GB1578228A

GB1578228A - Cylinders or cylinders liners with plated bores

Info

Publication number: GB1578228A
Application number: GB3162177A
Authority: GB
Original assignee: Laystall Engineering Co Ltd
Current assignee: Laystall Engineering Co Ltd
Priority date: 1977-07-27
Filing date: 1977-07-27
Publication date: 1980-11-05
Also published as: ES472116A1; DE2833204A1; FR2398578B1; FR2398578A1; DE2833204C2; JPS5464214A; JPS6113103B2

Description

(54) IMPROVEMENTS RELATING TO CYLINDERS OR CYLINDER LINERS WITH PLATED BORES (71) We, LAYSTALL ENGINEERING COMPANY LIMITED, a British company of Dixon Street, Wolverhampton WV2 2BU, England, do hereby declare the invention for which we pray that a patent may be granted to us and the method by which it is to be performed to be particularly described in and by the following statement: This invention relates to the manufacture of cylinders or cylinder liners with plated bores.

It is well known that certain materials have hard wedding properties which make them suitable to provide bearing surfaces, but such materials lack the natural surface porosity necessary to retain lubricant. In the case of cylinder bores, it is known to plate the bearing surface, and in view of the non-oil holding property of a smooth plated surface, to provide grooves, channels or recesses to break up the surface, whereby lubricating oil is retained. Broadly, an accurately dimensioned cylinder or cylinder liner is grooved by pouring a slurry of an abrasive powder in a carrier liquid, which particles of powder are screened accurately to predetermined maxiinum size, into the bore whilst urging particles of the powder into engagement with the cylinder wall on a helical path froin one end to the other and' back of the cylinder repetitionally.

It is found that the number of times a lap or like tool, which urges the powder particles against the cylinder wall, traverses the bore has no practical effect on the number of grooves cut thereby, this being determined by the particle size. Thus after the first complete traverse, the grooves are started, their spacing being determined by maximum particle size. On subsequent traverse, the particles tend to enter the started grooves:' The powder particles pre ferably are all of substantially standard size.

When the cylindrical bearing surface is that of a chromium plated cylinder liner, the bore is accurately ground and grooved as above described prior to plating, the bore being ground so as to take into account the thickness of the plating to be applied which is preferably between 0.0005 and 0.002 inches.

A grooved and plated cylinder liner may thereafter be subjected to a subsequent identical treatment with a slurry of an abrasive powder. This subsequent treatment serves to remove any minute nodules or particles of chromium which might be deposited in the bore, particularly in the grooves. Such subsequent treatment has little or no effect on the bore surface. The hardness of the plating resists any noticeable removal of the chromium.

The cylindrical liner for an engine may be manufactured by deep-drawing the cylinder from a steel blank, removing the bottom end and top waste, finishing by grinding, honing or like process to accurate external and internal dimensions, spinning over an end to form an outwardly-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 bores of the liners exhibiting extremely hard wearing properties. Liners, for example, with a wall thickness of as little as 1 mm. can be produced.

For producing the grooves, the liners can be set up in a jig, and a lapping tool consisting of a number of parallel blades or sticks arranged spaced apart around a circumference and spring-pressed outwardly can be used. Such ia tool is 'caused to' enter into a cylinder, the blades or sticks running parallel with the axis thereof, the tool being rotated at constant speed and simultaneously moved repeatedly up and down within the cylinder, each up and down movement being identical. At the same time a slurry of an abrasive powder, such as a silicon carbide powder, in a liquid (oil) is poured into the cylinder. The blades bear on the bore surface and press some of the powder thereon, resulting in the cutting of a multiplicity of minute helical grooves or channels.

The powder particles preferably are of substantially identical dimensions, and it is found that the first traverse of the tool initiates groove cutting, and that on subsequent traverses, the 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 particle size.

The plating layer follows the contours of the grooves, and the result is that the bore surface is broken up into a great number (thousands per square inch) of small islands surrounded by rough edge grooves.

It is an object of the present invention to improve the process as aforesaid in a number of material respects.

