JP2005214239A - Bearing unit and motor using the bearing unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent splashes of viscous fluid by an impact or the like by preventing leakage by expansion of residual air. <P>SOLUTION: A bearing unit 30 has: a shaft 31; a radial bearing 33 for supporting the shaft 31 circumferentially; a thrust bearing 46 for supporting one thrust end of the shaft 31; a passage forming member 34A disposed outside the radial bearing 33 and the thrust bearing 46; a housing 37 in which the passage forming member 34A is disposed and which is closed except for a shaft passing hole 41 in which the shaft 31 is passed; lubricating oil 42 filling the housing 37; and air flow passages 60 interconnecting passages 50 formed between the passage forming member 34A and the radial bearing 33 to interconnect the one thrust end and the other of the shaft 31 projected from the radial bearing 33, and a space S near the thrust bearing 46 formed by, for example, grooves Ga in a corner portion of a bottom portion 35B of the passage forming member 34A. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a bearing unit that rotatably supports a rotating shaft or rotatably supports a rotating body with respect to the shaft, and a motor using the bearing unit.

  2. Description of the Related Art Conventionally, as a bearing unit that rotatably supports a rotating shaft, one configured as shown in FIG. 21 is known.

  The bearing unit 120 shown in FIG. 21 supports the rotating shaft 123 in a rotatable manner, and has a cylindrical metal housing 122 with both ends open, and the rotating shaft 123 is rotated in the housing 122. A radial bearing 121 is attached to support it. A thrust bearing 124 that supports the thrust direction of the rotary shaft 123 that is rotatably supported by the radial bearing 121 is attached to one open end side of the housing 122.

  In the bearing unit 120, a hydrodynamic bearing is used for the radial bearing 121. The dynamic pressure fluid bearing is provided with a dynamic pressure generating groove for generating dynamic pressure on the inner peripheral surface of the radial bearing 121 facing the rotating shaft 123.

  The housing 122 is filled with lubricating oil, which is a viscous fluid that generates dynamic pressure by flowing through the dynamic pressure generating groove when the rotating shaft 123 rotates.

  The rotating shaft 123 is inserted into the radial bearing 121, and one end side is supported by the thrust bearing 124, and is rotatably supported in the housing 122.

  On the other open end side of the housing 122, an oil seal 125 formed in an annular shape made of metal for preventing leakage of the lubricating oil filled in the housing 122 from the inside of the housing 122 is attached. The rotating shaft 123 protrudes outside the housing 122 through a shaft insertion hole 126 provided at the center of the oil seal 125.

  A joint portion 127 between the oil seal 125 and the housing 122 is completely sealed with an adhesive to prevent leakage of lubricating oil filled in the housing. A surfactant is applied to the inner peripheral surface of the oil seal 125 so as to prevent the lubricating oil from moving from the shaft insertion hole 126 to the outside of the housing 122 due to centrifugal force generated by the rotation of the rotating shaft 123. ing.

  In the bearing unit 120 configured as shown in FIG. 21, the outflow path of the lubricating oil filled in the housing 122 is defined by the outer peripheral surface of the rotating shaft 123 and the inner peripheral surface of the shaft insertion hole 126 provided in the oil seal 125. Only the gap 131 is formed. Here, by reducing the width of the gap 131, leakage of the lubricating oil to the outside of the housing 122 can be prevented by the surface tension of the lubricating oil facing the gap 131.

  Further, a tapered portion 130 formed so as to be reduced in diameter toward the outside of the housing 122 is provided on the outer peripheral surface facing the inner peripheral surface of the shaft insertion hole 126 of the rotating shaft 123. By providing such a tapered portion 130, a pressure gradient is formed in the gap 131 formed by the outer peripheral surface of the rotating shaft 123 and the inner peripheral surface of the shaft insertion hole 126, and the centrifugal force generated when the rotating shaft 123 rotates is generated. The force generates a force that draws the lubricating oil filled in the housing 122 into the housing 122. Since the lubricating oil is drawn into the housing 122 when the rotating shaft 123 rotates, the lubricating oil surely enters the dynamic pressure generating groove of the radial bearing 121 constituted by the hydrodynamic fluid bearing to generate dynamic pressure. Thus, stable support of the rotating shaft 123 is realized, and leakage of the lubricating oil filled in the housing 122 can be prevented.

  In the bearing unit 120, since the housing 122, the thrust bearing 124, and the oil seal 125 are formed by independent members, the number of parts increases. In addition, it is necessary to apply a sealing agent such as an adhesive to the joint 127 between the housing 122 and the oil seal 125, which complicates the assembling work.

  Further, it is extremely difficult to completely seal the joint portion 127 between the housing 122 and the oil seal 125 with an adhesive, and it is impossible to prevent the leaking of the lubricating oil filled in the housing 122. In order to prevent such leakage of the lubricating oil, a process such as application of a surfactant to the surface of the oil seal 125 is required, which makes manufacturing more difficult.

  As described above, the conventionally used bearing unit has a large number of parts and is difficult to assemble, and cannot be surely sealed with lubricating oil, but also becomes expensive.

  A motor using such a bearing unit also has a large number of parts, is difficult to assemble, and is expensive.

  Moreover, what was comprised as shown in FIG. 22 as another bearing unit which supports a rotating shaft rotatably is known (for example, refer patent document 1).

  The bearing unit 140 shown in FIG. 22 supports the rotating shaft 141 in a rotatable manner, and includes a radial bearing 144 that supports the rotating shaft 141 in the circumferential direction, and a housing 145 that houses the radial bearing 144. .

  In this bearing unit 140, the radial bearing 144 constitutes a hydrodynamic bearing together with lubricating oil that is a viscous fluid filled in the housing 145, and the inner peripheral surface through which the rotating shaft 141 is inserted has a dynamic bearing. A dynamic pressure generating groove 151 for generating pressure is formed.

  The housing 145 that houses the radial bearing 144 that supports the rotating shaft 141 has a shape that encloses and surrounds the cylindrical radial bearing 144 as shown in FIG. 22, and is integrally molded with synthetic resin. It is one member formed.

  The housing 145 includes a cylindrical housing main body 146, a bottom closing portion 147 constituting an end portion side portion integrally formed with the housing main body 146 so as to close one end side of the housing main body 146, and the housing main body 146. It comprises an upper closing portion 148 formed integrally with the housing main body 146 constituting the other end side. The housing 145 configured as described above is formed by outsert-molding a synthetic resin material so as to surround the cylindrical radial bearing 144, so that the radial bearing 144 is disposed on the inner peripheral side of the housing main body 146 and integrally formed. It is formed.

  A shaft insertion hole 149 through which the rotation shaft 141 rotatably supported by the radial bearing 144 housed in the housing 145 is provided at the center of the upper closing portion 148. A thrust bearing 150 that rotatably supports a bearing support portion 142 provided at one end portion in the thrust direction of the rotary shaft 141 supported by the radial bearing 144 is integrally formed at the center portion on the inner surface side of the bottom closing portion 147. ing.

  The thrust bearing 150 is formed as a pivot bearing that supports the bearing support portion 142 of the rotating shaft 141 that is formed in an arc shape or a tapered tip shape.

  By the way, the shaft insertion hole 149 is formed with an inner diameter slightly larger than the outer shape of the rotating portion main body 143 without the rotating shaft 141 inserted through the shaft insertion hole 149 being in sliding contact with the inner peripheral surface of the shaft insertion hole 149. At this time, the shaft insertion hole 149 has a gap 152 between the peripheral surface and the outer peripheral surface of the shaft body so that the lubricating oil 153 filled in the housing is prevented from leaking out of the housing 145. Formed as follows.

