JP2933811B2 - Small motor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a small motor capable of preventing vibration of a small motor in the axial direction and improving the torque of the motor.

[0002]

2. Description of the Related Art FIG. 6 shows a conventional example of a general small motor with a core. In FIG. 6, an end plate 2 is fixed to an open end of a cup-shaped motor case 1. Sintered oil-impregnated bearings 3, 3 are press-fitted into cylindrical portions formed by drawing at the center of the bottom of the motor case 1 and the center of the end plate 2, respectively. Supported. Further, the rotating shaft 4 is attached to the thrust bearing 11.
The rotating shaft 4 is rotatably supported by contacting one end of the rotating shaft 4. The center hole of the rotor core 5 is press-fitted into the rotating shaft 4 in the motor case 1. Rotor core 5
Has an appropriate number of salient poles, and a driving coil 6 is wound around each salient pole. A ring-shaped driving magnet 8 is fixed to the inner peripheral surface of the motor case 1, and the inner peripheral surface of the magnet 8 is
At an appropriate interval. The rotor 10 is constituted by the rotor core 5 and the drive coil 6. Commutator 7 and brush 9 mounted on rotating shaft 4
The rotor 10 is continuously driven to rotate by energizing the drive coil 6 via the switch and switching the energization according to the rotational position of the rotor 10.

[0003] In the above-mentioned small motor, the dimensional accuracy and assembly dimensional accuracy of the components vary, so that an axial clearance P is provided between the rotor 10 and the bearing 3. Therefore, there is a problem in that the rotor 10 vibrates in the axial direction when the motor rotates, thereby generating thrust noise. As a means for solving such a problem, a technique is generally known in which the center of the axial width of the rotor core 5 and the magnet 8 is shifted to generate an attractive force in the axial direction and press the rotor in the axial direction. However, such means has a problem that the axial length of the small motor is increased and the size of the motor cannot be reduced. As a technique for solving such a problem, there is a technique in which a rotor is formed in a truncated cone shape, and an inner peripheral surface of a magnet is formed in a tapered shape and opposed to each other. The technique described in JP-A-64-8841 is an example. In addition, there is a type in which the shape of the magnet or the rotor core is deformed, or a type in which the gap between the magnet and the rotor core is enlarged. The description in JP-A-1-298924 is an example thereof.

[0004]

However, in the prior art described above, the gap between the magnet and the rotor core is enlarged and the magnetic resistance is increased to obtain an imbalance in the magnetic flux density distribution. As shown in FIG. 7, there is a problem that the magnetic flux density does not increase to the magnetic flux density originally obtained (indicated by a broken line in FIG. 7), and the torque generated by the small motor decreases. In addition, the cost of parts increases because the magnet and rotor core are deformed.
Since the parts have irregular shapes, the number of parts and the types of parts are increased, so that not only the management becomes complicated, but also the assembly cost becomes high.

SUMMARY OF THE INVENTION The present invention has been made to solve the problems of the conventional small motor, and does not reduce the generated torque and increase the axial length of the rotor without increasing the axial length of the small motor. It is an object of the present invention to provide a small motor capable of preventing directional vibration.

[0006]

In order to achieve the above object, the present invention comprises a shaft, a bearing, a stator, and a rotor rotating opposite to the stator, wherein one of the rotor and the stator is provided. In a small-sized motor, one of which is formed by a core wound with a winding and the other is formed by a magnet, the center of the core in the axial direction of the core is a thrust center and the magnet is
The drive magnetized part is applied to the
When it is formed symmetrically in the circumferential direction with respect to the
And forming a non-magnetized portion in a part of the magnet in the axial direction.
Accordingly, the center angle of the drive magnetized portion is made different on both sides with respect to the center of the thrust , and the center angle of the core in the thrust direction is changed.
Imbalance the magnetic force of the part that contributes to the attraction
An axial suction force is generated, and the suction force
The thrust bearing against the thrust bearing. When the number of magnetic poles is A, the number of salient poles of the core is B, and the greatest common divisor of AB is C, the central angle θ of the drive magnetized portion at the center of the thrust is θ =
{(B−C) / (A × B)} × 360 ° was made to have a tolerance of ± 10 °.

