High-effect surface cladding manufacturing method of motion pairs system

Description

BACKGROUND OF THE INVENTION

(1) Field of the Invention

This invention relates to a high-effect surface cladding manufacturing method of motion pairs system, in particular, a method that enables submicron and nano-based tetrafluoroethylene macromolecule particles to be well mixed in Ni—P-based composite electrolyte, thereby making those particles to be evenly cladded on the surface of sintered parts, based on diverse proportions of nano particles and/or micron-sized particles.

(2) Description of the Prior Art

Generally, the motion pairs system that is applied in the industry is able to be divided into contact type and non-contact type, wherein the non-contact system is based on the design of magnetic suspension or air-pressure suspension. However, excepting those devices with high precision and high value characteristics, ordinary motion pairs components are mainly based on the designs of rolling or sliding contact type motion pairs, taking the factors of manufacturing cost, system control and the complexity of high-priced device maintenance into consideration.

The sliding motion pairs design mostly applies lubricating oil, self-lubricating oil sleeve or flexible transition material to each two sliders, the lubricating oil adding is a more economical way among those method. Nevertheless, such a lubricating oil adding method is not able to be applied to closed mechanisms and those mechanisms that have to avoid being polluted from oil stains. Said soft transition material possesses the easy abrasion and replacement characteristics to reduce the attrition of a product, nonetheless, the abrasion of such a transition material enables variation in size precision; in addition, such a transition material generates fine particles to bring serious pollution into a product system, owing to considerable abrasion thereon. Moreover, seeing that those self-lubricating oil-impregnated sleeves or bearings possess the function of automatically lubricating straight-line motion and orbiting motion components, those sleeves or bearings have lower prices on average and are considerably applied in the industry. Furthermore, owing to suitable common difference design of the size in the combination of revolving spindles and bearings, the components generate lower noise during revolving, so as to be widely applied to small cooling fan products. However, the lubricating oil consumption and the oil-immersion rate are influenced by workplace temperature, the density of material and higher friction factor value on the surface of material, said bearings have shorter/poor life-spans to the motion pairs with higher motion speeds required; for example, an average life span of a self-lubricating bearing is about 20,000 hours, far less than 50,000 hours of a roller bearing, so as to impose restrictions on the application fields.

The rolling motion pairs design mostly applies to conventional roller bearings, which have longer life-spans for use and enable slight deviation of inclination angles and acceptance of heavier radial load upon the assembly of those bearings, therefore, the rolling bearings have been applied to rolling products as radial and part of axial supporting parts thereof. The straight-line motion pairs design applies a plurality of roller bearings to be installed on fixed straight sideways for straight-line motions, however, the problems of noise resulting from the contact between a roller and the track, having much more higher average bearing price than the self-lubricating oil bearing and being restricted within the adjustment technique of the linear assembly of a plurality of rollers are subject to be solved.

