GB2265181A - I.c.engine cylinder liner support - Google Patents

Abstract

A liner has a top boss which is an interference fit in the engine block, and a mid-stop flange. The portion of the liner between the top boss and the flange forms a wall of a coolant passage and the portion of the liner below the flange is at least 30% of the length of the liner, and has a groove 17 in the outer surface thereof adjacent to its bottom end. In the groove is a resilient radial support for the bottom end of the cylinder liner to abut a surrounding cylinder block surface. The support comprises an undulating and flexible inner core 20 which is a sliding fit within a coiled spring 22. The core and spring may be of steel and dimensions are disclosed. <IMAGE>

Description

Cylinder Liners This invention relates to cylinder liners, and in particular to cylinder liners which are designed as wet liners with a mid-stop flange incorporated into the liner.

For convenience in this specification and the accompanying claims, each constituent cylinder liner in an engine block in accordance with the present invention is considered to have an axis of symmetry which extends vertically above a co-operating crankshaft. The end of the liner remote from the crankshaft is referred to as the top or upper end, and the other end (closest to the crankcase) is referred to as the lower or bottom end. Approximately from the level of the mid-stop flange to the upper end of the liner is considered the outer portion of the liner, and the remaining portion from said mid-stop flange level to the bottom end is considered the inner portion of the liner.

However, it will be understood that references describing the relative positions of the ends, and of the two constituent portions, of any arrangement within an engine block of a liner in accordance with the present invention, are included in the corresponding references given above with respect to the arrangement of a liner extending vertically above the crankshaft.

Further, the term radial, or radially-extending, is used in respect of any distance, or feature, extending in any direction in a plane at right angles to the axis of the cylinder liner; and the term axial, or axially-extending, is used in respect of any distance, or feature, extending parallel to the liner axis.

A cylinder liner of the general type to which the present invention relates is described and claimed in UK Patent No 2 035 452. This specification describes a cylinder liner which has, in combination, a series of features which include a top boss on the liner the top boss having an axially extending cylindrical surface forming an interference fit with the engine block when in position; a mid-stop flange with a surface which extends radially outwardly from the liner and engages a complimentary radially extending ledge in the engine block; an upper portion between the top boss and the mid-stop flange which forms a wall of a coolant passage, the axial length of which passage wall is not more than 30% of the axial length of the liner; and an inner portion which has an axial length of at least 30% of the axial length of the liner, and which is wholly free of direct supporting and heat conducting contact with the engine block.

In practice this liner design suffers from the disadvantage that lack of radial support at its bottom end allows the inner portion of the liner to ovalise during use to an undesirable extent, and under extreme conditions this is liable to lead to cracking of the liner.

From a practical point of view, however, it is difficult for the cylinder block to provide an adequate support at the bottom end of the liner. The bottom end of the liner is to be inserted into the block first, and the liner has an interference fit on the top boss, as stated above. If the bottom end of the liner is to be supported by direct contact with the cylinder block, when the required interference fit is provided at the top of the liner distortion of the internal surface of the liner may occur.

Further, the bottom end of the liner has to be capable of passing through the mid liner stop provided by the cylinder block. Thus it is required that the diameter of the bottom end of the liner has to be less than the diameter of the aperture through the mid liner stop, and the diameter of this aperture has to be less than the diameter of the midstop flange on the liner. The diameter of the mid-stop flange has to be less than the diameter of the top boss provided by the liner. Hence, it is dictated that the liner wall generally has to be tapered from the top end to the bottom end.

However, in UK patent application No. 91 24140 there is described and claimed a modified arrangement for a liner of the kind described and claimed in UK patent No. 2,035,452, the modification comprising providing a resilient support means located in a groove in the outer surface of the liner adjacent to the bottom end of the liner. The support means is of a form which, when the liner is fitted in the associated cylinder block, is compressed by contact with a substantially annular radial support section provided by the associated cylinder block for the bottom end of the liner. Such a modified arrangement for the liner has adequate radial support at its bottom end, and yet is readily fitted in the engine block.The embodiment of resilient support means particularly described, and illustrated in UK patent application No. 91 24140 is fashioned from a strip of spring steel of a width which fits comfortably in the groove in the liner, and is of a corrugated shape. The corrugations are substantially square section, the bases of the corrugations are seated in the base of the groove, the sides of the corrugations extend approximately radially relative to the cylinder liner, each radially outer part of the corrugations is provided with a tang, and the sides are of a length so that only the tangs extend beyond the liner surface , the tangs to be pressed against the bottom end support section of the cylinder block.

It is an object of the present invention to provide a novel and advantageous construction for resilient support means located in a groove in the outer surface of a liner referred to above, and adjacent to the bottom end of the liner.

