JPH0545380B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to metal surface finishing, and more particularly to an improved machine for fine finishing metal surfaces using an abrasive-coated tape.

Many types of mechanical components must maintain a highly accurate surface finish in order to perform their functions satisfactorily. Maintaining the accuracy of the surface finish or precision finishing, for example, the crankshaft, camshaft of an internal combustion engine, etc.
This is especially important when manufacturing the journal bearing surfaces, cam surfaces, and other finished surfaces of power transmission shafts. For journal type bearings, a very precisely manufactured cylindrical surface is essential in order to obtain the required bearing effect when lubricating oil is pumped between the journal and the corresponding bearing. be. Improper finishing of these bearing surfaces can lead to premature bearing failure and reduce the bearing's load carrying capacity.

Currently, in the production of internal combustion engines, greater durability is required to make the product more reliable.
The higher operating speeds required of modern engines (particularly for automobiles) and the increased bearing loads associated with improvements in the efficiency of engine structures require even higher finishing accuracy on journal surfaces. .

In addition to the bearing surfaces, the engine cylinder walls must also maintain a high precision finish to provide the necessary oil and gas seals with the piston rings. Many other mechanical components also require precise surface finishes, particularly in areas where sliding contact between parts is made.

B. Prior Art and its Problems Precision finishing in the prior art is primarily accomplished by two different types of machining techniques. One is precision honing, in which a stationary honing stone is pressed against the desired surface. When precision finishing a cylindrical journal bearing surface, the workpiece is rotated relative to the honing stone while the honing stone is laterally driven back and forth from one edge of the journal to the other. This method has some significant drawbacks. The honing wheel must have the required material cutting performance for the part to be finished, but must also be soft enough to allow self-refinishing. Therefore, the whetstone begins to take on the shape of the part as it is used. This method therefore does not correct deviations in the shape of the finished part, but actually creates such deviations. In addition, since the honing stone is easily broken, it must be replaced and refurbished frequently. Additionally, it is very difficult to obtain honing wheels of consistent quality, resulting in significant differences between parts finished with different wheels.

Another major disadvantage of precision finishing of journal bearings using honing wheels is that the journals typically have outwardly projecting rounded edges, making it difficult to drive the wheel laterally beyond the surface area to be machined. This results in uneven wear of the grindstone. Such uneven wear changes the profile shape of the honing wheel, and this shape is then transferred to the workpiece. Additionally, honing wheels typically have sharp corner edges and cannot be used for precision finishing near rounded edges of bearing surfaces.

Another precision finishing method is conventional abrasive coated tape precision finishing in which the surface to be finished is turned and the abrasive coated tape is pressed into contact with the surface. As the part rotates, the abrasive removes the roughness of its surface. In this conventional method, typically urethane
The tape is brought into contact with the rotating surface by pressure created by a compressible elastomeric insert made of a plastic compound. This conventional abrasive coated tape precision finishing method overcomes some of the drawbacks associated with abrasive precision finishing. Because the tape is relatively flexible, this method allows precision finishing of the fillet radius area of the journal. Also, new abrasive tape used in this method can be purchased in a uniform quality. However, this method does not solve another drawback of precision grinding. Chief among these drawbacks is the fact that the inserts that back the abrasive-coated tapes are of flexible material and therefore do not correct geometric deviations of the part as the tape conforms to the profile of the part surface to be finished. be.

C. Means for Solving the Problems In order to eliminate the above-mentioned drawbacks of the precision finishing devices and methods of the prior art, the present invention has as its first object a precision finishing device capable of correcting the imperfect shape of a finished surface. I will provide a. Another object of the invention is to eliminate the need for rework or replacement of main cutting tools in precision finishing. Yet another objective is to ensure the production of surfaces with greater smoothness and shape accuracy than is obtainable with the prior art.

a relatively incompressible abrasive-coated tape made from a polymeric plastic, having a device for retaining the tape and contacting the tape to urge the tape into contact with the workpiece surface; By a precision finishing machine having a shoe assembly having a rigid surface, the rigid surface having a hardness exceeding a value of 90 durometer A, and a device for effecting relative rotation between the workpiece and the shoe assembly. , achieved.

