Method And Apparatus For Rebuilding Valve Guides

Abstract

This disclosure relates to a method and system for rebuilding valve guides for internal combustion engines wherein the old worn guides are first reamed and then have slitted tubular members forced into the reamed guides. The tubular member inserts can then be reamed to size. The operation can also include knurling and broaching of the tubular members after insertion of the tubular member into the the reamed valve guide. The tubular member has an outer diameter greater than the inner diameter of the reamed guide so that a press fit between the tubular member and the guide results.

Parent Case Text

This is a division of application Ser. No. 847,927 filed Aug. 6, 1969, now abandoned.

Description

This invention relates to rebuilding valve guides. In one of its aspects, it relates to rebuilding valve guides wherein the old guides are first reamed and slitted tubular members are then forced into the reamed guides.

In another of its aspects, the invention relates to a system for rebuilding valve guides in which a reaming means is provided to ream out the old valve guide, a tubular member having a longitudinal slit is provided, and means are provided for forcing the tubular member into a reamed valve guide to provide a press fit between the reamed valve guide and the tubular member.

Valve guides for internal combustion engines become worn through extended use. It is necessary for the valve guide to have close tolerances between the valve stem and the valve guides in order for the engine to operate efficiently.

Tools have been devised for effectively reducing the diameter of a hole such as valve guides. In U.S. Pat. No. 3,097,426, for example, there is disclosed a tool for reducing the effective diameter of a hole by forming flat crested threads within the hole. This tool cannot always be used for rebuilding valve guides, however, because in many instances the valve guides are so badly worn that there is insufficient metal to form the desired inner diameter of the guide.

Other systems have been developed for rebuilding valve guides. One such system drills and reams out valve guides and then inserts a tubular cast iron cylinder into the reamed out hole. The excess portion of the cylinder is then trimmed off. The thickness of the cast iron cylinder is necessarily about 75 to 100 thousands of an inch. Substantial amounts of metal must be removed from the valve guide necessitating the use of precision drilling equipment. Numerous jigs, dies, guides and leveling devices, and special power units are required with the system. As a result a large capital investment is required to use the same. Further, the wearability of the new valve guide is about the same as that of the original valve guide.

Another system first drills an anchor hole in a valve guide. Then a self-piloting tap is threaded into the valve guide. A phosphor bronze spiral bushing is then threaded into the threaded valve guide with a special tool. Excess material is removed from the ends of the bushing and a broach is forced through the guide to set the bushing in place. The valve guide is then reamed to size. The tapping of the valve guide is a complicated operation and the insertion of the spiral bushing is difficult.

I have now discovered still another system and method for rebuilding valve guides wherein the use of a slotted tubular member as a valve guide permits a simple system of tools to be used to quickly, easily and effectively rebuild the guides.

By various aspects of this invention one or more of the following, or other, objects can be obtained.

It is an object of this invention to provide a system and method for rebuilding valve guides wherein a few simple tools are employed.

It is another object of this invention to provide a system and method for quickly and easily rebuilding valve guides wherein the rebuilt valve guides have improved wear characteristics.

It is a further object of this invention to provide a system for rebuilding valve guides in which durable inserts used in the system are inexpensively and quickly made to the proper size needed for the job.

It is still another object of this invention to provide a system and method for rebuilding valve guides in which the valve guides are first reamed but said reaming operation requires only simple and inexpensive tools.

It is yet another object of this invention to provide a method and system for rebuilding valve guides wherein the rebuilt guides have maximum heat transfer properties to minimize wear of the rebuilt guides.

It is another object of this invention to provide an improved rebuilt valve guide having improved wear characteristics and closer tolerances for more efficient engine operation.

Other aspects, objects, and the serveral advantages of this invention are apparent to one skilled in the art from a study of this disclosure, the drawings, and the appended claims.

