JPH11303858A - Porous hydrodynamic bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the lubricity of a porous bearing used in information equipment, imaging equipment, acoustic equipment of the like. SOLUTION: Recesses 2 for producing dynamic pressure are formed the inner peripheral surface or the end face of a bearing 1, and a negative pressure side inclined surface 3 of each of the recess 2 is in a zigzag shape so as to be longer than the line of a positive pressure side inclined surface 4 thereof. With this arrangement, the pumping function of the bearing can be maximumly exhibited so as to promote the formation of a stable oil film, thereby it is possible to enhance the rotational accuracy and the reliability of the bearing 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bearing device such as a motor having a structure in which a load in a radial direction or a thrust direction is received by a porous bearing, and has a long life, low shaft friction loss, and low vibration. The present invention relates to a bearing such as a spindle motor which is required to have characteristics such as low noise or reduction of shaft runout.

[0002]

2. Description of the Related Art In recent years, information equipment and video / audio equipment
As represented by D (Digital Video Disk), as the recording density of devices has increased, bearing devices used in these devices have also been required to have higher rotational accuracy. .

[0003] In a conventional bearing device using a sintered oil-impregnated bearing, as a mechanism for supporting a radial load on a shaft, a bearing having an inner diameter processed into a perfect circle and a so-called journal bearing in which a perfect-circular shaft rotates and slides are used. Most are configured as: When a sintered oil-impregnated bearing rotates with its shaft eccentric, it exhibits good sliding characteristics due to the oil circulation and wedge effect called pump action.However, journal bearings have a radial direction unless the shaft is eccentric. Due to the structural problem that no pressure is generated, the whirling of the shaft becomes large, and there is a basic problem that it is difficult to ensure the rotational accuracy.

To improve the problem of such a sintered oil-impregnated bearing, as described in Japanese Utility Model Laid-Open Publication No. 61-101124, a spiral groove is formed in the inner diameter of the bearing so that the shaft can be rotated. In addition, by introducing the lubricant to the inside, a high degree of rotation accuracy is achieved, energy loss is reduced, and because the bearing is made of sintered metal, machining of the groove shape is easy and inexpensive. . Further, Japanese Unexamined Patent Publication No.
2-167921 and JP-A-62-16792.
Japanese Patent Application Publication No. 2 (1995) -195566 discloses a bearing having a combination of three or more arcuate surfaces having a curvature larger than an arcuate surface centered on an axis on an inner peripheral surface of the bearing, and an inner surface in which the arcuate surface is planar, It describes that the contact with the shaft is a line contact, so that the friction loss can be reduced. Also, Japanese Patent Application Laid-Open No. H5-111514
The bearing described in Japanese Patent Publication No. 6 is a sintered oil-impregnated bearing having a plurality of substantially rectangular grooves on the inner diameter surface, and achieves improved dynamic pressure function and reduced noise and wear by a simple structure. Things.

[0005] As described above, any of the techniques disclosed in the prior art has a clearance for forming a bearing inner diameter groove and supporting the shaft in response to an increase in the fluid resistance of the fluid lubricant accompanying a reduction in the clearance and an increase in the rotational speed. It is intended to reduce the fluid resistance without increasing the pressure. Also, the bearing rigidity of the shaft supporting portion is increased by the dynamic pressure effect in the groove portion, thereby improving the rotation accuracy.

[0006] On the other hand, in a conventional bearing device using a sintered oil-impregnated bearing, sufficient sliding characteristics cannot be realized in the thrust direction sliding without a mechanism for supplying oil or generating hydraulic pressure.

To improve the problem of such a sintered oil-impregnated bearing, Japanese Patent Laid-Open Publication No. 1-12121 discloses at least three or more peaks in a circumferential direction and a radial direction on a surface of a sintered oil-impregnated cake receiving surface. The three-dimensional irregularities having a wavy shape are used to support the thrust load at the convex part, and a positive or negative pressure is generated in the lubricating oil by the height difference between the convex part and the concave part to form an oil film on the sliding surface. In addition, oil is supplied to the sliding surface to receive a load in the thrust direction.