In the carrying out of the processes a'bove described it was always thought to be essential to remove from the cylinder liner bore all traces of the silicon carbide or other hard grit or abrasive powder used in the operations, otherwise very rapid wear and deterioration would take place when the liner was put into service in an engine. We have now discovered that, contrary to previous thought, the inclusion of residual grit particles as an impregnation in the chromium plating is, in fact, highly beneficial.

According to the present invention, there is provided a process for making a cylinder or cylinder liner with a plated bore, especially a chromium-plated bore, characterised by a finishing step in which hard 5--10 micron grit particles, especially carbide grit particles. are deposited in the plating to an extent greater than 600 particles per sq. mil. Preferably, the grit particles are deposited to an extent of 600 to 1600 particles per sq. mil.

In one embodiment, the process is characterised by performance of the finishing steps of: a) lapping with 400 mesh grit for substantially one minute; b) polishing with flexible sticks and a lapping medium for substantially 2 minutes. The flexible sticks used for finishing may be rubberhonded or of fibre and extend the full height of the liner. These give a better finish to the surface.

In another embodiment finishing is performed with a slurry of carbide grit which forms a multiplicity of grooves in the chromium-plated surface and also deposits carbide grit therein. Preferably, a twostage finishing operation is performed with 400 mesh carbide grit slurry and 600 mesh carbide grit slurry, respectively. This gives rough and very fine carbide impregnation of the chromium-plated surface which consequently has a considerably longer life.

In a further embodiment, the bore surface is first lapped with 200 mesh grit before plating, plate is deposited to a depth of about 0.001", the plated surface is polished with a carbide grit lapping medium for about 2 minutes, and then a final lapping is performed with flexible sticks and a lapping oil. This produces a surface that is impregnated with carbide grit particles both beneath the chromium plate and in the plate itself.

One method of carrying the invention into effect will now be described by way of example.

In the example described, a chromium plated steel cylinder liner is to be produced for an automobile engine.

An extruded cylindrical steel workpiece is used rather than ordinary tubular stock.

The first operation is centreless grinding of the external diameter which takes about 4 minutes. Then, on a capstan lathe the workpiece is parted off to length, and the end flange is rolled and turned; this takes about another 4 minutes. The workpiece is next bored internally, in an operation occupying about 21 minutes, after which the bore is power honed to size on a vertical 4 spindle machine, which takes about t minute.

The bore of the workpiece is next chromium plated, and finally the workpiece is lapped internally for 2 minutes, with a 400 mesh silicon carbide lapping medium to perform the impregnation characteristic of the invention. Finally, the workpiece is polished externally for 1 minute.

WHAT WE CLAIM IS: 1. A process for making a cylinder or cylinder liner with a plated bore, especially a chromium-plated bore, characterised by a finishing step in which hard 5-10 micron grit particles, especially carbide grit particles, are deposited in the plating to an extent greater than 600 particles per sq.

mil.

2. A process according to claim 1, wherein the grit particles are deposited to an extent of 600 to 1600 particles per sq. mil.

3. A process according to claim 1 or claim 2, characterized by performance of the finishing steps of: a) lapping with 400 mesh grit for substantially one minute; b) polishing with flexible sticks and a lapping medium for substantially 2 minutes.