  A tapered portion 154 is provided on the outer peripheral surface facing the inner peripheral surface of the shaft insertion hole 149 of the rotating shaft 141. The tapered portion 154 is inclined so as to expand a gap 152 formed between the outer peripheral surface of the rotating shaft 141 and the inner peripheral surface of the shaft insertion hole 149 toward the outside of the housing 145. The tapered portion 154 forms a pressure gradient in the gap 152 formed between the outer peripheral surface of the rotating shaft 141 and the inner peripheral surface of the shaft insertion hole 149, and the lubricating oil 153 filled in the housing 145 is supplied to the housing 145. A force to pull into the inside of the door is generated. Since the lubricating oil 153 is drawn into the housing 145 when the rotary shaft 141 rotates, the lubricating oil 153 surely enters the dynamic pressure generating groove 151 of the radial bearing 144 constituted by the hydrodynamic fluid bearing. A dynamic pressure is generated, stable support of the rotating shaft 141 is realized, and leakage of the lubricating oil 153 filled in the housing 145 can be prevented.

  In the bearing unit 140 configured as shown in FIG. 22, the rotation shaft 141 is exposed only at one end on the shaft insertion hole 149 side, and the housing member is seamlessly covered except for a slight gap c of the shaft insertion hole 149. Yes. Therefore, this bearing unit 140 can prevent the lubricating oil 153 from leaking out of the housing 145. In addition, since the communication portion with the outside is only the gap of the shaft insertion hole 149, scattering of the lubricating oil due to impact can be prevented.

  However, in the bearing unit 140 described above, when the rotating shaft 141 and the housing 145 rotate relatively to generate dynamic pressure, the static pressure inside the bearing unit 140 is extremely reduced. As the pressure inside the housing 145 decreases, the air slightly remaining inside the housing 145 and the air dissolved in a viscous fluid such as lubricating oil expand. When the air inside the housing 145 or the air dissolved in a viscous fluid such as lubricating oil is expanded, the viscous fluid may be pushed out to the exposed side of the shaft and leak. In the bearing unit 140, the lubricating oil leaks and cannot be held, so that good lubrication cannot be obtained.

  As described above, in the bearing unit 140 shown in FIG. 22, the internal air expands due to the generation of dynamic pressure due to the relative rotation of the shaft 141 and the housing 145, and the lubricating oil may leak.

  Moreover, what was comprised as shown in FIG. 23 as another bearing unit which rotatably supports a rotating shaft is known (for example, refer patent document 1).

  The bearing unit 160 shown in FIG. 23 is obtained by deforming the bearing unit 140, and is reliable even when the pressure in the housing filled with the viscous fluid is changed due to an environmental change such as a change in atmospheric pressure or a change in temperature. In addition, it is possible to prevent leakage of viscous fluid to the outside of the housing.

  In this bearing unit 160, the same reference numerals are given to the parts common to the bearing unit 140, and detailed description thereof is omitted.

  This bearing unit 160 is provided with a radial bearing 144 and a thrust bearing 150, rotatably supporting a rotating shaft 141, and providing an air vent passage 162 in a housing 161 filled with lubricating oil 153.

  The air vent road 162 is provided to prevent the lubricating oil 153 from leaking outside the bearing unit 160 due to expansion of the air in the housing 161 of the bearing unit 160 due to a decrease in atmospheric pressure due to a temperature change or the like. . One or more air vent passages 162 may be provided in the housing 161, for example. For example, in the bearing unit 160, three are formed at predetermined angles on the outer periphery of the housing 161. The air vent passage 162 can be easily formed at the same time when the housing 161 accommodates the radial bearing 144 and is integrally outsert-molded with the thrust bearing 150. That is, even if the air vent passage portion 162 has a relatively complicated shape, it can be molded simultaneously with the resin molding of the synthetic resin housing 161 and the thrust bearing 150.

  By providing such an air vent passage portion 162, when the rotary shaft 141 is inserted and attached to the radial bearing 144, the air can be vented along with the insertion.

  In the bearing unit 160, the air vent passage 162 has a first passage 163 and a second passage 164. The first passage 163 is a passage formed along the radial direction of the housing 161 from the internal space 165 in the vicinity of the thrust bearing 150. The inside of the first passage 163 is connected to an internal space 165 in which the thrust bearing 150 formed so as to protrude from the bottom closing portion 147 of the housing 161 is located. The outside of the first passage 163 is connected to the second passage 164. The second passage 164 is formed so as to be exposed on the outer peripheral surface of the housing 161 and parallel to the axial direction of the housing 161. Thus, even when the air vent passage portion 162 having a relatively complicated shape such as the first passage 163 and the second passage 164 is formed, the synthetic resin housing 161 and the thrust bearing 150 are formed. It can be easily molded at the same time.

  In the bearing unit 160, since the air vent path 162 is provided in this way, the inside of the housing 161 is not sealed, so even if the rotation shaft 141 rotates relative to the housing 161, Static pressure does not decrease. Therefore, the air remaining in the housing 161 does not expand and push out the lubricating oil.

  However, the bearing unit 160 has a plurality of air vent passage portions 162 and exposed portions of the rotating shaft 141 at the communication portion with the outside, so that one serves as an air suction port and the other serves as a lubricant discharge port. Therefore, there is a possibility that the lubricating oil may be scattered due to the impact. Thus, the bearing unit 160 is vulnerable to impact.

  Further, as another bearing unit that rotatably supports a rotating shaft, one configured as shown in FIG. 24 is known (see, for example, Patent Document 2).

  The bearing unit 180 shown in FIG. 24 supports the rotary shaft 181 in a rotatable manner. The radial bearing 182 that supports the rotary shaft 181 in the circumferential direction, the thrust bearing 183 that supports the thrust direction, A radial bearing 182 and a housing 185 that houses a thrust bearing 183.

  In this bearing unit 180, the radial bearing 182 constitutes a hydrodynamic bearing together with lubricating oil that is a viscous fluid filled in the housing 185, and the inner circumferential surface through which the rotating shaft 181 is inserted has a dynamic bearing. A dynamic pressure generating groove 184 for generating pressure is formed.

  On the outer peripheral surface of the radial bearing 182, a groove-shaped axial air passage 186 and a radial air passage 187 are provided as air vents for inserting a shaft member into the inner diameter portion of the bearing body.

  As shown in FIG. 24, the housing 185 that houses the radial bearing 182 that supports the rotating shaft 181 is formed in a bottomed cylindrical shape so as to surround the side surface portion and the bottom surface portion of the radial bearing 182 formed in a cylindrical shape. .

  An elastic body 188 is provided in the open upper surface of the housing 185 so as to be crimped to the inner diameter side in a compressed state.

  In the bearing unit 180, the rotating shaft 181 is inserted into the housing 185 in which the elastic body 188 is caulked. At this time, since the air in the housing 185 passes through the axial air passage 186 and the radial air passage 187 and is discharged to the outside of the housing 185, the insertion operation of the rotating shaft 181 can be performed smoothly.

However, since the bearing unit 180 has a configuration in which the periphery of the bearing main body is surrounded by two parts including the housing 185 and the elastic body 188, there is a risk that the lubricating oil may ooze out from the joint portion between the housing 185 and the elastic body 188. There is.
International Publication No. WO03 / 027521 Pamphlet JP 2000-352414 A

  An object of the present invention is to cause viscous fluid such as lubricating oil filled in the housing to be pushed out of the bearing unit due to expansion of residual air caused by a decrease in pressure in the housing due to relative rotation between the shaft and the housing. It is an object of the present invention to provide a bearing unit that can prevent the leakage phenomenon and obtain good lubrication, and a motor using the bearing unit.

  In particular, the air remaining in radial bearings and lubricating oil oozes out over time, and the residual air stays in the vicinity of the thrust bearing, and the retained air expands during use of the bearing unit and becomes lubricating oil. An object of the present invention is to provide a bearing unit capable of preventing the leakage phenomenon of viscous fluid such as lubricating oil, and a motor using this bearing unit.

  Another object of the present invention is to provide a bearing unit in which a viscous fluid such as lubricating oil is hardly scattered by an impact or the like and a motor using the bearing unit.

  A further object of the present invention is to provide a bearing unit that prevents a viscous fluid such as lubricating oil from seeping out from a housing surrounding the bearing, and a motor using the bearing unit.