The commonly used products of DU un-oil bearings are developed by GLACIER METAL CO., LTD. and have been patented in the UK, Japan, USA, Canada, France, Italy, Germany, Switzerland, etc., (Japan Patent No. 223605 and No. 438282). DU un-oil bearings apply the technology of sintering bronze powder to produce sintered porous bronze parts on alloy steel and Teflon Lead mixture is filled on the surface thereof to form Teflon Lead thin film. Seeing that the surface of a bearing has low friction because of Teflon Lead, lubricating oil is not applied thereto; Teflon Lead enables a sintered bronze layer to be immersed in a thickness of 0.3 mm, so that the bearing abrasion at the initial stage is about 0.01 mm, in addition, alloy steel is applied to ensure the necessary strength of immobility, size precision, stability and proper torque in tightening of a bearing. The products apply the manufacturing technology include ordinary sleeves, thrust ball bearings, flange sleeves, sliding plates, etc. With reference to the cross-sectional structural drawing of a product from the manufacturing technology in FIG. 1, the technology allows the surface of alloy steel to be covered with a layer of copper base (bronze) powder in advance for sintering, thereby enabling the surface of alloy steel to form a porous layer, and then, Teflon Lead mixture is filled over the surface of alloy steel forming Teflon Lead thin film, so that the copper base (bronze) powder and particles become the Teflon Lead filling. The manufacturing technology is used for porous surface sintering taking the bonding of material and copper base (bronze) powder in high temperature into consideration, or the problems of layer segregation is easily generated, in addition, the temperature of copper base (bronze) powder sintering is around 760° C., easily enables a thermal deformation on the alloy steel material. After Teflon Lead mixture is filled over the porous surface of alloy steel, the temperature above 360° C. is required to make the filling of Teflon Lead and copper base (bronze) bonded, however, Teflon easily releases pernicious gases under high temperature manufacturing operation. Moreover, it is not a practicable way to enable micron-based motion pairs to have a 0.3 mm of sintering thickness and a 0.01 mm thickness of abrasion; in addition, it violates the regulation of having lead contained in raw materials for manufacturing information products in view of environment protection (by June 2006, nearly all products manufactured by VIA will be RoHS compliant in the EU countries).

SUMMARY OF THE INVENTION

In view of the forgoing, the objective of the invention is to provide a method of producing self-lubricating oil-bearing parts that possesses the characteristics of having a life-span similar to a roller bearing, low friction factor thereon (the friction factor of a commonly applied sleeve ranges from 0.15 to 0.30), wear-resisting, low noise, reducing the pollution resulting from lubricating grease and the manufacturing cost of a roller bearing, heightening the manufacturing technology of an un-oil bearing. Therefore, the invention enables the motion pairs to possess the characteristics of low friction factor, wear-resisting, high hardness, accuracy in size, lower manufacturing cost and higher system capacity efficiency.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional structural drawing showing a conventional DU un-oil bearing of a prior art;

FIG. 2 is a manufacturing flowchart of the invention;

FIG. 3 is an enlarged perspective view showing powder sintering on the surface of a sintered workpiece according to the invention;

FIG. 4 is a perspective view showing the surface cladding of the invention after the adherence treatment;

FIG. 5 is a perspective view showing revolving motion pairs according to the invention; and

FIG. 6 is a perspective view showing the assembly of experimental fan revolving portion according to the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Further aspects, objects, and desirable features of the invention will be better understood from the detailed description and drawings that follow in which various embodiments of the disclosed invention are illustrated by way of examples.

With reference to FIG. 2, the invention directly applies copper base (bronze) alloy powder and particles that are produced by spray, those powder particles with different diameters (0.5˜30 μm) are mixed with a plurality of micro-metallic alloy in certain proportions after a preliminary screening, and then a lubricator (e.g. graphite, stearic acid, etc.) is added in accordance with the manufacturing process requirement for sufficiently carrying out the mixed powder operation.

The mixed powder operation is carried out for the purpose of increasing the chemical and physical properties of evenly mixing raw materials; therefore, the theory of movement of particles enables a variety of granulations with different diameters to be well mixed. Consequently, the factors of mixture speed and mixture mechanism have the influence on the degree of the mixed powder operation. Therefore, the mixed powder operation must be carried out according to the powder properties, such as the particle sizes, the spread diversity and specific gravity diversity, etc., so that the problem of layer segregation is able to be avoided. In view of the aforegoing characteristics, the invention applies a upright spiral type mixer with proper rotational speed (60˜120 rpm) to enable the powder and particles to be evenly mixed.

The powder an particles that have been fully mixed during the mixed powder operation are filled inside a hollow mode of a press machine, subsequently, upper and botton punches and a middle mole are pressurized and extruded to enable the powder and particles to be formed, there is a relation between the pressure for shaping, the punch area and expected green density and the values are generated based on the analysis result concluded by the invention green test, so that the optimal green density should ultimately be above 7.9˜8.0 g/cm3. If the green density value is lower than said standard, the follow-up manufacturing process and the stability of quality are impacted, even though the finished goods satisfies the original design requirement. Therefore, it is imperative to request the optimal forming density, in order to stabilize the product quality during the mass production and reduce the manufacturing cost.