Similarly, Japanese Unexamined Utility Model Publication No. Sho 57-63121 discloses a method of forming a concavo-convex portion on the end surface of a sintered oil-impregnated bearing in order to generate a dynamic pressure in order to receive a load in the thrust direction. This provides an arbitrary number of shallow recesses on the end face,
This recess is a two-dimensional inclined surface formed by a straight line,
Its axial inclination angle is within 20 ° and the maximum depth is 0.3mm
In the following, this concave portion is used as an oil supply portion,
It is intended to improve the sliding conditions by generating dynamic pressure by the wedge effect of the oil film.

Japanese Patent Application Laid-Open No. 4-15311 discloses a method of forming a shape in which positive dynamic pressure is expected to be applied to the end face of a sintered oil-impregnated bearing in the thrust direction. This is to provide a dynamic pressure generating groove on one of the bearing end face or the opposed face of the washer where the inner circumference side becomes high pressure by relative rotation, to prevent the scattering of lubricating oil by simple and inexpensive means,
It is intended to improve durability.

[0010] The above-mentioned technology is applied to thrust sliding.
This mechanism is designed to generate a dynamic pressure in order to form an uneven portion or a tapered portion on an end face portion and to effectively contribute oil existing in the end face portion to thrust lubrication.

[0011]

However, the above-mentioned prior art has the merit of low cost of the sintered oil-impregnated bearing or easiness of processing, but when the pressure of the sintered oil-impregnated bearing is generated, the lubricating oil is applied to the bearing. Due to the property of penetrating inside, the pressure generated is lower than that of a hydrodynamic bearing using ingot material, and the load capacity is smaller than that of a hydrodynamic bearing using ingot material, or the rotational accuracy is low. Had a point.

Most of the dynamic pressure generating mechanisms using the above-described sintered oil-impregnated bearings apply the structure of a hydrodynamic bearing using a molten material to a sintered body. However, most of the lubrication effects obtained by the oil circulation action referred to as the pump action are not fully utilized, and most of the sintered oil-impregnated bearings do not fully utilize the excellent lubrication characteristics inherent in the oil-impregnated bearing.

The present invention minimizes the pressure drop of a porous bearing typified by a sintered oil-impregnated bearing due to the characteristic that lubricating oil permeates into the bearing when pressure is generated. To maximize the lubrication effect by the oil circulation function called pump action, provide optimal dynamic pressure and provide excellent lubrication performance, improve rotational accuracy, and provide bearings with excellent reliability. It is an object.

[0014]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention relates to a porous bearing in which an inner diameter portion which slides on a shaft is formed in a bearing body formed of a porous body. The peripheral portion has a concave portion for generating dynamic pressure, and the shape of the negative pressure side inclined surface of the concave portion is formed in a zigzag shape so as to be longer than the line length of the positive pressure side inclined surface of the concave portion. .

As a result, it is possible to maximize the lubricating effect by the oil circulating action called the pump action of the porous body bearing, and to provide optimal dynamic pressure generation and excellent lubricating performance.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention is directed to a porous bearing in which a bearing body formed of a porous body is formed with an inner diameter portion that slides with a shaft. A concave portion for generating dynamic pressure in the portion, the shape of the negative pressure side inclined surface of the concave portion is formed in a zigzag shape, longer than the line length of the positive pressure side inclined surface of the concave portion, Maximize the lubrication effect by the oil circulation function called the pump action of the bearing, and generate the optimal dynamic pressure,
Excellent lubrication performance can be provided.

According to a second aspect of the present invention, there is provided a porous bearing which receives a thrust load at an end face of a substantially cylindrical body formed of a porous body, wherein the end face of the bearing has a concave portion for generating dynamic pressure. By forming the shape of the negative pressure side inclined surface of the concave portion in a zigzag shape, it is made longer than the length of the line of the positive pressure inclined surface of the concave portion, and the lubrication effect by the oil circulation action called pumping action of the bearing. Pulling out to the maximum, optimal dynamic pressure generation and excellent lubrication performance can be provided.

[0018]

(Embodiment 1) FIG. 1 shows a bearing of this embodiment. In FIG. 1, a bearing 1 is formed by sintering a metal powder such as iron, copper or the like in a high-temperature furnace, followed by sizing. In the bearing inner diameter portion subjected to the sizing processing, three inner diameter concave portions 2 are further formed by rolling.

