GB2103302A

GB2103302A - Lubrication system for assemblies for internal combustion engines and other devices

Info

Publication number: GB2103302A
Application number: GB08122855A
Authority: GB
Inventors: Richard Furneaux Kinnersly
Original assignee: Individual
Current assignee: Individual
Priority date: 1981-07-24
Filing date: 1981-07-24
Publication date: 1983-02-16

Abstract

An internal combustion engine or gas compressor has a crankshaft (12) lubrication system comprising a first chamber (21) in the locality of a support bearing (15) for the crankshaft (12) and a second chamber (25) in the locality of a crank pin (20) of the crankshaft (12), a first duct (26) extending through the crankshaft (12) between the first and second chambers (21, 25), a second duct (32) also extending through the crankshaft (12) to form, in combination with the chambers (21, 25) and first duct (26), a circuit for lubricant. A scoop (36) promotes flow of lubricant around the circuit. <IMAGE>

Description

SPECIFICATION Lubrication system for assemblies for internal combustion engines and other devices This invention relates to assemblies (hereinafter referred to as being of the kind specified) of the kind commonly employed in internal combustion engines and gas compressors and which comprise a cylinder to and from which working fluid is admitted and exhausted, means controlling the admission and exhaust of the working fluid, a piston reciprocable in the cylinder longitudinally of the axis thereof, a crank case, a crankshaft rotatable in the crank case about an axis at right angles to that of the cylinder and adjacent to one end (herein referred to as the base end) of the cylinder, and having a crank pin spaced radially from the axis of rotation of the crankshaft, and a connecting rod connecting the piston to the crankshaft to transmit motion between the reciprocatory piston and the rotary crankshaft.

When the assembly forms part of an internal combustion engine in which the mixture of the working fluid and fuel undergoes ignition by generation of an electric spark within the cylinder, ignition means are then provided for effecting such ignition. In other cases, for example where ignition is effected by way of compression of the mixture of working fluid and fuel no such ignition means need be provided, nor need such ignition means be provided where the assembly of the kind specified forms part of a gas compressor, for example an air compressor.

An assembly of the kind specified forming part of an internal combustion engine is described and claimed in the specification of British patent No. 1,296,830 granted to the inventor of the present application and in which the engine comprises a cylinder, a piston mounted for reciprocating sliding movement within said cylinder, a connecting rod rotatably connected with said piston, a crankshaft, a crank pin rotatably connecting said connecting rod with a crank web of said crankshaft, an engine housing, said crankshaft being rotatably mounted in said housing, and further comprising:: (a) a first lubricant storage chamber extend ing about said crankshaft and defined between said crankshaft and said housing, (b) first bearing means rotatably mounting said crankshaft in said housing and located in said first lubricant storage chamber, (c) lubricant pre-stored in said first lubricant storage chamber and in direct contact with said first bearing means to permanently lubricate said first bearing means, (d) means sealing the ends of said first lubricant storage chamber to retain said lubricant permanently therein, (e) a second lubricant storage chamber extending about said crank pin and defined between said crank pin and said crank web, (f) second bearing means mounting said crank pin for rotation in said crank web and located in said second lubricant storage chamber, (g) lubricant pre-stored in said second lubricant storage chamber afld in direct contact with said second bearing means to permanently lubricate said second bearing means, and (h) means sealing said second lubricant storage chamber to permanently retain said lubricant therein.

In this form of internal combustion engine of the kind specified, it is necessary that the crank pin should be rotatably mounted in, and relatively to, the web of the crank whereas in certain case it would be more convenient to adopt a more conventional construction in which the crank pin is fast relatively to the web of the crank and the big end of the connecting rod is rotatable on and with respect to the crank pin.

Both aspects of the invention, as hereinafter defined, have been developed primarily for application to a "oilless" engine. By "oilless" is meant that the crank case (in the case of a four stroke engine) does not, in operation, contain lubricant which is free in the sense of forming a reservoir which is used to lubricate big end and little end bearings and crankshaft supporting bearings by reason of such reservoir being agitated by entry of the crankshaft and associated similarly moving parts, and which results in significant consumption or contamination of lubricant over a period of time, and that (in the case of a two stroke engine) there is no introduction of lubricant by way of the fuel or working fluid.

It is to be understood, however, that although the primary application of the invention is to "oilless" engines, both aspects of the invention may be applied to engines where there is some free lubricant in the crank case (in the case of four stroke engines) and where there is some introduction of lubricant by way of the fuel or working fluid supply (in the case of two stroke engines).

