JP2004125070A - Bearing device, and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To maintain favorable bearing characteristics for a long period by simple and low-cost constitution. <P>SOLUTION: For copper-based metal to compose a bearing member 3 comprising a sintered body, phosphor bronze with added quantity of phosphor set in a range of 0.4 wt%-2.0 wt% is used. For solid lubricant to a bearing surface of the bearing member 3, fluorine resin impregnated in the sintered body is used. By baking the sintered body in a high phosphor content state with larger added quantity of phosphor than usual (0.1-0.3 wt%, approx.), abrasion resistance and corrosion resistance can be improved. Fluorine resin is filled in sufficient quantity in pores that are relatively large formed in the sintered body. A layer of the solid lubricant can be favorably formed in sufficient quantity on the bearing surface of the bearing member. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a bearing device in which a solid lubricant is used for a bearing member made of a copper-based metal sintered body that supports a shaft member so as to be relatively rotatable, and a method of manufacturing the same.
[0002]
[Prior art]
DESCRIPTION OF RELATED ART Conventionally, the bearing apparatus which employ | adopted the bearing member which consists of a sintered body of a metal powder is widely known. For example, in the case of an air dynamic pressure bearing device using the dynamic pressure of air, in order to obtain good dynamic pressure while improving wear resistance, the bearing surface of a bearing member formed from a sintered body of metal powder is used. , A solid lubricant composed of molybdenum disulfide, graphite, BN, or the like is formed in a layer by an electrodeposition method or the like. According to the bearing device having such a configuration, it is possible to reduce wear of the bearing surface particularly when starting and stopping rotation by a simple and low-cost configuration.
[0003]
[Problems to be solved by the invention]
However, a bearing device using a solid lubricant for a bearing member made of a sintered body as described above still has the following problems.
In other words, the transfer of the shaft member to the bearing member is likely to occur, and seizure and galling occur between the bearing member and the shaft member. In some cases, for example, the frictional resistance between the bearing member and the shaft member increases. Further, when a copper-based metal is used for the sintered body, rust easily occurs and the corrosion resistance may be poor.
[0004]
In the case of a hydrodynamic bearing device, so-called crushing is performed by performing a sizing process on a bearing surface provided on the inner peripheral side of the sintered body. Cannot be completely eliminated, the dynamic pressure of the lubricating fluid escapes there, and the dynamic pressure may not be efficiently obtained.
[0005]
Therefore, an object of the present invention is to provide a bearing device and a method for manufacturing the same, which are capable of maintaining good bearing characteristics such as wear resistance over a long period of time with a simple and inexpensive configuration.
[0006]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, in the bearing device according to claim 1 of the present invention, as a copper-based metal constituting the sintered body of the bearing member, the amount of phosphorus added is 0.4% by weight to 2.0% by weight. Is used, and a fluorocarbon resin impregnated in the sintered body is used as a solid lubricant.
According to the bearing device according to claim 1 having such a configuration, the sintered body is fired in a high phosphorus content state in which the amount of phosphorus added is more than usual (about 0.1 to 0.3% by weight). Because of this, the bonding force between the powders increases, and good toughness is imparted as a bearing member to improve wear resistance and corrosion resistance.At the same time, the sintered body is formed by liquid phase sintering by melting phosphorus. Relatively large pores (porous) are formed, and the large pores (porous) are filled with a sufficient amount of fluororesin. As a result, a layer of a good solid lubricant composed of a sufficient amount is formed on the bearing surface of the bearing member, transfer between the bearing member and the shaft member is greatly reduced, and better wear resistance is obtained. In the case of a hydrodynamic bearing device, a good dynamic pressure can be obtained, and the corrosion resistance of the fluorine resin can be obtained well.
[0007]
Further, in the bearing device according to claim 2 of the present invention, the receiving member according to claim 1 is formed of a sintered body fired at a temperature in a range of 640 ° C to 750 ° C.
According to the bearing device of claim 2 having such a configuration, since the phosphorus is fired at a temperature at which the phosphorus is melted to be in a liquid state, the above-described operation can be reliably obtained.
[0008]
Further, in the bearing device according to claim 3 of the present invention, the fluororesin impregnated in the sintered body of the bearing member in claim 1 is formed by impregnating the resin after the firing step of the sintered body.
According to the bearing device according to the third aspect having such a configuration, the fluorine resin is surely filled to the deep layer into the pores (porous) of the sintered body without being damaged by the high temperature during firing. It has become.