  To achieve this object, a bearing unit according to the present invention includes a shaft, a radial bearing that supports the shaft in a circumferential direction, a thrust bearing that supports one end of the shaft in the thrust direction, and the radial bearing. And a passage forming member provided outside the thrust bearing, a housing for sealing the outer periphery of the passage forming member and the radial bearing, except for a shaft insertion hole through which the shaft is inserted, and the housing is filled A viscous fluid, a passage formed between the passage forming member and the radial bearing over the protruding end side in the thrust direction of the shaft protruding from the radial bearing and the other end side in the thrust direction of the shaft, and the thrust bearing An air circulation passage configured to communicate with the space of the portion.

  The space is formed by forming at least one radial groove on the inner surface of the passage forming member in the vicinity of the thrust bearing.

  The air circulation passage includes at least one of a groove formed on the outer peripheral surface of the radial bearing over the protruding end side of the shaft protruding from the radial bearing and the other end side of the shaft in the thrust direction, and the passage forming member. It may be formed by communicating with at least one radial groove formed on the inner surface in the vicinity of the thrust bearing, and one end side of the radial bearing in the thrust direction and the other on the inner peripheral surface of the passage forming member. It may be formed by forming a groove along the thrust direction of the outer peripheral surface of the radial bearing and at least one radial groove in the vicinity of the thrust bearing over the end side.

  The radial bearing is preferably made of sintered metal.

  The radial bearing is a hydrodynamic bearing provided with a dynamic pressure generating groove.

  Furthermore, it is desirable that the housing is integrally formed of a synthetic resin molding.

Furthermore, the motor according to the present invention includes a bearing unit that rotatably supports the rotor with respect to the stator, wherein the bearing unit includes a shaft and a radial bearing that supports the shaft in a circumferential direction. Except for a thrust bearing that supports one end of the shaft in the thrust direction, a passage forming member provided outside the radial bearing and the thrust bearing, and a shaft insertion hole through which the shaft is inserted, A housing that seals the outer periphery of the radial bearing, a viscous fluid filled in the housing, the protruding end side in the thrust direction of the shaft protruding from the radial bearing, and the passage across the other end side in the thrust direction of the shaft An air flow passage configured to communicate a passage formed between the forming member and the radial bearing and a space of the thrust bearing portion. Characterized in that a bearing unit comprising and.

  As described above, the bearing unit according to the present invention includes one end side in the thrust direction of the shaft protruding from the radial bearing which is the non-axis exposed side sealed in the housing, and the shaft release side provided with the shaft insertion hole. The air flow passage extending over the other end in the thrust direction of the shaft protruding from the radial bearing communicated with the space near the thrust bearing. Therefore, when the shaft and the housing rotate relative to each other, the non-shaft opening side communicates with the shaft opening side, thereby suppressing a decrease in pressure on the non-shaft opening side. By suppressing the pressure drop on the non-shaft opening side, expansion of residual air in the housing is suppressed, and viscous fluid such as lubricating oil is not pushed out and leaked.

  Further, in the bearing unit according to the present invention, the non-shaft opening side and the shaft opening side are communicated, but only the other end side in the thrust direction of the shaft protruding from the radial bearing on the non-shaft opening side is minimal. It is communicated with the outside only by the gap of the shaft insertion hole. In other words, the air flow passage is formed in the housing, and the housing is sealed except for the shaft insertion hole, so that it is possible to prevent the scattering of viscous fluid such as lubricating oil with respect to the impact, and further the bleeding of the viscous fluid. It is possible to prevent the sticking out.

  Further, in the bearing unit according to the present invention, since the space in the vicinity of the thrust bearing communicates with the air circulation passage, a minute amount of air or viscosity that oozes out from the radial bearing, particularly the radial bearing formed of sintered metal. The air contained in the lubricating oil, which is a fluid, can be exhausted to the outside through the air circulation passage without staying in the space near the thrust bearing.

  A motor according to the present invention proposed to achieve the above object is a motor including a bearing unit that rotatably supports a rotor with respect to a stator. Something like that is used.

  According to the present invention, it is formed between the passage forming member and the radial bearing, and is formed across the non-shaft open side which is one end side in the thrust direction of the shaft protruding from the radial bearing and the shaft open side which is the other end side. Since the air circulation passage that communicates the passage and the space formed in the vicinity of the thrust bearing is provided, the relative rotation between the shaft and the housing can prevent the pressure in the sealed housing from being lowered. It is possible to prevent the viscous fluid from being pushed out by the expansion of the air dissolved in the viscous fluid such as the residual air in the housing and the lubricating oil filled in the housing due to the pressure drop inside the housing.

  In particular, according to the present invention, the air dissolved in the lubricating oil or the air remaining in the sintered metal radial bearing tends to be exhausted and retained in the space in the vicinity of the thrust bearing. The air is not exhausted from the flow passage through the shaft insertion hole, and the air does not expand and the lubricating oil is not pushed out from the shaft insertion hole through the air flow passage.

  According to the present invention, the communication passage that communicates the non-shaft open side and the shaft open side is sealed by the housing except for the shaft insertion hole, so that the non-shaft open side communicates with the shaft open side. It is possible to prevent the viscous fluid from scattering due to the impact.

  Furthermore, according to the present invention, since it is sealed except for the housing shaft insertion hole for housing the radial bearing and the thrust bearing, it is possible to prevent the bleeding of the viscous fluid.

  Embodiments of a bearing unit to which the present invention is applied and a motor using the bearing unit will be described below with reference to the drawings.

  Here, a motor used for a heat dissipation device provided in an electronic apparatus such as a portable computer, which is an information processing apparatus that performs arithmetic processing of various types of information, will be described. Inside the portable computer or the like, a heat dissipation device is provided. The heat dissipation device includes a metal base, a motor 1 attached to the base, a fan 3 that is rotated by the motor 1, a fan case 4 that houses the fan 3, and a heat sink. The motor 1 that rotationally drives the fan 3 of the heat dissipation device will be described in detail with reference to FIG.

  As shown in FIG. 1, the motor 1 using the bearing unit 30 according to the present invention includes a rotor 11 and a stator 12.

The stator 12 is integrally provided on the upper surface plate 4 a side of the fan case 4 that houses the fan 3 that is rotated by the motor 1 together with the motor 1. The stator 12 includes a stator yoke 13, a bearing unit 30 according to the present invention, a coil 14, and a core 15 around which the coil 14 is wound. The stator yoke 13 may be formed integrally with the upper surface portion 4a of the fan case 4, that is, may be formed by a part of the fan case 4, or may be formed separately. The stator yoke 13 is made of, for example, iron. The bearing unit 30 is fixed by press-fitting or bonding into a cylindrical holder 16 formed at the center of the stator yoke 13, and further by pressing and bonding together. The holder 16 into which the bearing unit 30 is press-fitted is formed in a cylindrical shape integrally with the stator yoke 13.

  As shown in FIG. 1, a core 15 around which a coil 14 to which a drive current is supplied is attached is attached to an outer peripheral portion of a holder 16 formed integrally with the stator yoke 13.

  The rotor 11 that constitutes the motor 1 together with the stator 12 is attached to a rotary shaft 31 that is rotatably supported by the bearing unit 30, and rotates integrally with the rotary shaft 31. The rotor 11 includes a rotor yoke 17 and a fan 3 having a plurality of blades 19 that rotate integrally with the rotor yoke 17. The blade 19 of the fan 3 can be formed integrally with the rotor yoke 17 by outsert molding on the outer peripheral surface of the rotor yoke 17.

  A ring-shaped rotor magnet 20 is provided on the inner peripheral surface of the cylindrical portion 17 a of the rotor yoke 17 so as to face the coil 14 of the stator 12. The magnet 20 is a plastic magnet in which S and N poles are alternately magnetized in the circumferential direction, and is fixed to the inner peripheral surface of the rotor yoke 17 with an adhesive.

  The rotor yoke 17 is rotated by press-fitting a boss portion 21 provided with a through hole 21a provided in the central portion of the flat plate portion 17b into an attachment portion 32 provided on the distal end side of the rotating shaft 31 supported by the bearing unit 30. The shaft 31 and the shaft 31 are rotatably attached.

