GB2025518A - Cylinder head insert for internal combustion engines - Google Patents

Abstract

A circular insert 22 absorbs heat of combustion and thereby prevents distortion and/or cracking of the cylinder head 10 due to thermal stresses. The insert 22 is mounted by a central boss 26 extending axially into a bore 12' machined in the cylinder head 10. Apertures are provided in the insert 22 for exposing the engine inlet and exhaust valves and for either a spark plug or fuel injector 18, the aperture for the plug or injector being at the centre of the insert. A method of repairing or converting an engine is disclosed comprising machining out the cylinder head to receive the insert which is also machined. <IMAGE>

Description

SPECIFICATION Firing deck insert for internal combustion engines The firing deck in a cylinder of an internal combustion engine is subject to great stresses created by intensive variations in temperatures to which they are subjected during operation of the engines. These stresses frequently cause distortion and/or cracking of the firing deck so that a new head is required or the cracks in the head must be sealed and machined for reuse.

To preclude and/or minimize the foregoing problems, U.S. Patent No. 2,949,901 discloses an insert removably seated in a recess in the firing deck area of the engine body, with clearance between the periphery of the insert and the peripheral wall of the recess.

The exposed wall of the insert constitutes the firing deck and is subjected to at least the greatest heat generated during operation of the engine, but the insert is free to expand due to the peripheral clearance without subjecting the material of the engine body to undue stress.

Although the firing deck area can be located in the peripheral wall of a cylinder in some engines, in the normal engine the firing deck is in the end wall of the cylinder that is constituted by the surface of the engine head that is engaged with the engine block containing the cylinder.

According to the foregoing patent, the insert is secured by bolts or the peripheral portion of the insert is sandwiched between the engine head and block. While these inserts have been highly successful in precluding cracking of heads and prolonging the operational life of engines, extensive operation of the engines have resulted in some problems.

As an example of problems that have occurred, expansion of the insert is inhibited to some degree by location of the bolts which necessarily are spaced from the axis of the insert. In addition, excessive vibration of the engine can cause loosening of the bolts or over-torquing of the bolts upon insertion can create excessive stress on the head. Moreover, if the insert is secured only by being sandwiched between the head and body, repeated expansion and contracton of the insert, plus the vibration during operation of the engine, can cause migration of the insert toward a point of the cylindrical wall of the recess within which the insert is seated.

BRIEF SUMMARY OF THE INVENTION All engine bodies of the liquid cooled type are provided with an integral tube-like structure extending through the coolant jacket of chamber between the internal firing deck of the cylinder and an external surface of the body for the reception of an ignition device such as a sparkplug or a fuel injector unit for producing the explosion that drives the engine, the greatest heat being generated in the firing deck surrounding the ignition device and the ignition device usually being disposed axially or centrally of the firing deck or cylinder. According to the present invention, the body, usually the head, is provided with a cylindrical recess in the firing deck coaxial with the tube and also with an internally threaded bore extending from the inner surface of said recess coaxially with and extending into said tube structure.

The firing deck insert comprises a circular plate of a thickness substantially equal to the depth of said recess so that the firing deck surface of said insert is substantially coplanular with the engine body surface. The insert has a diameter sufficient to encompass the inlet and outlet ports but slightly less than that of the recess to provide peripheral clearance therebetween to accommodate expansion of said insert due to increase of temperature during operation of the engine. An axially disposed, externally threaded integral boss extends from the inner face of the insert and the insert and boss has an axially disposed bore therethrough for seating the inner end of the ignition device and exposing the latter to the combustion chamber.

The insert boss is threaded into the internally threaded bore in the engine body until the inner surface of the insert is firmly engaged with the floor of the firing deck recess of the body. To prevent possible loosening of the insert by threading due to vibration, expansion and contraction, the insert is provided with a radially disposed bore opening through its periphery and a dowell or dal pin is inserted through a bore through the body radially of the recess into the radial insert bore to secure the insert against rotation, but permit planar expansion.