[0009]
Further, in the method for manufacturing a bearing device according to claim 4 of the present invention, the amount of phosphorus added as a copper-based metal constituting the sintered body of the bearing member is set within a range of 0.4% by weight to 2.0% by weight. Using the set phosphor bronze, the phosphor bronze powder is fired to form a sintered body of the bearing member, and thereafter, a solid lubricant made of a fluororesin is applied to the sintered body of the bearing member. A bearing member is formed by impregnating a resin and curing the resin-impregnated fluororesin.
According to the method of manufacturing a bearing device according to claim 4 having such a configuration, the sintered body is fired in a high phosphorus-containing state in which the amount of phosphorus added is more than usual (about 0.1 to 0.3% by weight). Is performed, the bonding force between the powders is increased and good toughness is imparted as a bearing member to improve wear resistance and corrosion resistance, and sintering is performed by liquid phase sintering due to melting of phosphorus. Relatively large pores (porous) are formed in the body, and the large pores (porous) are filled with a sufficient amount of fluororesin. As a result, a sufficient amount of a good solid lubricant layer is formed on the bearing surface of the bearing member, and a better wear resistance is obtained. In the case of a hydrodynamic bearing device, a good dynamic pressure is obtained. You can get it.
[0010]
Further, in the method of manufacturing a bearing device according to claim 5 of the present invention, the molding density of the phosphor bronze powder performed before the firing step of the sintered body according to claim 4 is reduced to 70% to 80% of the true density. Is set to
According to the method of manufacturing a bearing device according to claim 5 having such a configuration, a sufficient amount of fluororesin is secured on the bearing surface while imparting sufficient rigidity to the sintered body. .
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Prior to that, an example of the structure of a polygon mirror driving motor in an optical deflection device to which the present invention is applied will be described.
[0012]
As shown in FIG. 1, a substantially hollow cylindrical bearing holder 2 is attached to a substantially central portion of a motor board 1 which also serves as a printed board so as to stand substantially vertically. A bearing sleeve 3 as a dynamic pressure bearing member using air dynamic pressure is joined to the inner peripheral wall surface side of the bearing holder 2 by press fitting or shrink fitting. The bearing sleeve 3 is made of a sintered body using copper-based metal powder, and its detailed structure will be described later. A rotating shaft 4 made of a hollow cylindrical stainless steel material constituting a rotor portion is rotatably inserted into a central hole formed through the bearing sleeve 3.
[0013]
A dynamic pressure surface formed on the inner peripheral wall portion of the bearing sleeve 3 is disposed so as to face a dynamic pressure surface formed on the outer peripheral wall surface of the rotary shaft 4 via a minute gap in a radial direction. A radial dynamic pressure bearing portion RB is formed in the minute gap. That is, in the radial dynamic pressure bearing portion RB, the dynamic pressure surface on the bearing sleeve 3 side and the dynamic pressure surface on the rotary shaft 4 side are circumferentially opposed to each other with a small gap of several μm therebetween. Air as a lubricating fluid is interposed in the bearing space.
[0014]
A radial dynamic pressure generating means is provided on at least one of the two dynamic pressure surfaces of the bearing sleeve 3 and the rotary shaft 4. At this time, the radial dynamic pressure is generated by, for example, as shown in FIG. 2, a curved tapered dynamic pressure surface 3a extending in a substantially arcuate shape in the circumferential direction, and a concave sectional shape extending in the axial direction. The grooves 3b are alternately formed along the circumferential direction, and grooves for radial dynamic pressure generation are formed in an annular shape so as to be arranged in a ring shape. The established ones are adopted. At the time of rotation, the air (air) as a lubricating fluid is pressurized by the pumping action of the radial dynamic pressure generating means to generate a dynamic pressure, and the dynamic pressure of the air (air) as the lubricating fluid causes the above-described rotation. A rotor case 7 to be described later, together with the shaft 4, is configured to be axially supported in a non-contact state in the radial direction with respect to the bearing sleeve 3.
[0015]
On the other hand, an annular stator core 5 made of a laminated body of electromagnetic steel sheets is formed on the outer peripheral wall surface of the bearing holder 2 at a position where the bearing holder 2 protrudes upward from the motor substrate 1 in the drawing. The plurality of salient pole portions which are fitted in the axial direction with respect to the mounting surface and which are provided so as to project radially outward from the center side of the stator core 5 toward the radially outward side. Each of the windings 6 is wound.