  When the motor 1 having the above-described configuration is supplied with a drive current in a predetermined energization pattern from the drive circuit unit provided outside the motor 1 to the coil 14 on the stator 12 side, the magnetic field generated in the coil 14 and the rotor The rotor 11 rotates integrally with the rotating shaft 31 by the action of the magnetic field from the 11-side rotor magnet 20. As the rotor 11 rotates, the fan 3 having a plurality of blades 19 attached to the rotor 11 also rotates integrally with the rotor 11. As the fan 3 rotates, the air outside the apparatus is sucked through an opening provided in the casing constituting the computer, and further, the inside of the casing is circulated, and the through-hole is circulated through the heat sink provided in the casing. By exhausting to the outside of the housing through the heat, the heat generated from the heating element is radiated to the outside of the computer main body, and the computer main body is cooled.

  Next, the bearing unit 30 used in the motor 1 will be described in more detail with reference to FIGS.

  2 is a top view of the appearance of the bearing unit of the present invention, FIG. 3 is a side view of the appearance of the bearing unit shown in FIG. 2, and FIG. 4 is a cross-sectional view of the bearing unit of the present invention on the YY line shown in FIG. FIG. 5 is a cross-sectional view of the bearing unit shown in FIG. 4 taken along line XX, and FIG. 6 is an example of a dynamic pressure generating groove formed on the inner peripheral surface of the radial bearing used in the bearing unit of the present invention. 7 is a perspective view showing the shape of the passage formed between the passage forming member and the radial bearing, and FIG. 8 is a passage forming suitable for use in the passage forming member of the bearing unit of the present invention. FIG. 9A is a perspective view of the whole, FIG. B is a top view of FIG. A, FIG. C is a cross-sectional view on the AA line of FIG. B, and FIG. FIG. 1 is a top view of a passage forming member in which a groove different from the shape of the groove of the passage forming member shown in FIG. FIG. 11 is a top view of a passage forming member in which another shape of groove different from the shape of the passage forming member shown in FIG. 8B is formed, and FIG. 11 shows a passage formation different from the passage forming member shown in FIG. It is a figure corresponding to Drawing 7 using a member.

  As shown in FIGS. 1 to 5, the bearing unit 30 that rotatably supports the rotating shaft 31 of the motor 1 includes a radial bearing 33 that supports the rotating shaft 31 in the circumferential direction, and the radial bearing 33. A passage forming member 34A formed on the outside, a housing 37 in which the passage forming member 34A is accommodated, a passage 50 formed between the passage forming member 34A and the radial bearing 33, and a thrust bearing 46 communicating with the passage 50 Is provided with an air circulation passage 60 composed of a groove Ga or the like that forms a space S.

  The radial bearing 33 is formed in a cylindrical shape from sintered metal. The radial bearing 33 constitutes a dynamic pressure fluid bearing together with the lubricating oil 42 that is a viscous fluid filled in the housing 37, and has a dynamic pressure generating groove 43, in the inner peripheral surface through which the rotary shaft 31 is inserted. 44 is formed.

  As shown in FIG. 6, the dynamic pressure generating grooves 43 and 44 are formed so that a pair of grooves 43 a and 44 a having a U-shape on the inner peripheral surface of the radial bearing 33 are continuous with the connecting grooves 43 b and 44 b in the circumferential direction. It is formed and configured. The dynamic pressure generating grooves 43 and 44 are formed such that the distal ends of the pair of grooves 43 a and 44 a having a letter-shaped shape face the rotation direction R <b> 1 of the rotating shaft 31. In this example, the dynamic pressure generating grooves 43 and 44 are formed in parallel in the axial direction of the radial bearing 33 having a cylindrical shape, and the shaft 31 is opened in the dynamic pressure generating grooves 43. The shaft exposure side and the dynamic pressure generating groove 44 are formed on the non-axis exposure side where the shaft 31 is not opened, that is, on the thrust bearing side described later. The number and size of the dynamic pressure generating grooves 43 and 44 provided in the radial bearing 33 are appropriately selected depending on the size and length of the radial bearing 33. The radial bearing 33 may be made of brass, stainless steel, or a polymer material.

  The radial bearing 33 formed as a hydrodynamic bearing is filled in the housing 37 when the rotary shaft 31 inserted through the radial bearing 33 continuously rotates in the direction of the arrow R1 in FIG. The lubricated oil 42 flows through the dynamic pressure generating grooves 43, 44 and supports the rotating shaft 31 that rotates by generating dynamic pressure between the outer peripheral surface of the rotating shaft 31 and the inner peripheral surface of the radial bearing 33. . The dynamic pressure generated at this time makes the friction coefficient between the rotating shaft 31 and the radial bearing 33 extremely small, and realizes smooth rotation of the rotating shaft 31.

  In this bearing unit 30, the width of the dynamic pressure generating groove 44 in the thrust direction is formed wider than the width of the other dynamic pressure generating groove 43 in the thrust direction. Thus, the relationship between the dynamic pressure amount P43 generated by the dynamic pressure generating groove 43 on the shaft exposed side and the dynamic pressure amount P44 generated by the dynamic pressure generating groove 44 on the non-axial exposed side is P43 <P44. It has become a relationship.

  Here, the point which makes the dynamic pressure amount P44 on the non-axis exposed side larger than the dynamic pressure amount P43 on the shaft exposed side will be described. The generation of dynamic pressure simultaneously causes a change in static pressure. Here, when the dynamic pressure generating groove is formed so as to satisfy the relationship of P43> P44 opposite to the above, that is, the amount of dynamic pressure on the shaft exposed side becomes larger than the amount of dynamic pressure on the non-shaft mist side. Thus, since the static pressure distribution is opposite to the dynamic pressure distribution, the static pressure on the sealed shaft end side, which is the non-shaft exposed side, is higher than that on the shaft exposed side. The static pressure generated simultaneously with the rotation of the shaft causes a phenomenon of pushing the shaft upward, that is, a shaft floating phenomenon.

  In order to prevent this shaft floating phenomenon, in this bearing unit 30, the width of the dynamic pressure generating groove 43 is made narrower than the width of the dynamic pressure generating groove 44, so that the dynamic pressure amount P43 on the shaft exposed side and the non-axis exposed side are The dynamic pressure amount P44 is set to P43 <P44, the static pressure on the shaft exposure side is made larger than the static pressure on the non-axis exposure side, and the shaft is pulled to the non-axis exposure side, that is, the thrust bearing side described later. A state like this is created.

  The passage forming member 34A provided on the outer side of the radial bearing 33 is formed in a cup-shaped structure that accommodates and surrounds the cylindrical radial bearing 33 as shown in FIGS. For example, it is integrally formed with a synthetic resin.

  As shown in FIGS. 5, 7 </ b> C, and 8, the passage forming member 34 </ b> A includes a cylindrical passage forming member main body 35 </ b> A that surrounds the side surface portion of the radial bearing 33 and a circular bottom surface portion 35 </ b> B that surrounds the bottom surface portion of the radial bearing 33. And a donut-shaped passage forming member lid portion 36 (FIGS. 2 and 7) formed so as to surround the upper surface portion of the radial bearing 33. As shown in FIGS. 7 and 8, a space S is formed in the radial direction on the inner surface of the corner portion of the cylindrical passage forming member main body 35A and the circular bottom surface portion 35B in the vicinity of a thrust bearing 46 described later. At least one groove Ga to be formed is formed. In the case of this embodiment, a total of three are formed at an angular interval of 120 degrees. In addition, a shaft insertion hole 36 a through which the rotation shaft 31 rotatably supported by the radial bearing 33 is inserted is provided at the center of the passage forming member lid portion 36.

  Note that the shape of the groove Ga formed in the corner portion of the passage forming member 34A may not be linear in the radial direction of the circular bottom surface portion 35B, and as shown in FIG. It may be a passage forming member 34B in which arcuate grooves Gb having the same orientation are formed. Even if the groove Ga is linear, it is not only formed on the inner surface of the corner portion corresponding to the passage forming member main body 35A as in the passage forming member 34C shown in FIG. Correspondingly, the grooves Ga are formed, and a large number of grooves can be formed to increase the volume of the space S. The same applies to the passage forming member 34B.