[0007]

The drive magnetizing portion is applied to the magnet with the axial center position of the core in the axial direction as the thrust center.
Is formed circumferentially symmetrical with respect to the boundary of switching
At the same time, a non-magnetized portion is formed in a part of the magnet in the axial direction.
As a result, the center angle of the drive magnetized portion is made different on both sides with respect to the thrust center , and
The magnetic force of the applied part is formed unbalanced,
A suction force is generated, and this suction force causes the rotor to thrust.
Since the rotor is pressed against the bearing, the rotor is constantly pressed against the thrust bearing by the axial suction force generated by the magnetic imbalance in the thrust direction, so that the axial vibration of the rotor can be prevented. In addition, since one magnet is provided with a magnetic unbalance, it is not necessary to deform the parts such as forming the inner peripheral surface of the magnet into a tapered shape, so that the manufacturing cost can be reduced.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a small motor according to the present invention will be described below. 1 and 2, an end plate 22 is fixed to an open end of a cup-shaped motor case 21. Sintered oil-impregnated bearings 23, 23 are press-fitted into the central cylindrical portion and the concave portion of the bottom of the motor case 21 and the center of the end plate 22, and the rotating shaft 24 is rotatably supported by the bearings 23, 23. The center hole of the rotor core 25 is press-fitted into the rotating shaft 24 in the motor case 21. The rotor core 25 has an appropriate number of salient poles (three in the illustrated embodiment), and a driving coil 26 is wound around each salient pole. The rotating shaft 24, the rotor core 25, the drive coil 2
6 form a rotor 30.

A ring-shaped driving magnet 28 is fixed to the inner peripheral surface of the motor case 21.
The stator 32 is constituted by the magnets 3 and 23 and the driving magnet 28. The inner peripheral surface of the magnet 28 faces the outer peripheral surface of the rotor core 25 at an appropriate interval. The rotating shaft 2
By energizing the drive coil 26 via the commutator 27 and the brush 29 attached to the rotor 4 and switching the energization according to the rotational position of the rotor 30, the rotor 30 is continuously driven to rotate. Further, one end of the rotating shaft 24 is in contact with and supported by the thrust bearing 31.

The thickness and the axial width of the magnet 28 are substantially uniform over the entire circumference. Also, both end surfaces 28a of the magnet 28 are substantially along the entire circumference with respect to each single surface perpendicular to the axis. The circumferential gap between the rotor core 25 and the magnet 28 is substantially uniform over the entire circumference. The magnet 28 does not have a special shape such as being formed in a tapered shape or having a step.

FIG. 2 (a) shows the C of the small motor shown in FIG.
FIG. 2B is a cross-sectional view taken along the line C, and FIG.
FIG. 2C is a cross-sectional view along the line D, and FIG.
The cross-sectional views along the line are respectively shown. FIG.
(A) is a development view of a surface of the magnet 28 facing the rotor core 25. In FIG. 3A, N indicates a magnetized portion of the N pole, and S indicates
Indicates a magnetized portion of the S pole, O indicates a non-magnetized portion, and Lc indicates a magnetic center position of the rotor core 25 in the thrust direction. In FIG. 3 (a)
As shown in the figure, the magnetized portion is positioned on the boundary between the N and S switching.
And are formed symmetrically in the circumferential direction. The magnet 28 has S
A pole main pole MS and an N pole main pole MN are provided, and a triangular non-magnetized portion O is provided between the main poles MS and MN. The axial centers of the rotor core 25 and the magnet 28 substantially coincide with each other.

In the above embodiment, as shown in FIG. 3A, the main magnetic poles MS and MN have a substantially trapezoidal shape. For this reason, in FIGS. 2A to 2C, the center angle of the main magnetic pole MS in the sectional view (a) along the line CC on the thrust bearing 31 side with respect to the magnetic center Lc in the thrust direction of the rotor core 25 is represented by θ. ₁ , if the central angle of the main pole MS is θ _{3 in} the cross-sectional view (c) along the line EE, then θ ₁ > θ ₃ . The main magnetic pole MN is formed similarly to the main magnetic pole MS. According to the above embodiment, the main magnetic poles MS, MN
2A has a stronger magnetic force than the one end shown in FIG. 2C than the one end shown in FIG. 2C, and the rotor core 25 has an axial direction due to the unbalance of the magnetic force. A suction force (upward in FIG. 1) is generated, and the rotor 30 is constantly pressed against the thrust bearing 31.

