Patent Application
20140325840
The present disclosure relates to a method of manufacturing a cylinder liner for an engine.
Conventional methods of manufacturing cast or extruded cylinder liners used in internal combustion engines involves a complex series of cylinder bore finishing steps that together provide a surface hardness and textures critical to the engine lubrication, wear and ultimately the performance and life of the liner. Standard processing will typically sequence through a rough turning operation, an induction harden and temper step followed typically by a multiple stage honing process depending on surface finish requirements. The term honing can include: standard honing, plateau honing, brush honing, fluid jet honing, laser honing, spiral slide honing, or smooth slide honing. Regardless of the method by which honing is accomplished, each step represents additional handling and processing time.
Honing operations require investment and maintenance of expensive high grade abrasive tooling and equipment along with a higher level of skilled manual labour or automation that can result in high liner manufacturing cost structures. Reducing the number of processing steps and processing time creates the opportunity for significantly reduced processing times and cost for competitive advantage.
For reference, U.S. Pat. No. 5,916,390 relates to a blank that can be formed by cold extrusion to create a shape approximating the cylinder lining. After pre-machining, the surface is fine machined, honed in at least one stage and then hard particles lying at the surface are mechanically exposed to form plateau areas of hard particles which project above the remaining surface of the base microstructure of the alloy. The mechanical exposure of the primary crystals or particles is carried out by a honing process using felt strips which are cylindrically shaped on the outside of a slurry of SiC particles in honing oil.
In one aspect of the present disclosure, a method of manufacturing a cylinder liner for an engine includes forming a semi-finished cylinder liner having an inner surface and an outer surface; rough machining the inner surface and the outer surface of the semi-finished cylinder liner; precision machining the inner surface and outer surface of the rough machined cylinder liner; and machining the inner surface of the precision machined cylinder liner by a roll skiving operation and a roll burnishing operation.
Other features and aspects of this disclosure will be apparent from the following description and the accompanying drawings.
Reference will now be made in detail to specific embodiments or features, examples of which are illustrated in the accompanying drawings. Wherever possible, corresponding or similar reference numbers will be used throughout the drawings to refer to the same or corresponding parts.
As shown, the engine 100 includes an engine block 102 and a cylinder head 104. The engine block 102 includes a plurality of cylinder bores 106. Each of the cylinder bores 106 includes a piston 108 and a cylinder liner 110 disposed within the cylinder bore 106. Although six cylinders are positioned in an inline configuration in the illustrated embodiment of
As illustrated in
In an embodiment as shown in
For manufacturing the cylinder liners 110, a casting operation may be used. Optionally, the cylinder liners 110 may also be manufactured using cold extrusion, or powder metallurgy. Typically, the cylinder liners 110 are manufactured from iron (Fe) or steel. However, other suitable metals or alloys may also be used to manufacture the cylinder liners 110.
Referring to
The cylinder liner 120 may include a rough inner diameter D1 and a final outer diameter d2, where rough inner diameter D1 is less than the inner diameter d1 of the finished cylinder liner 110 (See
The cylinder liner 120 is machined to achieve finished inner and outer surfaces 112, 114 that are of predetermined inner and outer diameters d1, d2. In addition, other operations may be performed on the cylinder liner 120 to improve the hardness, toughness and surface finish and form the cylinder liner 120 as will be explained hereinafter.
A series of surface finishing operations may be performed on the cylinder liner 120. An abrasive machining operation as part of the finish machine operations, for example, honing may be performed on the cast cylinder liner to form the cylinder liner 120. Typically, a first honing operation may be performed on the cast cylinder liner. Through the first honing operation, the surface finish of an external surface and an internal surface of the cylinder liner may be improved. Accordingly, the cylinder liner 120 disclosed herein and illustrated in
At step 304, the method further includes rough machining the inner surface and the outer surface of the semi-finished cylinder liner. In an exemplary embodiment, the inner surface of the semi-finished cylinder liner may be rough machined by performing a first honing operation of the semi-finished cylinder liner, such as, for example, an abrasive machining process. The rough machining of the cylinder liner may also result in the formation of the cylindrical grooves 118.
At step 306, the method 300 includes performing a precision machining operation on the outer surface of a rough machined cylinder liner. The precision machining of the outer surface 114 may be performed by executing a precision cutting process on the rough machined cylinder liner.
The method may include roll burnishing at least a portion of the outer surface 114 of the precision machined cylinder liner 120 (See
At step 310, the method further includes roll skiving the inner surface 112 of the precision machined cylinder liner 120. Explanation pertaining to the roll burnishing and roll skiving operation of the precision machined cylinder liner 120 will be made in conjunction with
As shown in
The wear pads 132 are configured to maintain an alignment of the skiving head 124 within the precision machined cylinder liner 120 during the roll skiving operation. Also, the wear pads 132 may be provided to beneficially absorb vibrations during rotation of the skiving head 124 within the cylinder liner 120.