Further, as is evident from the preceding description, both of the aspects of the invention may be applied to gas compressors.

A first aspect of the invention provides for adoption of this alternative by the modification that the second lubricant storage chamber is formed as a cavity in the connecting rod itself, and that the crank pin is integral with or fast with the crank web.

A second aspect of the invention is concerned with a more sophisticated lubrication system for providing lubrication at the bearing between the connecting rod and the crank pin, and at a supporting bearing in the crank case or the crankshaft itself. This aspect of the invention is applicable to internal combustion engines of the kind specified and is hence broader in its application than the specific form of those engines described and claimed in the aforementioned British Patent Specification.

According to the second aspect of the invention, an assembly of the kind specified includes a lubrication system for a crankshaft supporting bearing means, and a bearing means at the connection between the connecting rod and crank pin, such system comprising a first lubricant storage chamber at the supporting bearing means, a second lubricant storage chamber at the connecting rod bearing means, a first duct extending through the crankshaft serving to connect the first chamber to the second chamber, a second duct also extending through the crankshaft serving to connect the second chamber to the first chamber to form a lubricant circuit, and means responsive to rotation of the crankshaft to cause lubricant to circulate around the circuit.

The second lubricant storage chamber may move in an orbit in consequence of crankshaft rotation, having a first outer part which is radially beyond the first lubricant storage chamber and having a second inner part extending radially inwardly of at least part of the first lubricant storage chamber, the first duct means being so arranged as to connect the first chamber with the outer part of the second chamber, and the second duct being so arranged as to connect the inner part of the second storage chamber with the first chamber.

Preferably, there is provided in, or in association with the first chamber, a pressure inducing means which is operable in response to rotation of the crankshaft for causing a pressure gradient to be established along the first duct in a direction to bring about flow of the lubricant from the first chamber to the second chamber, the pressure in the former however being maintained below a value which would prevent delivery of lubricant from the second part of the second chamber back to the first chamber.

That end of the second duct which communicates with the second part of the second chamber may be situated radially inwardly of, or at the same radius as, the end of the second duct which communicates with the first chamber. With this arrangement, there may also be a pressure gradient promoting flow of lubricant from the second chamber back to the first chamber through the second duct, or at least absence of any pressure gradient counteracting such flow.

The means for producing a pressure gradient in the first duct may comprise a scoop means provided on the crankshaft and rotating therewith for collecting lubricant from the first chamber as the crankshaft rotates and feeding it into that end of the first duct which communicates with the first chamber.

An engine provided with a lubrication system in accordance with the second aspect of the invention may, like that disclosed in the aforementioned British Specification, be characterised in that no free lubricant is present in the crank case (other than in said lubricant storage chamber) and no free lubricant is required to be introduced by admixture with the fuel or by metered introduction from a separate supply of lubricant.

The invention may however be applied advantageously to an engine wherein lubrication is effected by means of a mixture of the lubricant with the fuel, that is in accordance with the so-called "petroil" system.

The invention will now be described, by way of example, with reference to the accompanying drawings wherein: Figure 1 is a fragmentary view in side elevation and in vertical cross-section medially of the cylinder and crank case of one embodiment of internal combustion engine of the kind specified in accordance with the second aspect of the present invention; Figure 2 is a fragmentary cross-sectional view on the line 2-2 of Fig. 1 on an enlarged scale; Figure 3 is a view similar to that of Fig. 1 of an embodiment of the first aspect of the invention; Figure 4 is a fragmentary view on an enlarged scale of the big end of the connecting rod viewed along the axis of the crank pin; Figure 5 is a view in section on the line 5-5 of Fig. 4; Figure 6 is a view similar to Fig. 4 showing a modification; Figure 7 is a view of the modification of Fig. 6 in section on the line 7-7 of Fig. 6;; Figure 8 is a view of the modification of Fig. 6 in section on the line 8-8 of Fig. 6; Figure 9 is a fragmentary view of a modification of the embodiment of Fig. 1 in which the crank pin is supported between a pair of axially spaced crank webs.

In the embodiment illustrated in Fig. 1, the invention is applied to a single cylinder internal combustion engine designed to operate in accordance with a two stroke cycle.

The engine comprises the following main parts, namely a cylinder 10 having a head and a reciprocatory piston (not shown), a crank case 11 in which is mounted a crankshaft 1 2 for rotation about an axis 13, and a connecting rod 14 serving to connect the piston with the crankshaft.

