JP3597944B2 - Motor using dynamic pressure bearing - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a motor using a hydrodynamic bearing using a lubricating fluid used for rotating a recording disk such as an optical / magnetic disk.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, in order to relatively rotatably support a shaft member and a sleeve member, a dynamic pressure bearing utilizing the fluid pressure of a lubricating fluid interposed between the two has been used. In this type of fluid dynamic pressure bearing, a radial dynamic pressure bearing portion for supporting a radial load and a thrust dynamic pressure bearing portion for supporting a thrust load are disposed between a shaft member and a sleeve member. When such a dynamic pressure bearing is used for a motor, one of a shaft member and a sleeve member is fixed. That is, when the shaft member is fixed, the motor becomes a fixed shaft motor, and when the sleeve member is fixed, the motor becomes a shaft rotating motor.
[0003]
[Problems to be solved by the invention]
This type of dynamic bearing has the following problems to be solved. That is, the viscosity of the lubricating fluid, that is, the lubricating oil used in the dynamic pressure bearing usually decreases at a high temperature and increases at a low temperature. Therefore, the dynamic pressure generated by the dynamic pressure bearing is large at a high temperature and small at a low temperature. Therefore, if the bearing specifications are set to ensure the bearing rigidity at the upper limit of the operating temperature range, the bearing rigidity at low temperatures will be excessive, and if the bearing rigidity at room temperature is set appropriately, There is a problem that the rigidity is insufficient near the upper limit of the temperature, and the temperature dependence of the bearing rigidity is very large.
[0004]
The present invention has been made in consideration of such problems of the prior art, and an object of the present invention is to significantly reduce the temperature dependence of the bearing stiffness in a dynamic pressure bearing and to reduce the operating temperature range. It is an object of the present invention to provide a motor using a dynamic pressure bearing capable of stably obtaining appropriate bearing rigidity within the motor.
[0005]
[Means for Solving the Problems]
In order to achieve the above object, in a motor using the dynamic pressure bearing of the present invention, a shaft member having a cylindrical outer peripheral surface and a shaft member having a cylindrical inner peripheral surface opposed to the cylindrical outer peripheral surface are provided. A sleeve member that is relatively rotatable, and a pair of radial dynamic pressure generating grooves formed on one or both of the cylindrical outer peripheral surface and the cylindrical inner peripheral surface and arranged at intervals in the axial direction; And a lubricating fluid interposed between the cylindrical outer peripheral surface and the cylindrical inner peripheral surface, and the shaft member and the sleeve member are connected to a fixed side of the shaft member and the sleeve member so as to communicate a high dynamic pressure region and a low dynamic pressure region. A passage is provided, and a control valve having an opening having a smaller opening area at a high temperature and a larger opening area at a low temperature is arranged in the communication path.
[0006]
In this case, the communication passage is provided between the cylindrical outer peripheral surface and the cylindrical inner peripheral surface, between the pair of radial dynamic pressure generating grooves formed by the pair of radial dynamic pressure generating grooves and the pair of radial dynamic pressure generating grooves. The control valve is preferably provided so as to communicate with each other, and the control valve is preferably formed of a cylindrical body having an opening having a fan-shaped cross section and having a larger thermal expansion coefficient than the material on the fixed side.
[0007]
In order to achieve the above object, in a motor using the dynamic pressure bearing of the present invention, a shaft member having a cylindrical outer peripheral surface and a shaft having a cylindrical inner peripheral surface facing the cylindrical outer peripheral surface are provided. A sleeve member rotatable relative to the member, and a pair of radial dynamic pressure generation members formed on one or both of the cylindrical outer peripheral surface and the cylindrical inner peripheral surface and arranged at intervals in the axial direction. The groove, comprising a lubricating fluid interposed between the cylindrical outer peripheral surface and the cylindrical inner peripheral surface, a high dynamic pressure region and a low dynamic pressure region on the fixed side of the shaft member and the sleeve member. And a control valve having an opening in which the opening area becomes large when the pressure is high and the opening area becomes small when the pressure is low is provided in the communication path.
