the stator-side magnets, brushes, and the like that are not directly related to the thrust receiving structure is omitted.

A cylindrical commutator 34 having a plurality of commutator segments 35 is fixed to the shaft 7 of the small motor. The tubular member 31 formed of an insulating material is fixed to the shaft 7 concentrically with the commutator 34 by fitting the commutator 34. An armature coil 33 is fixed on the outer periphery of the tubular member 31. A bearing member 39 for rotatably bearing the shaft 7 to which the commutator 34 and the armature coil 33 are fixed is provided at the center of one end surface of the case 2. Further, a round recess 40 as shown in detail in FIG. 10 is formed in the center of the case lid 5 that closes the open end of the case 2. An elastic thrust plate (a thin metal disk 36 and a plastic disk 37) is locked in the concave portion 40 by using the step 38 so that a predetermined distance from the bottom surface of the concave portion 40 is maintained. Is kept.

[0006] With this configuration, the shaft 7 is stably supported in the radial direction by the bearing member 39 having an increased axial length, and the shaft 7 can withstand the axial thrust force. Since the tip of 7 is supported by an elastic thrust plate, a favorable rotation operation is always performed. In particular, since a space is provided between the elastic thrust plate and the bottom surface of the concave portion 40, the shaft 7
When an abnormal thrust force is temporarily applied to the tire, the thrust plate can absorb and relieve the force.

However, the thrust plate provided in the recess 40 is locked by the step 38 but is not fixed, so that the thrust plate receives a thrust force from the shaft 7 at the center thereof. Sometimes, the thrust plate is easily deformed. Therefore, the air between the bottom of the recess and
There was a problem that this air layer could not be effectively used as an elastic layer in order to easily escape.

Further, such a thrust receiving structure considers only support in the thrust direction, and
Since it does not function as a bearing in the radial direction, there is a problem that a bearing member 39 having a longer axial length is required separately.

Further, an attractive force always acts between the stator side magnet and the laminated core of the rotor. Conventionally, to stabilize the contact between the commutator and the brush,
The magnet is biased to the brush side so that the rotor is attracted to the brush side. However, the thrust in the axial direction during rotation of the motor is much larger than the force of the magnet in the axial direction, so that the force of the magnet during the rotation of the motor is practically useless. Rather, there is a problem that the force attracted by the magnet acts when the motor is stopped, increasing the noise of the shaft collision.

[0010]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems, and combines a radial bearing structure for supporting a shaft in a radial direction with a thrust receiving structure for supporting a shaft in a thrust direction. By using the structure to fix the periphery of the thrust plate, the function of the thrust plate as an elastic plate is enhanced, and the space between the thrust plate and the bottom of the concave portion is effectively used as an elastic layer. The purpose is to suppress the impulsive sound that is emitted.

Further, the present invention reduces the force acting on the magnet in the axial direction when the motor is stopped by arranging the shaft to be in a neutral position where the shaft is not deviated to the left or right in the axial direction when the motor is stopped. Therefore, it is intended to suppress the impact sound at the time of a collision.

[0012]

The small motor according to the present invention comprises:
A hollow cylindrical case 2 with a bottom attached to a magnet 1 on the inner peripheral surface, a case lid 5 fitted to close the opening of the case 2 and having a brush 6 attached thereto, and a laminated core 8 on a shaft 7 , A winding 9 wound around the iron core, and a rotor to which a commutator 10 is attached. As for the shaft 7, the shaft end is supported in the thrust direction and the radial direction on one side of the bottom of the bottomed hollow cylindrical case 2 or the case lid 5, and is supported in the radial direction on the other side. And project therethrough for mechanical coupling to an external load. The thrust and radial bearings at the end of the shaft form a recess 20 at the bottom of the case 2 or at the center of the case lid 5 and a support (projection 24 or step 25) on the inner surface of the bottom 22 of the recess. Then, an elastic thrust plate 4 for supporting the end of the shaft in the thrust direction is placed thereon, and the sliding bearing 3 is further press-fitted into the recess 20 as a radial bearing on the thrust plate 4. I have. The thrust plate 4 has a concave bottom 2
2 so as to form a closed space 21 in the inner surface thereof, the periphery of the thrust plate 4 is sandwiched and fixed between the supporting portion (projection 24 or step 25) formed on the bottom surface of the concave portion and the press-fitted slide bearing 3. Is done. According to the present invention, the impact when the tip of the shaft 7 collides with the thrust plate 4 is effectively absorbed by the elasticity of the thrust plate 4 at the time of a load change or the like. It can be effectively absorbed by the working closed void 21. Also,
In the compact motor of the present invention, a spacer is provided below the plain bearing, and the spacer can be press-fitted into the recess. By providing the spacer 26 below the slide bearing 3 in this way, the entire inner periphery of the slide bearing works for sliding with the shaft 7. In other words, "the" R "portion at the tip of the shaft is applied to the inner periphery of the slide bearing" is eliminated.

