JP2005351375A - Dynamic pressure bearing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a dynamic pressure bearing which can be used in regular and reverse rotation directions. <P>SOLUTION: A bearing sleeve 3 is formed out of sintered metal. A dynamic pressure groove zone A1 generating dynamic pressure action at a time of regular rotation and a dynamic pressure groove zone A2 generating dynamic pressure action at a time of reverse rotation are formed on an inner circumference of the bearing sleeve 3 in different shapes. Non-contact support in a radial direction of a shaft member 2 in the regular and reverse rotation direction is established by dynamic pressure action of fluid generated in a radial bearing gap between an outer circumference 2a of the shaft member 2 and the dynamic pressure groove zones A1, A2 on the inner circumference of the bearing sleeve 3 at a time of rotation of the shaft member 2. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a dynamic pressure bearing.

  The hydrodynamic bearing has features such as high rotational accuracy, high speed rotation, low cost, and low noise. In recent years, these features have been utilized to make spindle motors for disk devices such as HDDs, CD-ROMs, DVD-ROMs, Or, it is widely used as a bearing for small motors such as polygon scanner motors of laser beam printers (LBP), DLP video projectors, and other axial fans.

  In this dynamic pressure bearing, a shaft member is inserted into the inner periphery of the bearing sleeve, and fluid pressure is generated by the dynamic pressure action of the dynamic pressure groove in the radial bearing gap between the inner periphery of the bearing sleeve and the outer periphery of the shaft member. The shaft member is non-contact supported by this pressure.

In this dynamic pressure bearing, the dynamic pressure groove is formed on the inner periphery of the bearing sleeve or the outer periphery of the shaft member. Particularly when the dynamic pressure groove is formed on the inner periphery of the bearing sleeve, the dynamic pressure groove having a complicated shape is formed. It is generally difficult to form accurately and efficiently. Conventionally, a method of rolling a dynamic pressure groove by inserting a special jig into the inner periphery of a soft metal bearing sleeve has been mainly used, and an example thereof is disclosed in Japanese Patent Laid-Open No. 2000-312943 (Patent Document 1). Has been described.
JP 2000-312943 A

  By the way, in the conventional dynamic pressure bearing, the rotation direction of the shaft member is limited to one direction (forward rotation), but if this can be used in the reverse rotation direction, it is beneficial for further expansion of the application of the dynamic pressure bearing. It is.

  On the other hand, in order to be able to be used even in reverse rotation, it is necessary to newly form a dynamic pressure groove inclined in the opposite direction separately from the dynamic pressure groove for forward rotation. Conventionally, since the dynamic pressure grooves are formed by rolling, it is difficult to form the dynamic pressure grooves for forward and reverse rotation that have a more complicated shape, and it is difficult to meet the above requirements. Even if the dynamic pressure groove for forward and reverse rotation can be formed, if the bearing sleeve is made of a solid metal material, negative pressure is generated from the reverse rotation dynamic pressure groove during forward rotation. This may cause the occurrence of whirl and oil leakage.

  Accordingly, an object of the present invention is to provide a dynamic pressure bearing that can be used in both forward and reverse rotational directions.

  In order to achieve the above object, in the present invention, a bearing sleeve having a dynamic pressure groove region in which a plurality of dynamic pressure grooves are arranged in a circumferential direction on an inner periphery, and a shaft member inserted in the inner periphery of the bearing sleeve are provided. Dynamic pressure that supports the shaft member in the radial direction by the dynamic pressure action of the fluid generated in the radial bearing gap between the outer periphery of the shaft member and the inner periphery of the bearing sleeve during relative rotation of the shaft member and the bearing sleeve In the bearing, the bearing sleeve is made of sintered metal, and a dynamic pressure groove region during forward rotation and a dynamic pressure groove region during reverse rotation are formed on the inner periphery of the bearing sleeve, and both dynamic pressure groove regions have different shapes. In addition, the inner peripheral surface of the bearing sleeve having these dynamic pressure groove regions is a die-formed surface.

  The dynamic pressure groove region is a portion that generates a dynamic pressure action according to the rotation direction during forward rotation or reverse rotation, and is configured by a region including at least a dynamic pressure groove and a back portion between adjacent dynamic pressure grooves. The The dynamic pressure groove region at the time of forward rotation and the dynamic pressure groove region at the time of reverse rotation are formed separately from each other (see FIG. 1), and can also be formed by overlapping at least a part thereof (see FIG. 1). 5, see FIG.