According to the invention there is provided a method for rebuilding valve guides comprising the steps of reaming said valve guides so as to expand the diameter thereof, forcing a tubular longitudinal insert into the reamed valve guides to provide a new surface for the guide. The inserts have an outer diameter greater than the inner diameter of the reamed hole and have a longitudinal slit extending the length thereof so that the tubular member conforms in a press fit to the inner diameter of the reamed valve guide.

Further according to the invention, the metal of the insert is flowed to join the slit thereby preventing the oil from flowing through the slit within the valve guides. Preferably the tubular insert is made from phosphor bronze for greater wearability of the rebuilt guides.

Further according to the invention, the tubular member is formed by progressively forming cut blanks from sheet stock into a tubular shape. The longitudinal slit in the tubular member can be formed by offset portions such that the slit is nonlinear, or can be formed by interengaging finger portions which abut each other at the circumferential edges thereof.

Still further according to the invention there is provided a system for rebuilding valve guides comprising a means for reaming the valve guide, a tubular member having a slit extending longitudinally from one end to the other and adapted to fit coextensively within said valve guide. The outer diameter of the tubular member is slightly greater than the outer diameter of the reaming means. Means are also provided for forcing the tubular member into a reamed valve guide, thereby making a press fit between the tubular member and the reamed valve guide.

Still further according to the invention a valve guide for an internal combustion engine has a valve guide formed from a cylindrical hole in the engine block, a cylindrical thin wall tubular member is firmly secured in the cylindrical hole, the tubular member having a longitudinal seam from one end to the other. The wall thickness of the tubular member is preferably in the range of 10 to 25 thousands of an inch and the tubular member is preferably made from a phosphor bronze.

The invention will now be described with reference to the accompanying drawings in which:

FIG. 1 is a partial side elevational view in section of a typical valve guide and valve stem in operating position;

FIG. 2 is a view of the valve guide similar to FIG. 1 illustrating a first step of the method of the invention;

FIG. 3 is a perspective view of a tubular insert used in practicing the invention;

FIG. 4 is a side elevational view of the valve guide like FIG. 2, but showing a second step of the process;

FIG. 5 is a side elevational view of the valve guide illustrated in FIGS. 2 and 4 showing a further step in the process;

FIG. 6 is a view similar to FIG. 5 showing the rebuilt valve guide after a knurling operation;

FIG. 7 is a perspective view of a modified tubular member; and

FIG. 8 is a perspective view of still another modified tubular member.

Referring now to the drawings, and to FIG. 1 in particular, an overhead valve engine head 10 has machined therein a valve guide 11 with an exposed shoulder portion indicated generally by the reference numeral 12 through which the valve stem 13 is passed during assembly. Ordinarily, the exposed shoulder 12 will be integrally cast with the remainder of the head and thereafter machined to proper dimensions. A valve spring 14 encircles exposed shoulder portion 12 of the valve guide assembly and the valve is conventionally retained with respect thereto by a pair of valve keepers 18. While not shown, of course, the valve stem 13 extends downwardly and terminates in a valve portion having a suitable seat machined into the lower surface of the head 10. The valve spring 14 retains the valve in closed position with respect to the seat except when forced downwardly by a rocker arm (not shown) or the like in proper operational sequence. An oil seal 20 prevents oil from flowing between the valve stem 16 and the valve guide 11 and into the combustion chamber of the engine.

The seal 20 is retained in compressive abutment by means of the retaining boot assembly 22 which has a tubular base member 24 adapted to telescopically engage the outer diameter of the valve guide 12 through indent 26. The seal structure is more fully described and claimed in U.S. Pat. application Ser. No. 675,586, filed Oct. 16, 1967.

Referring now to FIG. 2, there is shown a first step in the valve rebuilding guide method. The valve stem 16 and its associated components are removed from the shoulder portion 12. A reamer tool 30 having a threaded section 32 with a tapered leading portion 34 and a sizing portion 36 is forced through the valve guide. The reamer tool 30 is a self-piloting tool so that the axis of the reamed valve guide is the same as the original axis of the guide. The reamer tool 30 has a reamer section comprised of longitudinal flutes 38 which cuts away and thereby expands the diameter of the valve guide.