  Now, referring back to FIG. 5 and FIG. 8, a bearing support portion provided at one end portion in the thrust direction of the rotary shaft 31 supported by the radial bearing 33 is provided at the center portion on the inner surface side of the bottom surface portion 35 </ b> B of the passage forming member 34 </ b> A. A thrust bearing 46 that rotatably supports 31a is integrally formed. In the thrust bearing 46, the passage forming member 34A is formed of resin, and is shared as a thrust bearing. The thrust bearing 46 is formed as a pivot bearing that supports the bearing support portion 31a of the rotary shaft 31 that is formed in an arc shape or a tapered tip shape.

  A claw-shaped restricting portion 35a for fixing the passage forming member lid portion 36 so as to cover the upper surface portion of the radial bearing 33 is provided on the circumference of the upper portion of the passage forming member main body 35A. Further, an opening 35b is provided on the side surface of the passage forming member main body 35A so that the outer peripheral surface of the radial bearing 33 faces outside when the radial bearing 33 is accommodated.

  The passage forming member 34A is made of resin, but may be made of metal, and may be a combination of resin and metal, and the material is not limited. Here, when the passage forming member 34A is made of resin, there is an advantage that the shape can be devised, such as a phase index with the radial bearing 33, and the cost is low. For example, as the resin material used for the passage forming member 34A, fluorine-based synthetic resins such as polyimide, polyamide, and polyacetal, synthetic resins such as polytetrafluoroethylene Teflon (registered trademark) and nylon, and further, PC (polycarbonate) , Synthetic resin such as ABS (acrylonitrile butadiene styrene) may be used.

  A passage 50 is formed between the passage forming member 34A and the radial bearing 33 as shown in FIG. The communication passage 50 communicates one end portion and the other end portion of the shaft 31 protruding from the radial bearing 33 in the thrust direction. That is, the communication passage 50 communicates one end side on the side where the thrust bearing 46 is formed and the other end portion on the shaft insertion hole 36 a side of the passage forming member lid portion 36.

As shown in FIG. 7, the communication passage 50 includes a first groove 51 formed in the thrust direction on the outer peripheral surface of the radial bearing 33 and a first groove formed on one end surface of the radial bearing 33 on the thrust bearing 46 side. 2 grooves 52 and a third groove 53 formed on the other end surface of the radial bearing 33.

  Note that this communication path may be provided on the path forming member 34D side as shown in FIG. That is, the communication passage 70 is formed in the first groove 71 formed in the thrust direction on the inner peripheral surface of the passage forming member main body 35 of the passage forming member 34D and the inner surface of the corner portion of the bottom surface portion 35B of the passage forming member main body 35. You may make it consist of the formed 2nd groove | channel Ga and the 3rd groove | channel 72 formed in the inner surface side of the channel | path formation member cover part 36. FIG. Furthermore, the first to third grooves 51 to 53 provided on the radial bearing 33 side and the first to third grooves 71, 72, and Ga provided on the passage forming member 34D may be combined.

  These communication passages 50 and 70 communicate with the grooves Ga formed in the corner portion inner surface of the bottom surface portion 35 </ b> B of the passage forming member main body 35, thereby forming an air circulation passage 60. For this reason, the space S formed in the vicinity of the thrust bearing 46 is released to the outside of the bearing unit 30 through the passages 53 and 72 on the shaft exposed side.

  Therefore, as described above, in the bearing unit 30 of the present invention, the dynamic pressure generating groove 44 is formed wider than the dynamic pressure generating groove 43 so that the non-shaft exposed side dynamic pressure amount P44 is set to the shaft exposed side. Therefore, the shaft levitation phenomenon due to shaft rotation can be suppressed.

  When there is no space S, due to a decrease in static pressure at the shaft end on the non-shaft exposed side, in the case of the radial bearing 33 of residual air or sintered metal, the air contained therein oozes out, A leakage phenomenon that air expands at the sealed shaft end on the non-shaft exposed side and pushes out the lubricating oil 42 occurs as a problem, but the shaft end portion (thrust) is formed by forming the groove Ga as in the present invention. Since the space S is formed in the vicinity of the bearing portion), even if the air accumulates in the space S and the air expands, the expanded air does not push out the lubricating oil 42 before the air circulation passage 60 is formed. Since the oil is discharged to the outside of the bearing unit 30, the lubricating oil 42 does not leak.

  Air bubbles are less likely to be released when the cross section of the passage is smaller, that is, the impedance is larger. However, by providing the groove Ga in the passage forming member 34A, this impedance is reduced, and the residual air bubbles are discharged more smoothly to the outside.

  Furthermore, since the air circulation passage 60 communicates the open side and the non-open side of the rotating shaft 31 protruding from the radial bearing 33, the static pressure at the shaft end on the non-shaft exposed side does not decrease. It is possible to prevent the lubricating oil from being pushed out due to expansion of the residual air inside, the air inside the radial bearing 33, the air dissolved in the lubricating oil, and the like. Further, since the air circulation passage 60 can short-circuit the pressures at both ends of the dynamic pressure generating grooves 43 and 44 provided in the radial bearing 33, there is no pressure difference, and thus shaft levitation may occur. Absent.

  As shown in FIG. 5, the housing 37 that houses the passage forming member 34A has a shape that encloses and surrounds the substantially cylindrical passage forming member 34A, and is formed by integrally molding synthetic resin. One member.

  As shown in FIG. 5, the housing 37 has a cylindrical housing main body 38, and a bottom portion closing part constituting one end side portion integrally formed with the housing main body 38 so as to close one end side of the housing main body 38. Part 39 and an upper closing part 40 formed integrally with the housing main body 38 constituting the other end side of the housing main body 38. A shaft insertion hole 41 through which the rotation shaft 31 rotatably supported by the radial bearing 33 housed in the housing 37 is inserted is provided at the center of the upper closing portion 40.

  In the housing 37 configured as described above, the passage forming member 34A is disposed on the inner peripheral side of the housing body 38 by outsert molding the synthetic resin material so as to enclose the substantially cylindrical passage forming member 34A. It is integrally formed.

  At this time, since a part of the outer peripheral surface of the radial bearing 33 is exposed to the outside through the opening 35b of the passage forming member main body 35A, it is integrated with the housing 37 to be outsert molded.

  The synthetic resin material constituting the housing 37 is not particularly limited, but it is desirable to use a material that increases the contact angle with respect to the lubricating oil 42 that repels the lubricating oil 42 filled in the housing 37. Since the passage forming member 34A is integrally formed in the housing 37, it is preferable to use a synthetic resin material having excellent lubricity. For example, the housing 37 is preferably formed using a fluorine-based synthetic resin such as polyimide, polyamide, or polyacetal, or a synthetic resin such as polytetrafluoroethylene Teflon (registered trademark) or nylon. Furthermore, synthetic resins such as PC (polycarbonate) and ABS (acrylonitrile butadiene styrene) may be used. Furthermore, it is formed of a liquid crystal polymer that can be molded with extremely high accuracy. In particular, when a liquid crystal polymer is used as the housing 37, the lubricating oil is retained and the wear resistance is excellent.

  By the way, this bearing unit 30 is a so-called both-shaft open type in which both ends of the shaft 31 protruding from the radial bearing 33 are communicated by providing the air circulation passage 60. In the conventional open shaft type bearing unit, there is a problem that scattering of the lubricating oil easily occurs due to an impact. In this bearing unit 30, since the housing 37 has a seamless structure in which both the radial bearing 33 and the passage forming member 34A are sealed except for the shaft insertion hole 36a, the shaft open side and the non-shaft open side protruding from the radial bearing 33 of the shaft are air. The communication passage 60 communicates, but the outside is sealed except for the shaft insertion hole 36 a provided in the housing 37. That is, the bearing unit 30 is provided with a seamlessly formed air circulation passage 60 and provided in a housing sealed from the outside, so that scattering of lubricating oil due to impact can be prevented.