Thus, according to the present invention there is provided in an internal combustion engine, having a block containing a cylinder cavity extending between an engine head and a crankshaft to which a piston is connected for reciprocating travel within the cylinder cavity, a liner stop positioned intermediate the ends of the cylinder cavity, a liner coolant passage adapted to provide coolant to the outer surface of a cylinder liner, and a substantially annular radial support section for a bottom end of the liner, a substantially cylindrical, replaceable cylinder liner having top and bottom ends which comprises: i) a top end boss having a cylindrical axially extending outer surface forming an interference fit within the cylinder cavity, ii) a mid-stop flange having a radially extending surface which engages the liner stop in the cylinder cavity, iii) a portion between said top boss and said mid-stop flange which forms a wall of the coolant passage, iv) a substantially cylindrical portion below said mid stop flange which forms at least 30% of the axial length of the liner, v) an annular groove in an outer surface of the liner adjacent to said bottom end of the liner, vi) a resilient support means located in said groove, the support means having a form which, when the liner is fitted in said block, is compressed by contact with the substantially annular support section, and vii) the resilient support means comprises an annular member having a composite construction, with a flexible inner core in the form of a strip undulating in the plane in which the annular member lies in the groove adjacent to the bottom end of the liner, the undulating strip is a sliding fit within an outer sheath in the form of a coiled spring, and when the undulating strip is within the coiled spring.

In order that the resilient support means is located in a satisfactory manner in the groove adjacent to the bottom end of the liner the coiled spring is required to be a sliding fit in the groove at least before the liner is inserted into the cavity in the associated cylinder block.

Thus, the coiled spring holds the flexible undulating strip in the required way in the groove.

The radially outer parts of the undulating resilient support means are required to protrude beyond the groove, when the radially inner parts of the support means are contiguous with the base of the groove, and so that the support means is compressed, as required, by contact with the support section for the bottom end of the liner.

The arrangement for the resilient support means in accordance with the present invention is advantageous in that the exposed portions of the support means protruding beyond the groove are parts of the coiled spring, facilitating the insertion of the bottom end of the liner into the associated cylinder block. In particular, when the protruding portions of the support means initially contact a portion of the cylinder block, whilst the liner is being inserted into the block, further passage of the liner towards its final position, without damage to the resilient support means, is facilitated because the contact is with the coiled spring which is flexible in all directions, and because progressive compression of the resilient support means occurs.

The arrangement of the resilient support means in accordance with the present invention also is advantageous because it enables the inner undulating core strip not to extend around the whole of the circumference of the groove, but to be supported within a coiled spring which extends further around the whole of the circumference of the groove. Thus, when the resilient support means is not compressed the two ends of the inner undulating core strip are spaced apart. These ends of the flexible strip are to be displaced towards each other when the support means is compressed, the flexible strip extending circumferentially relative to the coiled spring. Hence, the support means may be compressed at least until the ends of the flexible strip abut within the coiled spring.

Conveniently, the arrangement is such that there is a significant pressure between the bottom end of the liner and the cylinder block when the liner is inserted into its final position in the block.

The ends of the coiled spring may be secured together, in any convenient way. In one such arrangement one end of the spring is tapered and is secured to the other end by being inserted therein, both ends of the coiled spring providing co-operating screw threads. The ends are secured by one end being rotated in the appropriate direction relative to the other end.

The coiled spring may be of circular section metal wire.

In addition, or alternatively, the undulating strip is of circular section metal wire.

The preferred material for the resilient support means is steel. When at least the coiled spring is of a heat conductive material it is ensured that the support means does not form a thermal barrier between the cylinder liner and the bottom end support section of the block.

The substantially annular radial support section for the bottom end of the liner may be configured to permit engine oil to drain passed the resilient support means, for example, provided that sufficient of the support section is present to provide support against excessive ovalisation in practice. Preferably the support section is present at those locations on the block which are opposite to the thrust and non-thrust faces of the liner, which faces are centred in the plane within which a connecting rod will move when it is attached to a piston located in the liner, said plane also being perpendicular to the axis of rotation of the crankshaft of the engine.

The invention will now be described in more detail, by way of example only, with reference to the accompanying drawings.

Figure 1 is a side view of a cylinder liner in accordance with the invention at the time of fitting, partly in section, the sectional part of the figure also showing schematically in section adjacent portions of the engine block, Figure 2 is an enlarged view of a fragment of figure 1 showing resilient support means provided in a groove at the bottom end of the liner, and being in contact with the engine block, the support means having a composite construction including, in accordance with the present invention, an undulating flexible strip which is a sliding fit within a coiled spring, to provide an annular member, Figure 3 is a plan view of the resilient support means of figures 1 and 2, Figure 4 is a fragmentary, partly sectioned, representation of the support means when included in the groove at the bottom end of the liner, and Figure 4A corresponds to figure 4 but is of a different portion of the annular member comprising the support means, this figure showing the ends of the coiled spring secured together, and the ends of the undulating strip being spaced apart.