4. A process according to claim 3, wherein the flexible sticks used for finish polish

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. down movement being identical. At the same time a slurry of an abrasive powder, such as a silicon carbide powder, in a liquid (oil) is poured into the cylinder. The blades bear on the bore surface and press some of the powder thereon, resulting in the cutting of a multiplicity of minute helical grooves or channels. The powder particles preferably are of substantially identical dimensions, and it is found that the first traverse of the tool initiates groove cutting, and that on subsequent traverses, the 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 particle size. The plating layer follows the contours of the grooves, and the result is that the bore surface is broken up into a great number (thousands per square inch) of small islands surrounded by rough edge grooves. It is an object of the present invention to improve the process as aforesaid in a number of material respects. In the carrying out of the processes a'bove described it was always thought to be essential to remove from the cylinder liner bore all traces of the silicon carbide or other hard grit or abrasive powder used in the operations, otherwise very rapid wear and deterioration would take place when the liner was put into service in an engine. We have now discovered that, contrary to previous thought, the inclusion of residual grit particles as an impregnation in the chromium plating is, in fact, highly beneficial. According to the present invention, there is provided a process for making a cylinder or cylinder liner with a plated bore, especially a chromium-plated bore, characterised by a finishing step in which hard 5--10 micron grit particles, especially carbide grit particles. are deposited in the plating to an extent greater than 600 particles per sq. mil. Preferably, the grit particles are deposited to an extent of 600 to 1600 particles per sq. mil. In one embodiment, the process is characterised by performance of the finishing steps of: a) lapping with 400 mesh grit for substantially one minute; b) polishing with flexible sticks and a lapping medium for substantially 2 minutes. The flexible sticks used for finishing may be rubberhonded or of fibre and extend the full height of the liner. These give a better finish to the surface. In another embodiment finishing is performed with a slurry of carbide grit which forms a multiplicity of grooves in the chromium-plated surface and also deposits carbide grit therein. Preferably, a twostage finishing operation is performed with 400 mesh carbide grit slurry and 600 mesh carbide grit slurry, respectively. This gives rough and very fine carbide impregnation of the chromium-plated surface which consequently has a considerably longer life. In a further embodiment, the bore surface is first lapped with 200 mesh grit before plating, plate is deposited to a depth of about 0.001", the plated surface is polished with a carbide grit lapping medium for about 2 minutes, and then a final lapping is performed with flexible sticks and a lapping oil. This produces a surface that is impregnated with carbide grit particles both beneath the chromium plate and in the plate itself. One method of carrying the invention into effect will now be described by way of example. In the example described, a chromium plated steel cylinder liner is to be produced for an automobile engine. An extruded cylindrical steel workpiece is used rather than ordinary tubular stock. The first operation is centreless grinding of the external diameter which takes about 4 minutes. Then, on a capstan lathe the workpiece is parted off to length, and the end flange is rolled and turned; this takes about another 4 minutes. The workpiece is next bored internally, in an operation occupying about 21 minutes, after which the bore is power honed to size on a vertical 4 spindle machine, which takes about t minute. The bore of the workpiece is next chromium plated, and finally the workpiece is lapped internally for 2 minutes, with a 400 mesh silicon carbide lapping medium to perform the impregnation characteristic of the invention. Finally, the workpiece is polished externally for 1 minute. WHAT WE CLAIM IS:

1. A process for making a cylinder or cylinder liner with a plated bore, especially a chromium-plated bore, characterised by a finishing step in which hard 5-10 micron grit particles, especially carbide grit particles, are deposited in the plating to an extent greater than 600 particles per sq.

mil.

ing are rubber-bonded or of fibre and extend the full height of the bore.

5. A process according to claim 1 or claim 2, wherein the finishing is performed with a slurry of carbide grit which forms a multiplicity of grooves in the chromium-plated surface and also deposits carbide grit therein.

6. A process according to claim 5, wherein a two-stage finishing operation is performed with 400 mesh carbide grit slurry and 600 mesh carbide grit slurry, respectively.

7. A process according to claim 1 or claim 2, wherein the surface is first lapped with 20G mesh grit before plating, plate is deposited to a depth of about 0.001", the plated surface is polished with a carbide grit lapping medium for about 2 minutes, and then a final lapping iis performed with flexible sticks and a lapping oil.

8. A process according to claim 1 or claim 2. for manufacturing a chromium plated cylinder liner, wherein the starting workpiece material is extruded stock and the following operations are carried out: 1) Centreless grinding of the outside diameter of the workpiece.

2) Parting off the workpiece to length.

3) Rolling an end flange on the work piece.

4) Turning the outside diameter of the end flange.

5) Finishing the workpiece bore.

6) Power honing of the workpiece bore.

7) Chromium plating the workpiece bore.

8) Lapping the workpiece bore with silicon carbide grit to impregnate the plating.

9. A process of manufacturing a chromium plated steel cylinder liner for an automobile engine, substantially as described herein.

9) Polishing the exterior of the work piece.