In the above embodiment, as shown in FIG. 2B, the center angle of the main magnetic pole MS at the magnetic center in the thrust direction is θ ₂ , the number of main magnetic poles of the small motor is A, and the salient poles of the rotor core are A. When the number is B and the greatest common divisor of A and B is C, θ ₂ {(B−c) / (A × B)} × 360 °
As a result, the distribution of the magnetic flux density along the magnetic center Lc in the thrust direction of the rotor core 25 of the magnet 28 becomes as shown in FIG. 3F, and the magnetic force of the portion contributing to the rotational driving of the rotor 30 can be balanced. As a result, a small-sized motor having a small torque loss and a smooth rotation with a small cogging torque and a small torque ripple can be obtained. It should be noted that θ ₂ is not strictly required to be θ ₂ {(B−c) / (A × B)} × 360 °, but may be within a tolerance of ± 10 °.

Next, a second embodiment of the present invention will be described. FIG. 3B is a developed view of a surface of the magnet 28 facing the rotor core 25 according to the second embodiment of the present invention. In FIG. 3B, the main magnetic poles MS and MN are formed in a substantially pentagonal shape, and a triangular non-magnetized portion O is formed between the main magnetic pole MS and the main magnetic pole MN. The central angle of the main pole MS in the cross section on the thrust bearing side from the magnetic center Lc in the thrust direction of the rotor core 25 is defined as θ _1, and the main axis MS in the cross section on the other end side is θ _1.
Assuming that the central angle is θ ₃ , θ ₁ > θ ₃ . The main magnetic pole MN is similarly formed. Therefore, also in the second embodiment, similarly to the above embodiment, the attraction force of the main magnetic poles MS and MN to the rotor core 25 is closer to one end side (downward in FIG. 3B) than the thrust bearing (FIG. 3B).
The magnetic force is stronger than that in the upper part of FIG. 1B, and the rotor core 25 is unbalanced in the axial direction (FIG. 1).
, The rotor 30 is constantly pressed against the thrust bearing 31, and axial vibration during rotation can be prevented.

[0015]

[0016]

FIG. 3D is a developed view of a surface of the magnet 28 facing the rotor core 25 according to the fourth embodiment of the present invention. In FIG. 3D, the main magnetic poles MN and MS have a substantially trapezoidal shape, and a line Cp (an axial line passing through the center in the circumferential direction on Lc of the main magnetic pole MS is Cs, and the electric angle is smaller than the line Cs by an electrical angle). With respect to an axial line passing through a position shifted by 90 °), boundary lines QN and PN, QS and P on both sides of the main magnetic poles MS and MN.
FIG. 3 shows the main magnetic poles MS and MN with different inclination angles of S.
In (d), the lower side is configured to be wider than the upper side. A triangular non-magnetized portion is formed between the main poles MS and MN. By changing the central angle of the main magnetic pole in the axial direction in this manner, an axial attractive force is generated in the rotor core 25, and the rotor 30 is constantly pressed against the thrust bearing 31, thereby preventing axial vibration during rotation.
Further, imbalance also occurs in the magnetic force for attracting the rotor 25 in the radial direction, and the rotating shaft 24 is biased in one direction in the radial bearings 23, 23 as in the third embodiment.
Radial vibration of the rotor 30 and the rotating shaft 24 can be prevented at the same time as axial vibration.

FIG. 3E is a development view of a surface of the magnet 28 facing the rotor core 25 according to the fifth embodiment of the present invention. In FIG. 3E, the driving magnet 28 has a main magnetic pole MS.
And a main magnetic pole MN, and a rhombic auxiliary magnetic pole MP is provided along a line Cp passing through a position shifted by 90 ° in electrical angle from a line Cs passing through a central position in the circumferential direction of the main magnetic pole MS. The auxiliary magnetic pole MP has a magnetized portion MPS of the S pole and a magnetized portion MPN of the N pole.
The magnetized portions MPS and MPN are provided symmetrically with respect to the Lc. The main poles MS and MN are formed in the same shape as in the first embodiment, and generate the same axial attractive force as in the first embodiment. The remaining portion is a non-magnetized portion O. According to the above embodiment, each auxiliary magnetic pole portion M
Since the magnetic forces of PS and MPN cancel each other, the magnetic forces of main poles MS and MN act on rotor core 25,
The magnetic flux density distribution in the rotation direction is as shown in FIG. Therefore, the magnetic force is unbalanced between the upper and lower parts of the spindle,
Due to this imbalance, an axial suction force is generated, and the rotor 30 is constantly pressed against the thrust bearing 31, thereby preventing axial vibration during rotation.

