METHOD OF MOLDING DOUBLE-LAYER SLIDING BEARING
A method of molding a double-layer sliding bearing made of a sintered double-layer green compact comprises an inner layer and an outer layer. A circular bearing surface is formed on either an inner periphery of the inner layer or an outer periphery of the outer layer, wherein either the inner layer or the outer layer with the bearing surface is defined as a first layer that has a thinner wall thickness and a higher forming density than the other layer without the bearing surface defined as a second layer. The invention provides molding processes for the reinforced and perforated first layer and also for the double-layer green compact to combine a prepared first layer with a compressed powder forming the second layer.
This application is divisional application of U.S. patent application Ser. No. 15/611,664, filed on Jun. 1, 2017
FIELD OF THE INVENTIONThe invention relates to sliding bearing molding techniques, particularly to a double-layer sliding bearing made of a sintered double-layer green compact having notable radial differences in forming density and porosity for improving performance under severe operating conditions.
BACKGROUND OF THE INVENTIONVarious types of sliding bearings possessing self-lubricating feature have been developed; one of the important types being those made from a uniform porous structure via compacted and sintered metals formed by a technique known as powder metallurgy. In such sliding bearings to achieve a high porosity cannot balance a high density need for overall structural robustness and wear resistance of a bearing surface which is referred to a sliding surface for bearing relative rotation. In contrast, to achieve the high density cannot balance the high porosity need for sufficient lubricating media content. Hence to apply those to severe operating conditions, such as shaft rotating at high speed, heavy load and strong vibration, especially when contact pressure and velocity (PV) limit larger than 500 MPa·m/min will be subject to stern challenges. The lubricating media means lubricating oil and lubricant having a higher viscosity than the lubricating oil.
SUMMARY OF THE INVENTIONThe method of molding the double-layer sliding bearing made of a sintered double-layer green compact comprises an inner layer and an outer layer wherein either the inner layer or the outer layer with a bearing surface is defined as a first layer that has a thinner wall thickness and a higher forming density than the other layer without the bearing surface defined as a second layer. The invention provides a molding process for the green compact to combine a prepared first layer with a compressed powder forming the second layer.
The invention of the method of molding the double-layer sliding bearing can notably provide many advantages, such as:
The invention provides the second layer with high porosity to impregnate sufficient lubricating media and prolong the service life.
The invention provides the first layer with high density to enhance wear resistance and anti-fatigue friction of the bearing surface.
The invention provides at least one groove axially indented on the bearing surface of the inner layer to accommodate debris or oxides.
The invention provides a molding process for a reinforced first layer to optimize density uniformity and enhance structural strength.
The invention provides a molding process for a reinforced and perforated first layer to smooth transmission of the lubricating media.
The invention provides a molding process for the green compact to combine a prepared first layer with a compressed powder forming the second layer.
The invention provides a novel sliding bearing with good lubricity, robustness and anti-abrasion to apply to the severe operating conditions.
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The inner layer 10 and the outer layer 20 of the double-layer green compact 1, 1a can be made respectively by a blending powder 22 from a commonly used base element such as at least one of Fe powder, Cu powder and C powder 22 and the anti-abrasion element such as at least one of Ni powder, Cr powder, Mo powder and Mn powder 22.
In fact, by combining the two embodiments mentioned above, the double-layer green compact 1 or 1a can be simplified to comprise a prepared first layer and a second layer wherein either the inner layer 10 or the outer layer 20 with the bearing surface 10A or 20A is defined as the prepared first layer that has a thinner wall thickness and a higher forming density than the second layer without the bearing surface. As such, the prepared first layer may have a considerable degree of structural strength and abrasion resistance, and the second layer may have a higher porosity for containing sufficient lubricating medium and shock-absorbing capability.
Further, the inner layer 10 and the outer layer 20 can also be made from the base element only. The Fe powder 22 includes at least one of pure Fe powder 22 and Cu coated Fe powder 22. The Cu in the Cu powder 22 and Cu coated Fe powder 22 includes at least one of copper, brass and bronze.