The abrasive-coated tape is made of a relatively incompressible polymer plastic, has a predetermined shape relative to the desired workpiece surface shape, and is in contact with the tape to force the tape against the workpiece surface. The surface to be contacted is a highly rigid surface with a hardness of 90 durometer or more, so the shape of the surface affects the workpiece surface through the tape,
When precision finishing the surface of a workpiece, the high rigidity of the surface and the incompressibility of the tape allow the surface shape to be accurately transferred to the workpiece surface, achieving a smooth surface roughness and achieving the desired shape accuracy ( Specifically, it becomes possible to achieve particularly high roundness. A rigid surface with a hardness of 90 durometer or more is compared to a surface with a hardness of less than 90 durometer.
It can be proven through experiments that a special effect is achieved in improving the shape accuracy (specifically, in particular, roundness) of the surface of the workpiece.

D. Embodiments Other advantages of the invention will become apparent from the embodiments of the invention, which will now be described in conjunction with the accompanying drawings.

In FIG. 1, a polishing shoe assembly, designated generally by the reference numeral 10, is shown. The polishing shoe assembly 10 is shown with an attached support mechanism shown schematically and positioned for precision polishing the bearing surface of a crankshaft of an internal combustion engine. As shown in the figure, both ends of the crankshaft 12 are connected to the headstock 14.
and a tailstock 16, and are rotated about the longitudinal central axis by these. crankshaft 12
The engine has a plurality of cylindrical bearing surfaces that must be ground, including a pin bearing 18 that is connected to the piston connecting rod in use, and a main bearing 20 for rotationally supporting the crankshaft within the engine block. The polishing shoe assembly 10 is reciprocated laterally along the surface to be machined by reciprocating it or by reciprocating the workpiece relative to the shoe assembly. Since the bearing journal of the pin bearing 18 is eccentric with respect to the center of rotation of the main bearing 20, the arm 22 causes the polishing shoe assembly 10 to orbit in a manner that follows the pin bearing 18.

FIG. 2 shows a prior art abrasive shoe assembly.
The polishing shoe assembly 10 includes two halves, an upper shoe 32 and a lower shoe 34 (shown in phantom). These shoe halves each have a hydraulic or pneumatic biasing cylinder for use therewith, or are connected to a support structure supported by scissor-type linkages. Polishing shoe assembly 10 includes a semicircular surface 24 having a plurality of spaced apart dovetail grooves 26 therein. A complementary urethane insert 28 is mounted in the dovetail groove 26.
These inserts 28 are relatively flexible and compressible, with a durometer of 90 or less due to the material they are made of. Each shoe section includes means for engaging an abrasive-coated tape 30, where the abrasive tape 30 is forced into contact with the surface of the pin bearing 18. Once the precision finishing of one pin bearing 18 is completed, the upper shoe 3
2 and lower shoe 34 are separated and then returned to their original positions with another pin bearing 18 or main bearing 20 in between. Or again, 1
A plurality of polishing shoe assemblies are provided to polish the entire workpiece in one polishing operation. During shoe separation and reengagement, the tape 30 is indexed to provide a predetermined length of tape 30 of fresh abrasive material to the shoe assembly 10. By this index feeding, the polishing surface of the tape 30 is constantly updated.

FIG. 3 is a cross-sectional view of FIG. 2 showing the contact between insert 28 and pin bearing 18. The insert 28 has a pin as shown by arrow A.
It is moved laterally relative to the plane of the bearing 18.
Because the insert 28 is made of a flexible material, it conforms to the existing surface profile of the pin bearing 18. Therefore, if there are imperfections in the surface of the bearing, such as undulations, tapers, convex curvatures, or concave curvatures, the abrasive-coated tape will conform to the imperfect shapes. As a result, the precision finishing methods of the prior art described above cannot correct shape deviations of parts to be precision finished.