Further, in the small-sized motor of the present invention, the diameter d1 of the air gap is made equal to or larger than the diameter d of the shaft, and the diameter d2 of the thrust plate is made twice as large as the diameter L1 of the air gap. And the diameter of the thrust plate d2
Is made smaller than the inner diameter d3 of the case lid concave portion, the thrust plate 4 held and held can be more stably held.

Further, the small motor of the present invention can further enhance its function as an elastic layer by putting grease 23 in the gap.

Further, in the small-sized motor of the present invention, the axial center of the magnet 1 and the axial center of the laminated core 8 substantially coincide with each other. The power to move is
Can be relaxed.

The shaft 7 of the small motor of the present invention projects outside the motor and is connected to the worm 12, and can be mechanically connected to the load via the worm wheel 13.

[0017]

FIG. 1 is a sectional view of a small motor according to the present invention, and illustrates a case where a worm 12 and a worm wheel 13 of a speed reducer are connected to a shaft tip. The magnet 1 is attached to an inner peripheral surface of a case 2 formed in a hollow cylindrical shape with a bottom by a metal material. A case lid 5 is fitted into the opening of the case 2 and is closed thereby. The case lid 5 is provided with a concave portion 20 at the center thereof, which accommodates a structure for bearing the shaft end in the radial direction and the thrust direction, which will be described later in detail, which is a feature of the present invention. The other end of the shaft 7 is supported by a slide bearing 3 provided at the center of the bottom of the bottomed hollow cylindrical case 2 and protrudes out of the motor therefrom for mechanical coupling to a load. In the illustrated example, the concave portion 20 is provided in the case lid. However, the concave portion 20 is provided in the center of the bottom surface of the case 2 and the shaft is radially and thrust-bearing there, and the shaft is placed on the side of the case lid 5. It is also possible to constitute so that it may penetrate from.

The shaft 7 has, as usual, an iron core obtained by caulking a laminated core 8 and a winding 9 wound on the iron core.
The commutator 10 is provided to constitute a rotor of a small motor. The brush 6 that contacts the commutator 10
Also, as usual, an input terminal connected to the brush 6 is supported by the case lid 5 and protrudes outside through the case lid for electrical connection.

The small motor according to the present invention can be used for any purpose. However, the small motor can be used for thrust for moving the shaft in the axial direction in response to a load change such as load on / off.
For example, the present invention is suitable for solving the above-mentioned problem of generating an impact sound by applying the present invention to an application for driving a load such as an electric component of an automobile via a reduction gear. The motor illustrated in FIG.
The worm 12 is connected to the
A worm wheel 13 is provided which meshes with. The load is driven by being directly or indirectly coupled to the output shaft of the worm wheel 13.

FIG. 2 shows the details of the radial and thrust bearing structures accommodated in the recess 20 at the center of the case lid 5. A preferably circular projection 24 is provided on the inner surface of the bottom 22 of the preferably circular recess 20 as a support for the thrust plate 4. Thereby, when the preferably circular thrust plate 4 is placed on the inner bottom surface of the recess 20, the closed gap 2 is cut off from the outside.
1 is formed. Further, on this thrust plate 4, a sliding bearing 3 as a radial bearing is provided with a concave portion 20 of the case lid 5.
Pressed into the inside and fixed. As a result, the periphery of the thrust plate 4 is clamped and held between the projection 24 and the slide bearing 3 to be fixed.

As the thrust plate 4, any elastic sheet member can be used, but a resin sheet is preferably used. The plain bearing 3 used as a radial bearing is a normal one, and can be formed by solidifying powder of a metal material such as iron, copper, and zinc.

When DC power is externally supplied to the input terminal of such a small motor, the motor rotates in a direction corresponding to the polarity. At that time, the motor shaft 7
For example, as shown, when connected to a load via the worm 12 and the worm wheel 13, depending on the rotation direction of the motor, the shaft 7 is connected to the worm wheel 1.
In response to the reaction from 3, a force is exerted to move in the axial direction in the direction indicated by arrow C in FIG. For example, the rotor of this type of small motor is manufactured with a clearance of 0.2 to 0.4 mm, that is, an axial displacement. It is virtually impossible to reduce this to zero if a manufacturing error is taken into consideration using a plain bearing. In other words, it is unavoidable that the rotor is configured to be slightly movable in the axial direction. This clearance is defined by the end plate 15 made of a resin washer shown in FIG. 1 and is attached to the slide bearing 3 with a slight gap. It should be noted that a collision noise is also generated between the end plate 15 and the slide bearing 3, however, here, the collision noise is not particularly large because the collision occurs between surfaces. On the other hand, the tip of the shaft 7 collides with the thrust plate at a point, so that the collision sound becomes loud enough to require suppression.