  A rotary shaft 31 rotatably supported by a radial bearing 33 disposed in the housing 37 and a thrust bearing 46 provided integrally with the housing 37 is a bearing support portion supported by the thrust bearing 46 of the shaft body 31b. 31a is formed in an arc shape or a tapered shape at the tip end, and a mounting portion 32 to which the rotor 31 of the motor 12, for example, is attached is provided on the other end side. Here, the shaft body 31b and the mounting portion 32 are formed to have the same diameter.

  As shown in FIG. 5, the rotary shaft 31 is mounted on the other end side with the bearing support portion 31a on one end supported by the thrust bearing 46 and the outer peripheral surface of the shaft portion main body 31b supported by the radial bearing 33. The portion 32 is protruded from a shaft insertion hole 41 provided in the upper closing portion 40 of the housing body 38 and supported by the housing 37.

  Further, the rotary shaft 31 is provided with a groove portion 31c for preventing the shaft from dropping between the bearing support portion 31a and the shaft portion main body 31b. A washer 49 is provided on the passage forming member 34 as a means for preventing the shaft from slipping off so as to correspond to the shaft retaining groove 31c. By engaging the shaft retaining groove 31c and the washer 49, handling during assembly is improved. The washer 49 is made of a polymer material such as nylon, polyamide or polyimide, or a metal such as stainless steel or phosphor bronze.

  By the way, the shaft insertion hole 41 is slightly larger than the outer diameter of the shaft body 31b so that the rotation shaft 31 inserted through the shaft insertion hole 41 rotates without slidingly contacting the inner peripheral surface of the shaft insertion hole 41. It is formed with an inner diameter. At this time, the shaft insertion hole 41 has a gap c between the inner peripheral surface and the outer peripheral surface of the shaft portion main body 31 b with an interval c sufficient to prevent the lubricating oil 42 filled in the housing 37 from leaking from the housing 37. 45 is formed. Thus, the upper closing portion 40 in which the shaft insertion hole 41 is formed so that the gap 45 is formed between the rotating shaft 31 and the lubricating oil 42 filled in the housing 37 to prevent leakage. The oil seal part is configured.

  Since the upper closing portion 40 formed integrally with the housing 37 is formed of a synthetic resin such as polyimide, polyamide, or nylon, the contact angle of the inner peripheral surface of the shaft insertion hole 41 with the lubricating oil 42 is about 60 degrees. It can be secured. The bearing unit 30 according to the present invention includes a contact of the lubricating oil 42 to the upper closing portion 40 without applying a surfactant to the upper closing portion 40 including the inner peripheral surface of the shaft insertion hole 41 constituting the oil seal portion. Since the angle can be increased, the lubricating oil 42 can be prevented from moving to the outside of the housing 37 through the shaft insertion hole 41 due to the centrifugal force generated by the rotation of the rotating shaft 31.

  Further, a tapered portion 47 is provided on the outer peripheral surface facing the inner peripheral surface of the shaft insertion hole 41 of the rotating shaft 31. The tapered portion 47 is inclined so as to expand a gap 45 formed between the outer peripheral surface of the rotating shaft 31 and the inner peripheral surface of the shaft insertion hole 41 toward the outside of the housing 37. The taper portion 47 forms a pressure gradient in a gap 45 formed by the outer peripheral surface of the rotating shaft 31 and the inner peripheral surface of the shaft insertion hole 41, and allows the lubricating oil 42 filled in the housing 37 to flow inside the housing 37. A force to pull in is generated. Since the lubricating oil 42 is drawn into the housing 37 when the rotary shaft 31 rotates, the lubricating oil 42 surely enters the dynamic pressure generating grooves 43 and 44 of the radial bearing 33 constituted by the dynamic pressure fluid bearing. Thus, dynamic pressure is generated, stable support of the rotating shaft 31 is realized, and leakage of the lubricating oil 42 filled in the housing 37 can be prevented.

  In the bearing unit 30 according to the present invention, the lubricating oil 42 that enters the dynamic pressure generating grooves 43 and 44 provided in the radial bearing 33 constituting the dynamic pressure fluid bearing and generates dynamic pressure is shown in FIGS. 5 and 12. As described above, the housing 37 is filled so as to face the gap 45 formed by the tapered portion 47 formed on the rotary shaft 31 and the inner peripheral surface of the shaft insertion hole 41. That is, the lubricating oil 42 is filled in the gap in the housing 37 and further impregnated in the radial bearing 33 made of sintered metal.

  Here, the gap 45 formed between the tapered portion 47 formed on the rotating shaft 31 and the inner peripheral surface of the shaft insertion hole 41 will be described. The minimum interval of the gap 45 corresponds to the interval c formed between the outer peripheral surface of the rotating shaft 31 and the inner peripheral surface of the shaft insertion hole 41, and this interval c is preferably 20 μm to 200 μm, and about 100 μm. Most preferred. If the interval c is smaller than 20 μm, it is difficult to ensure the molding accuracy when the housing 37 of the bearing unit 30 is made of synthetic resin by integral molding. On the other hand, if the gap c of the gap 45 is larger than 200 μm, the impact resistance that the lubricating oil 42 filled in the housing 37 scatters outside the housing 37 when an impact is applied to the bearing unit 30 decreases. End up.

  The impact resistance G in which the lubricating oil 42 filled in the housing 37 scatters to the outside of the housing 37 due to an impact is expressed by the following formula (1).

  From equation (1), the impact resistance G is inversely proportional to the square of the distance c of the gap 45.

  Further, the oil level increase amount h due to thermal expansion is expressed by the following equation (2).

  From equation (2), the oil level rise amount h is inversely proportional to the size of the interval c. Therefore, if the interval c is narrowed, the impact resistance G is improved, but the oil level of the lubricating oil 42 due to the temperature rise is increased. The increase in the height h becomes severe, and the axial thickness of the shaft insertion hole 41 is required.

According to the calculation, in the bearing unit 30 having the rotating shaft 31 having a shaft diameter of 2 mm to 3 mm in diameter, the gap c of the gap 45 formed between the rotating shaft 31 and the shaft insertion hole 41 is set to about 100 μm. When the height H ₁ of the insertion hole 41, that is, the thickness of the upper closing portion 40 of the housing 37 is about 1 mm, the impact resistance is 1000 G or more, and the temperature resistance characteristic of 80 ° C. can be endured. A highly reliable bearing unit 30 that prevents scattering of the lubricating oil 42 filled therein can be configured.

  Further, the bearing unit 30 according to the present invention increases the distance c of the gap 45 formed between the outer peripheral surface of the rotating shaft 31 and the inner peripheral surface of the shaft insertion hole 41 toward the outside of the housing 37. Therefore, a pressure gradient is formed in the gap c between the gaps 45 formed by the outer peripheral surface of the rotating shaft 31 and the inner peripheral surface of the shaft insertion hole 41, and the rotating shaft 31 is Due to the centrifugal force generated when it rotates, a force for drawing the lubricating oil 42 filled in the housing 37 into the housing 37 is generated.

  That is, in the bearing unit 30 according to the present invention, the gap 45 formed between the outer peripheral surface of the rotating shaft 31 and the inner peripheral surface of the shaft insertion hole 41 prevents the lubricating oil 42 from being scattered by the surface tension seal. ing.

Here, the surface tension seal will be described. The surface tension seal is a sealing method using the capillary action of fluid. Increase the height h ₁ of the liquid by capillary as shown in FIG. 13 is obtained as follows.

  m is represented by the following formula (4).

  The following equation (5) is derived from equations (3) and (4).

  Generally, the relationship between the pressure P and the fluid height is expressed by the following formula (6).

  Here, the pressure P can be obtained from Equation (5) and Equation (6) as shown in Equation (7).

  In the equation (7), the pressure P means a drawing pressure for drawing in the fluid. From formula (7), the pull-in pressure P increases as the capillary is thinner.

The above explanation is an expression when the cross-sectional shape of the capillary is circular, but the bearing unit 30 according to the present invention is formed between the outer peripheral surface of the rotating shaft 31 and the inner peripheral surface of the shaft insertion hole 41. The lubricating oil 42 that has entered the gap 45 has an annular shape shown in FIG. The rising height h ₁ of the lubricating oil 42 as a liquid in this case is obtained as shown in the following formula (8).