FIG. 4 shows a polishing shoe assembly 60 according to a first embodiment of the present invention. The polishing shoe assembly 60 includes an upper shoe 62 and a lower shoe 64. The basic differences of the polishing shoe assembly 60 of the present invention from the polishing shoe assembly 10 of FIGS. 2 and 3 are as follows.
The difference is that a stone insert 36 is used instead of a urethane insert 28. This insert 36
is preferably made of honing stone material. The stone insert 36 is relatively non-deformable, with a durometer hardness of 90 or higher, yet is easily machined and coated with abrasive tape 38.
It is characterized by being able to frictionally engage with.
Each stone insert 36 is attached to a holder 38. The stone insert 36 and holder 38 are preferably "floating" mounted for a small amount of rotation relative to the upper and lower shoes, as indicated by arrow B in FIG. This relative rotation is
In the illustrated embodiment, holder 38 is attached to mounting pin 40.
This is possible by mounting the As with the shoe assembly 10, the abrasive coated tape 30 is supported by the shoes 62 and 64, and when these shoes are engaged against the surface of the pin bearing 18, the tape 30 is exposed to its precision finish. It is brought into contact with the bearing surface 18.

The basic advantages of the construction of polishing shoe assembly 60 are best illustrated in FIG. stone insert 36
has a rigid, curved surface that applies a compressive load that forces the abrasive tape 30 against the pin bearing 18. The stone insert 36 is rigid and relatively non-compliant so that the pin bearing 18
Corrugations, tapers, convex curvatures, and concave curvatures of the surface are corrected. This is because the non-compliant parts of the surface of the pin bearing 18 are then pressed with a greater contact pressure against the abrasive-coated tape 30 and are therefore forced into contact with each other until the pin bearing 18 has the required surface profile. This is because more material is removed from the part. Abrasive coated tape 30 is preferably made of a variety of polymers that are themselves relatively incompressible.
Made of plastic film. Abrasive coated paper products are generally not suitable for use in the present invention because they are highly compressible compared to polymer plastic tape materials. Additionally, the particle size of abrasive coated papers is generally not as uniform as the particle size of abrasive coated polymer plastic tape materials. As in the prior art, as pin bearing 18 rotates relative to shoe assembly 60, shoe assembly 60 and insert 36 rotate relative to pin bearing 18 as indicated by arrow A in FIG. It is driven back and forth. Such lateral movement may cause the workpiece to move relative to the polishing shoe assembly 60 or
Alternatively, the shoe assembly 60 may be moved relative to the workpiece, or a combination of both. When relative lateral movement is initiated, a frictional engagement must exist between the abrasive-coated tape 30 and the stone insert 36 in order to move the tape 30 to a new lateral position. For this reason, hard materials with very smooth surfaces, such as machined metals, are generally
It is unsuitable for use in insert 36. It is necessary to have sufficient roughness to frictionally engage the back surface of the abrasive-coated tape 30. A material that has been found suitable for insert 36 is conventional honing stone material. This material has the required hardness and friction properties and is known to yield excellent results.

Other types of abrasive coated tapes 30 may also be used with the present invention. For example, there are metal-backed abrasive coated tapes.

6 and 7 show a second embodiment of the invention.
In this embodiment, the insert portions 136 are machined in relief so that they do not increase the contact pressure between the abrasive coated tape 30 and the pin bearing 18. FIG. 6 shows a pair of opposing relief portions 142 defined by arcuate boundaries 144. The surface of pin bearing 18 is aligned with arrow C relative to insert 136.
move in the direction of In this second embodiment, more material is removed at both ends of the face of the pin bearing 18. This embodiment thus creates a somewhat barrel-shaped bearing surface where the diameter at each end of the pin bearing is slightly smaller than the diameter at the center. Such a "barrel surface" is sometimes desirable as the optimum bearing surface.