The objective of using a lubricator during the shaping process is to facilitate the green mold release and reduce the pressure on mold release. Generally, the lubrication method is divided into the following two ways. One is to enable a dry lubricator and metallic powder to be fully mixed together and directly filled in a mold for being pressurized and shaped therein; the other is to apply lubrication to a mold surface, prior to the filling of metallic powder in the mold, by spreading or spraying a liquid lubricator that is easily dissolved in a volatile organic solvent on said mold surface and the surface of said punches. After said organic solvent is vaporized, a lubrication layer is formed on the surface of the mold and particles. According to the experimental result of the invention, if electrolytic coppers alloy powder or powder with appropriate sizes are applied under appropriate shaping pressure, the density of shaping the green without any lubricator added in advance is able to be higher than 7.97 g/cm3, so as to meet the optimal density requirement of forming a green during the manufacturing process.

The formed green is sent to a sintering furnace for carrying out sintering in reduction atmosphere. Sintering is the extension of thermodynamics and the theory of diffusion for facilitating effective powder and particles controlling in the furnace atmosphere following the increase in temperature. Consequently, the diffusion phenomenon of generating part of solid or liquid state enables the powder and particles to be bonded together. In general, the significant variables in the sintering process comprise time, temperature curve, the selection of furnace atmosphere, the gas flow rate, the time in high temperature and the furnace structure design, etc. To sum up, the foregoing factors are prerequisite, in order to ensure a successful sintering.

The three steps of carrying out sintering process are as follows in sequence:

• 1—preheat zone: for achieving the dewaxing and degreasing effects via thermal energy, at the same time, controlling particles not be deformed during dewaxing.
• 2—sintering zone: for facilitating the green densification after the dewaxing treatment in said preheat zone via higher temperature.
• 3—cooling zone: for controlling the cooling rate of sintered workpiece that is formed via the thermal treatment in high temperature in said sintering zone, so as to determine the metallic form and the property of a finished goods.

The dewaxing and degreasing processes should be carried out prior to any sintering, i.e., a proper preheat degreasing is the prerequisite for achieving a better sintering result. The setting of the preheat zone temperature is determined according to the lubricator type. For example, the frequently used Zinc Stearate is able to melt at the temperature degree of 130° C., vaporize at 260° C. and completely remove at 427° C. The temperature in the preheat zone of the invention is set at 450° C., considering different lubricator characteristics, if the heating speed is too fast or the temperature is too high during the whole sintering process, part of the lubricator in the preheat zone is decomposed, owing to the chemical compound composition, so as to generate the carbon deposition the surface of a workpiece, in addition, easily enable the workpiece to be deformed or cracked. Therefore, it is vital to control the sintering speed. The experimental results of the invention show that a better sintered workpiece is able to be obtained by controlling the sintering speed at 45˜55 mm/min.

The sintering zone design is established based on the material properties, namely, different materials have to be sintered under different temperature, sintering atmosphere and air flow. During the sintering process, the invention has obtained the results from repeated experiments in continuous belt furnace that the optimal transition temperature in the preheat zone is set at 710° C.˜730° C., the optimal sintering zone temperature in the sintering zone is set at 800±5° C. and the optimal time in sintering is controlled for 25˜35 min. As to the control of the sintering furnace atmosphere, the invention applies cracked ammonia gas to obtain the furnace gas by heating and decomposing ammonia, so that the sintering zone is suitable for meeting the requirement of sintering copper-based parts for its strong reduction without carburization.

The cooling zone design generally comprises a slow cooling part and a rapid cooling part. Said slow cooling part is to avoid the furnace from being deformed owing to a rapid temperature change in moving the mold from the sintering zone to said rapid cooling part. The rapid cooling design is to reduce the temperature of a sintered workpiece during a specific period of time, so that the workpiece is able to be properly moved or processed. According to the experiment results of the invention, a sintered workpiece is able to be placed in the cooling zone for 30 minutes under said sintering speed.