[0008]
In this case, the communication passage is provided between the cylindrical outer peripheral surface and the cylindrical inner peripheral surface, between the pair of radial dynamic pressure generating grooves formed by the pair of radial dynamic pressure generating grooves and the pair of radial dynamic pressure generating grooves. Desirably, they are provided so as to communicate with each other. Further, it is preferable that the control valve is formed of an elastic member having micro holes. In particular, the micro holes are formed such that the diameter of the side communicating with the high dynamic pressure region is larger than the side communicating with the low dynamic pressure region. May be.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
Embodiments of the present invention will be described in detail with reference to the drawings.
First, an example of an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a sectional view showing a fixed shaft type spindle motor for rotating a magnetic disk, for example. In this example, the lower end of a fixed shaft member 6 having a vertical axis is fitted and fixed to the base of the recording medium driving device or the circular fitting hole 4 of the motor bracket 2 fixed thereto. . The shaft member 6 has a thrust plate 8 fixed at the upper portion and a cover plate 10 fixed at the upper end thereof, and a cylindrical outer peripheral surface 12 is formed on the outer peripheral surface below the thrust plate 8.
[0010]
A rotating sleeve body 14 is rotatably fitted to the shaft member 6. The small-diameter sleeve portion 16 at the lower portion of the rotary sleeve body 14 has a cylindrical inner peripheral surface 18 on the inner peripheral surface, and is externally fitted to a portion of the shaft member 6 below the thrust plate 8. Reference numeral 18 faces the cylindrical outer peripheral surface 12 of the shaft member 6. The enlarged diameter portion 20 at the upper part of the rotary sleeve body 14 surrounds the upper and lower portions and the outer peripheral portion of the thrust plate 8 together with the thrust cover 22 fixedly fitted at the upper end portion.
[0011]
A substantially cylindrical hub 24 is externally fitted and fixed to an outer peripheral portion of the rotating sleeve body 14, and a rotor magnet 26 is internally fixed to a lower inner peripheral side of the hub 24. A stator 28 having a stator coil wound around a stator core is externally fitted and fixed to a support cylinder 30 protruding from the bracket 2 coaxially with the circular fitting hole 4, and is rotationally driven relative to the rotor magnet 26 in the radial direction. Unit.
[0012]
An inner lower portion of the thrust cover 22 is formed in a tapered portion 32 inclined inward and upward, and a portion of the outer peripheral portion of the shaft member 6 facing the lower end of the sleeve portion 16 is formed in a tapered portion 34 inclined inward and downward. Is formed. A gap between the shaft member 6 and the rotary sleeve body 14 is filled with a lubricating oil 36 as an example of a lubricating fluid (liquid). One end, that is, the inner peripheral end of the lubricating oil 36 in the gap above the thrust plate 8 faces between the base of the tapered portion 32 of the thrust cover 22 and the upper surface of the thrust plate 8, and communicates with the outside air. The lubricating oil 36 is held between the base of the tapered portion 34 and the inner peripheral surface of the sleeve portion 16 and exposed to the outside air by capillary action.
[0013]
On the upper and lower surfaces of the thrust plate 8 and on the inner peripheral surface (cylindrical inner peripheral surface 18) of the sleeve portion 16, respectively, thrust dynamic pressure generating grooves 38 and 40 such as herringbone grooves and radial dynamic pressure generating grooves 42 and 44 ( (Shown by broken lines) are provided, and a forward rotation of the rotary sleeve body 14 and the thrust cover 22 generates a thrust load supporting pressure and a radial load supporting pressure respectively in the lubricating oil 36 at each position. As a result, thrust dynamic pressure bearing means are formed above and below the thrust plate 8, and radial dynamic pressure bearing means are formed on the outer peripheral portion of the sleeve portion 16. Note that these grooves may be provided on the sides of the members facing each other.