These component parts may be in the form more fully disclosed in our copending application filed and entitled "Assemblies for internal combustion engines and other devices" to which reference may be had and which is to be deemed to be part of the present disclosure, although, as hereinafter indicated, the invention may also be applied to internal combustion engines of the kind specified which are not necessarily so constructed.

The lubrication system incorporated in the embodiment illustrated is intended to provide lubrication for the bearing means comprising bearing 15 mounted in a sleeve-like extension 16 of that part 11 a of the crank case which is connected to the cylinder 10 and also for the bearing means comprising bearing 1 7 contained in the boss or sleeve 1 9 forming the big end of connecting rod 14, and by means of which the latter is rotationally connected to the crank pin 20.

The lubrication system now described is intended to provide all the lubrication required for these bearings without the necessity for providing a quantity of lubricant in the base of the crank case defined by the part 1 a and the separable part 11 b in combination. Further, the lubrication provided may be sufficiently effective to eliminate the need to introduce lubricant by add mixture with the fuel in accordance with the known "petroil" system.

The lubrication system comprises a first chamber 21 defined between the sleeve-like extension 1 6 of the crank case, a shaft proper 22 of the crankshaft 12, and sealing means indicated diagrammatically at 23 and 24 at opposite ends of the sleeve-like extension 16, and which may be in the form of known garter-type seals.

The lubrication system further comprises a second chamber 25 enclosing the bearing 1 7 and which is defined between the big end boss 1 9 and the crank pin 20. This chamber is effectively sealed at its ends by sealing means, for example garter seals 1 8. Alternatively the seal at the outer end of the crankpin interposed between the big end bore and a cover 1 9e may be a plug, such as a welch plug.

These two chambers 21 and 25 are connected by a first duct 26 which comprises a radially extending portion 27 opening from the surface of the shaft proper 22, a main portion 28 extending obliquely with respect to the axis 1 3 of rotation of the crankshaft in a direction from the portion 27 towards the chamber 25 through the shaft portion proper and the web 29 of the crankshaft, and a terminal portion 30 extending radially of the crank pin axis 31 to emerge onto the surface of the crank pin and communicate with chamber 25.

Further, the lubrication system comprises a second duct 32 which also communicates at one end with the second chamber 25 and at its other end with the chamber 21 in the upper part of the latter.

To promote flow of lubricant around the system, a pressure inducing means 35 is provided which may be in the form of a scoop element 36 providing a scoop or pick-up surface 37 which, in response to rotation of the crankshaft in the direction indicated by the arrow 38, causes lubricant in the chamber 1 5 to be fed under pressure into the entrance of the radial portion 27 of the first duct.

As a consequence of rotation of the crankshaft, the chamber 25 (which is of annular form) will itself move orbitally and will describe an annular path, one annular (outer) part of which, herein called the first part, is radially beyond the outer boundary of the chamber 21 but the inner part, herein calied the second part, of which overlaps radially with the chamber 21 when viewed along the axis 1 3 of the crankshaft.

Due to centrifugal forces, lubricant present in that part of the portion 28 of the first duct which extends obliquely from the axis 1 3 towards the terminal portion 30 of this duct will be subject to a pressure tending to cause it to flow towards the terminal portion 30 of the duct and into the chamber 25.Lubricant contained in the remainder of the main portion 28 of the duct leading from the radial portion 27 as far as the axis 13, and the lubricant in the radial portion 27 itself, will tend, owing to centrifugal forces, to flow towards the outlet of the duct portion 27 and this tendency will be overcome partly by the greater centrifugal force applied to the lubricant in the duct portion 28 between the axis 13 and the duct portion 30 compared with that generated in the lubricant in the remaining part of duct portion 28 and in radial portion 27, and partly by reason of the pressure generated by operation of the scoop 36.

Consequently lubricant will be fed in response to rotation of the crankshaft from the first chamber 21 towards the second chamber 25.

The second duct 32 may be parallel to the axis 1 3 but is preferably divergent with respect from this axis in a direction from the second chamber 25 towards the first chamber 21 so that there will be pressure on the lubricant therein as a result of centrifugal force tending to make this lubricant flow from the second chamber 25 back to the first chamber 21. Even, however, if the second duct 32 were parallel to the axis 13, the greater pressure in the chamber 25 compared with that in the chamber 21, would promote such flow.