The invention can be widely applied to different devices; the position and form for the installation of the double-layer sliding bearing are not limited to the drawings shown in the mounting surface 20B, 10B; and also, the first layer and the second layer need not be limited to the same length. To meet such application requirements, a similar modeling process for the double-layer sliding bearing can be realized by modifications or adjustments of the embodiments of the invention via the disclosed technical means and features, such as dimensions of the relevant mould components, configuration of the cavity 31, number and length of the dummy part 38 (if necessary), filling position of the powder 22, compressing length and position of the upper punch 34 and the lower punch 36, which do not depart from the spirit and scope of the invention.
While the preferred embodiments of the invention have been set forth for the purpose of disclosure, they are not the limitations of the invention, modifications of the disclosed embodiments of the invention as well as other embodiments thereof may occur to those skilled in the art. Accordingly, the appended claims are intended to cover all embodiments which do not depart from the spirit and scope of the invention.
Claims
1. A method of molding a double-layer sliding bearing made of a sintered double-layer green compact, comprising:
- an inner layer and an outer layer, a circular bearing surface being formed on either an inner periphery of the inner layer or an outer periphery of the outer layer;
- wherein either the inner layer or the outer layer with the bearing surface is defined as a first layer that has a thinner wall thickness and a higher forming density than the other layer without the bearing surface defined as a second layer;
- wherein the double-layer green compact is formed by molding the first layer in advance and loading the first layer in a cavity of a mould before filling a powder forming the second layer therein;
- wherein a predetermined axial length of a filled powder of the second layer is longer than a length of the first layer, and compressing only on the filled powder to a length equal to the length of the first layer.
2. The method of molding the double-layer sliding bearing of claim 1, wherein said molding the first layer comprises the steps of:
- filling a powder forming the first layer into a cavity of a mould with an axial length of a filled powder longer than the length of the first layer;
- compressing the filled powder to a length equal to the length of the first layer.
3. The method of molding the double-layer sliding bearing of claim 1, wherein the first layer includes at least two units, in which two adjacent end faces between each pair of two adjacent units of the at least two units are in contact with each other;
- wherein molding each of the at least two units comprises the steps of:
- filling a powder forming the first layer into a cavity of a mould with an axial length of a filled powder of the first layer longer than a length of each of the at least two units;
- compressing the filled powder to a length equal to the length of each of the at least two units with a same diameter of the bearing surface and a same wall thickness as the first layer;
- wherein said molding the first layer comprises the steps of:
- loading the at least two units arranged in an axially butted manner into the cavity with a total length of the at least two units longer than the length of the first layer;
- compressing the at least two units to a length equal to the length of the first layer.
4. The method of molding the double-layer sliding bearing of claim 3, wherein said loading the at least two units arranged in an axially butted manner into the cavity with a total length of the at least two units longer than the length of the first layer further includes at least one penetrating notch, which is radially indented on at least one of two adjacent end faces between at least one pair of two adjacent units of the at least two units, and compressing the at least two units to a length equal to the length of the first layer.
5. The method of molding the double-layer sliding bearing of claim 1, wherein molding the double-layer green compact comprises the steps of:
- preparing a dummy part with a same diameter of the bearing surface and a same wall thickness as the first layer;
- loading the first layer and the dummy part into the cavity axially and making the bearing surface against a wall of the cavity;
- filling the powder forming the second layer into a remaining space of the cavity to a length equal to the predetermined axial length which is equal to a total length of the first layer and the dummy part;
- compressing the filled powder to a length equal to the length of the first layer.
6. The method of molding the double-layer sliding bearing of claim 1, wherein molding the double-layer green compact comprises the steps of:
- preparing an annular groove with an axial depression formed on the mould to fit just right for accommodating the first layer therein;
- loading the first layer in the annular groove;
- filling the powder forming the second layer into a remaining space of the cavity to a length equal to the predetermined axial length;
- compressing the filled powder to a length equal to the length of the first layer.
Type: Application
Filed: Aug 1, 2019
Publication Date: Nov 21, 2019
Inventor: WEN-CHEN LAI (Hsinchu City)
Application Number: 16/528,983