[0014]
The shaft member 6 is provided with a communication passage 46 for communicating a high pressure area and a low pressure area in the radial dynamic pressure bearing means. That is, an axial vertical hole 48 is formed at the axial center position of the shaft member 6 from the lower end surface to a position slightly below the thrust plate 8, and the cylindrical outer peripheral surface 12 corresponding to the radial dynamic pressure generating grooves 42, 44 is formed. From the cylindrical outer peripheral surface 12 corresponding to the middle between the radial dynamic pressure generating grooves 42 and 44, and extending from the cylindrical outer peripheral surface 12 to the vertical hole 48. A low-pressure side hole 54 that is orthogonal to the vertical hole 48 in the axial direction is formed, and the vertical hole 48 below the lowermost horizontal hole 52 is closed by a sealing member 56 so that the cylindrical outer peripheral surface 12 and the cylindrical inner peripheral surface are formed. A communication passage 46 is formed in the gap between the shaft member 6 and the gap between the radial dynamic pressure generating grooves 42 and 44 and the portion between the radial dynamic pressure generating grooves 42 and 44 in the shaft member 6. .
[0015]
A control valve 58 having an opening having a small opening area at a high temperature and having a large opening area at a low temperature is disposed in the low-pressure side hole 54 of the communication passage 46. Specifically, as shown in FIG. 2, the control valve 58 has a columnar body 62 having a fan-shaped opening 60 and formed of a material having a larger thermal expansion coefficient than the shaft member 6. The control valve 58 is attached to the low-pressure side hole 54 by shrinking the cylindrical body 62 so that both side surfaces of the opening 60 are shifted inward and inserting the same into the low-pressure side hole 54.
[0016]
In such a configuration, when the spindle motor rotates, the pressure of the lubricating oil 36 existing in each of the radial dynamic pressure bearing means having the two radial dynamic pressure generating grooves 42, 44 is increased, and the pressure is increased through the oil layer. To support the radial load acting on the rotating sleeve body 14. Further, in each thrust dynamic pressure bearing means having both thrust dynamic pressure generating grooves 38, 40, the pressure of the lubricating oil 36 existing in them is increased, and the thrust load acting on the rotary sleeve body 14 via this oil layer. Support.
[0017]
During this operation, the lubricating oil 36 filled between the cylindrical outer peripheral surface 12 of the shaft member 6 and the cylindrical inner peripheral surface 18 of the sleeve portion 16 partially circulates, bypassing the communication passage 46. . That is, in the two radial bearing means, the central portion of each of the dynamic pressure generating grooves 42 and 44, which is a herringbone groove, has the highest pressure. On the other hand, between the two radial bearing means, the lubricating oil 36 in this portion is supplied by the two radial bearing means. The pressure is low because it is sucked into the side. The high-pressure side holes 50 and 52 of the communication passage 46 are respectively opened at the high pressure portions of both radial bearing means, and the low-pressure side hole 54 is opened at the low pressure portion between the two radial bearing means. Therefore, due to the above-mentioned pressure difference, the lubricating oil 36 of the respective high pressure portions flows from the low pressure side horizontal holes 54 to the low pressure portions via the high pressure side holes 50 and 52 and the vertical hole 48 in the communication passage 46, The lubricating oil 36 is circulated.
[0018]
When the lubricating oil 36 circulates through the communication passage 46, the lubricating oil 36 passes through the opening 60 of the cylindrical body 62 in the control valve 58 of the low-pressure side hole 54. Is significantly smaller than the opening area (passage area), the generated dynamic pressure is not unnecessarily reduced, and the lubricating oil 36 is circulated in a state in which the radial load acting on the rotating sleeve body 14 is sufficiently supported. .