To increase the volume of lubricant present locally within the big end boss 19, and to provide for axial transfer from one end of the bearing 1 7 and associated garter seal 1 8 to the other end of the bearing 1 7 and the other garter seal 18, the big end boss, as seen particularly in Figs. 4 and 5, is provided with a system of passageways.

These comprise annular grooves, for example of part-circular section as shown at 1 9a concentrically on respective ends of the big end boss 19, such grooves being connected by equi-distantly spaced axially extending bores 1 9b. The grooves 1 9a further communicate with the locality of the bearing 1 7 by way of radial grooves 19c. Although in Fig. 1 the second duct 32 is shown as opening into an axially presented face of the crank web opposite to the bearing 17, the duct 32 could be so arranged that it communicates at its end nearest the bearing 1 7 with an appropriate one of the radial grooves 1 9c anywhere between the inner and outer end thereof.

It will be evident that by virtue of the greater volume of the first chamber 21 compared with that of the chamber 25, the bearing 1 7 has potential access to a greater quantity of lubricant than would be the case were it exposed only to lubricant stored in the chamber 25 and not circulated. Further, this lubricant, by virtue of the circulation and the geometry of the two chambers especially the chamber 21, can be kept cooler than would be the case for lubricant confined to a chamber such as 25 Thus, the generally more severe conditions as regards bearing loading which have to be met in respect of bearing 1 7 are catered for more effectively by the lubricating system now described than would be the case by provision only of the chamber 25 in isolation.

In order to avoid unwanted pressure rise in the lubricant circulating system due to temperature rise after the engine has been in operation for some time, a venting means 39 is provided conveniently in association with chamber 21.

This may comprise bellows 41 of elastic material such as neoprene, the base of which 42 is normally pressed onto a seating surrounding a bore 43 in the extension of the crank case, the bellows being contained in a housing 40 having a screw-threaded closure cap 45 bearing on the upper end of the bellows.

Referring now to Fig. 3, this illustrates a modified lubrication system in accordance with the first aspect of the invention hereinbefore referred to.

In this embodiment parts corresponding to those already referred to are designated by corresponding references and the preceding description is to be deemed to apply.

In this embodiment the chamber 25 is extended as indicated at 25a, into the boss 1 9 of the big end of the connecting rod 14 and therefore provides an increased volume for storage of lubricant compared with that which would be available to the bearing 1 7 were such enlargement not provided.

This arrangement avoids the complications of mounting the crank pin 20 rotatably in the crank web 29 as in the specific embodiment disclosed in the British patent specification already referred to, such crank pin here being integral with, or structurally separate from, but secured non-rotatably in or to the web.

Instead of providing a chamber 25a as shown in the embodiment of Fig. 3, it would be possible to make use of the arrangement illustrated in Figs. 4 and 5 in which the bores 1 9 b, grooves 19 a, and grooves 19 c, act as a substitute for the chamber 25a. Similarly the arrangement illustrated in Figs. 6 to 8 (hereinafter described) may likewise be used in this case to perform the function of the chamber 25a, such function being in effect carried out by bores 11 9b and grooves 11 9c. In all cases lubricant is also stored in the cavities afforded by the garter seals 1 8 which contribute to that available for lubrication of the big end bearing.

Although both aspects of the present invention have been specifically described with reference to the drawings as applied to a single cylinder internal combustion engine operating in accordance with a two stroke cycle, it is to be understood that the invention may be applied to a four stroke engine.

As regards the circulatory lubrication system specifically illustrated in Fig. 1, when such a system is applied to a four stroke engine the valve operating mechanism may be lubricated by virtue of enclosure in a chamber which is effectively an extension of the main lubricant chamber 16 or the enlargement 16a. Sealing means may be provided in association with the valve stems substantially as described in the prior British patent specification already .referred to.

Where a four stroke engine is provided with overhead valves, whether operated by push rods from a lower camshaft, or whether operated from an overhead cam shaft, a cover for the rocker for the upper part of the push rod mechanism would be provided on the cylinder head and this may be so arranged as effectively to form an extension of the chamber 1 6 in the sense of containing a reservoir of lubricant. In either overhead valve arrangement the lubricant would reach the valve and rocker assembly for the camshaft and follower assembly via appropriate ducts, for example ducts provided in the guides or passageways through which the push rods operate or ducts provided through the housing or opening in which the chain or gear drive to the camshaft is accommodated.

It will be further understood that the invention may be applied to an assembly of the kind specified arranged and adapted to operate as a gas compressor, for example air compressor, the arrangement of the lubricating system being substantially as shown in Fig. 1.

