US 3171189 A
Description (OCR text may contain errors)
United States Patent 3,171,189 METHOD OF MAKING CYLINDRICAL BEARING SURFACES Stanley Hedgecock, deceased, late of Wolverhampton,
England, by Vivien Janet Hedgecocir and John Hedgecock, executors, both of Wolverhampton, England, assignors to Laystall Engineering Company Limited, London, England, a company of the United Kingdom of Great Britain and Northern Ireland No Drawing. Filed Oct. 26, 1962, Ser. No. 233,482 7 Claims. (Cl. 29149.5)
This invention relates to a method of making cylindrical bearing surfaces, primarily to cylinder liners for internal combustion engines, pumps and like machines. It is well known that certain materials have hard wearing properties which make them suitable to provide bearing surfaces, but such materials lack the natural surface porosity necessary to retain lubricant. Thus, premature breakdown and seize-up is likely it hard wearing non-oil retaining surfaces are used.
In the case of cylinder bores, proposals have been made for plating the bearing surface, and in view of the nonoil holding property of the smooth surface, to provide grooves, channels or recesses to break up the surface, whereby lubricating oil is retained. Thus, it has been proposed to cut spiral grooves of opposite hand in the bearing surface by knurling or by means of diamond chips mounted in a tool, or to etch or sand blast the surface thereby to form a great number of small oil retaining channels or pockets. In the case of knurling or cutting, highly skilled work is called for if the grooves are to be cut accurately. Further, there is the possibility of burrs or irregularities being formed at the groove sides, which have to be removed.
With sand blasting or etching, it is difficult to ensure that the recesses or pockets are distributed evenly and of substantially identical size. With stand blasting, for example, the pitting depends on a number of factors such as the force of air blast, angle of attack and size of sand grain, which may vary as the process proceeds. In the case of chemical or electrochemical etching, depth of penetration may vary, owing to differences in the nature of the cylinder surface, some areas being more prone to attack than others. Similarly, with sand blasting the nature of the material may result in unevenness of penetration.
It is known that effective oil retention in a hard bearing surface and long working life thereof, can only be obtained if the oil retaining grooves or pockets are made with accuracy both in regard to spacing and depth. It has been found that if minute grooves of accurate size and spacing are cut, a surface is produced which is extremely hard wearing and also retains lubricant in sufiicient quantity without excess.
It is the main object of this invention, therefore, to provide a process which results in the production of hard, cylindrical bearing surfaces with effective oil retaining properties. More specifically, it is an object of the invention to provide a process for the manufacture of a cylinder liner having a hard bearing surface with effective oil retaining properties. It is a further object of the invention to provide a process for the manufacture of a chromium plated cylinder liner which enables same to be mass-produced by semi-skilled labour, said cylinder liner having adequate oil retaining properties.
Broadly according to the present invention, a cylinder or cylinder liner has its bore machined or ground accurately, and then it is grooved with an abrasive grit powder in a liquid carrier, which powder particles are screened accurately to substantially standard dimensions, said grit or powder medium being poured into the bore whilst a m./ms. depth and Width and spacing are made.
3,171,189 Patented Mar. 2, 1965 ice spring pressed lapping tool or the like traverse the bore repeatedly from top to bottom and on a spiral path, the tool pressing some of the grit on to the surface of the bore, in which it cuts a multiplicity of close-spaced spiral grooves, the tool being moved up and down on its spiral path until the grooves are cut to sufiicient depth.
It is found that the number of times the lap or like tool traverses the bore has no practical effect on the number of grooves cut, this being determined by the particle size. Thus after the first complete traverse, the grooves are started, their spacing being determined by grit size. On subsequent traverses, the grit will naturally tend to enter the started grooves.
It is to be understood that the grooves are of small dimensions. For example, the grit size and spiral path of the tool is such that grooves in the region of 0001-0003 It is possible to form grooves in the bore surface which result in the production of in the region of 50,000-60,000 islands per square inch, each bounded by rough edged grooving or channelling. This grooving or channelling will hold a small but almost exact and evenly spaced quantity of lubricant.
In the preferred case of a chromium plated cylinder liner, the bore is accurately ground prior to plating, taking into account the thickness to be applied which preferably is between 0.0005 and 0.002 inch.
The invention also comprises a method of manufacturing a chromium-plated cylinder liner, which method consists in finishing the bore accurately to desired diameter by machining, honing or like process, and then in forming on the bore a plurality of grooves or channels, utilising an abrasive grit or powder of substantially standard dimension in a liquid medium and pressing same against the bore surface with spring-urged blades, which blades are moved to traverse the cylinder in the bore from top to bottom and on a spiral path and repeatedly until the grooves are cut to required depth, and then chromium plating the liner to bring same to the final bore dimension.
As stated above, the grooves or channels produced are extremely small both as to depth and width and close spaced, the determining factor being the grit size.
