JP3720143B2 - Electric motor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electric motor in which a rotating sleeve is supported by a dynamic pressure with respect to a fixed shaft, such as a spindle motor applied to an HDD (hard disk drive) or the like.
[0002]
[Prior art]
Conventionally, as this type of electric motor, there is a spindle motor as shown in FIG. This spindle motor has a fixed shaft 102 whose both ends in the axial direction are fixed to the fixed portions 101A and 101B, and a rotating sleeve 103 fitted coaxially to the fixed shaft 102. An outer cylinder 113 is fixed to the outer peripheral surface of the rotating sleeve 103. The fixed shaft 102 has a flange portion 105. The flange portion 105 is opposed to the axial end wall surfaces 106A and 106B of the inner circumferential recess 106 of the rotating sleeve 103 via minute gaps S1 and S2. Further, dynamic pressure grooves 107 and 108 that generate axial dynamic pressure are formed on both surfaces 105A and 105B of the flange portion 105. A radial support dynamic pressure groove 115 is formed on the outer peripheral surface of the shaft portion 102A of the fixed shaft 102.
[0003]
On the other hand, the stator coil 110 is fixed to the fixed portion 101B. The stator coil 110 faces the outer periphery of the rotating sleeve 103. A rotor magnet 111 is fixed to the inner peripheral surface of the outer cylinder 113. The rotor magnet 111 faces the outer periphery of the stator coil 110.
[0004]
In the spindle motor configured as described above, the rotor magnet 111 is rotated by the rotating magnetic field generated by the stator coil 110. At the same time, the rotating sleeve 103 rotates and the dynamic pressure grooves 107 and 108 formed in the flange portion 105 generate axial dynamic pressure. This axial dynamic pressure supports the rotary sleeve 103 in the axial direction with respect to the fixed shaft 102. The radial support dynamic pressure groove 115 generates a radial dynamic pressure to support the rotary sleeve 103 in the radial direction with respect to the fixed shaft 102.
[0005]
[Problems to be solved by the invention]
By the way, in the conventional electric motor, when stopped, as shown in FIG. 4A, the wall surface 106A of the concave portion 106 of the rotating sleeve 103 is in contact with the surface 105A of the flange portion 105 of the fixed shaft 102 (the offset state ( 1) ) may occur.
[0006]
Further, as shown in FIG. 4B, the wall surface 106B of the concave portion 106 of the rotating sleeve 103 may be in a state of being in contact with the surface 105B of the flange portion 105 of the fixed shaft 102 (an offset state (2) ).
[0007]
Furthermore, in the conventional electric motor, when stopping may also be in any state between the offset and the state (2) shown in FIG. 4 (B) and offset state (1) in FIG. 4 (A).
[0008]
Therefore, in the conventional electric motor, when the motor is stopped, the variation V in the axial position of the outer cylinder 113 as shown in FIG. 4 occurs. This causes, for example, a decrease in disk position accuracy when the electric motor is assembled to the HDD.
[0009]
In general, a method of shifting the magnetic balance between the rotor magnet and the stator coil in the axial direction is used to suppress variations in the axial position of the stator and rotor of the motor. However, this method impairs the driving efficiency of the motor. Moreover, high assembly accuracy is required to shift the magnetic balance in the axial direction.
[0010]
Accordingly, an object of the present invention is to provide an electric motor capable of preventing the occurrence of variations in the axial position of the rotating sleeve at the time of stopping without impairing the driving efficiency of the motor and without causing an increase in necessary assembly accuracy. .