BRIEF DESCRIPTION OF DRAWINGS Figure 1 is a plan view of the firing face or deck of an internal combustion engine of the fuel injector or diesel type; Figure 2 is a cross-sectional view taken on line 2-2 of Fig. 1; Figure 3 is an enlarged fragmentary crosssectional view taken on line 3-3 of Fig. 1; and Figures 4, 5 and 6 are cross-sectional views similar to Fig. 2 but showing modifications.

DETAILED DESCRIPTION OF INVENTION The head 10 of an engine, as better shown in Fig. 2, has a tubular structure 1 2 extending therethrough to the firing face axially of the combustion cylinder 1 4 of the blocl < 16, the tube structure 1 2 defining a passageway between the cylinder 1 4 and the exterior of the engine and supporting an ignition device 18 which, in this instance, is a fuel injector.The firing face of the head 10 is provided with a circular recess 20 for removably receiving a circular insert 22, there being peripheral clearance between the peripheral wall of the recess and the periphery of the insert to provide a gap 24 for accommodating expansion of the insert relative to the head to relieve the head of undue stress because of temperature variations, particularly excessive heat.

The head 10 has an internally threaded bore 12' disposed axially of the tube 1 2 and recess 20, said bore extending into the tube, and the insert 22 has an integral boss or collar 26 that is threaded externally to be secured in said bore 1 2' coaxially with the tube 1 2, said boss or collar 26 also having a seat 28 for the ignition device 1 8 which in this instance comprises a frusto-conical recess for seating the injector end of the fuel injector 18. Centrally securing the insert enables it to expand uniformly in all directions from the hottest point of the firing deck.

A dowell of dal pin 30 is inserted and threaded through a bore 31 in the head 10, said bore being disposed radially of the recess 20 and opening through the peripheral wall thereof, and said pin 30 being slidably fitted in a radially extending bore 31' opening through the periphery of the insert 22 to prevent rotation of the insert due to vibration.

The shank of the pin 30 has a sliding fit with the bore 31' in the insert 22 to permit relative movement as the insert 22 expands and contracts. Alternatively, the pin 30 may be threaded into the insert and have a sliding fit with the bore 31 through the head, but in this case the free end of the pin should be recessed in the head bore to avoid possible extension of the head of the pin beyond the outer wall of the head when the insert is expanded.

The insert 22, as shown in Fig. 1, has a fuel inlet 32 aligned with the fuel injector 18, two valve openings 34 and 36 for alignment with the intake and exhaust passages and, as also shown in Fig. 3, an opening 37 that is aligned with a starter air inlet 38 that is surrounded by a bushing 40 that is inserted through the insert opening 37 with peripheral clearance defining a gap 42, and said bushing is fixed by a dowell 44 threaded into the head 10. The dowell 44 fixes the bushing 40 relative to the head 10 and prevents loosening due to vibration, while the gap 42 permits movement, due to expansion and contraction of the insert 22 relative to the head 10 and bushing 40.

Figs. 4 and 5 show heads that do not have an integral tube 1 2 or in which the original tube is of insufficient thickness to accommodate the threaded bore 12' without undue weakening of the tube wall at that point. This embodiment of the invention primarily is concerned with the repair of used heads and in this case a bore 50 is drilled through the upper walls and a bore 51 through the lower wall of the head to remove the original tube, and bore 50 being of sufficient diameter to receive a replacement tube 1 2a having walls of sufficient thickness to accommodate an internally threaded bore 12a' at its lower end for receiving the threaded boss 26 of the insert.

In Fig. 4, the tube 1 2a is inserted through the bore 50 through the top wall of a head 10a. The tube has a collar 52 around its upper end that is seated in a recess 50' surrounding the outer end of the bore 50, and has an internally threaded bore 12a' at its lower end for receiving the threaded collar or boss 26 on the insert 22. The tube is sealed relative to the head by an O-ring 54 surrounding its upper end and a gasket 56, preferably of copper, at its lower end and recessed in the inner wall of the head. One or more internally threaded bores 57 are drilled spanning the head 10a and collar 52 and set screws 58 are inserted between the collar 52 and the head into said bores 57 to prevent rotation of the tube. The set screw or screws 58 provided additonal strength and preclude extreme overtorquing of the fuel injector.