[0019]
The lubricating oil 36 has a high viscosity at a low temperature and a low viscosity at a high temperature, and if no measures are taken, the dynamic pressure generated by the dynamic pressure bearing portion is high at a low temperature and low at a high temperature. Since the cylindrical body 62 of the control valve 58 is formed of a material having a larger thermal expansion coefficient than the shaft member 6, the cylindrical body 62 which was in the state of the solid line in FIG. As shown by the dashed line, both side surfaces of the opening 60 are shifted toward the inside of the opening, and the opening cross-sectional area is reduced. Therefore, at high temperatures, the viscosity of the lubricating oil 36 decreases and the generated dynamic pressure decreases. However, since the opening area of the opening 60 in the control valve 58 of the communication passage 46 decreases, the circulation amount of the lubricating oil 36 is limited. The pressure drop of the generated dynamic pressure in the radial dynamic pressure bearing means is suppressed, and as a result, it is possible to maintain a pressure at substantially the same level as the generated dynamic pressure at low temperatures.
[0020]
As described above, by changing the opening area of the opening 60 in the control valve 58 according to the temperature, it is possible to reduce the circulation amount of the lubricating oil 36 whose viscosity changes according to the temperature as the viscosity decreases. As a result, the dynamic pressure generated in the radial dynamic pressure bearing means can be made constant, and the bearing rigidity can be maintained at substantially the same level within the operating temperature range. As a result, the temperature dependence of the bearing stiffness can be reduced, so even if the required bearing stiffness is secured at the upper limit temperature, the shaft loss can be maintained at substantially the same level over the entire operating temperature range. Reduction of shaft loss in a low temperature region can be realized, which can contribute to reduction of rated current.
[0021]
The material (thermal expansion coefficient) and length of the cylindrical body 62 and the opening angle of the opening 60 in FIGS. 2 and 3 are set so that the bearing rigidity can be maintained at substantially the same level over the entire operating temperature range. It is appropriately selected according to the dynamic pressure generated by the radial bearing means in the spindle motor, the characteristics (viscosity) of the lubricating oil 36, and the like.
[0022]
Next, another example of the embodiment of the present invention will be described with reference to FIG. FIGS. 4A and 4B show the vicinity of the end of the low-pressure side hole 54 in the communication passage 46 formed in the shaft member 6 of FIG. 1, and those having the same reference numerals as those described above are the same or equivalent. Shall be shown.
[0023]
FIG. 4 shows a control valve 64 having an opening having a large opening area when the pressure is large and a small opening area when the pressure is small. The control valve 64 has a cylindrical outer peripheral surface 12 in the low pressure side hole 54 of the communication passage 46. A thin disk-shaped elastic member 66 is arranged at the end on the side to close the lateral hole 54, and a minute hole 68 that opens the communication passage 46 on the low pressure side is formed in the center of the elastic member 66.
[0024]
In such a configuration, during the rotation of the motor, if the dynamic pressure generated in the two radial bearing means is relatively low, the difference between the pressure in the bearing means and the pressure between the two bearing means is not so large. As shown in FIG. 4A, the elastic member 66 that receives the pressures of the high pressure side and the low pressure side on both surfaces through the communication passage 46 hardly deforms, and the lubrication circulates from the high pressure side to the low pressure side through the communication passage 46. The oil 36 is greatly constricted by the minute holes 68. As a result, the high-pressure side pressure does not decrease so much, and the bearing load is supported by this pressure.
[0025]
On the other hand, when the dynamic pressure generated in the two radial bearing means is large, the difference between the pressure in the bearing means and the pressure between the two bearing means becomes large, and as shown in FIG. The elastic member 66 which receives the pressures of the pressure side and the low pressure side on both sides is greatly deformed to the low pressure side, and accordingly, the minute holes 68 also expand so as to increase the opening area. As a result, a large amount of the high-pressure side lubricating oil 36 flows from the communication passage 46 to the low-pressure side through the minute holes 68 of the elastic member 66, relieves the pressure, reduces the pressure on the high-pressure side, and causes the two bearing means to generate the above-described dynamic power The pressure is maintained substantially equal to the case where the pressure is low, and the bearing load is supported.