[0011]
[Means for Solving the Problems]
In order to achieve the above object, an electric motor according to a first aspect of the present invention includes a fixed shaft having a flange portion and an axial end portion fixed to the fixed portion, and is externally fitted coaxially with the fixed shaft. A rotating sleeve having two bearing surfaces facing the flange portion through a minute gap so as to sandwich the flange portion of the fixed shaft from both sides in the axial direction, and attached to the fixed portion, facing the outer periphery of the rotating sleeve The stator coil, the rotor magnet connected to the rotating sleeve so as to face the outer periphery of the stator coil, and both axial end surfaces of the flange portion or two bearing surfaces of the rotating sleeve. In an electric motor having a dynamic pressure generating groove,
When the rotating sleeve is stopped, one bearing surface of the rotating sleeve is brought into substantially parallel contact with one axial end surface of the flange portion, while when the rotating sleeve is rotating, the rotating sleeve An annular magnetic member that attracts the rotor magnet toward the fixed portion is attached to the fixed portion such that the rotor magnet floats from the flange portion,
When the rotating sleeve is stopped, one end surface in the axial direction of the annular magnetic member and the other end surface in the axial direction of the rotor magnet are opposed substantially in parallel,
The radial width of the other axial end of the rotor magnet that is axially opposed to one axial end of the annular magnetic member is equal to one axial end of the annular magnetic member. Smaller than the radial width of
The radially inner end of the rotor magnet is positioned radially outward from the radially inner end of the annular magnetic member, and the radially outer end of the rotor magnet is the annular magnetic member. positioned radially inward of the outer end of the radial direction,
One end face in the axial direction of the annular magnetic member is a plane extending from the inner end to the outer end in the radial direction of the annular magnetic member .
[0012]
According to the first aspect of the present invention, the magnetic member attached to the fixed portion attracts the rotor magnet connected to the rotating sleeve toward the fixed portion.
[0013]
Since this suction force is weaker than the dynamic pressure generated by the dynamic pressure generating groove of the rotating sleeve, when the rotating sleeve rotates, the rotating sleeve is in a state of floating from the flange portion. On the other hand, when the rotating sleeve is stopped, the suction force moves the rotating sleeve toward the fixed portion, and makes one bearing surface of the rotating sleeve abut on one end surface of the flange portion.
[0014]
Therefore, according to the present invention, since the rotating sleeve can be brought into contact with the flange portion reliably at the time of stoppage by the attractive force between the rotor magnet and the magnetic member, the stop caused by the minute gap for generating dynamic pressure. This eliminates variations in the axial position of the rotating sleeve. Therefore, according to the present invention, the axial position of the rotating sleeve at the time of assembly (when stopped) can be set with high accuracy without impairing the drive efficiency of the motor and without causing an increase in necessary assembly accuracy, and as an assembly. An electric motor with high accuracy can be provided.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the illustrated embodiments.
[0016]
[First Embodiment]
FIG. 1 shows an HDD spindle motor as a first embodiment of the electric motor of the present invention. In this spindle motor, a fixed shaft 3 and a rotating sleeve 5 are disposed between two fixed portions 1 and 2 that are separated from each other by a predetermined axial gap. One end 3 </ b> A of the fixed shaft 3 is fixed to the fixed portion 1, and the other end 3 </ b> B of the fixed shaft 3 is fixed to the fixed portion 2. The rotating sleeve 5 is fitted on the fixed shaft 3 coaxially.
[0017]
The fixed shaft 3 has a flange portion 6 slightly more than one side in the axial direction. The rotating sleeve 5 has an annular recess 7 on the inner periphery. The annular recess 7 has one end wall 8 in the axial direction and the other end wall 10 in the axial direction. The one end wall 8 faces one end face 6A of the flange portion 6 and the other end wall 10 faces the other end face 6B of the flange portion 6. The one end wall 8 and the other end wall 10 of the annular recess 7 are separated from each other by a predetermined axial gap S100. When the rotary sleeve 5 is rotated, the end walls 8 and 10 are the end surfaces 6A of the flange portion 6. , 6B is separated from the minute gap for generating dynamic pressure. On the end surfaces 6A and 6B of the flange portion 6, dynamic pressure generating grooves 17 and 18 are formed. Further, a radial support dynamic pressure groove 20 is formed on the outer peripheral surface of the shaft portion 3 </ b> C of the fixed shaft 3.