In FIG. 2 showing details, as described above,
When a leftward moving force is acting on the shaft 7,
The shaft 7 is separated from the thrust plate 4 and a gap is formed therebetween. In this state, when the power is off, the shaft 7 moves to the right under the action of the magnet 1 or when the rotation direction is reversed. The tip of the shaft 7 collides with the thrust plate 4, and the impact at that time is absorbed by the elasticity of the thrust plate 4 and further absorbed by the closed gap 21 acting as an elastic layer. Since the periphery of the thrust plate 4 of the present invention is sandwiched and fixed by the projection 24 and the press-fitted slide bearing 3, not only the thrust plate itself effectively functions as an elastic plate, but also, The air gap 21 is closed and formed from the outside, and the air there cannot be easily escaped, so that it can effectively work as an elastic layer.

As shown in FIG. 2, the diameter of the gap 21 is d
1. The diameter of the thrust plate 4 is d2, the inner diameter of the case cover recess 20 is d3, the diameter of the shaft is d, and the depth of the gap 21 is L. At this time, by securing the diameter d1 of the gap to be equal to or larger than the diameter d of the shaft (d ≦ d1), when the shaft 7 moves in the axial direction and gives an impact to the thrust plate 4, the impact of the thrust plate 4 is reduced. The received portion sufficiently penetrates into the gap (FIG. 3), and an effect of cushioning can be expected.

Further, by ensuring that the diameter d2 of the thrust plate 4 is at least as large as the diameter d1 of the gap plus twice the depth L of the gap (d1 + L × 2 <d2), There is no burial in the entire space of the thrust plate 4 which occurs when a large load exceeding the limit is applied.
The thrust plate 4 is sandwiched and held between the projection 24 and the slide bearing 3. FIG. 3 shows a state in which the thrust plate 4 is sandwiched and held and is not buried even though a load exceeding the limit is applied.

Further, by making the diameter d2 of the thrust plate 4 smaller than the inner diameter d3 of the recess (d2 <d3),
The thrust plate 4 can be positioned horizontally without bending in the case lid recess 20.

For example, assuming that the thrust plate 4 is formed of a resin such as polyester, the thickness is 0.35 mm, the diameter of the gap 21 is 3.5 mm, and the depth of the gap is 0.15 mm, the diameter of the thrust plate 4 is Needs to be larger than 3.80 mm, preferably 4.20 mm.

When the motor is stopped, the force acting in the axial direction of the rotor of the small motor as shown in FIG. 1 is only the force of the magnet 1 acting on the rotor laminated core 8. This force is applied to the center of magnet 1 (the midpoint 17 between A and A '),
It acts so that the axial center of the laminated core 8 (the middle point 18 between B and B ') coincides. In other words, if the center of the magnet 1 and the center of the laminated core 8 in the axial direction coincide with each other when the motor stops, no axial force acts on the rotor. The small motor of the present invention is configured such that the center of the magnet 1 and the center of the laminated core 8 in the axial direction substantially coincide with each other, so that at least the magnet 1 moves the motor rotor left and right when the motor stops. The force can be relaxed. This can also suppress the impact sound at the tip of the shaft.

FIG. 4 shows an example in which grease 23 is put in the space shown in FIG. Since grease has a higher viscosity than air, it can function more effectively as an elastic layer. Furthermore, by inserting grease into the gap, it becomes possible to easily insert the thrust plate 4 because the grease serves as an adhesive in the step of inserting the thrust plate 4 into the recess 20 during motor production.
FIGS. 5 to 7 show a configuration in which a spacer 26 is press-fitted below the sliding bearing 3 in addition to the configuration of FIGS.

FIG. 8 shows still another example of supporting the thrust plate 4. The thrust plate 4 placed on the inner surface of the bottom portion 22 of the recess 20 is necessarily a circular protrusion as illustrated in FIG. 2 as long as the thrust plate 4 is supported so as to form a closed gap on the inner bottom surface. There is no need, and a step 25 as illustrated in FIG. 8 can be used. As in FIG. 2, the periphery of the thrust plate 4 is fixed and the closed gap 21 is formed by the step portion 25 and the press-fitted spacer 26.