[0026]
Therefore, by changing the opening area of the opening 68 in the control valve 64 in accordance with the pressure generated in the dynamic pressure bearing means, even if the viscosity of the lubricating oil 36 changes in accordance with the temperature and the generated pressure changes, especially when the temperature is low, When the viscosity increases and the pressure becomes excessive, the amount of circulation of the lubricating oil 36 can be increased and the pressure can be released, so that the dynamic pressure generated in the radial dynamic pressure bearing means can be made constant and used. Within the temperature range, the bearing stiffness can be maintained at substantially the same level.
[0027]
Next, still another example of the embodiment of the present invention will be described with reference to FIG. FIG. 5 shows a control valve 70 having an opening having a large opening area when the pressure is high and a small opening area when the pressure is low as in the case of FIG. An elastic member 72 in the form of a thin disk is disposed at the end of the cylindrical outer surface 12 on the side of the cylindrical outer peripheral surface 12 so as to close the lateral hole 54, and a minute hole that opens the communication passage 46 at the center of the elastic member 72 on the low pressure side. In particular, a tapered surface 76 is formed on the communication passage 46 side of the minute hole 74 so that the diameter of the hole communicating with the region of high dynamic pressure is larger than the diameter of the hole communicating with the region of low dynamic pressure.
[0028]
With such a configuration, the small holes 74 of the elastic member 72 are easily subjected to the high-pressure side pressure by the tapered surface 76, and the deformation of the elastic member 72 and the change in the opening area of the small holes 74 due to the high-pressure side pressure are reduced. It is performed more accurately, the temperature dependence of the bearing stiffness is further reduced, and constant control of the bearing stiffness is ensured.
[0029]
The elastic coefficients and thicknesses of the elastic members 66 and 72 in FIGS. 4 and 5, the diameters of the minute holes 68 and 74, and the taper angle of the tapered surface 76 in FIG. It is appropriately selected according to the dynamic pressure generated by the radial bearing means in the spindle motor, the characteristics (viscosity) of the lubricating oil 36, and the like so as to maintain the level.
[0030]
Although the embodiments of the motor using the dynamic pressure bearing according to the present invention have been described in detail above, the present invention is not limited to these examples, and various changes and modifications can be made without departing from the gist of the present invention. It is possible.
[0031]
For example, in the above-described embodiment, a case where the present invention is applied to a fixed shaft type spindle motor has been described. However, the present invention can be similarly applied to a shaft rotating type motor. In this case, the fixed sleeve member into which the rotating shaft member is inserted may be provided with a communication path for communicating the high and low dynamic pressure areas, and the control valve may be disposed in this communication path.
[0032]
【The invention's effect】
The present invention is configured as described above, and has the following effects.
In the motor using the dynamic pressure bearing according to claim 1, a communication path that connects a high dynamic pressure area and a low dynamic pressure area is provided on a fixed side of the shaft member and the sleeve member, and the communication path is provided in the communication path. Since a control valve having an opening with a small opening area at high temperature and a large opening area at low temperature is arranged, the opening of the communication passage is enlarged at low temperature to release high dynamic pressure generated by a viscous large lubricating fluid. At the time of high temperature, the opening of the communication passage can be made small to maintain a low dynamic pressure generated by the low-viscosity lubricating fluid. Therefore, the generated dynamic pressure can be made constant within the operating temperature range, the bearing stiffness can be maintained at substantially the same level, and the temperature dependency of the bearing stiffness can be reduced. As a result, even if the required bearing stiffness is secured at the upper limit temperature, the shaft loss can be maintained at substantially the same level over the entire operating temperature range. This can greatly contribute to reduction.
[0033]
In the motor using the dynamic pressure bearing according to claim 4, a communication path that connects a high dynamic pressure area and a low dynamic pressure area is provided on the fixed side of the shaft member and the sleeve member, and the communication path is provided in the communication path. Since a control valve having an opening having a large opening area when the pressure is large and having a small opening area when the pressure is small is arranged, a large dynamic pressure and a large opening of the communication passage are released to release a high generated dynamic pressure. With a small dynamic pressure, the opening of the communication passage can be made small and a low generated dynamic pressure can be maintained, the generated dynamic pressure can be kept constant, and the bearing rigidity can be maintained at almost the same level. Can be obtained.