[0018]
A stator coil 12 is fixed to the fixed portion 2 via a support member 11, and the stator coil 12 faces the outer peripheral surface 5 </ b> A of the rotating sleeve 5. An outer cylinder 13 is fixed to one axial end portion of the outer peripheral surface 5 </ b> A of the rotating sleeve 5. An annular rotor magnet 15 is fixed to the inner peripheral surface 13A of the outer cylinder 13. The rotor magnet 15 faces the stator coil 12.
[0019]
Further, an annular iron plate 16 as a magnetic member is fixed to the fixing portion 2. The iron plate 16 applies an attractive force to the rotor magnet 15. When the rotary sleeve 5 is stopped and the dynamic pressure generating grooves 17 and 18 are not generating dynamic pressure, the attractive force is generated by attracting and moving the rotor magnet 15 toward the fixed portion 2. 1, the end wall 8 of the rotating sleeve 5 is brought into contact with the end surface 6 </ b> A of the flange portion 6. On the other hand, when the rotary sleeve 5 is rotating and the dynamic pressure generating grooves 17 and 18 generate axial dynamic pressure, the dynamic pressure overcomes the attractive force between the rotor magnet 15 and the iron plate 16. The end wall 8 of the rotating sleeve 5 is lifted from the end surface 6A of the flange portion 6 so that the rotating sleeve 5 and the flange portion 6 are not in contact with each other.
[0020]
In the spindle motor configured as described above, the rotor magnet 15 is rotated together with the outer cylinder 13 and the rotating sleeve 5 by the rotating magnetic field generated by the stator coil 12. Then, the dynamic pressure generating grooves 17 and 18 formed on the end surfaces 6A and 6B of the flange portion 6 of the fixed shaft 3 generate axial dynamic pressure, and the rotating sleeve 5 is lifted from the flange portion 6 and is not moved. Keep in contact. The radial support dynamic pressure groove 20 generates a dynamic pressure in the radial direction and supports the rotary sleeve 5 in the radial direction with respect to the fixed shaft 3. Thereby, the rotation sleeve 5 can rotate smoothly with respect to the fixed shaft 3.
[0021]
On the other hand, when the stator coil 12 does not generate a rotating magnetic field and the rotating sleeve 5 is stopped, the rotor magnet 15 is attracted to the iron plate 16 and moves in the direction of the arrow X. 5 end wall 8 abuts on end surface 6A of flange portion 6. Therefore, according to this spindle motor, the axial position variation of the rotating sleeve 5 at the time of stopping due to the dynamic pressure generating gap between the end walls 8 and 10 forming the bearing surface of the rotating sleeve 5 and the flange portion 6 is reduced. Can be resolved. Therefore, according to this spindle motor, the accuracy of the assembly at the time of stopping (at the time of assembly) can be increased without impairing the driving efficiency of the motor and without causing an increase in the required assembly accuracy [second embodiment] ]
FIG. 2 shows an HDD spindle motor as a second embodiment of the electric motor of the present invention. In this spindle motor, a fixed shaft 33 and a rotating sleeve 35 are disposed between two fixed portions 31 and 32 that are separated from each other by a predetermined axial gap. The rotating sleeve 35 is fitted on the fixed shaft 33 coaxially.
[0022]
The fixed shaft 33 has a flange portion 36 and a shaft portion 33B at one end in the axial direction. The shaft 33 </ b> B is fixed to the fixing portion 32.
[0023]
The rotating sleeve 35 has an inner cylinder part 37, an outer cylinder part 38, and a lid part 39. One end surface 37A of the inner cylindrical portion 37, the inner peripheral surface 38A of the outer cylindrical portion 38 adjacent to the end surface 37A, and the concave portion 39A at the center of the lid portion 39 surround the flange portion 36. The bottom surface 40 of the concave portion 39A is opposed to one end surface 36A of the flange portion 36, and the end surface 37A of the inner cylinder portion 37 is opposed to the other end surface 36B of the flange portion 36. The bottom surface 40 and the end surface 37A form a bearing surface, and the bottom surface 40 and the end surface 37A separate an axial gap S200. When the rotary sleeve 35 rotates, the bottom surface 40 and the end surface 37A are separated from the end surfaces 36A and 36B of the flange portion 36 by a minute gap for generating dynamic pressure.