[0031]

According to the small motor of the present invention, a recess is formed at the bottom of the case or at the center of the case lid, and an elastic thrust plate for supporting the shaft end in the thrust direction is placed thereon. The thrust plate is fixed by sandwiching the periphery of the thrust plate between the support portion formed on the bottom surface of the recess and the `` press-fit spacer or press-fit sliding bearing '' so as to form a closed gap on the bottom surface of the recess. In addition, the impact when the tip of the shaft collides with the thrust plate at the time of a load change or the like is absorbed by the elasticity of the thrust plate, and can be effectively absorbed by the closed gap acting as the elastic layer.

Further, according to the present invention, the thrust plate 4 held and held is more stably held by setting the diameter d1 of the gap, the diameter d2 of the thrust plate, and the depth L of the gap in a predetermined relationship. be able to.

Further, according to the present invention, the function as an elastic layer can be further enhanced by putting grease in the gap, and at the time of motor production, the grease serves as an adhesive so that the thrust plate can be easily formed. It can be inserted into the recess.

Further, according to the present invention, since the axial center of the magnet and the axial center of the laminated core are substantially coincident with each other, at least the force for moving the motor rotor left and right by the magnet when the motor is stopped is reduced. The impact noise at the tip of the shaft can also be suppressed.

[Brief description of the drawings]

FIG. 1 is a sectional view of a small motor according to the present invention.

FIG. 2 is a diagram showing details of a thrust receiving structure of the present invention different from that shown in FIG.

FIG. 3 is an enlarged cross-sectional view of a case cover recess at the moment when a thrust direction impact is applied to the thrust receiving structure of the present invention.

FIG. 4 is a view showing another example of supporting a thrust plate of the thrust receiving structure of the present invention.

FIG. 5 is a view showing details of the thrust receiving structure of the present invention shown in FIG. 1;

6 is an enlarged cross-sectional view of a case cover recess at the moment when a thrust direction impact is applied to the thrust receiving structure illustrated in FIG. 5;

FIG. 7 is a view showing another example of supporting the thrust plate having the thrust receiving structure illustrated in FIG. 5;

8 is a diagram showing still another example of supporting a thrust plate having the thrust receiving structure illustrated in FIG.

FIG. 9 is a right half cross-sectional view showing the entire structure of a conventional small motor.

FIG. 10 is a view showing details of a conventional thrust receiving structure at the shaft end shown in FIG. 9;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Magnet 2 Case 3 Slide bearing 4 Thrust plate 5 Case lid 6 Brush 7 Shaft 8 Laminated core 9 Winding 10 Commutator 12 Warm 13 Warm wheel 15 End plate 20 Case lid recess 21 Air gap 22 Case lid recess bottom 23 Grease 24 Projection 25 Step 26 Spacer

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Masao Yagi 430 Matsuhidai, Matsudo-shi, Chiba Fuchi term in Mabuchi Motor Co., Ltd. 3J011 AA03 BA02 BA08 BA10 5H605 AA05 BB05 BB09 CC04 DD09 EA09 EB03 EB06

Claims (6)

[Claims] 1. A bottomed hollow cylindrical case having a magnet attached to an inner peripheral surface thereof, a case lid fitted so as to close an opening of the case and having a brush attached thereto, and a laminated core on a shaft. An iron core, a winding wound on the iron core, and a rotor having a commutator attached thereto, wherein the shaft has a shaft end radially aligned with a thrust direction on either the bottom of the case or the case lid. A small motor that is axially bearing and radially bearing on the other side and protruding through to mechanically couple to an external load, wherein the thrust and radial bearings at the shaft end are A concave portion is formed at the bottom of the case or the center of the case lid, a supporting portion is formed at the bottom surface of the concave portion, and an elastic member for supporting the shaft end in the thrust direction thereon. A thrust plate is placed thereon, and a sliding bearing is further formed thereon by press-fitting into the recess as a radial bearing, and the thrust plate is formed so as to form a closed gap at the bottom of the recess. Is fixed by being sandwiched between a support portion formed on the bottom surface of the concave portion and a press-fitted slide bearing,
A small motor characterized by the above. 2. The small motor according to claim 1, wherein a spacer is provided below the slide bearing, and the spacer is press-fitted into the recess. 3. The recess, the slide bearing, the thrust plate, and the gap are each circular, the diameter d1 of the gap is equal to or greater than the diameter d of the shaft, and the diameter d2 of the thrust plate is The diameter d2 of the gap is equal to or greater than twice the depth L of the gap, and the diameter d2 of the thrust plate is smaller than the inner diameter d3 of the case cover recess. Small motor as described. 4. The small motor according to claim 1, wherein grease is put in the gap. 5. The small motor according to claim 1, wherein the axial center of the magnet and the axial center of the laminated core substantially coincide with each other. 6. The small-sized motor according to claim 1, wherein the shaft projects out of the motor and is connected to a worm, and is further mechanically connected to a load via a worm wheel. .