A third embodiment of the invention is shown in FIGS. 8 and 9. This example also has a slightly barrel-shaped journal.
The bearing surface is made, but the method is different from that of FIGS. 6 and 7. The modified cylindrical shape of the insert 236 is created such that the radius of the curved surface of the insert 236 at both ends of the journal bearing is smaller than the radius at the center of the journal bearing. As shown in FIG. 8, relative movement of pin bearing 18 with respect to insert 236 is in the direction of arrow C. As shown in FIG. 9, the portion of the face of the insert 236 near the edges is designated by the numeral 254 and has a radius of curvature that is somewhat smaller than the radius of curvature of the central show segment 256 (the difference in these radii is exaggerated in Figure 9 for clarity).
As mentioned above, this embodiment creates a non-cylindrical surface of the workpiece by another method. According to this embodiment, the desired surface shape is machined directly into the stone insert 236 and the shape is stamped into the workpiece.

FIG. 10 shows a fourth embodiment of the present invention in which the sidewall portion 68 of the pin bearing 18 can be finished and any burrs formed between the fillet radius 46 and the bearing surface can be removed. In this embodiment, the flexible insert 3 together with the insert 36
48 and 350 are provided. These flexible inserts apply a compressive force against the abrasive coated tape 30 when moved to the lateral-most position. Although the flexible material of inserts 348 and 350 has drawbacks associated with conventional methods, the profile shape of the side portions does not need to be as precisely finished. Because the abrasive tape 30 is bent significantly when contacting the sidewall portion 68, the tape edges may have to be scored, as is well known in the art. The use of inserts 348 and 350 also
If the workpiece is deeply milled with fillet radii 46 (as shown in FIG. 10), burrs or sharp edges can be removed on the edges of the bearing surface of journal 18. insert 348, 35
By mounting the inserts so that the inserts exert a light compressive load against the face of the bearing 18, the abrasive tape 30 is forced into the fillet 46 by the inserts, thereby eliminating the burr. Removal takes place.

FIG. 11 shows a fifth embodiment of the invention. This embodiment uses the upper shoe 62 and lower shoe 64 and insert 36 described in FIG.
This embodiment differs from previously described embodiments in that the abrasive-coated tape 430 includes a number of small holes 452 along its length. These small holes 452
can pass lubrication or cutting fluid to the workpiece surface. The lubricating or cutting fluid is delivered by holes 70 in the upper and lower shoes 62 and 64.

A sixth embodiment of the invention is shown in FIG. As shown, lower shoe 564 is mounted within cradle 566 by mounting pin 540. The mounting pin 540 allows the lower shoe assembly 564 to rotate relative to the cradle 566. A similar mounting structure may be provided for the upper shoe assembly (not shown). This mounting structure has each insert 36
This provides the desired "floating" properties similar to the embodiment of FIG. 4 in which each mounting pin 40 is provided. 1st
The main advantage of the configuration of Figure 2 is its simple construction. The operation of this embodiment is similar to the previously described embodiments.

While preferred embodiments of the invention have been described, it will be appreciated that many variations are possible without departing from the scope of the invention.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a rotating crankshaft with one pin journal precision-finished between grinding shoe assemblies; FIG. 2 is a cross-sectional view of a prior art grinding shoe assembly; , Figure 3 is the second
4 is a cross-sectional view of the polishing shoe assembly according to the present invention; FIG. 5 is a sectional view taken along line 5-5 of FIG. 4; and FIG. 6 has a relief portion. Drawings of a second embodiment of the invention using a rigid backing insert; FIG. 7 is a sectional view taken along line 7--7 of FIG. 6; FIG. 8 is a drawing of a third embodiment of the invention using a modified rigid insert. , FIG. 9 is a cross-sectional view taken along line 9--9 of FIG. 8, and FIG. 10 shows a fourth embodiment of the invention in which a rigid backing insert is used in conjunction with a flexible insert to precisely finish the fillet radius. Figure 11 is a drawing of a fifth embodiment of the present invention in which a rigid backing insert is used with a perforated abrasive-coated tape to improve the flow of lubricant to the surface to be precision finished; Figure 12 is an abrasive Drawings of the sixth embodiment of the present invention showing variations in the mounting structure of the shoe assembly, 10, 60... Polishing shoe assembly, 12... Crankshaft, 18... Pin bearing, 20...
Main bearing, 30,430... Abrasive coated tape, 36,136,236... Rigid insert,
38...Holder, 40,540...Mounting pin,
62... Upper shoe, 64,564... Lower shoe, 142... Relief portion, 254... Side edge, 348, 350, 672... Flexible insert, 452... Small hole, 566... Cradle.