In FIG. 1, the concave portion 2 provided on the inner diameter
When viewed from the bearing inner peripheral side, the shaft has a shape in which a plurality of straight concave portions are arranged so as to be suitable for generating dynamic pressure when the shaft rotates in the direction of the arrow, and the negative portion on the upstream side in the rotation direction of the concave portion is formed. The compression-side inclined surface 3 is formed by a zigzag line, and the area of the suction-side inclined surface 3 is made larger than that of the case where the suction-side inclined surface 3 is formed by a smooth curve. Further, at the upper and lower ends of the bearing inner diameter, a perfect circular sliding portion 5 is formed in order to prevent oil in the concave portion 2 from leaking to the end face of the bearing 1.

FIG. 2 shows a lubrication mechanism for the inner diameter portion of the bearing. In FIG. 2, when the shaft 6 placed on the inner diameter of the bearing rotates, the depth of the concave portion changes in the rotating direction, so that a pressure is generated by the wedge action of the oil. As shown in FIG. 2, the generated pressure is a negative pressure on the negative pressure inclined surface 3 on the upstream side in the rotation direction where the depth of the recess gradually increases, and a positive pressure side on the downstream side in the rotation direction where the depth of the recess gradually decreases. Slope 4
Then a positive pressure is generated.

On the positive pressure side inclined surface 4 on the downstream side in the rotation direction where the positive pressure is generated, as shown in the figure, oil permeates into the bearing and the pressure decreases. On the other hand, on the negative pressure side inclined surface 3 on the upstream side in the rotation direction where a negative pressure is generated, the oil that has permeated inside the bearing on the positive pressure side inclined surface 4 on the downstream side in the rotational direction seeps out and is supplied again to the sliding surface. This action is a lubrication action called a pump action peculiar to the porous body, and has an action of providing stable sliding even when the entire bearing is not sufficiently filled with oil.

At this time, in the positive pressure side inclined surface 4, the porosity of the bearing surface is made as small as possible, and the permeation of oil is reduced, so that the pressure on the bearing surface can be increased and the rotational accuracy of the shaft can be increased. The above is advantageous. Conversely, on the negative pressure side inclined surface 3, if the porosity of the bearing surface is reduced, oil hardly seeps into the bearing surface, so that the supply of oil to the bearing sliding surface cannot catch up, and metal contact And it becomes difficult to ensure not only rotational accuracy but also reliability. Therefore, ideally, the porosity of the bearing surface is made as small as possible on the positive pressure side inclined surface 4 to prevent a pressure drop, and the porosity of the bearing surface is made large on the negative pressure side However, it is desirable to make the state easily ooze out on the bearing surface.

However, the porosity of the inner diameter of the bearing can be controlled by making the porosity almost constant over the entire circumference. However, the processing of changing the porosity of the surface of the concave portion depending on the location is practical. At present, there is almost no practical processing method that is very difficult.

Therefore, the bearing of the present invention is obtained by forming a concave portion by rolling and forming a negative-pressure-side inclined surface 3 of the concave portion with a zigzag line in a bearing in which the porosity of the inner diameter is substantially constant. The area of the negative pressure side inclined surface 3 is increased to create a state in which oil easily seeps out, as in the case where the porosity of the negative pressure side inclined surface 3 is increased.

With this configuration, the porosity of the bearing inner diameter is controlled to a state where the overall porosity is somewhat small in accordance with the pressure side inclined surface 4, so that the pressure drop at the bearing inner diameter is reduced and the negative pressure side is reduced. By forming the inclined surface 3 with a zigzag line and enlarging the area, oil is easily exuded, so that the pumping action of the bearing is maximized, and the exuded lubricating oil is supplied to the positive pressure side inclined surface 4. By doing
It is possible to provide a bearing device that promotes formation of a stable oil film, has high rotational accuracy, and is excellent in reliability.

The concave shape of the above embodiment is a case where the shape viewed from the inner diameter side is a straight shape.
The same applies when applied to any other shape, such as a so-called herringbone shape in which arrow-shaped concave portions are arranged as shown in FIG. 4, or a shape in which concave portions are formed to be inclined with respect to the axial direction as shown in FIG. effective.

(Embodiment 2) The above-described embodiment 1 relates to a radial dynamic pressure bearing in which the shaft slides on the inner diameter of the bearing, and the same form is applied to a thrust dynamic pressure bearing that supports a load at the bearing end face. It is also possible.