ｍは、下記の式（９）で表される。

m is represented by the following formula (9).

  The following equation (10) is obtained from the equations (8) and (9).

  Assuming that (R−r) is an interval c of the gap 45 formed between the outer peripheral surface of the rotating shaft 31 and the inner peripheral surface of the shaft insertion hole 41, the equation (10) becomes as shown in the equation (11). .

  Therefore, when the cross-sectional shape of the lubricating oil 42 is an annular shape, the pulling pressure is expressed by the following formula (12).

  Here, a specific calculation example is shown.

The gap c formed between the outer peripheral surface of the rotary shaft 31 and the inner peripheral surface of the shaft insertion hole 41 is 0.02 cm (0.2 mm), the surface tension γ of the viscous fluid is 30 dyn / cm ² , and lubrication When the contact angle θ of the oil 42 is 15 °, the drawing pressure is 2.86 × 10 ⁻³ atm (atm) according to the equation (13).

P = 2 × 30 × cos 15 ° / 0.02 = 3.00 × 10 ³ / cm ²
= 2.86 × 10 ⁻³ atm (atm) (13)
According to the equation (12), the pull-in pressure P increases as the gap c between the gaps 45 decreases. Therefore, the provision of the tapered portion 47 on the rotating shaft 31 makes it possible to draw the lubricating oil 42 as a viscous fluid in the direction in which the interval c of the gap 45 is narrow, that is, in the inner direction of the housing 37.

For example, as shown in FIG. 15, pull the pressure P1, P2 of the diameter of different portions _{t 1} and _{t 2} of the tapered portion 47 provided on the rotary shaft 31, the outer peripheral surface and the shaft insertion of the rotary shaft 31 in the portion of _{t 1} Since the relationship of the distance c ₂ between the outer peripheral surface of the rotating shaft 31 and the inner peripheral surface of the shaft insertion hole 41 at the interval c ₁ and t ₂ between the inner peripheral surface of the hole 41 is c ₁ <c ₂ , According to the equation (12), P1> P2, and the pulling pressure P of the lubricating oil 42 into the housing 37 is a gap 45 formed between the outer peripheral surface of the rotating shaft 31 and the inner peripheral surface of the shaft insertion hole 41. It can be seen that the distance c increases as the distance c decreases.

  As described above, the gap formed between the outer peripheral surface of the rotating shaft 31 and the inner peripheral surface of the shaft insertion hole 41 constituting a seal portion that prevents leakage of the lubricating oil 42 filled in the housing 37 to the outside of the housing 37. By providing the tapered portion 47 so that the interval c of 45 becomes smaller toward the inside of the housing 37, it is positioned in the gap 45 formed by the outer peripheral surface of the rotating shaft 31 and the inner peripheral surface of the shaft insertion hole 41. A pressure gradient is generated in the lubricating oil 42. That is, the pressure gradient applied to the lubricating oil 42 increases toward the inside of the housing 37 where the gap c between the gaps 45 decreases. When such a pressure gradient is generated in the lubricating oil 42, the pressure P that is always drawn inward of the housing 37 acts on the lubricating oil 42. Therefore, the rotation shaft 31 rotates. However, air is not involved in the lubricating oil 42 present in the gap 45.

  When the tapered portion 47 is not provided, that is, the distance c between the outer peripheral surface of the rotating shaft 31 and the inner peripheral surface of the shaft insertion hole 41 is the height of the shaft insertion hole 41 as shown in FIG. When the direction is constant, no pressure gradient is generated in the lubricating oil 42 that has entered the gap 45 between the outer peripheral surface of the rotating shaft 31 and the inner peripheral surface of the shaft insertion hole 41, and therefore the lubricating oil 42 has a gap 45. Uniformly present inside. In other words, the lubricating oil 42 that has entered the gap 45 functioning as a seal portion by narrowing the gap c of the gap 45 between the outer peripheral surface of the rotary shaft 31 and the inner peripheral surface of the shaft insertion hole 41 rotates the rotary shaft 31. May move in the gap 45 and entrain the air E. When the air E is entrained in the lubricating oil 42 as described above, the air E expands due to a change in temperature, a change in atmospheric pressure, or the like, and the lubricating oil 42 is scattered outside the housing 37 from the gap 45 constituting the seal portion.

  On the other hand, as in the bearing unit 30 according to the present invention, the interval c of the gap 45 formed between the outer peripheral surface of the rotating shaft 31 and the inner peripheral surface of the shaft insertion hole 41 is inward of the housing 37. By providing the tapered portion 47 that becomes smaller toward the inside, a pressure gradient is generated in the lubricating oil 42 that has entered the gap 45 so that the pressure increases toward the inside of the housing. It is possible to prevent the air E from being caught in the lubricating oil 42.

  Furthermore, the provision of the taper portion 47 as described above allows the outer peripheral surface of the rotary shaft 31 and the inner periphery of the shaft insertion hole 41 even when the rotary shaft 31 is eccentric with respect to the shaft insertion hole 41 provided in the housing 37. In addition to preventing the lubricant 42 that has entered the gap 45 formed between the surface and the housing 37 from being scattered outwardly, the lubricant 42 can enter the entire circumference of the rotary shaft 31. It is possible to prevent the lubricating oil 42 around the rotating shaft 31 from running out and to ensure stable rotation of the rotating shaft 31.

  When the rotating shaft 31 is eccentric with respect to the shaft insertion hole 41 provided in the housing 37, if the tapered portion 47 is not provided as described above, as shown in FIG. The distance c between the outer peripheral surface of the rotating shaft 31 and the inner peripheral surface of the shaft insertion hole 41 is concentrated in a narrower direction, and the lubricating oil 42 is cut off at a portion where the distance c on the opposite side is wide and air E is entrained. It will end up. When the air E is entrained in the lubricating oil 42, the air E expands due to a change in temperature, a change in atmospheric pressure, or the like, and the lubricating oil 42 is scattered outside the housing 37 from the gap 45 constituting the seal portion.

  On the other hand, when the rotary shaft 31 is eccentric with respect to the shaft insertion hole 41 provided in the housing 37 by providing the rotary shaft 31 with the taper portion 47 as in the bearing unit 30 according to the present invention, FIG. As shown in FIG. 18, there is always a gap 45 of the same interval c on the elliptical orbit where the eccentric rotating shaft 31 rotates, and the outer peripheral surface of the rotating shaft 31 and the inner periphery of the shaft insertion hole 41 on the elliptical orbit. As shown in FIG. 19, the interval c between the gaps 45 formed with the surface is constant over the entire circumference of the rotating shaft 31, so that the lubricating oil 42 is concentrated toward the narrower interval c. Since such a phenomenon does not occur, it is possible to prevent the lubricating oil 42 from being released from the gap 45 and thus from the housing 37.

  The bearing unit 30 is provided with the tapered portion 47 on the rotating shaft 31 side. However, as shown in FIG. 20, the tapered portion 48 is provided on the inner peripheral surface of the shaft insertion hole 41 on the housing 37 side. Also good.

  In the bearing unit 30, the housing 37 is formed of a synthetic resin molded body. However, the housing 37 is not limited to the synthetic resin, and synthetic resin and other molding materials obtained by mixing metal materials that can be molded using a mold apparatus are used. It may be formed by using. When the housing 37 is formed of a material other than synthetic resin, the contact angle with the inner peripheral surface of the shaft insertion hole 41 of the lubricating oil 42 filled in the housing 37 may not be sufficiently maintained. Thus, when there is a possibility that the contact angle of the lubricating oil 42 cannot be maintained large, the outer peripheral surface of the upper closing portion 40 including the inner peripheral surface of the shaft insertion hole 41 and further the inner peripheral surface of the shaft insertion hole 41. In addition, a surfactant may be applied to increase the contact angle.

  In the bearing unit 30, the thrust bearing 46 is formed as a part of the housing 37, but the bottom closing portion 39 provided with the thrust bearing 46 is formed independently of the housing body 38, and this bottom closing portion is formed. The housing main body may be integrated using a technique such as heat fusion or ultrasonic fusion.