[0016]
Further, a center boss portion 7a of a rotor case 7 made of an aluminum alloy is press-fitted or pressed into the rotating shaft 4 at an output portion where the rotating shaft 4 projects upward from the bearing sleeve 3 in the drawing. It is fixed through a shrink fitting process such as shrink fitting. Further, a rotor case main body 7b formed in a substantially dish shape is integrally connected to a lower end portion of the center boss 7a in the drawing so as to protrude radially outward. A ring-shaped rotor magnet 8 is annularly mounted on an inner peripheral wall surface of a flange-shaped standing wall provided on an outer peripheral portion of the rotor case main body 7b. The inner peripheral wall surface of the rotor magnet 8 is disposed so as to closely face the outer end surface of each salient pole portion of the stator core 5 in the radial direction.
[0017]
On the other hand, a deflecting polygon mirror 11 for deflecting and scanning optical information is axially inserted into the outer peripheral side wall surface of the center boss 7a of the rotor case 7 described above. The deflecting polygon mirror 11 is pressed in the axial direction by a substantially disk-shaped pressing member 12 attached to the outer peripheral side of the center boss 7a of the rotor case 7, and the pressing member 12 and the rotor case It is fixed so as to be sandwiched in the axial direction with the main body 7b.
[0018]
Further, a sealing cap member (thrust rotating portion) 4a made of a synthetic resin material is fitted into an opening provided on the lower end side of the rotating shaft 4 in the drawing so as to close the opening. Have been. The illustrated lower end surface of the sealing cap member 4a is formed so as to form a circular flat surface.
[0019]
On the other hand, a thrust receiving holder 13 is screwed so as to close the opening at the lower end side in the figure of the bearing holder 2 described above, and a substantially hemispherical surface shape is formed on the upper end part of the thrust receiving holder 13 in the drawing. A thrust plate (thrust bearing member) 14 made of a stainless (SUS) material and projecting upward in the drawing is screwed. The top portion of the substantially hemispherical surface formed on the upper end surface of the thrust plate 14 in the figure is formed on the flat surface on the lower end side of the sealing cap member 4a formed of the above-mentioned flat disk-shaped synthetic resin material. The contact forms a pivot-shaped thrust bearing portion SB.
[0020]
The sealing cap member (thrust rotating portion) 4a on the rotating shaft 4 side and the thrust plate (thrust bearing member) 14 on the stator member side, which constitute the pivot bearing-shaped thrust bearing portion SB, are formed by these two members. The contact portions are formed of members having different surface hardnesses, and a thrust plate (thrust bearing member) 14 having a high surface hardness is formed so as to have a protruding surface that protrudes in the axial direction. In addition, since the sealing cap member (thrust rotating portion) 4a having a low hardness surface hardness is formed to have a flat surface, a thrust plate (thrust bearing member) having a protruding projecting surface is formed. 14) The abrasion of No. 14 is satisfactorily reduced, the occurrence of adhesion phenomenon and seizure are prevented, the durability is improved, and the generation of abrasion powder is suppressed to improve the cleanliness. It has become the jar.
[0021]
On the other hand, the sintered body of the bearing sleeve 3 as the above-described bearing member is formed by molding a phosphor bronze powder of various copper-based metals into an appropriate shape, and then firing it to form the bearing member. However, in the present embodiment, the molding density at the time of shape molding is set to 70% to 80% of the true density in a state without pores, and the addition amount of phosphorus in phosphor bronze is set to 0.4% by weight to 2.0%. It is set within the range of weight%.
[0022]
More specifically, the raw material powder of copper tin and copper phosphorus constituting the phosphor bronze is blended so as to be 10% by weight of tin and 0.4% by weight to 2.0% by weight of phosphorus, and then mixed. It is carried out. The amount of phosphorus added at this time affects the wear resistance and galling resistance. In an air dynamic pressure bearing device that does not have lubricating oil and metal contact is likely to occur, phosphorus is added to the wear resistance and galling resistance. The larger the amount, the better, but too much phosphorus will increase the shrinkage due to sintering. Further, fine powder of ceramics can be added to the phosphor bronze at this time as a sintering matrix. For example, wear resistance and galling resistance can be improved by adding 2 to 3% by weight of SiC having a particle diameter of several microns.