In an embodiment, the shaft 126 may be hollow and define a primary coolant channel (not shown) therein. The skiving head 124 may further include one or more secondary coolant channels (not shown) in fluid communication with the primary coolant channel of the hollow shaft 126. A plurality of openings may be disposed near the pair of skiving knives 130 to allow the coolant to exit therefrom. However, in other embodiments, it may be optionally contemplated to supply the coolant externally during the roll skiving operation.
Each of the skiving knives 130 defines a cutting edge 134 that extends away from the rotational axis A-A′. Further, the skiving knives 130 may be adjustably mounted on the skiving head 124 such that a radial distance of the cutting edge 134 from the rotational axis A-A′ may be adjusted. Accordingly, suitable mechanisms for adjusting the skiving knives 130, such as a screw mechanism, a chuck mechanism and the like, may be provided on the skiving head 124.
The cutting edges 134 are configured to perform the machining operation on the inner surface 112 of the cylinder liner 120. Moreover, the coolant provided through the primary and secondary coolant channels may perform plurality of functions during the roll skiving operation. For example, the coolant may provide lubrication to the roll skiving head 124 when the roll skiving head 124 rotates against the inner surface 112. Further, the coolant may cool the skiving knives 130 and the machined areas of the inner surface 112. Moreover, the coolant may flush debris 136 accumulated due to the machining operation performed by the skiving knives 130.
In an embodiment, the roll skiving and/or burnishing operation may be performed by clamping the cylinder liner 120 and rotating the roll skiving and/or burnishing tool 138 within the cylinder liner 120. The skiving knives 130 may be adjusted such that the cutting edge 134 may machine the rough inner diameter D1 to the specified or predetermined inner diameter smaller than d1 to allow for material deformation by the roll burnishing tool to form the desired inner diameter d1. When the cylinder liner 120 is clamped, the roll skiving and/or burnishing tool 124 may be inserted from one end 140 of the cylinder liner 120. The roll skiving and/or burnishing tool 124 rotates within the cylinder liner 120 such that the cutting edge 134 of the skiving knives 130 contacts the inner surface 112 and machines the inner surface 112 of the cylinder liner 120.
At this point, the coolant supply may be switched on to provide lubrication to the roll skiving and/or burnishing tool 124, cooling to the skiving knives 130, burnishing rollers 137 and the inner surface 112, and flushing off the machined metal debris 136 from other end 142 of the cylinder liner 122. When the roll skiving and/or burnishing tool 124 exits from the other end 142 of the cylinder liner, the rough inner diameter D1 of the cylinder liner 120 is machined to the predetermined inner diameter d1.
Hereafter, the cylinder liner 120 may now be referred to as “the cylinder liner 110” barring a washing step mentioned below. As such, the step of washing is an optional step for purposes of the present disclosure as it may be carried out to flush out any metal debris or surface contaminants. Hence, after the roll skiving and/or burnishing operation, the inner and the outer surface 112, 114 of the cylinder liner 110 may be optionally washed using a suitable chemical solution to flush out any metal debris or surface contaminants. Further, the cylinder liner 110 may then be inspected for any surface deformities with the use of methods such as, but not limited to, eddy current inspection or other methods commonly known to one skilled in the art.
The cylinder liner 110 may now be considered ready for fitment onto a cylinder of the engine 100.
With use of the method 300 disclosed herein, numerous steps previously required to be performed on cylinder liners, for e.g., a work hardening process is now achieved by way of the roll burnishing process. When the roll burnishing tool 124 deforms the inner surface 112 of the cylinder liner 120, the inner surface 112 undergoes localized hardening due to a cold working of the material forming the cylinder liner 120. This material deformation improves the surface finish of the cylinder liner 120. Further, the roll skiving and/or burnishing process as disclosed herein eliminates the use of successive and/or repeated honing and machining operations that were typically performed on inner surfaces of cylinder liners. Thus, with implementation of the method 300 disclosed herein, specific tooling, machinery and/or labour previously required for accomplishing honing and other surface finishing operations are now mitigated. Moreover, with use of the method 300 disclosed herein, costs associated with manufacturing of cylinder liners may be reduced. Further, as the method 300 described herein involves less steps and processes, costs and cycle times associated with the manufacture of cylinder liners is reduced.
While aspects of the present disclosure have been particularly shown and described with reference to the embodiments above, it will be understood by those skilled in the art that various additional embodiments may be contemplated by the modification of the disclosed machines, systems and methods without departing from the spirit and scope of what is disclosed. Such embodiments should be understood to fall within the scope of the present disclosure as determined based upon the claims and any equivalents thereof.