Referring to the modification shown in Figs.

6 to 8 parts corresponding to those already described with reference to Figs. 4 and 5 are designated by like references with the prefix 1 and the preceding description is to be deemed to apply.

In the modification, bores 11 9b are inclined with respect to the crank pin axis either helically or rectilinearly to promote flow of lubricant through these bores by virtue of a scoop effect. There will be two annular layers of lubricant, one at each end of the big end.

These layers will be subjected to shear by virtue of the drag effect of contact with axially presented faces of the seals 1 8 and the drag effect of contact with the opposing relatively rotating axially presented faces of the big end itself.

Thus, the holes presented where the bores break into the end face at one end of the big end can exert a scoop effect at the trailing boundaries of the holes, thereby promoting lubricant flow as shown by arrows 119d. Also if the radial grooves 11 9c are approximately inclined, instead of being truly radial, the equivalent drag effect will tend to assist lubricant flow as shown by the arrows 11 9d in one direction at one end, and in the other direction at the other end, of the big end.

The invention may be applied to engines having a crankshaft in which the crank pin, or each crank pin, extends between a pair of axially spaced webs, instead of projecting as a cantilever from a single web, and whether such crankshaft is used in a single cylinder engine or an engine having more than one cylinder.

Such an application is illustrated in Fig. 9 in which parts corresponding to those already shown are designated by like references with the prefix 2 and to which the preceding description is to be deemed to apply. The second web 229a of the crankshaft may be a structurally separate part with respect to the remainder of the crankshaft and may be a drive fit or otherwise secured to the crank pin 220.

Claims

1. An assembly of the kind specified which includes a lubrication system for a crankshaft supporting bearing means, and a bearing means at the connection between the connecting rod and crank pin, such system comprising a first lubricant storage chamber at the supporting bearing means, a second lubricant storage chamber at the connecting rod bearing means, a first duct extending through the crankshaft serving to connect the first chamber to the second chamber, a second duct also extending through the crankshaft serving to connect the second chamber to the first chamber to form a lubricant circuit, and means responsive to rotation of the crankshaft to cause lubricant to circulate around the circuit.

2. An assembly according to claim 1 wherein the second lubricant storage chamber moves in an orbit in consequence of crank shaft rotation, having a first, outer, part which is radially beyond the first lubricant storage chamber and having a second, inner, part extending radially inwardly of at least part of the first lubricant storage chamber, the first duct means being so arranged as to connect the first chamber with the outer part of the second chamber, and the second duct being so arranged as to connect the inner part of the second storage chamber with the first chamber.

3. An assembly according to either of claims 1 and 2 wherein there is provided in, or in association with the first chamber, a pressure inducing means which is operable in response to rotation of the crankshaft for causing a pressure gradient to be established along the first duct in a direction to bring about flow of the lubricant from the first chamber to the second chamber, the pressure in the former however being maintained below a value which would prevent delivery of lubricant from the second part of the second chamber back to the first chamber.

4. An assembly according to either of claims 2 and 3 wherein that end of the second duct which communicates with the second part of the second chamber is situated radially inwardly of, or at the same radius as, the end of the second duct which communicates with the first chamber.

5. An assembly according to either of claims 3 and 4 wherein the means for producing a pressure gradient in the first duct comprises a scoop means provided on the crankshaft and rotating therewith for collecting lubricant from the first chamber as the crankshaft rotates and feeding it into that end of the first duct which communicates with the first chamber.

6. An internal combustion engine of the kind specified wherein the second lubricant storage chamber is formed as a cavity in the connecting rod itself, and the crank pin is integral with or fast with the crank web.

7. An assembly of the kind specified sub stantially as hereinbefore described with refer ence to and as shown in Figs. 1 and 2 of the accompanying drawings.

8. An assembly of the kind specified sub stantially as hereinbefore described with refer ence to and as shown in Fig. 3 of the accompanying drawings.

9. An assembly according to either of claims 7 and 8 modified substantially as here inbefore described with reference to and as shown in Figs. 4 and 5 of the accompanying drawings.

10. An assembly according to either of claims 7 and 8 modified substantially as here inbefore described with reference to and as shown in Figs. 6, 7 and 8 of the accompany ing drawings.

11. An assembly according to any one of claims 7 to 10 modified substantially as here inbefore described with reference to and as shown in Fig. 9 of the accompanying draw ings.