[0023]
The firing temperature at the time of firing the phosphor bronze powder mixed to have such a high phosphorus content is set in the range of 640 ° C. to 750 ° C. so that only phosphorus can be melted. For example, the firing step is performed in an atmosphere of ammonia decomposition gas. The firing temperature corresponds to the phosphorus content. When the phosphorus content is 0.4% by weight, the firing temperature is 750 ° C., and when the phosphorus content is 2.0% by weight, the firing temperature is 640 ° C.
[0024]
Next, the sintered body of the bearing sleeve 3 obtained by such a firing step is impregnated with a solid lubricant made of a fluororesin such as PTFE. In the resin impregnation at that time, first, impregnation in a vacuum state is performed, and then impregnation in a pressurized state is performed. The fluororesin in which the sintered body of the bearing sleeve 3 has been impregnated with the resin by such a resin impregnation step is cured with a resin to improve the adhesion.
[0025]
In this case, the fluororesin may be mixed with a resin material having good slidability, such as polyamide and polyacetal. In this case, the cost of the resin material can be reduced, and the fluidity of the resin is increased, so that the surface roughness in the bearing surface is improved and the frictional resistance is reduced.
[0026]
Further, a sizing process using a mold is performed on the inner peripheral surface corresponding to the bearing surface of the obtained bearing sleeve 3 material to form the above-described dynamic pressure generating means and the like. obtain. The amount of the fluororesin on the bearing surface of the bearing sleeve 3 after the sizing step is important for the reliability of the bearing surface. In the present embodiment, the area ratio to the total bearing area is about 40%, and at least 20% or more. Have secured. The amount of the fluororesin on the bearing surface is directly related to the molding density at the time of the above-mentioned shape molding, in addition to the crushing allowance in the above-mentioned sizing step, and as in the present embodiment, the molding density is the true density. By setting the amount to 70% to 80%, the amount of the fluororesin can be secured to about 30% to 40% of the total bearing area.
[0027]
The corrosion resistance of the bearing sleeve 3 can be further improved by impregnating the entire bearing sleeve 3 formed by the final sizing step described above with rust preventive oil or the like.
[0028]
As described above, in the present embodiment, since the sintered body of the bearing sleeve 3 is fired in a high phosphorus content state in which the added amount of phosphorus is larger than usual (about 0.1 to 0.3% by weight), As a result, the bearing sleeve 3 is provided with good toughness due to an increase in the bonding force between the bodies, thereby improving wear resistance and corrosion resistance and forming relatively large pores (porous) in the sintered body. In other words, the large pores (porous) are filled with a sufficient amount of fluororesin. As a result, a sufficient amount of a good solid lubricant layer is formed on the bearing surface of the bearing sleeve 3, so that better wear resistance is obtained and escape of air (air), which is a dynamic pressure fluid, is achieved. It is prevented so that a good dynamic pressure can be obtained.
[0029]
Further, in the present embodiment, the firing temperature of the sintered body of the bearing sleeve 3 described above is set to a temperature in the range of 640 ° C. to 750 ° C., and the firing is performed at a temperature at which phosphorus melts and becomes a liquid phase. Therefore, the above-described operation can be surely obtained. At this time, if the firing temperature is too low, the strength is reduced, and the pores (porous) are also reduced, so that the resin impregnation cannot be performed well.
[0030]
Furthermore, since the fluororesin impregnated in the sintered body in this embodiment is impregnated after the firing step of the sintered body, the fluororesin is not damaged by the high temperature during firing, and the pores of the sintered body are not damaged. (Porous) is surely filled to a deep layer.
[0031]
Furthermore, in the present embodiment, since the molding density at the time of molding the phosphor bronze powder performed before the sintering step of the sintered body is set to 70% to 80% of the true density, it is sufficient for the sintered body. A sufficient amount of fluororesin is secured while providing rigidity.
[0032]
As described above, the invention made by the inventor has been specifically described based on the embodiment. However, the present invention is not limited to the above embodiment, and various modifications can be made without departing from the gist of the invention. Needless to say.
[0033]
For example, in the above-described embodiment, the present invention is applied to a polygon mirror driving motor having an air dynamic pressure bearing device, but is similarly applied to an oil dynamic pressure bearing device other than the air dynamic pressure bearing device. can do. In this case, the bearing member is impregnated with oil, but since the fluororesin is contained in a large amount as a solid lubricant, metal contact at the time of oil film rupture or the like is favorably avoided.