Claims (1)

[Claims] 1. A precision finishing machine for microfinishing the surface of a workpiece, comprising: a relatively incompressible abrasive-coated tape made of polymer plastic; and a device for holding the tape. and a rigid surface that contacts the tape and urges the tape into contact with the workpiece surface, the rigid surface having a hardness greater than 90 durometer A; and the workpiece. A precision finishing machine comprising: a device for causing relative rotation between the shoe assembly and the shoe assembly. 2. The precision finishing machine according to claim 1, wherein the insert is mounted on the shoe assembly by a mounting pin so that the insert can rotate slightly relative to the shoe assembly. Precision finishing machine. 3. In the precision finishing machine of claim 1, the insert is mounted on the shoe assembly, and the shoe assembly is mounted such that the shoe assembly can rotate slightly relative to the workpiece. A precision finishing machine that is mounted so that it rotates around a mounting pin. 4. The precision finishing machine of claim 1, wherein the insert is comprised of a honing stone material. 5. A precision finishing machine according to claim 1, wherein the machine is used for precision finishing the outer surface of a workpiece, the insert having a predetermined surface shape related to the desired workpiece surface shape, A precision finishing machine in which an insert surface forces the tape into contact with the workpiece, thereby conforming the workpiece surface to the insert surface shape. 6. The precision finishing machine of claim 1, wherein the shoe assembly comprises an upper shoe portion and a lower shoe portion, each portion having at least one rigid insert. 7. The precision finishing machine of claim 1, wherein the insert surface extends the same circumferential distance. 8. The precision finishing machine of claim 1, wherein the insert surface spans a greater circumferential distance at opposite ends thereof so as to remove more material from selected areas of the workpiece surface. Extensive precision finishing machines. 9. The precision finishing machine of claim 1, wherein the insert surface is shaped with cylindrical surface segments of varying radius, thereby forming the desired profile shape in the workpiece. 10. In the precision finishing machine according to claim 1, both ends of the workpiece surface are surfaces projecting radially outward, a fillet roundness is formed between these both surfaces, and the insert further comprises:
A precision finishing machine including at least one resilient insert mounted adjacent to the insert to urge the tape into contact with the fillet radius. 11. The precision finishing machine of claim 1 further comprising one or more second inserts of resilient material having a lateral width greater than that of the insert, the second insert having a radially outwardly projecting surface of the workpiece. A precision finishing machine that applies pressing force to finish the surface. 12. The precision finishing machine of claim 11, further comprising a resilient mounting device for the second insert that bends when the shoe assembly moves to opposite end positions. 13. The precision finishing machine of claim 1, wherein the insert is made of stone. 14. The precision finishing machine of claim 1, wherein the insert presses the abrasive-coated tape against a substantially cylindrical workpiece surface, the insert forming a surface of a portion of the cylinder. . 15. The precision finishing machine of claim 14, wherein all portions of the insert surface extend along the same circumferential distance. 16. The precision finishing machine of claim 1, wherein a portion of the insert surface extends along a greater circumferential distance than the other portion. 17. The precision finishing machine of claim 14, wherein the insert surface is shaped to have a cylindrical surface with a varying radius.