According to a further feature, the grooved plated cylinder liner is subjected to a subsequent identical treatment with abrasive grit or powder. This subsequent treatment serves to remove any minute modules or particles of chromium which might be deposited in the bore, particularly in the grooves, and which might have a harmful effect on the operation in the engine.
This subsequent treatment has little or no effect on the bore surface. The hardness of the plating resists any noticeable removal of the chromium.
The invention also comprises a method of manufacturing a cylindrical liner for an engine, the method consisting in deep-drawing the cylinder from a blank, finishing same by grinding, honing or like process to accurate external and internal dimensions and removing the bottom blank and top waste spinning over an end thereof to form an outer-turned flange, and then grooving the bore and plating as set forth above. This enables thin walled liners to be mass produced, which liners can be pressed into engine blocks, the bore of the liners exhibiting extremely hard wearing properties. Liners, for example, with a wall thickness of as little as 1 mm. can be produced.
In producing the grooves, the liners can be set up in a jig, and a lapping tool consisting of a number of blades or slats aranged spaced apart around a circumference and spring pressed outwardly can be used. Such .a tool is caused to enter into a cylinder, the blades or slats running parallel with the axis thereof, the tool being rotated at constant speed and moved repeatedly up and down within the cylinder, each up and down movement being identical. At the same time an abrasive grit slurry such as a silicon carbon powder in a liquid (oil) medium is poured into the cylinder. The blades bear on the bore surface and press some of the grit thereon, resulting in the cutting of a multiplicity of minute grooves or channels.
The grit particles must be of substantially identical dimensions, and it is found that the first traverse of the tool initiates groove cutting, and that on subsequent traverses, the grit particles run in the cuts, so that subsequent traverses do not increase the number of grooves but only their depth, up to the maximum determined by the grit size.
The plating layer follows the contoursof the grooves, and the result is that the bore surface is broken up into a great number (thousands per square inch) of small islands surounded by rough edge grooves.
It will be appreciated that the number of grooves and their width and depth can be varied according to the size of the liner and the use to which it is to be put.
The invention can be applied to cylinders of glass ceramics or hard steel, although obviously the material must be such that the grit will be capable of cutting into its surface.
What is claimed is:
1. A method of forming an oil retaining surface on a bore wall of a cylinder, which method consists in firstly removing metal from said bore wall until said cylinder is of desired internal diameter and has a smooth surface, applying to said bore wall a slurry of an abrasive grit powder of predetermined particulate size, said slurry being pressed into contact with said bore wall by spring-urged blades traversing said cylinder on a helical path, the axis of said helical path coinciding with the axis of said cylinder, to thereby produce, in said bore wall, a multiplicity of closely spaced helical grooves substantially par-' allel to one another, and subsequently traversing the blades in said cylinder with the abrasive particles naturally tending to enter the previously started helical grooves and being free to follow said grooves, whereby substantially no additional grooves are started.
2. The method according to claim 1 wherein said cylinder is formed by a cylinder liner.
3. The method according to claim 2 wherein the said bore wall, after grooving, is chromium plated.
4. The method according to claim 3 wherein, after said chromium plating, said bore wall is again grooved by a slurry of an abrasive grit powder'of predetermined particulate size, said grooving being effected by means of spring-urged blades traversing a helical path coaxial with said cylinder liner.
5. The method according to claim 1 wherein said spring-urged blades are caused accurately to follow said helical path 'until grooves cut thereby are of a desired depth.
6. The method according to claim 5 wherein said particulate size of said abrasive grit powder is chosen to be equal to the desired depth of grooves cut thereby.
7. A method of forming an oil retaining surface on a bore wall of a cylinder liner, said method consisting in deep drawing said cylinder lining from a blank, finishing said cylinder liner to desired internal and external dimensions, removing a bottom blank and top waste, flaring an end of said cylinder liner, applying to said bore wall a slurry of an abrasive grit powder of predetermined particulate size equal to a desired depth of grooving in said bore wall, pressing said slurry into grooving contact with said bore wall by means of spring-urged blades, causing said spring-urged blades repeatedly to traverse a helical path coaxial with said cylinder liner until said desired depth of grooving is achieved, plating said bore wall with a wear resistant metal, and subsequently re-grooving said bore wall with a further slurry of an abrasive grit powder of particulate size equal to the particulate size of said first slurry powder.
References Cited in the file of this patent UNITED STATES PATENTS 325,692 Parker Sept. 8, 1885 1,944,380 Vance Jan. 23, 1934 2,128,614 Kobayshi Aug. 30, 1938 2,445,934 Bodine July 27, 1948 2,468,169 Carlson et al. --Apr. 26, 1949 2,577,818 Shaw Dec. 11, 1951 2,674,782 Surtees Apr. 13, 1954 FOREIGN PATENTS 653,708 Great Britain May 23, 1951 679,496 Great Britain Sept. 17, 1952