[0019] Incidentally, since the magnetic force of the auxiliary magnetic pole portion MP in the fifth embodiment for the rotor core 25 to act as a suction force, the radial force f ₃ on the rotor 30 as shown in FIG. 4 Acting, the rotating shaft 24 can be biased in one direction in the bearing. Therefore, in this embodiment, the radial vibration of the rotor 30 and the rotating shaft 24 can be prevented simultaneously with the axial vibration, as in the fourth embodiment. In the above embodiment, the magnetized portion MPS,
Although the MPN has a triangular shape, it may have a rectangular shape or a polygonal shape, and a plurality of auxiliary magnetic pole portions MPS and MPN may be provided. Neither is limited to the above embodiment.

FIG. 4 is a diagram showing the magnetic flux distribution of each embodiment described above .
3 (f), (g), (i), and (j) , each is substantially symmetric with respect to a certain point R. When the central angle between the effective radial magnetic center of the main magnetic pole and the magnetic center of the adjacent main magnetic pole is α, α is substantially equal to 360 ° / the number of magnetic poles. That is, α {360} / 2P (where P is a natural number). Further, similarly to the first embodiment, the second embodiment,
Also in the fourth and fifth embodiments, FIG.
(D) As shown in (e), the magnetized portion switches between N and S.
It is formed symmetrically in the circumferential direction with respect to the boundary line of the front.

In each of the first to fifth embodiments described above, the number of main magnetic poles is one each for N and S.
The present invention is applicable even if the N and S main magnetic poles are each a P pole (P is a natural number), that is, a total of 2 P poles. Further, the non-magnetized portion between the main magnetic pole and the main magnetic pole may be a defective portion of the magnet, and the S pole and the N pole are magnetized in reverse to the magnetized pattern of the embodiment. Is also good.

Also, the thrust bearing does not necessarily need to be configured to support one end of the rotating shaft as in the above embodiment. For example, the rotor end face or the step formed on the rotating shaft is supported by a radial bearing. You may make it.

As in the first embodiment, also in the second to fifth embodiments, the central angle of the main pole MS at the magnetic center in the thrust direction is θ ₂ , the number of main poles of the small motor is A, and the rotor core is A. Let B be the number of salient poles and C be the greatest common divisor of A and B, θ ₂ {(B−C) / (A × B)} ×
By setting the angle to 360 °, the distribution of the magnetic flux density along the magnetic center Lc in the thrust direction of the rotor core 25 of the magnet 28 is changed as shown in FIG.
(G) to (j), since the magnetic force of the portion contributing to the rotational drive of the rotor 30 is balanced, the motor has a small torque loss, and a smooth rotation motor with little cogging torque and torque ripple. Is obtained. Note that strictly, θ ₂ is θ ₂ ≒ ｛(B−c) / (A ×
B) It does not have to be Δ × 360 ° but may be within a tolerance of ± 10 °.

A magnetic pole portion adjacent to the magnetic pole portions of S and N,
Alternatively, the boundary with the non-magnetized portion is not limited to a straight line as illustrated, but may be a continuation of a plurality of straight lines or a curve. Further, the magnetized portion is not limited to the saturated magnetized portion, and may have a non-saturated magnetized portion with a sinusoidal magnetization intensity distribution, for example. Although various examples have been shown solely as means for biasing the rotation axis in a certain direction, a plurality of these means may be combined.

Next, another embodiment in which the present invention is applied to a brushless motor will be described. In FIG. 5, a stator core 36 is mounted on a substrate 33 via a spacer 35. The stator 36 and the spacer 35 have center holes, and one sintered oil-impregnated bearing 34 is fitted in these center holes. The bearing 34, the spacer 35, and the stator core 36 are integrally fixed to the substrate 33 by screws 44. The stator core 36 has an appropriate number of salient poles,
A driving coil 37 is wound around each salient pole. Bearing 3
A thrust bearing 42 is attached to the bottom surface of 4.
A bearing set is constituted by the bearing 34 and the thrust bearing 42, and the rotating shaft 38 is rotatably supported by the bearing set. The stator 40 is constituted by the bearing set, the stator core 36 and the like.

An inverted cup-shaped rotor case 39 is press-fitted and fixed to one end of the rotating shaft 38, and the rotating shaft 38 and the rotor case 39 are integrated. Rotor case 3
An annular drive magnet 43 is fixed to the inner peripheral surface of the peripheral wall 9. The inner peripheral surface of the magnet 43 faces the outer peripheral surface of the stator core 36 at an appropriate interval. The rotor 41 is constituted by the rotating shaft 38, the rotor case 39, the magnet 43 and the like.