  If the bearing sleeve is made of sintered metal in this way, the dynamic pressure groove region is provided with a groove shape having an uneven shape corresponding to this, and a bearing force is applied to the bearing sleeve by applying a pressing force to the bearing sleeve. It can be formed by pressing the inner peripheral surface of the sleeve against the groove mold. In this case, the inner peripheral surface of the bearing sleeve undergoes plastic deformation, and the groove-shaped irregularities are transferred to the inner peripheral surface of the bearing sleeve, so that a dynamic pressure groove region molded on the inner peripheral surface is formed. With this mold forming, it is possible to accurately and efficiently form an inner peripheral surface of a bearing sleeve having a complex shape with two types of dynamic pressure groove regions during forward rotation and reverse rotation. A dynamic pressure bearing that can be used in the rotational direction can be provided. Also, when negative pressure is generated in the reverse rotation dynamic pressure groove during forward rotation, oil oozes out from the bearing sleeve through the surface opening into the radial bearing gap, so that the negative pressure can be reduced or offset. Can do. At this time, it is desirable to set the surface area ratio of the inner peripheral surface of the bearing sleeve, particularly the dynamic pressure groove region for both forward and reverse rotations, in the range of 2 to 20%. This is because if it is less than 2%, the effect of reducing the negative pressure becomes insufficient, and if it exceeds 20%, sufficient dynamic pressure action cannot be obtained.

  In particular, as in the present invention, when the dynamic pressure groove region during forward rotation and the dynamic pressure groove region during reverse rotation have different shapes, the fluid pressure generated by the dynamic pressure action differs between forward rotation and reverse rotation. It becomes size. Accordingly, it is possible to increase the fluid pressure during either one of the forward and reverse rotations, and a motor that is high when the drive target is raised, such as a mechanism that moves the drive target up and down with a motor (for example, a power window mechanism). Even when a torque is required and a lower motor torque is sufficient when the motor is lowered, it can be used as a bearing for supporting the rotating shaft of the motor.

  Here, “different shapes” means that the shapes of the dynamic pressure groove region during forward rotation and the dynamic pressure groove region during reverse rotation are not mirror images. When part or all of both dynamic pressure groove regions overlap, whether or not they have different shapes depends on whether they are a dynamic pressure groove region during forward rotation or a dynamic pressure groove region during reverse rotation. Judgment is made based on whether or not they are mirror images.

  The dynamic pressure groove regions at the time of forward rotation and reverse rotation can be arranged with the same axial position in addition to being shifted in the axial position.

  When the present invention is applied to the motor exemplified above (for example, a power window motor), the shaft member can be used as a rotating shaft of the motor.

  As described above, according to the present invention, it is possible to support both forward and reverse rotations and to obtain a hydrodynamic bearing having different bearing performance in both rotational directions at low cost, contributing to further expansion of applications of the hydrodynamic bearing. can do.

  Hereinafter, embodiments of the present invention will be described.

  As shown in FIG. 2, the hydrodynamic bearing 1 according to the present invention includes a shaft member 2 and a cylindrical bearing sleeve 3 in which the shaft member 2 is inserted on the inner periphery as main components.

  The shaft member 2 is formed of a metal material such as stainless steel, and the outer peripheral surface 2a facing the inner periphery of the bearing sleeve 3 is formed into a smooth cylindrical surface. The bearing sleeve 3 is formed of a sintered metal, such as copper or iron, or an oil-containing sintered metal obtained by impregnating a lubricating metal (or lubricating grease) with a sintered metal mainly composed of both. On the inner peripheral surface of the bearing sleeve, as shown in FIG. 1, dynamic pressure groove regions A1 and A2 in which a plurality of dynamic pressure grooves 4 are arranged in the circumferential direction are provided at a plurality of axial positions (four positions in the illustrated example). It is formed.

  Each of the dynamic pressure groove regions A1 and A2 is a region that generates a dynamic pressure action according to the rotation direction, and is adjacent to the dynamic pressure grooves 4 that are inclined with respect to the axial direction and arranged at a plurality of locations in the circumferential direction. And at least a back portion 6 formed between the dynamic pressure grooves 4. FIG. 1 illustrates a so-called herringbone shape as an example of the dynamic pressure groove region. However, this arrangement is merely an example, and dynamic pressure groove regions having other shapes can be formed.