Fig. 5 shows a modification of the Fig. 4 structure in that the tube 1 2b has an externally threaded collar 52' of reduced diameter at its upper end for cooperation with a rind nut 60 which may have a tool slot 62 of the like for threading the nut on the collar 52'.

The head 1 Ob has a recess 50b' of increased diameter in its upper wall, and surrounding the tube receiving bore 50, to receive the nut 60. The tube 1 2b has an internally threaded bore 12b' in its lower end for receiving the boss 26 of the insert.

Although the foregoing modifications illustrate engines wherein the ignition device 1 8 is a fuel injection unit, the invention equally is applicable to engines that employ an ignition device of the spark-plug type, as shown in Fig. 6. In this case, a head 10' comprises a tube structure 1 2c that freely receives the threaded boss 26' of an insert 22' that is nested in a recess 20' in the firing deck wall of the head with a peripheral clearance gap 24' therebetween. The seat 28' in the boss 26' is planar to accommodate the base end of the spark-plug 18' and the bore 32' is internally threaded to receive the threaded end of the plug and expose the spark-gap structure in the combustion cyinder 14' in the block 16'.

A pin 30' is inserted through a bore 31a in the head 10' into a bore 31b in the insert.

The foregoing embodiments illustrate that the invention is applicable either to new engine bodies or heads in which event the recess 20 and bore 12' can be cast at the time that the body or head is cast and the recess and bore then machined to provide smooth surfaces for the recess and the inter nal threads in the bore. Alternatively, if the tube 1 2 is of sufficient diameter and wall thickness at the inner end thereof, a used head can be modified by machining out the recess 20 and then the bore 12'.

In heads or engine bodies in which the tube 1 2 is not of sufficient diameter or the wall thickness at the point of the bore 12' is insufficient to accommodate the bore, then the head or body may be machined completely through to provide the bores 50-51 and a new tube 12a, 1 2b inserted therein as shown in Figs. 4 and 5. Also, in such heads usually the recess 20 and bore 12' must be machined into the firing deck wall of the body or head.

In the vast majority of instances, at the present time, the invention is applied to used heads which have been cracked in the firing deck surface due to the terrific stresses imposed by temperature variations and normally these cracks will appear between the point of ignition and the exhaust passage. In applying the invention to this type of used head, the crack is usually sealed in a normal manner and the firing deck surface is machined to provide the recess 20 and the bore 12', the internal threads being cut into the bore at the time of machining.

Preferably, the insert 22 is of such a diameter as to completely span the combustion cylinder 1 4 and overlap the edges thereof so that the edge portions of the insert are sandwiched between the body and the bottom of the recess. Having determined the diameter of insert that is necessary, the recess 20 then is machined to provide it with a diameter that will permit a peripheral clearance 24 between the periphery of the insert and the peripheral wall of the recess. The insert 22 then is threaded into place with the proper degree of torque so that it is firmly seated but not subjected to strain producing over-torquing.

When the insert is threaded into the engine body recess with the required tightness but without over-torquing, the bore 31 is drilled and internally threaded through the engine body and drilling also proceeds into the periphery of the insert to provide the bore 31', which bores jointly receive the pin 30. The pin 30 retains the insert 22 against unthreading or tightening due to vibrations and temperature variations in the insert and retains the insert in proper position during further operations.

When the insert is properly seated and anchored, it then is properly marked to locate the centres of the inlet and exhaust openings 34 and 36. This can be accomplished in various ways but most conveniently the centres for the openings are determined by insertion of the marking too, such as a small diameter drill, through the valve guides in the engine body. A drill of the proper diameter for the openings 34 and 36 then can be aligned with the marked centres for drilling the openings. The center for the opening 37 for the compress air inlet 38, if such is necessary, can be determined by measurement with respect to the valve openings, the ignition opening or other physical features.After the insert is properly seated and completely finished, including the sealing of the bushing 40 if required, the firing deck surface of the insert and contiguous surface of the engine body or head are machined to be co-planar.