The magnetized pattern on the inner peripheral surface of the magnet 43 is
The magnetization pattern is the same as that of any one of the first to fifth embodiments. Thus, the same effects as those of the first to fifth embodiments can be obtained in the brushless motor. Also, conventionally, since the entire surface of the magnet was magnetized,
There was a problem that the suction force in the thrust direction (downward in FIG. 5) was too strong and the life of the thrust bearing was shortened. However, by using a magnetized pattern having a non-magnetized portion as described above, The suction force in the thrust direction can be reduced, and the life of the thrust bearing and the small motor as a whole can be extended.

The present invention can also be applied to a fixed shaft type small motor in which a rotor rotates with respect to a fixed shaft.

[0029]

According to the present invention, there is provided a bearing, a rotating shaft rotatably supported by the bearing, a stator, and a rotor rotating opposite to the stator. any form one core wound winding, in a small motor which form the other with a magnet, the magnet and magnetic axial center position of the core as a thrust center
The drive magnetized part is applied to the
When it is formed symmetrically in the circumferential direction with respect to the
And forming a non-magnetized portion in a part of the magnet in the axial direction.
Accordingly, the center angle of the drive magnetized portion is made different on both sides with respect to the center of the thrust , and the center angle of the core in the thrust direction is changed.
Imbalance the magnetic force of the part that contributes to the attraction
An axial suction force is generated, and the suction force
As the rotor is pressed against the thrust bearing , the rotor is pressed in the thrust direction by the attraction force in the axial direction resulting from the magnetic imbalance in the thrust direction, thereby preventing the rotor from vibrating in the axial direction. Since magnets and cores are not deformed in obtaining the attraction force, it is possible to suppress the increase in parts cost and the decrease in the torque generated by the motor, and to prevent the rotor from vibrating in the axial direction by devising the magnetization pattern of one magnet. Therefore, it is possible to suppress an increase in the number of component types and an increase in manufacturing cost. Also, compared to the case where the center of the axial width between the core and the magnet is shifted to generate an attractive force in the axial direction and press the rotor in the axial direction, the axial length of the rotor is increased without increasing the axial length of the small motor. Vibration can be prevented. Also, the radial absorption of the core
The magnetic force of the part contributing to pull
Because it was formed so as to be deflected in a certain direction inside the receiving,
Elimination of backlash in the bearing of the rolling shaft eliminates swinging of the rotating shaft.
Can also be reduced. In addition, a magnet facing the core
The magnetization pattern of
Because it was formed to balance energy,
There is little torque crossing, and cogging torque and torque
Less ripple, less uneven rotation and smooth
A small rotating motor can be provided.

[0030]

[0031]

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing one embodiment of a small motor according to the present invention.

FIG. 2 is a cross-sectional view taken along lines CC, DD, and EE in FIG.

FIG. 3 is a development view of magnets in the embodiment and another embodiment and their magnetic flux density distribution diagrams.

FIG. 4 is a cross-sectional view of another embodiment of the small motor according to the present invention.

FIG. 5 is a sectional view showing another embodiment of the small motor according to the present invention.

FIG. 6 is a longitudinal sectional view and a transverse sectional view of a conventional small motor.

FIG. 7 is a magnetic flux density distribution diagram of the conventional example.

[Explanation of symbols]

 23 Bearing 24 Rotating shaft 25 Rotor core 28 Magnet 30 Rotor 31 Thrust bearing 32 Stator 34 Bearing 38 Rotating shaft 40 Stator 41 Rotor 42 Bearing 43 Magnet

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H02K 5/00-5/24 H02K 15/03

Claims (2)

(57) [Claims] 1. A motor comprising a shaft, a bearing, a stator, and a rotor rotating in opposition to the stator, wherein one of the rotor and the stator is formed by a core wound with a winding, and the other is The motor is formed by magnets, and the axial center position of the core in the axial direction is
A driving magnetized portion is applied to the magnet, and the driving magnetized portion includes N, S
Is formed circumferentially symmetrical with respect to the boundary of switching
At the same time, a non-magnetized portion is formed in a part of the magnet in the axial direction.
Thus, the center angle of the drive magnetized portion is made different on both sides with respect to the center of the thrust, so that the thrust direction of the core is
Unbalanced magnetic force of the part contributing to the attraction of the direction
To generate an axial suction force, and the suction force
A small motor characterized in that the rotor is pressed against a thrust bearing . 2. The number of magnetic poles of the driving magnetized portion of the magnet is A,
When the number of salient poles is B and the greatest common divisor of AB is C, the thrust
When the center angle θ of the drive magnetized portion at the center of the drive is θ = ｛(B−C)
/ (A × B)｝ × 360 ゜ with a tolerance of ± 10 ゜
The small motor according to claim 1.