Referring now to FIG. 3 a tubular member 40 is stamped from a blank of phosphor bronze and progressively formed into a tubular shape, leaving a longitudinal slit 42.

Referring now to FIG. 4, the tubular insert 40 is forced into the reamed valve guide 11' by means of an adapter 44 having a tapered inner diameter 46. The outer diameter of the tubular member 40 is greater than the reamed valve guide 11' so that the tubular insert 40 must be radially compressed in order to force the same into the reamed valve guide 11'. The adaptor 44 is annular shaped. At the upper portion, the inner diameter of the adaptor is greater than the outer diameter of the tubular insert 40. At the lower portion, the inner diameter of the adaptor 44 is equal to or less than the inner diameter of the reamed valve guide 11'.

A forcing tool 48 is positioned in the upper portion of the tubular insert 40 and is struck at the top portion thereof to force the tubular insert through the adaptor 44 and into the reamed valve guide 11'. The forcing tool 48 may have a lower circumferential rim as illustrated in the drawing or may be flat.

The tubular insert 40 can be cut from a blank so as to be exactly the length of the valve guide. Alternately standard size blanks can be used with an excess length trimmed off when the tubular members have been inserted into the valve guides. Thus, when the tubular insert 40 is completely within the valve guide as illustrated in FIG. 5, with the top portion of the tubular insert 40 even with the top surface of the shoulder portion 12, the tubular insert 40 will be coextensive with the reamed valve guide 11'. Further, the blanks are so dimensioned that the slit 42 is closed forming a longitudinal seam as the tubular insert is forced into the reamed valve guide. The wall thickness of the tubular inserts can be in the range of 10 to 25 thousands of an inch and preferably in the range of 15 to 20 thousands of an inch. Preferably the tubular inserts are made from phosphor bronze for maximum wearability.

At this point, the valve guide is ready for use. However, additional steps can also be performed to improve still further the rebuilt valve guide structure.

For example, as illustrated in FIG. 6, the inner surface of the tubular insert 40 can be knurled as at 50 to flow the metal of the tubular insert. This knurling process flows the metal of the tubular insert 40 so as to seal off the passage through slit 42. By this step, the oil within the engine is prevented from seeping through the valve guide 11. In addition, the knurling operation more firmly seats the insert 40 within the reamed valve guide. Many tools are available for this knurling operation. One such tool is disclosed in U.S. Pat. No. 3,038,253.

After the knurling operation, the valve guide can then be reamed again to a predetermined size diameter if necessary. The rebuilt valve guide will then be as good as or better than the original valve guide of the engine.

In a modified procedure, the rebuilt valve guide illustrated in FIG. 5 can be broached with a common broaching tool in order to flow the metal in the same manner as was done with the knurling tool.

The modified tubular insert 52 illustrated in FIG. 7 has circumferentially offset slits 54 and 56 which are contiguous and form a longitudinal slit in the tubular insert. This modified tubular insert 52 can be formed in the same manner as the tubular insert 40, i.e. stamped from tubular stock and progressively formed in dies into a tubular shape.

Another modified tubular insert 60 is illustrated in FIG. 8. This modified insert has interlocking fingers 62 and 64 which form in the tubular insert longitudinal slit 66 having a tortuous path. The interlocking fingers 62 and 64 abut at the circumferential edges thereof so that when the tubular member 60 is inserted within the valve guide, oil will not be able to flow through the longitudinal slit 66 from one end to another. However, oil pockets can be left at the open slit portion 66 to provide oil retaining means for lubricating the valve stem within the valve guide.

This modified tubular insert 60 is formed in the same manner as the tubular insert 40, i.e. by stamping the same out of blanks of metal, preferably phosphor bronze, and then progressively forming the stamped blanks into a tubular shape as illustrated.