Generally, a finished parts after being formed by sintering is slightly deformed, therefore, if the requirement of a workpiece precision is not high, said sintered workpiece is able to be under subsequent surface modifications and cladding treatment, on the other hand, if the size precision of a workpiece is required to be higher, a size precision adjustment process is then required to be carried out, prior to a subsequent cladding treatment.

Said sintered workpiece after the completion of the size precision adjustment process has the surface thereof carried out the thermal degreasing treatment and the invention carries out a prior cleaning or supersonic/ultrasonic degreasing treatment by selecting a proper lyophilic or acidity dissolving agent (solvent), based on different grease types, in order to degrease the surface of the workpiece, or the quality of the cladding surface thereof will be affected. FIG. 3 shows the surface of a sintered workpiece according to the invention.

A product is treated under the surface cladding treatment after the completion of prior sintering and size precision processes by using the density of the surface of the powder and particles as the filling body in the subsequent processes.

Generally, adding a plurality of slurry that is made by micro and nano-based particles based on polytetrafluoroethylene into a normal electroless nickel plating, those particles are able to be evenly spreaded in composite electrolyte with an average diameters range from 90 to 500 nm and 3%˜10% of the total quantity of composite electrolyte. After being evenly mixed by a power mixer, all particles in composite electrolyte are able to be evenly suspended based on the mixing speed, so as to obtain composite electrolyte composed by metallic nickel ions and nano particles.

Without continued applied voltage, metal ions that is coexisted in composite electrolyte with a reducing agent is reduced to metal in solid state on the surface of the solid body via a chemical reaction of auto-catalysis, in addition, mixed up with 15%˜30% of polytetrafluoroethylene superfine particles, thereby the solid metal is gradually accumulated on the surface of a solid body. Said reaction is a response that the electron communication is not from an external conducting wire, but directly from a substance in electrolyte at the same time while it is reacted on said solid surface. Therefore, the temperature at 90° C. during the manufacturing process is required.

The manufacturing technology of the invention enables to obtain a complex cladding material combining the characteristics of hardness, wear-resisting and low friction factor in integral, the average friction factor of the complex cladding material is ½ of Ni—P plating surface. Prior to the cladding treatment, all cleaning processes on the surface of the materials comprise surface activation treatments, surface modifications and respective water cleaning and activation processes must be truly completed, or the cladding quality will be seriously affected.

The composite electrolyte comprises:

• 1—metal ions: the source of metal cladding material.
• 2—reducing agent: for turning metal ions to metal.
• 3—catalyst: for catalyzing the material surface.
• 4—complexing agent: for avoiding hydroxide from precipitating, adjusting precipitating rate, avoiding the plating bath from dissolution and stabilizing plating bath.
• 5—stabilizer: for absorbing particle impurities, avoiding plating bath from natural dissolution, in order to prolong the life-span of plating bath.
• 6—buffer: for controlling the pH value within a specific operation area.
• 6—buffer: for controlling the pH value within a specific operation area.
• 7—wetting agent: for influencing the surface of material.
• 8—Dispersion: enabling superfine wear-resisting material to be evenly covered.

A reducing agent is usually Sodium Hypophosphite, PH value is to control the P quantity contained in cladding material. Generally, the PH value is higher with less P quantity contained, so that the cladding property is changed; a cladding layer with lower P quantity contained has poor corrosion-resisting ability than that with higher P quantity contained. If the P quantity contained is higher than 8%, the cladding is a non-magnetical layer. If the surface cladding material of the invention has a 6% of the P quantity contained and the volume of polytetrafluoroethylene riches 30%, the color of surface cladding is close to black; if the surface cladding material of the invention has a 9% of the P quantity contained and the volume of polytetrafluoroethylene riches 20%, the surface of cladding colored bright grey; nevertheless, the overall efficacy of cladding show similar results from different experiments. The cladding hardness value of surface cladding that is colored close to black without being proceeded by thermal treatment is able to reach 280˜380 VHN, subsequently, the cladding layer of a workpiece is placed under 15 min., the surface of cladding is treated under the densification process, after that, the post-baking process has an obvious influence on the cladding structure.