As shown in figure 1 a cylinder liner has a smooth cylindrical inner surface 2, against which a piston is to run, and also has an outer surface profile with several features. The top end of the cylinder liner 1, which is adjacent to a cylinder head (not shown) when in an engine, has a top boss 3 with an axially extending cylindrical outer surface 4 which makes an interference fit with an engaging section 5 of the engine block when the liner is in position in the cylinder cavity. Adjacent the mid-length of the liner is located a mid-stop flange 6, the lower surface 7 of which extends radially outwardly from the liner axis, and forms a sealing, and axially locating, engagement with an annular liner stop 8 in the engine block.

Between the top boss 3 and the mid-stop flange 6 lies a portion of the liner 9 which forms one wall of a channel 10 for coolant for the liner.

This coolant channel 10 is sealed at the top of the liner by the interference fit between the top boss 3 and engaging block section 5, with a back-up seal being provided in the engine by a cylinder head gasket (not shown). At the mid-stop flange the coolant channel is sealed first by the engagement of the lower flange surface 7 with the annular liner stop 8. A second seal is provided by means of a rubber sealing ring 11 located in a groove 12 in the liner below the mid-stop flange 6. The rubber sealing ring 11 seals against an annular sealing surface 13 provided in the engine block below the liner stop 8. A second groove 14 is provided on the liner surface below the groove 12 and may be used for further sealing material if required.

An inner portion 15 of the liner extending from below the seal or seals beneath the mid-stop flange 6 has an accurately defined register 16 on the bottom end of the liner. Within this register 16 there is provided a groove 17 extending around the liner and containing an annular member comprising resilient support means 18.

The support means 18 is shown in more detail in Figures 2 to 4, and as shown in Figures 1 and 2 a support section 19 for the bottom end of the liner is provided within the engine block adjacent the bottom register 16 on the liner.

The support means 18 has a composite construction and includes a strip of steel 20 formed into undulations in the plane in which the support means extends when located in the groove 17. The support means 18 is of a width which will fit comfortably into the groove 17 (Figure 2), comprising a sliding fit in the groove when the support means is not compressed, and will be seated on the base 21 of the groove. The base 21 of the groove conforms substantially to the shape of the support means 18, being semi-circular in cross-section. The strip 20 is a sliding fit within an outer sheath comprising a coiled spring 22 also of steel.

As illustrated in Figure 4A, the ends 25 and 26 of the coiled spring 22 are secured together by one end 25 of the spring being tapered and inserted in the other end 26.

Both ends of the spring provide co-operating screw threads, and the ends are secured by one end being rotated in the appropriate direction relative to the other end.

Alternatively, the ends of the spring are secured together in any convenient way, for example, by spot welding; or may not be secured together. The arrangement is such that when the support means 18 is not compressed by contact with the cylinder block the two ends 27 and 28 of the inner undulating core strip 20 are spaced apart within the coiled spring 22. The so completed resilient support means 18 is an undulating composite annular member, corresponding to the shape of the strip 20. The flexibility of the inner core strip 20 of the means 18 illustrated allows the means 18 to be expanded to be fitted into the groove 17 at the bottom end of the cylinder liner.

When fitted in the groove 17 at the bottom end 16 of the liner 1 the radially outer parts of the undulating support means 18 protrude beyond the groove as shown in Figure 4.

The exposed parts of the support means 18 beyond the groove 17 are portions of the coiled spring 22. Thus, when the protruding parts of the support means initially contact a portion of the cylinder block, whilst the liner is being inserted into the block, the resilient support means becomes compressed. The arrangement is such that an upwardly directed curved portion of the coiled spring 22 is contacted by the cylinder block so that inevitably there is progressive compression of the resilient support means as the liner is inserted into the block; further passage of the liner towards its final position does not cause damage to the resilient support means; and the insertion of the liner into the block is facilitated.When the liner is being inserted into the cylinder block, such contact between the resilient support means and the cylinder block may occur above the bottom support section 19 of the block, in addition to the bottom support section. Intermediate between each such contact the resilient support means may not be compressed.

Because the ends 27 and 28 of the flexible undulating strip 20 within the coiled spring 22 are spaced apart when the resilient support means 18 is not compressed, when the support means is compressed by contact with the cylinder block, the ends 27 and 28 of the strip 20 are displaced towards each other, the flexible strip extending circumferentially relative to the coiled spring 22. The support means 18 may be compressed at least until the ends 27 and 28 of the flexible strip 20 abut within the coiled spring 22. Hence, there is a significant pressure between the bottom end 16 of the liner and the co-operating part 19 of the cylinder block when the liner is inserted into its final position in the block.