It has been found that the intense heat to which the insert is subject causes the insert to expand radially in all directions from its boss 26, there being no restrictions in such radial expansion even if the engine is of the type to have a compressed air inlet because of the clearance provided by the gaps 42 around the boss 40 surrounding the inlet, the gaps 42 permitting expansion and resultant movement of the insert relative to both the engine body and the bushing 40. While some of the heat absorbed by the insert is transferred through the firing deck wall of the engine body, the reduced thickness of such wall is maintained in a relatively cool condition by the coolant that flows through the water jacket and is in constant engagement with such wall. Moreover, the engine so modified produces greater horsepower because the insert retains the heat and causes more complete combustion.

Claims (12)

1. An insert for insertion in a firing deck of a combustion chamber in an engine body of an internal combustion engine, the insert comprising a circular body which is shaped complementally to and can be located in a circular recess in the firing deck to cover at least a portion of the firing deck with clearance between the outer periphery of the insert body and the inner periphery of the recess to accommodate thermal expansion of the insert body, the exposed surface of the insert body being arranged to conform substantially to the engine body surface surrounding the recess, and a centrally disposed boss of reduced diameter extending axially from the inner surface of the insert body and threadable into a bore in the engine body in axial alignment with an ignition device mounted in the engine body, the boss having an axially disposed opening therethrough and including a portion defining a seat for the ignition device and an opening for exposing the ignition device to the combustion chamber, whereby the insert body is centrally fixed by the boss relative to the point of combustion in the chamber but is free to expand radially from the boss without stress or strain as it absorbs heat of combustion.

2. A firing deck insert according to claim 1, wherein the insert has openings therethrough to coincide with passages including at least the inlet and exhaust passages through the engine body.

3. A firing deck insert according to claim 2 wherein the insert has a radially disposed bore opening through its peripheral wall for receiving a locking pin supported by the engine body to preclude rotation of the insert relative to the engine body.

4 An internal combustion engine fitted with an insert according to any of claims 1 to 3.

5. A method of repairing or converting an internal combustion engine including an engine body provided with a combustion chamber having a firing deck area surrounding an ignition device, comprising providing a circu iar recess in the firing deck area and a bore in the engine body in axial alignment with the ignition device, providing an insert comprising a circular body which is shaped complementally to and is located in the circular recess cover at least a portion of the firing deck with clearance between the outer periphery of the insert body and the inner periphery of the recess to accommodate thermal expansion of the insert body, the exposed surface of the insert body conforming substantially to the engine body surface surrounding the recess, and a centrally disposed boss of reduced diameter extending axially from the inner surface of the insert body threaded into the bore in the engine body, the boss having an axially disposed opening therethrough and including a portion defining a seat for the ignition device and an opening for exposing the ignition device to the combustion chamber, whereby the insert body is centrally fixed by the boss relative to the point of combustion in the chamber but is free to expand radially from the boss without stress or strain as it absorbs heat of radiation.

6. A method according to claim 5, comprising drilling a bore through the engine body from the exterior thereof to the wall of the recess and into the periphery of the insert radially of the recess and insert, and inserting a dowell pin into the bores to secure the insert against rotational movement.

7. A method according to claim 5 or claim 6, wherein the engine body has passages therethrough including at least inlet and exhaust passages opening into the area encompassed by the recess, comprising forming holes in the insert in alignment with the openings.

8. A method according to any one of claims 5 to 7, including machining the exposed firing deck surface of the insert and the surrounding contiguous area of the engine body to be co-planar.

9. A method according to any one of claims 5 to 8, wherein the firing deck area has been distorted and/or cracked due to thermal stresses, comprising repairing and sealing any crack in the firing deck area, providing the recess in the firing deck area and encompassing the repaired area to be covered by the insert.

1 0. A method according to any one of claims 7 to 9, wherein one of the passages is a compressed air inlet opening into the com- bustion chamber within the area of the recess, including inserting a bushing through the hole in the insert in alignment with the inlet and into the inlet with peripheral clearance between the bushing and the hole in alignment with the inlet.

11. A firing deck insert substantially as herein described with reference to any one of the Figures of the accompanying drawings.

1 2. A method of repairing an internal combustion engine substantially as herein described with reference to any one of the Figures of the accompanying drawings.

1 3. An internal combustion engine repaired by the method of any one of claims 5 to 10 and

12.