[0024]
Further, dynamic pressure generating grooves 41 and 42 are formed on the end faces 36A and 36B of the flange portion 36, respectively. A dynamic pressure generating groove 55 for radial support is formed on the outer peripheral surface of the shaft portion 33B.
[0025]
The fixed portion 32 has a support portion 45 extending in the axial direction, and a stator coil 46 is fixed to the support portion 45. The stator coil 46 is located between the inner cylinder part 37 and the outer cylinder part 38 of the rotary sleeve 35. An annular rotor magnet 47 is fixed to the inner peripheral surface 38 </ b> A of the outer cylindrical portion 38 of the rotating sleeve 35. The rotor magnet 47 faces the stator coil 46.
[0026]
Further, an annular iron plate 50 as a magnetic member is embedded and fixed in the fixing portion 32. This iron plate 50 applies an attractive force to the rotor magnet 47. When the rotary sleeve 35 is stopped and the dynamic pressure generating grooves 41 and 42 are not generating dynamic pressure, the attractive force is generated by attracting and moving the rotor magnet 47 toward the fixed portion 32. 2, the bottom surface 40 of the recess 39 </ b> A of the rotating sleeve 35 is brought into contact with the end surface 36 </ b> A of the flange portion 36.
[0027]
On the other hand, when the rotary sleeve 35 is rotating and the dynamic pressure generating grooves 41 and 42 generate axial dynamic pressure, the dynamic pressure overcomes the attractive force between the rotor magnet 47 and the iron plate 59. The bottom surface 40 of the concave portion 39A of the rotating sleeve 35 is lifted from the end surface 36A of the flange portion 36, and the rotating sleeve 35 and the flange portion 36 are not in contact with each other.
[0028]
In the spindle motor having the above configuration, the rotor magnet 47 is rotated together with the outer cylinder portion 38 and the inner cylinder portion 37 by the rotating magnetic field generated by the stator coil 46. Then, the dynamic pressure generating grooves 41 and 42 formed on the end surfaces 36A and 36B of the flange portion 36 of the fixed shaft 33 generate axial dynamic pressure, and the rotating sleeve 35 is lifted from the flange portion 36 to be non-actuated. Keep in contact. Thereby, the rotating sleeve 35 can rotate smoothly with respect to the fixed shaft 33.
[0029]
On the other hand, when the stator coil 46 does not generate a rotating magnetic field and the rotating sleeve 35 is stopped, the rotor magnet 47 is attracted to the iron plate 50 and moves in the direction of arrow Y. Then, the bottom surface 40 of the concave portion 39 </ b> A of the lid portion 39 of the rotating sleeve 35 contacts the one end surface 36 </ b> A of the flange portion 36. Therefore, according to this spindle motor, the axial position variation of the rotating sleeve 35 at the time of stopping due to the dynamic pressure generating gap between the bottom surface 40 and the end surface 37A forming the bearing surface of the rotating sleeve 35 and the flange portion 36 is reduced. Can be resolved. Therefore, according to this spindle motor, the accuracy of the assembly can be increased.
[0030]
In the first and second embodiments, an iron plate is used as the magnetic member. However, the magnetic member may be anything as long as it can apply a magnetic attractive force to the rotor magnet. In the above embodiment, the HDD spindle motor has been described. However, the present invention is useful when applied to a precision instrument motor in which the positional accuracy of the rotating sleeve is important when stopped (when assembled).