The component after being treated by the process of densification is under ultrasonic cleaning for about 2˜5 min., depending on the precision levels required, in order to remove the particles that is unable to be cladded on the surface of the material during the post stage of the electrochemistry reaction. Therefore, the particles that are not stabilized attached on the surface at the initial stage peel off, the change in size and the cladding thickness are controlled within the range of 6˜12 μm. Consequently, the invention has considerably high control in size precision of manufactured products. FIG. 4 shows the status of the product surface after being treated via surface cladding densification.

[Experimental Results]

Consequently, the experimental results of the high-effect surface cladding manufacturing method of motion pairs system of the invention achieves the characteristics of low friction factor, wear-resisting, high hardness, precision in size, lower manufacturing cost and higher system capacity efficiency, at the same time, the abrasion of surface cladding at the initial stage is about 0.1˜0.2 μm.

The basic physical and chemical properties of said product of the invention are as follows:

• 1—The temperature ranges from −30° C. to 200° C.
• 2—Protected by the inertia layer for resisting general chemical and oxidization and corrosion functions.
• 3—lower friction factor; the abrasion after an experiment on cooling fan test for operating 30 days is almost not occurred; the abrasion after continuous operating for 250 days is <1 μm under a small amount of lubricating oil.
• 4—tensile strength on the surface of a machine reaches 200 Kgf/cm2.
• 5—The value of thermal conductivity coefficient is around 0.5, the thermal expansion coefficient is at 5˜10/° C. via controlling the composition of the material.
• 6—Even thickness is generated without peeling off after surface modifications, so that the product precision under long term operation is able to be maintained.
• 7—densification resulting in non-porous surface.

Meanwhile, the invention applies the technology to revolving bearings

Meanwhile, the invention applies the technology to revolving bearings of a DC fan as shown in FIGS. 5 and 6. According to actual on-line test results, it is found that the MTBF value exceeds 50,000 hours and the test report is attached as shown in Appendix I for reference. The life-span of the invention is similar to that of a widely applied roller bearing on the market, in addition, if the invention applies to straight-line motion pairs the same effects will be generated.

CONCLUSION AND DISCUSSION

A product that is made by the technology of the invention is able to directly use those powder and particles on the surface of copper-tin base parts to be the tetrafluoroethylene macromolecule fillings, so that the invention possesses the characteristics of wear-resisting and high hardness, low friction factor, precision in size, lower manufacturing cost and higher system capacity efficiency, so that the invention is able to be efficiently applied to a sliding pairs system for straight-line motion and revolving motion, moreover, the invention provides a better technology than a prior art on the precision of the manufacturing process.

Simultaneously, if the metal is treated by metallic cutting under pre-powder metallurgy, as long as the invention is able to properly control the roughness value (Ra value around 0.6˜0.8) on the surface of materials, the cross-sectional side and the change in roughness on the surface of the materials as appropriate are able to be used as the filling under the post-manufacturing processes and the materials still possess the physical and chemical properties resulting from the manufacturing process, nevertheless, the manufacturing cost is higher than said powder metallurgy process. Consequently, to pursue high quality of products with lower manufacturing cost, the manufacturing technology of the invention is one method that is able to meet the requirement in the industrial sector.

New characteristics and advantages of the invention covered by this document have been set forth in the foregoing description. It is to be expressly understood, however, that the drawings are for the purpose of illustration only and are not intended as a definition of the limits of the invention. Changes in methods, shapes, structures or devices may be made in details without exceeding the scope of the invention by those who are skilled in the art. The scope of the invention is, of course, defined in the language in which the appended claims are expressed.