In the illustrated embodiment both the coiled spring 22 and the undulating strip 20 comprise circular section wire, and the coiled spring also is circular in cross-section, but other cross-sectional shapes are possible. If the undulating strip does not have a circular cross-section the coiled spring may not be circular in section, but instead conforms to the cross-sectional shape of the strip.

The coiled spring and/or the undulating strip may be of a material other than steel, which material may not be metallic. However, if the material of at least the coiled spring is heat conducting a heat transfer path between the cylinder and the cylinder block is provided thereby.

For the sake of clarity the shape of the composite support means 18 is exaggerated in the Figures. In particular, the amplitude of the undulations of the composite support means is shown to be much greater than would be provided.

It is required that each portion of the composite support means 18 contiguous with the base 21 of the groove 17 does not protrude beyond the groove.

In one particular embodiment of the resilient support means, the outside diameter of the coiled spring is 2.9 millimetres, and is of wire 0.5 millimetre in diameter.

The undulating strip is of wire 0.6 millimetre in diameter.

When the resilient support means is not compressed it protrudes 0.5 millimetre beyond the groove adjacent to the bottom end of the liner, which groove has a section 3.0 millimetres wide, and 3.0 millimeters deep at the bottom of its base. The gap between the bottom register of the liner and the co-operating support section provided by the engine block is 0.2 millimetre.

The arrangement is such that, when the liner is in position in an engine, the support means 18 is compressed by contact with the support section 19, and the section 19 supports ,the bottom register 16 of the liner.

Since the liner 1 is fitted into the engine block from the top, when fitting, the bottom register 16 has to pass through the annular liner stop 8; and into the support section 19, whilst providing the interference fit between the cylindrical outer surface 4 and the engaging sections 5 of the engine block. This is readily achieved with the liner of the present invention provided that proper attention is paid to the overall diameters of the various parts of the liner and the support means 18.

It will be understood that it is desirable that engine oil be able to pass the support means 18. Thus, for the liner shown in Figures 1 and 2 the bottom support section 19 in the block need not be a continuous annulus, so that passages (not shown) are left for oil to pass freely out from cavity 30 into the crankcase region. However, the bottom support section 19 must be arranged to provide the required radial support for the bottom end of the liner adjacent those zones of the liner which are the thrust and non-thrust faces. These faces are centred in or adjacent to the plane in which the piston connecting rod is moving, and which plane is perpendicular to the axis of rotation of the crankshaft of the engine.

Claims (6)

1. In an internal combustion engine, having a block containing a cylinder cavity extending between an engine head and a crankshaft to which a piston is connected for reciprocating travel within the cylinder cavity, a liner stop positioned intermediate the ends of the cylinder cavity, a liner coolant passage adapted to provide coolant to the outer surface of a cylinder liner, and a substantially annular radial support section for a bottom end of the liner, a substantially cylindrical, replaceable cylinder liner having top and bottom ends which comprises:: i) a top end boss having a cylindrical axially extending outer surface forming an interference fit within the cylinder cavity, ii) a mid-stop flange having a radially extending surface which engages the liner stop in the cylinder cavity, iii) a portion between said top boss and said mid-stop flange which forms a wall of the coolant passage, iv) a substantially cylindrical portion below said mid-stop flange which forms at least 30% of the axial length of the liner, v) an annular groove in an outer surface of the liner adjacent to said bottom end of the liner, vi) a resilient support means located in said groove, the support means having a form which, when the liner is fitted in said block, is compressed by contact with the substantially annular support section, and vii) the resilient support means comprises an annular member having a composite construction, with a flexible inner core in the form of a strip undulating in the plane in which the annular member lies in the groove adjacent to the bottom end of the liner, the undulating strip is a sliding fit within an outer sheath in the form of a coiled spring.

2. A replaceable cylinder liner as claimed in claim 1 in which one end of the coiled spring is tapered and is secured to the other end of the coiled spring by being inserted therein, both ends of the coiled spring providing co-operating screw threads.

3. A replaceable cylinder liner as claimed in claim 1, or claim 2, in which the coiled spring is of circular section metal wire.

4. A replaceable cylinder liner as claimed in claim 1, or claim 2, or claim 3, in which the undulating strip is of circular section metal wire.

5. A replaceable cylinder liner as claimed in any one of the preceding claims, in which said substantially annular radial support section for the bottom end of the liner is configured to permit engine oil to drain passed the resilient support means.

6. A replaceable cylinder liner substantially as described herein with reference to, and as illustrated in, the accompanying drawings.