[0034]
Further, the present invention can be similarly applied to a motor that does not use a hydrodynamic bearing device such as a metal bearing device, or a motor that rotationally drives a variety of rotating bodies.
[0035]
【The invention's effect】
As described above, in the bearing device according to claim 1 of the present invention and the method for manufacturing the bearing device according to claim 4, the addition amount of phosphorus is set to 0 as a copper-based metal constituting a bearing member made of a sintered body. Phosphor bronze set in the range of 0.4% to 2.0% by weight is used, and a fluororesin impregnated in the sintered body is used as a solid lubricant for the bearing member made of the sintered body. By sintering the sintered body with a higher phosphorus content than usual, the wear resistance and corrosion resistance are improved, and a sufficient amount of fluororesin is filled in the relatively large pores (porous) formed in the sintered body. Only, and a sufficient amount of solid lubricant layer is formed on the bearing surface of the bearing member. And fluorine Since the corrosion resistance fat is obtained, can be maintained for a long time good bearing characteristics, it is possible to improve the reliability of the bearing device.
[0036]
The bearing device according to claim 2 of the present invention fires the sintered body according to claim 1 at a temperature in the range of 640 ° C. to 750 ° C., so that the sintered body is fired at a temperature at which phosphorus melts and becomes a liquid phase. Because of this, the above-described effects can be reliably obtained.
[0037]
The bearing device according to claim 3 of the present invention is characterized in that the fluororesin impregnated in the sintered body according to claim 1 is impregnated after firing the sintered body, so that the pores (porous) of the sintered body are impregnated with the fluororesin. Is soaked and filled to a deep layer, so that the above-mentioned effects can be obtained reliably.
[0038]
Further, in the method of manufacturing a bearing device according to claim 5 of the present invention, the molding density of the phosphor bronze powder performed before the sintering step of the sintered body according to claim 4 is 70% to 80% of the true density. % Is set so that a sufficient amount of fluororesin is secured on the bearing surface while imparting sufficient rigidity to the sintered body, so that the above-described effects can be reliably obtained.
[Brief description of the drawings]
FIG. 1 is an explanatory longitudinal sectional view showing the entire structure of a polygon mirror driving motor of an optical deflector to which the present invention is applied.
FIG. 2 is an enlarged partial plan view showing an example of a bearing member used in the polygon mirror driving motor shown in FIG. 1;
[Explanation of symbols]
3 Bearing sleeve (dynamic pressure bearing member)
4 Rotary shaft 5 Stator core 7 Rotor case 8 Rotor magnet RB Radial dynamic pressure bearing SB Thrust bearing

Claims (5)

A shaft member, and a bearing member made of a sintered body of a copper-based metal that supports the shaft member so as to be relatively rotatable, and is solid with respect to the bearing surface of the bearing member facing the bearing surface of the shaft member. In bearing devices using lubricants,
As a copper-based metal constituting the sintered body of the bearing member, phosphor bronze in which the amount of phosphorus added is set in a range of 0.4% by weight to 2.0% by weight is used,
A bearing device, wherein a fluorine resin impregnated with resin in the sintered body is used as the solid lubricant. The bearing device according to claim 1, wherein the bearing member is formed of a sintered body fired at a temperature in a range of 640C to 750C. 2. The bearing device according to claim 1, wherein the fluororesin impregnated in the sintered body of the bearing member is resin-impregnated after a firing step of the sintered body. 3. In a method of manufacturing a bearing device, a bearing member that supports a shaft member so as to be relatively rotatable is formed from a sintered body of a copper-based metal, and a solid lubricant is provided on a bearing surface of the bearing member.
As the copper-based metal constituting the sintered body of the bearing member, phosphor bronze in which the amount of phosphorus added is set in a range of 0.4% by weight to 2.0% by weight is used.
Sintering the phosphor bronze powder to form a sintered body of the bearing member,
Thereafter, the sintered body of the bearing member is impregnated with a solid lubricant made of a fluororesin,
A method for manufacturing a bearing device, characterized in that a bearing member is formed by hardening the resin impregnated fluororesin. 5. The method for manufacturing a bearing device according to claim 4, wherein the molding density of the phosphor bronze powder performed before the firing step of the sintered body is set to 70% to 80% of the true density. .

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