  In FIG. 1, an annular smooth portion 5 having the same height as the back portion 6 is provided between the dynamic pressure grooves 4 adjacent in the axial direction, and the dynamic pressure grooves adjacent in the axial direction are partitioned by the smooth portion 5. The non-continuous type dynamic pressure groove area | region A1, A2 which made 4 discontinuous is illustrated. In this discontinuous type, in addition to the dynamic pressure groove 4 and the back portion 6, the smooth portion 5 is also a component of the dynamic pressure groove regions A1 and A2. In addition, it is also possible to use the continuous dynamic pressure groove regions A1 and A2 in which the smooth portion 5 is eliminated and the dynamic pressure grooves 4 adjacent in the axial direction are made continuous.

  In the present invention, as the dynamic pressure groove regions A1 and A2, a region A1 (dynamic pressure groove region during normal rotation) that generates a dynamic pressure during normal rotation and a region A2 (dynamic movement during reverse rotation) that generates a dynamic pressure during reverse rotation. There are two types of pressure groove regions), and this point is different from the conventional product (see FIG. 7) having only the dynamic pressure groove region A1 during forward rotation. The dynamic pressure groove 4 in the dynamic pressure groove area A1 during forward rotation (hereinafter referred to as the dynamic pressure groove 41 for forward rotation) has a portion that is reduced in the forward rotation direction, and the dynamic pressure groove area A2 during reverse rotation The pressure groove 4 (hereinafter referred to as a reverse rotation dynamic pressure groove 42) includes a portion reduced in the reverse rotation direction. In the present invention, the dynamic pressure groove region A1 during forward rotation and the dynamic pressure groove region A2 during reverse rotation have different shapes that are not mirror images. In this embodiment, the shapes of the two regions A1 and A2 are made different by increasing the number of the dynamic pressure grooves 41 for forward rotation as compared with the dynamic pressure grooves 42 for reverse rotation.

  In this dynamic pressure bearing, when one of the shaft member 2 and the bearing sleeve 3 (for example, the bearing sleeve 3) is fixed and the other (for example, the shaft member 2) is rotated in the forward direction, the dynamic pressure generated in the dynamic pressure groove 41 is obtained. Due to the action, pressure of a lubricating fluid such as oil is generated in the radial bearing gap between the dynamic pressure groove region A1 during forward rotation and the outer peripheral surface 2a of the shaft member 2 facing the dynamic pressure groove region A1, and this pressure causes the shaft member 2 and The bearing sleeve 3 is held in a non-contact manner. Similarly, when rotating in the reverse direction, the radial bearing between the dynamic pressure groove region A2 at the time of reverse rotation and the outer peripheral surface 2a of the shaft member 2 facing the same due to the dynamic pressure action generated in the dynamic pressure groove 42 is also provided. The pressure of the lubricating fluid is generated in the gap, and the shaft member 2 and the bearing sleeve 3 are held in non-contact by this pressure. Therefore, it is possible to support rotation in both forward and reverse directions with one dynamic pressure bearing 1.

  As shown in the figure, when the axial positions of the dynamic pressure groove area A1 during forward rotation and the dynamic pressure groove area A2 during reverse rotation are shifted and formed independently, two types of movement during rotation in either direction are shown. There is an advantage that the mutual interference of the dynamic pressure action in the pressure groove regions A1 and A2 can be suppressed.

  The dynamic pressure groove regions A1 and A2 on the inner periphery of the bearing sleeve 3 can be formed by molding. FIG. 3 shows an example of this mold forming process. In this process, as shown in the drawing, a core rod 11 having a groove die 11a having a shape corresponding to the inner peripheral surface shape of the bearing sleeve 3 is inserted into the inner periphery of a cylindrical sintered metal material 3 ′. In this state, the bearing sleeve 3 is pushed into the die 13 by restraining both end surfaces in the axial direction with the punches 12a and 12b. In the die 12, a pressing force is applied to the sintered metal material 3 ′ from the punches 12 a and 12 b and the die 12, and the inner peripheral surface thereof is pressed against the groove die 11 a of the core rod 11. As a result, the inner peripheral surface of the sintered metal material 3 ′ undergoes plastic deformation, the irregular shape of the groove mold 11 a is transferred, and the dynamic pressure groove areas A 1 and A 2 are molded. At this time, the dynamic pressure grooves 4, the back portion 6, and the smooth portion 5 of the dynamic pressure groove regions A1 and A2 are simultaneously formed by the unevenness of the groove mold 11a.