The bearing unit 30 configured as described above is very useful for preventing leakage of the lubricating oil 42. However, the residual air generated when the shaft 31 rotates and the expansion of the air dissolved in the lubricating oil (cavitation phenomenon). This solves the problem of the shaft piece open type hydrodynamic bearing unit having a seamless resin housing, which has a disadvantage that the lubricating oil 42 is easily pushed out.

  Conventionally, in this bearing unit 30, a housing part is composed of a plurality of parts, and a passage provided for pressure short-circuiting at both ends of the radial bearing is a non-shaft opening side-passage-housing outside-shaft opening side. On the other hand, the air flow passage 60 is a non-axial open space-passage-shaft open side, and the passage forming member 34 of any embodiment that forms the air flow passage 60 is covered with a seamless housing 37. It is what.

  That is, this bearing unit 30 is provided with a passage forming member 34, and at the upper and lower ends of the radial bearing 33 is provided with an air flow passage 60 whose path is a space at the lower end of the bearing-passage-upper end of the bearing. Since the static pressure drop on the non-shaft open side, which is the lower end, can be mitigated, the leakage of lubricating oil due to the pushing up of residual air can be prevented, and the path to the outside of the housing is only a slight gap between the shaft and the housing. Since a certain state is maintained, it is possible to prevent the lubricating oil from scattering due to an impact and to prevent the viscous fluid from oozing out. As a result, the bearing unit 30 can maintain good lubrication performance for a long time.

  The bearing unit uses lubricating oil as a viscous fluid filled in the housing, but various viscous fluids are appropriately selected as long as they have a constant viscosity and a constant surface tension. be able to.

  The bearing unit according to the present invention can be used not only as a bearing of a motor of a heat dissipation device or a spindle motor of a disk drive, but also as a bearing of various motors.

  Furthermore, the bearing unit according to the present invention can be widely used not only for a motor but also for a mechanism that includes a rotating shaft and a mechanism that supports a rotating component with respect to the shaft.

It is sectional drawing which showed the structure of the motor to which this invention is applied. It is a top view of the external appearance of the bearing unit of this invention. It is a side view of the external appearance of the bearing unit shown in FIG. It is sectional drawing on the YY line shown in FIG. 5 of the bearing unit of this invention. It is sectional drawing on the XX line of the bearing unit shown in FIG. It is a perspective view which shows a part of dynamic-pressure generation | occurrence | production groove | channel formed in the internal peripheral surface of the radial bearing used for the bearing unit of this invention. It is a perspective view which shows the shape of the channel | path formed between the channel | path formation member and the radial bearing. FIG. 1 is a perspective view of an overall view of the passage forming member suitable for use in the passage forming member of the bearing unit of the present invention, FIG. B is a top view of FIG. A, and FIG. It is sectional drawing on the AA line of the same figure B. FIG. It is a top view of the channel | path formation member in which the groove | channel different from the shape of the groove | channel of the channel | path formation member shown to FIG. 8B is formed. It is a top view of the channel | path formation member in which the groove | channel of another shape different from the shape of the groove | channel of the channel | path formation member shown to FIG. 8B is formed. It is a figure corresponding to FIG. 7 using the channel | path formation member different from the channel | path formation member shown in FIG. It is sectional drawing which shows the space | gap formed by the outer peripheral surface of a rotating shaft, and the internal peripheral surface of the shaft insertion hole provided in the housing. It is a figure explaining the capillary action of a fluid. It is a cross-sectional view showing a state of lubricating oil that has entered a gap formed between the outer peripheral surface of the rotating shaft and the inner peripheral surface of the shaft insertion hole. It is a longitudinal cross-sectional view which shows the space | gap formed between the outer peripheral surface of a rotating shaft used for description of the difference in drawing pressure in the part from which the diameter of the taper part provided in the rotating shaft differs, and the inner peripheral surface of a shaft insertion hole. . It is a longitudinal cross-sectional view which shows the state in which the air was caught in the lubricating oil which penetrate | invaded in the space | gap formed between the outer peripheral surface of a rotating shaft, and the internal peripheral surface of a shaft insertion hole. It is a cross-sectional view showing a state in which the lubricating oil that has entered the gap formed between the outer peripheral surface of the rotating shaft and the inner peripheral surface of the shaft insertion hole is cut. It is a longitudinal cross-sectional view which shows the state in which the rotating shaft is eccentric with respect to the shaft insertion hole provided in the housing. It is sectional drawing which shows the state of the lubricating oil which penetrate | invaded in the space | gap when the rotating shaft is eccentric with respect to the shaft insertion hole provided in the housing. It is sectional drawing which shows the other example of the bearing unit which concerns on this invention which provided the taper part in the shaft insertion hole side provided in the housing. It is sectional drawing which shows the bearing unit used conventionally. It is sectional drawing which shows the other bearing unit used conventionally. It is sectional drawing which shows the further another bearing unit used conventionally. It is sectional drawing which shows the further another bearing unit used conventionally.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Motor, 13 Stator yoke, 17 Rotor yoke, 30 Bearing unit, 31 Rotating shaft, 33 Radial bearing, 34A, 34B, 34C, 34D Passage formation member, 35A Passage formation member main body, 35B Bottom face part 37 Housing, 38 Housing main body, 39 Bottom closing part, 40 Top closing part, 41 shaft insertion hole, 42 Lubricating oil, 43, 44 Dynamic pressure generating groove 45 Air gap, 46 Thrust bearing, 47 Tapered part, 50 passage, 51 First groove, 52 Second groove , 53 Third groove 60 Air circulation passage Ga, Gb Groove S Space

Claims (9)

The axis,
A radial bearing for supporting the shaft in the circumferential direction;
A thrust bearing supporting one end of the shaft in the thrust direction;
A passage forming member provided outside the radial bearing and the thrust bearing;
Except for the shaft insertion hole through which the shaft is inserted, the passage forming member, a housing for sealing an outer peripheral portion of the radial bearing,
A viscous fluid filled in the housing;
A passage formed between the projecting end side in the thrust direction of the shaft projecting from the radial bearing and the other end side in the thrust direction of the shaft between the passage forming member and the radial bearing, and a space of the thrust bearing portion An air circulation passage configured to communicate with the bearing unit.   2. The bearing unit according to claim 1, wherein the space is formed by forming at least one radial groove on an inner surface of the passage forming member in the vicinity of the thrust bearing.   The air flow passage includes a groove formed on the outer peripheral surface of the radial bearing over the protruding end side in the thrust direction of the shaft protruding from the radial bearing and the other end side in the thrust direction of the shaft, and at least the thrust of the passage forming member. The bearing unit according to claim 1, wherein the bearing unit is formed by communicating with at least one radial groove formed on an inner surface in the vicinity of the bearing.   The air circulation passage extends at least in the vicinity of the thrust bearing and a groove along the thrust direction of the outer peripheral surface of the radial bearing, on one end side and the other end side in the thrust direction of the radial bearing on the inner peripheral surface of the passage forming member. The bearing unit according to claim 1, wherein the bearing unit is formed by forming one radial groove.   The bearing unit according to claim 1, wherein the radial bearing is formed of a sintered metal.   The bearing unit according to claim 1, wherein the radial bearing is a hydrodynamic fluid bearing provided with a dynamic pressure generating groove.   The bearing unit according to claim 1, wherein the housing is integrally formed of a synthetic resin molding. In a motor including a bearing unit that rotatably supports a rotor with respect to a stator,

The bearing unit includes a shaft, a radial bearing that supports the shaft in a circumferential direction, a thrust bearing that supports one end of the shaft in the thrust direction, and a passage formed outside the radial bearing and the thrust bearing. Except for a member, a shaft insertion hole through which the shaft is inserted, the passage forming member, a housing for sealing an outer peripheral portion of the radial bearing, a viscous fluid filled in the housing, and a shaft protruding from the radial bearing The thrust passage portion and the other end side of the shaft in the thrust direction are communicated with a passage formed between the passage forming member and the radial bearing and a space of the thrust bearing portion. A motor comprising a bearing unit having an air flow passage. The motor according to claim 8, wherein the housing is integrally formed of a synthetic resin molding.

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