FIG. 5 shows the bearing 7 of this embodiment.
In FIG. 5, the bearing 7 is obtained by sintering a metal powder such as iron, copper or the like in a high-temperature furnace after sintering in a high-temperature furnace, sizing, adjusting the porosity of the end face, and further performing a transfer process. Are formed on the end face. The shape of the concave portion 8 in this embodiment is a shape in which the dimension in the radial direction is asymptotically reduced in the rotation direction. Further, the suction side inclined surface 9 on the upstream side in the rotation direction of the concave portion 8 is formed by a zigzag line, and the area of the suction side inclined surface 9 is made larger than that when the suction side inclined surface 9 is formed by a smooth curve. I have to.

Further, by leaving a flat portion on the outer peripheral side of the bearing end face, oil on the bearing end face is suppressed from leaking in the outer peripheral direction of the bearing.

FIG. 6 shows a lubrication mechanism in the section AA 'of the bearing 7. As shown in FIG. In FIG. 6, the thrust receiving plate 1
When 1 rotates, the depth of the concave portion changes in the rotating direction, thereby generating a pressure due to the wedge action of the oil. As shown in FIG. 2, the generated pressure is a negative pressure on the suction side inclined surface 9 on the upstream side in the rotation direction where the depth of the recess gradually increases, and a positive pressure side on the downstream side in the rotation direction where the depth of the recess gradually decreases. Slope 1
At zero, a positive pressure is generated.

In this embodiment, the pressure-side inclined surface 1 of the concave portion is used.
0 changes the angle to two steps and forms a convex surface in the direction of the thrust receiving plate 11, thereby reducing the pressure gradient generated on the pressure-side inclined surface 10 and generating pressure over a wide area. Stabilization of the occurrence.

With this configuration, as in the case of the radial dynamic pressure bearing described in the first embodiment, the pumping action of the bearing is maximized to promote the formation of a stable oil film, and the thrust supporting rigidity of the bearing is reduced. A high-reliability bearing device can be provided.

Although the concave portion in the above embodiment shows a pump-in shape, it can be applied to any other shape such as a herringbone shape as shown in FIG. 7 or a tapered land shape as shown in FIG. There is a similar effect.

Although the first and second embodiments show the case of a sintered oil-impregnated bearing, the same effect can be obtained when another porous material is used as the bearing material, such as a porous resin bearing. Needless to say.

[0035]

As is clear from the description of the above embodiment,
According to the first aspect of the present invention, it is possible to provide a bearing that maximizes the pumping action of the porous radial dynamic pressure bearing, has high rotational accuracy, and is excellent in reliability.

According to the second aspect of the present invention, the pumping action of the porous thrust dynamic bearing is maximized.
A bearing with high rotation accuracy and excellent reliability can be provided.

[Brief description of the drawings]

FIG. 1A is a sectional perspective view of a bearing according to a first embodiment of the present invention, and FIG.

FIG. 2 is a diagram showing a bearing lubrication mechanism according to the first embodiment of the present invention.

FIG. 3A is a sectional perspective view of another example of the bearing according to the first embodiment of the present invention. FIG.

FIG. 4A is a sectional perspective view of another example of the bearing according to the first embodiment of the present invention; FIG.

FIG. 5 is a view of a bearing according to Embodiment 2 of the present invention.

FIG. 6 is a diagram showing a bearing lubrication mechanism according to a second embodiment of the present invention.

FIG. 7 is a sectional view of another example of the bearing according to the second embodiment of the present invention.

FIG. 8 is a sectional view of another example of the bearing according to the second embodiment of the present invention.

[Explanation of symbols]

 1, 7 bearing 2, 8 recess 3, 9 negative pressure side inclined surface 4, 10 positive pressure side inclined surface 5 perfect circular sliding part 6 shaft 11 thrust receiving plate

Claims (2)

[Claims] 1. A bearing body formed of a porous body,
In a porous bearing having an inner diameter portion that slides with a shaft, the bearing inner peripheral portion has a concave portion for generating dynamic pressure,
A dynamic pressure radial porous bearing, wherein the shape of the negative pressure side inclined surface of the concave portion is formed in a zigzag shape so as to be longer than the length of the line of the positive pressure side inclined surface of the concave portion. 2. A porous bearing which receives a thrust load at an end surface of a substantially cylindrical body formed of a porous body, wherein the end surface of the bearing has a concave portion for generating a dynamic pressure, and a concave portion of the concave portion on a negative pressure side of the concave portion. By forming the shape in a zigzag shape,
A hydrodynamic thrust porous bearing, wherein the length of the positive pressure inclined surface of the concave portion is longer than the length of the line.