  When the sintered metal material 3 ′ is taken out from the die 13 after the forming is completed, the inner peripheral surface thereof is enlarged by the spring back of the material 3 ′, so that the groove mold 11a and the hydrodynamic groove regions A1 and A2 after forming interfere with each other. The sintered metal material 3 ′ can be removed smoothly without causing it. The bearing sleeve 3 is obtained by impregnating the demolded sintered metal material 3 ′ with lubricating oil by means such as vacuum impregnation.

  In particular, in the present invention, the dynamic pressure groove regions A1 and A2 at the time of both forward and reverse rotations have different shapes, so that it is possible to cope with cases where different bearing performance is required in both the forward and reverse rotation directions. For example, as in the embodiment shown in FIG. 1, if the number of dynamic pressure grooves 41 in the dynamic pressure groove area A1 during forward rotation is greater than the number of dynamic pressure grooves 42 in the dynamic pressure groove area A2 during reverse rotation. Since the pressure of the fluid generated by the dynamic pressure action is greater during the forward rotation, the shaft member 2 that receives a higher surface pressure during the forward rotation can be supported.

  FIG. 4 shows a schematic configuration of a power window mechanism installed in a vehicle such as an automobile. As shown in the figure, in this mechanism, the driving force of the motor 16 is transmitted to the worm gear 17 and further to the gear 18 engaged therewith via the shaft member 2. As the gear 18 rotates forward and backward, the window moves up and down via a link (not shown). In the conventional power window mechanism, the rotation of the shaft member 2 is supported by the rolling bearing interposed between the housing 15 and the shaft member 2, but the rolling bearing is expensive and tends to increase space. . By using the dynamic pressure bearing 1 in place of the rolling bearing, the cost can be reduced and the mechanism can be made compact.

  As described above, the hydrodynamic bearing 1 of the present invention can support forward and reverse rotation of the shaft member 2 and can support higher surface pressure during forward rotation. In the power window mechanism, when the window rises due to gravity, the shaft member 2 is driven at a higher surface pressure than when the window is lowered. Therefore, by making the positive rotation direction of each dynamic pressure bearing 1 coincide with the rotation direction of the shaft member 2 when the window is raised, the shaft member 2 can be reliably supported in a non-contact manner regardless of whether the window is raised or lowered. It is possible to raise and lower the window stably.

  Hereinafter, another embodiment of the present invention will be described with reference to FIGS. 5 and 6.

  The embodiment shown in FIG. 5 is a partial region obtained by dividing the dynamic pressure groove region A1 for forward rotation in the embodiment shown in FIG. 1 by dividing the inner peripheral surface of the bearing sleeve 3 at a constant pitch in the circumferential direction. Thus, it is formed in a plurality of (preferably three or more) regions separated in the circumferential direction. The reverse rotation dynamic pressure groove region A2 is also arranged in the same manner, but its circumferential phase is shifted from the normal rotation dynamic pressure groove region A1. At both ends in the circumferential direction of both the dynamic pressure groove regions A1 and A2, the back portions facing each other in the axial direction are made common (the common back portion is indicated by reference numeral 6 '). As in the embodiment shown in FIG. 1, the dynamic pressure groove area A1 during forward rotation and the dynamic pressure groove area A2 during reverse rotation have different shapes. Specifically, in the dynamic pressure groove area A1 during forward rotation. The number of the dynamic pressure grooves 41 is larger than the number of the dynamic pressure grooves 42 in the dynamic pressure groove region A2 during reverse rotation. Therefore, similarly to the embodiment of FIG. 1, the pressure of the fluid generated in the radial bearing gap during forward rotation can be made larger than during reverse rotation, and the same effect as the embodiment shown in FIG. 1 can be obtained.