[Brief description of the drawings]
FIG. 1 is a cutaway front view showing an example of an embodiment in which a motor using a dynamic pressure bearing of the present invention is applied to a spindle motor.
FIG. 2 is a perspective view of the control valve of FIG. 1;
FIG. 3 is a front view of the control valve of FIG. 2;
FIG. 4 is a cutaway front view of a main part showing another example of the embodiment of the present invention, in which (a) shows a low pressure in the communication passage and (b) shows a high pressure.
FIG. 5 is a cutaway front view of a main part showing still another example of the embodiment of the present invention.
[Explanation of symbols]
6 Shaft member 12 Cylindrical outer peripheral surface 14 Rotating sleeve body 16 Sleeve portion 18 Cylindrical inner peripheral surface 36 Lubricating oil 42, 44 Radial dynamic pressure generating groove 46 Communication passage 58, 64, 70 Control valve 60 Opening 62 Cylindrical body 66, 72 Elastic members 68, 74 Micro holes 76 Tapered surface

Claims (7)

A shaft member having a cylindrical outer peripheral surface; a sleeve member having a cylindrical inner peripheral surface facing the cylindrical outer peripheral surface and rotatable relative to the shaft member; the cylindrical outer peripheral surface and the cylinder And a pair of radial dynamic pressure generating grooves formed on one or both of the inner peripheral surface and arranged at intervals in the axial direction, and were interposed between the cylindrical outer peripheral surface and the cylindrical inner peripheral surface. A motor provided with a lubricating fluid,
On the fixed side of the shaft member and the sleeve member, there is provided a communication passage communicating between a high dynamic pressure region and a low dynamic pressure region, and the communication passage has a small opening area at high temperature and an opening at low temperature. A motor using a dynamic pressure bearing, wherein a control valve having an opening having a large area is arranged. The communication passage may communicate between a dynamic pressure generating portion formed by the pair of radial dynamic pressure generating grooves and the pair of radial dynamic pressure generating grooves between the cylindrical outer peripheral surface and the cylindrical inner peripheral surface. A motor using the dynamic pressure bearing according to claim 1 provided in the motor. The motor using the dynamic pressure bearing according to claim 1 or 2, wherein the control valve is a cylindrical body having an opening having a fan-shaped cross section and having a larger thermal expansion coefficient than the material on the fixed side. A shaft member having a cylindrical outer peripheral surface; a sleeve member having a cylindrical inner peripheral surface facing the cylindrical outer peripheral surface and rotatable relative to the shaft member; the cylindrical outer peripheral surface and the cylinder And a pair of radial dynamic pressure generating grooves formed on one or both of the inner peripheral surface and arranged at intervals in the axial direction, and were interposed between the cylindrical outer peripheral surface and the cylindrical inner peripheral surface. A motor provided with a lubricating fluid,
On the fixed side of the shaft member and the sleeve member, there is provided a communication passage that communicates between a high dynamic pressure region and a low dynamic pressure region. A motor using a dynamic pressure bearing, wherein a control valve having an opening whose opening area becomes small when the motor is small is arranged. The communication passage may communicate between a dynamic pressure generating portion formed by the pair of radial dynamic pressure generating grooves and the pair of radial dynamic pressure generating grooves between the cylindrical outer peripheral surface and the cylindrical inner peripheral surface. A motor using the dynamic pressure bearing according to claim 4, wherein the motor is provided in the motor. The motor using the dynamic pressure bearing according to claim 4 or 5, wherein the control valve is configured by an elastic member having a minute hole. 7. The motor using the dynamic pressure bearing according to claim 6, wherein the minute hole of the elastic member has a larger diameter on a side communicating with a region having a high dynamic pressure than on a side communicating with a region having a low dynamic pressure.

Images