The use of the longitudinal slits facilitate the insertion of the tubular member into the reamed valve guide so that a press fit is maintained between the tubular insert 40 and the reamed valve guide. Further, the formation of the tubular inserts are simple and inexpensive with the stamping and forming operations. By the nature of the interlocking relationship of the tubular inserts 52 and 60, no material is wasted in the stamping operation.

The stamping operation is very precise and precision parts can be formed thereby. The tubular inserts formed by such process can be precisely formed from thin gage phosphor bronze or other similar material. The thinner the material is, the better the operation of the valve guides. The interface between the insert and the engine block retards the heat flow away from the valve guides during operation. It has been found that as the wall thickness of the inserts decreases, the retarding effect of the interface decreases. Therefore, it is desirable to use as thin a material as possible without mitigating the wearability of the valve guide. By the use of the blanks, the wall thickness can be reduced to about 10 thousands of an inch.

Further, with the use of the sheet stock to form the tubular inserts, the final inner diameter of the valve guide can be controlled with far greater accuracy than if the tubular inserts were cast or reamed.

A still further advantage of the use of the thin wall material is that only small amounts of material need be removed from the worn valve guides. This small amount of material can be removed with a single pass of a self-piloting reaming tool disclosed above. In the prior art systems, it is sometimes necessary to make multiple passes with reaming tools in order to remove enough material from the valve guide. When substantial amounts of material are removed from the valve guide, as with prior art systems, the alignment of the reaming tools is more critical and must be controlled with more complicated equipment and more complicated procedures.

Reasonable variation and modification are possible with the scope of the foregiong disclosure, the drawings, and appended claims without departing from the spirit of the invention.

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A method of rebuilding valve guides comprising the steps of:

reaming a valve guide so as to expand the diameter thereof:

providing a tubular metallic insert having an open longitudinal slit extending the length thereof, said slit being adapted to close upon radial compression of said insert, the outer diameter of said insert, with said slit completely closed under such radial compression, substantially equaling the diameter of said reamed guide;

forcing said insert into a tapered adapter having a minimum diameter substantially equal to the diameter of said reamed guide and thereby radially compressing said insert and completely closing said slit;

positioning said adapter over said valve guide with said insert in alignment with said valve guide;

driving said insert through said adapter into said valve guide until the leading extremity of said insert is flush with the adapter-remote extremity of said valve guide;

removing said adapter; and

trimming any excess portion of said insert such that said insert is thereafter substantially coextensive with said valve guide.

2. A method according to claim 1 further comprising the step of flowing the metal of said insert after said insert has been driven into said reamed valve guide to seal said slit thereby preventing oil from flowing through said slit within said valve guide.

3. A method according to claim 2 wherein said flowing step comprises narrowing the inner diameter of said insert.

4. The method according to claim 2 wherein said flowing step comprises broaching the inner surface of said insert.

5. The method of claim 2 further comprising the step of reaming said inner surface of said insert after said flowing step to make a pre-determined diameter bore for said valve guide.

6. A method according to claim 1 wherein said longitudinal slit is formed of interengaging finger portions which abut each other at the circumferential edges thereof so as to prevent flow of oil through said valve guide.

7. A method according to claim 1 wherein said tubular insert is made from phosphor bronze.

8. A method according to claim 7 wherein the wall thickness of said tubular insert is in the range of 10 to 25 thousands of an inch.

9. A method according to claim 1 wherein the wall thickness of said tubular insert is in the range of 10 to 25 thousands of an inch.

10. A method according to claim 1 wherein said tubular insert is formed by progressively forming cut blanks from sheet stock into a tubular shape.

11. A method according to claim 1 wherein said longitudinal slit is formed by offset portions so that said slit is nonlinear.

12. A method according to claim 1 further comprising the step of reaming the inner surface of said tubular insert after said tubular insert has been forced into said reamed valve guide, so as to provide the inner surface of said tubular insert with a pre-determined inner diameter.