  In the embodiment shown in FIGS. 1 and 5, the axial positions of the dynamic pressure groove area A1 during forward rotation and the dynamic pressure groove area A2 during reverse rotation are shifted, whereas the embodiment shown in FIG. The configuration is such that the two dynamic pressure groove regions A1 and A2 are completely overlapped by arranging the adjacent dynamic pressure groove regions A1 and A2 so that their axial positions coincide with each other. The overlapping dynamic pressure groove regions A1 and A2 are provided at both axial ends of the inner peripheral surface of the bearing sleeve 3. In this case, as compared with the embodiment shown in FIGS. 1 and 5, the axial pitch P between the dynamic pressure groove regions of the same type is increased, so that the moment rigidity of the bearing can be further increased.

  In the dynamic pressure groove regions A1 and A2, the dynamic pressure groove 41 for forward rotation and the dynamic pressure groove 41 for reverse rotation are arranged on the same circumference. The dynamic pressure groove 41, the back portion 61 for forward rotation, and the dynamic pressure groove region A1 during forward rotation formed by the smooth portion 5, the dynamic pressure groove 42, the back portion 62 for reverse rotation, and the smooth portion The dynamic pressure groove region A2 at the time of reverse rotation formed at 5 has a different shape that is not mirror-image-related. Specifically, the number of the dynamic pressure grooves 41 for forward rotation is the number of the dynamic pressure grooves 41 for reverse rotation. More than the number. Accordingly, as in the embodiment shown in FIG. 1, the pressure generated during forward rotation can be increased as compared with reverse rotation. In particular, in the present embodiment, the formation space of the dynamic pressure groove region is limited, and even when the dynamic pressure groove region during forward rotation and reverse rotation cannot be formed independently, the pressure generated according to the rotation direction is adjusted. Has the advantage of being able to.

1 is a cross-sectional view of a bearing sleeve according to a first embodiment of the present invention. It is sectional drawing of the dynamic pressure bearing using the bearing sleeve shown in FIG. It is sectional drawing which shows the formation process of a dynamic pressure groove area | region. It is sectional drawing of the power window mechanism using the dynamic pressure bearing shown in FIG. It is sectional drawing which shows 2nd embodiment of this invention. It is sectional drawing which shows 3rd embodiment of this invention. It is sectional drawing which shows the form of the conventional dynamic pressure groove area | region.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Dynamic pressure bearing 2 Shaft member 2a Outer peripheral surface 3 Bearing sleeve 4 Dynamic pressure groove 41 Dynamic pressure groove 42 for normal rotation 42 Dynamic pressure groove for reverse rotation 5 Smoothing part 6 Back part 11 Core rod 11a Groove type 12a, 12b Punch 13 Die 15 Housing 16 Motor A1 Dynamic pressure groove area (during forward rotation)
A2 Dynamic pressure groove area (during reverse rotation)

Claims (6)

A bearing sleeve having a dynamic pressure groove region in which a plurality of dynamic pressure grooves are arranged in a circumferential direction on an inner periphery, and a shaft member inserted in the inner periphery of the bearing sleeve, and when the shaft member and the bearing sleeve are relatively rotated In the hydrodynamic bearing that supports the shaft member in the radial direction by the hydrodynamic action of the fluid generated in the radial bearing gap between the outer periphery of the shaft member and the inner periphery of the bearing sleeve,
The bearing sleeve is made of sintered metal, and a dynamic pressure groove region at the time of forward rotation and a dynamic pressure groove region at the time of reverse rotation are formed on the inner periphery of the bearing sleeve, respectively, and both dynamic pressure groove regions have different shapes, A hydrodynamic bearing characterized in that the inner peripheral surface of the bearing sleeve having these hydrodynamic groove regions is a molded surface.   The hydrodynamic bearing according to claim 1, wherein the dynamic pressure groove regions during forward rotation and reverse rotation are arranged with their axial positions shifted.   2. The hydrodynamic bearing according to claim 1, wherein each of the dynamic pressure groove regions during forward rotation and reverse rotation is disposed with the same axial position.   2. The hydrodynamic bearing device according to claim 1, wherein the surface opening ratio of the inner peripheral surface of the bearing sleeve is 2 to 20%.   The hydrodynamic bearing device according to claim 1, wherein the shaft member is used as a rotating shaft of a motor.   6. The hydrodynamic bearing device according to claim 5, wherein the motor is a power window motor.

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