[0031]
【The invention's effect】
As is clear from the above, the electric motor according to the first aspect of the present invention is such that a magnetic member is attached to a fixed portion to which a fixed shaft having a flange portion and a stator coil are fixed, and is connected to the magnetic member and the rotating sleeve. An attractive force was applied to the rotor magnet. When the rotating sleeve is stopped, the suction force causes the rotating sleeve to move toward the fixed portion, causing one axial end surface of the flange portion to abut against one bearing surface of the rotating sleeve, while rotating the rotating sleeve. When the sleeve is rotating, the dynamic pressure generated by the rotation overcomes the suction force so that the rotating sleeve floats from the flange portion of the fixed shaft.
[0032]
Therefore, according to the present invention, the rotating sleeve can be reliably brought into contact with the flange portion at the time of stopping by the attractive force between the rotor magnet and the magnetic member. A variation in the axial position of the rotating sleeve can be eliminated. Therefore, according to the present invention, the axial position of the rotating sleeve at the time of assembly (when stopped) can be set with high accuracy without causing a decrease in the drive efficiency of the motor and an increase in the required assembly accuracy. An electric motor with high accuracy can be provided.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a spindle motor as a first embodiment of an electric motor according to the present invention.
FIG. 2 is a sectional view of a spindle motor as a second embodiment of the electric motor of the present invention.
FIG. 3 is a cross-sectional view of a conventional HDD spindle motor as an electric motor.
4A is a cross-sectional view showing a state in which the rotating sleeve is offset in one axial direction in the conventional example, and FIG. 4B is a sectional view in which the rotating sleeve is offset in the other axial direction in the conventional example. It is sectional drawing which shows the state.
[Explanation of symbols]
1, 2, 31, 32 ... fixed part, 3, 33 ... fixed shaft, 5, 35 ... rotating sleeve,
6, 36 ... flange portion, 6A, 6B, 36A, 36B ... end face, 7 ... annular recess,
8, 10 ... end wall, S100, S200 ... minute gap, 11 ... support member,
12 ... Stator coil, 13 ... Outer cylinder, 15 ... Rotor magnet,
16, 50 ... Iron plate, 17, 18, 41, 42 ... Dynamic pressure generating groove,
33B ... Shaft portion, 37 ... Inner tube portion, 38 ... Outer tube portion, 39 ... Lid portion,
39A ... concave portion, 40 ... bottom surface, 45 ... support portion, 46 ... stator coil,
47: Rotor magnet.

Claims (1)

A fixed shaft having a flange portion, the axial end of which is fixed to the fixed portion, and a small clearance so as to be fitted coaxially with the fixed shaft so as to sandwich the flange portion of the fixed shaft from both sides in the axial direction during rotation. A rotating sleeve having two bearing surfaces opposed to the flange portion via the stator, a stator coil attached to the fixed portion, facing the outer periphery of the rotating sleeve, and facing the outer periphery of the stator coil A rotor magnet coupled to the rotary sleeve, and a dynamic pressure generating groove formed on both axial end surfaces of the flange portion or two bearing surfaces of the rotary sleeve,
When the rotating sleeve is stopped, one bearing surface of the rotating sleeve is brought into substantially parallel contact with one axial end surface of the flange portion, while when the rotating sleeve is rotating, the rotating sleeve An annular magnetic member that attracts the rotor magnet toward the fixed portion is attached to the fixed portion such that the rotor magnet floats from the flange portion,
When the rotating sleeve is stopped, one end surface in the axial direction of the annular magnetic member and the other end surface in the axial direction of the rotor magnet are substantially parallel to each other,
The radial width of the other axial end of the rotor magnet that is axially opposed to one axial end of the annular magnetic member is equal to one axial end of the annular magnetic member. Smaller than the radial width of
The radially inner end of the rotor magnet is positioned radially outward from the radially inner end of the annular magnetic member, and the radially outer end of the rotor magnet is the annular magnetic member. positioned radially inward of the outer end of the radial direction,
The electric motor according to claim 1 , wherein one end face in the axial direction of the annular magnetic member is a plane extending from an inner end to an outer end in the radial direction of the annular magnetic member .

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