GB2318828A

GB2318828A - An internal combustion engine cylinder block has an oil-filled clearance between block and liner

Info

Publication number: GB2318828A
Application number: GB9622873A
Authority: GB
Inventors: John Anthony Dawson
Original assignee: MG Rover Group Ltd
Current assignee: MG Rover Group Ltd
Priority date: 1996-11-02
Filing date: 1996-11-02
Publication date: 1998-05-06
Also published as: GB9622873D0

Abstract

An engine cylinder block 10 is disclosed in which pre-finished cylinder liners 12A, 12B, 12C, 12D are fitted into cylinder bores 11A, 11B, 11C, 11D with a narrow clearance therebetween. The gap between the liners 12A, 12B, 12C, 12D and the bores 11A, 11B, 11C, 11D is sealed top and bottom to form respective hydraulic chambers 18A, 18B, 18C, 18D. An oil feed 300 supplies oil galleries 301, 302 which fill the chambers 18A, 18B, 18C, 18D with engine oil and the thin film oil jacket thus produced opposes distortion of the liners 12A, 12B, 12C, 12D by a squeeze film effect.

Description

An Internal Combustion Engine Cvlinder Block Assemblv This invention relates to internal combustion engines and in particular to the assembly of a cylinder liner into the cylinder block of such engines.

It is known to fit cylinder liners into the cylinder block of an internal combustion engine by pressing the liner into an interference fit cylinder liner housing bore machined out of the cylinder block. The liners can be distorted by a variety of factors such as: the interference fit itself; cylinder head clamping load; piston movement; and by forces generated during the combustion process. The liner distortion thus produced can result in piston blow-by, piston ring friction and reduced combustion efficiency, especially if the liner is pre-finished.

It is an object of this invention to provide a cylinder block for an internal combustion engine with reduced liner distortion.

According to the invention there is provided a cylinder block assembly for an internal combustion engine comprising a cylinder block defining a cylinder liner housing bore and a cylinder liner, in which the cylinder liner is fitted into the cylinder liner housing bore with a radial clearance therebetween sealed at both ends to form a hydraulic support chamber which contains a hydraulic fluid providing a thin film support jacket for the cylinder liner. The support jacket provides support for the liner to counteract distortion during engine running by opposing such distortion with resistance to the displacement of the thin film of hydraulic fluid in the hydraulic support chamber, conveniently referred to herein as a "squeeze film effect".

The cylinder block assembly may further comprise a hydraulic supply passage through which the hydraulic fluid is supplied to the hydraulic support chamber and conveniently the hydraulic fluid may be the engine lubricating oil which may advantageously be supplied by an engine oil pump through the supply passage.

The cylinder block assembly may further comprise additional cylinder liner housing bores and liner assemblies with hydraulic support chambers all hydraulically connected to the engine oil pump through further supply passages. Additionally, the cylinder block assembly may further comprise plural supply passages between two hydraulic support chambers.

The cylinder liner may be supported by the cylinder block at the top of the cylinder liner housing bore, which type of liner is known in the art as a "top-hung liner". The invention could also be applied to a cylinder block having mid-hung cylinder liners.

Conveniently, the liner may be sealed to the cylinder liner housing bore by a sealing means to form the hydraulic support chamber.

Advantageously, the sealing means may comprise an annular bead of sealing compound. Furthermore, there may be an upper and a lower sealing means either of which may be applied to the cylinder liner housing bore or to the cylinder liner before the assembly of the cylinder liner into the cylinder liner housing bore.

Part of the cylinder liner may be in direct contact with an engine cooling fluid, and is preferably the part of the cylinder liner which in use is immediately adjacent the cylinder head of the engine. Advantageously, the part of the cylinder liner may comprise a flange which in use is interposed between the cylinder head and an upper flange face of a recess in the cylinder block.

The invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 is a cross-section through one cylinder of a four cylinder internal combustion engine cylinder block according to the invention showing components during assembly; Figure 2 is a view similar to Figure 1 showing the components after assembly; Figure 3 is a diagrammatic cross-section through the assembled cylinder block showing certain oil passages; and Figure 4 shows the oil passages sectioned on line W to IV in Figure 3.

Referring to Figure 1, a cylinder block 10 defines a cylinder liner housing bore 11A which is shown on one side of its centre-line CL. A cylinder liner 12A is shown part assembled into the bore 11A and has a flange 13 at its upper end. The block 10 has an upper flange face 14 which is recessed into the block 10 around the bore 11A by the thickness of the flange 13.

An upper annular bead of sealant 15 is applied around the liner 12A under the flange 13 and a lower annular bead of sealant 16 is applied to the wall of the bore 11A towards its lower edge. The liner 12A has an outward facing chamfer 17 around its lower edge.

The liner 12A is then inserted into the bore 11A until the flange 13 is brought into abutment with the face 14, as shown in Figure 2. In this manner, the liner 12A is supported by the face 14 and is held in place by a clamping force applied through the cylinder head and head gasket (neither shown). This form of liner installation is known in the art as a "top-hung liner".

A coolant chamber 19 is formed between an outer face 20 of the liner 12A and the block 10 around the upper end of the bore 11A such that the outer face 20 of the flange 13 is in direct contact with coolant in the chamber 19.

A radial clearance C in the order of 0.05 mm to 0.075 mm exists between the outer radius of the liner 12A and the radius of the bore 11A.

As the liner 12A is inserted into the bore 11A, the upper sealant bead 15 is deformed and creates an upper seal 15A across the clearance C between the liner 12A and the bore 11A. The chamfer 17 rides over the lower sealant bead 16 and creates a lower seal 16A across the clearance C between the liner 12A and the bore 11A. The upper and lower seals 15A, 16A transform the clearance C into an annular hydraulic chamber 18A which surrounds the liner 12A from the flange 13 down to the chamfer 17.

The upper seal 15A also serves to seal the hydraulic chamber 18A from the coolant chamber 19.

Figure 3 shows the complete cylinder block 10 and all four bores 11A, 11B, 11C, 11D into which have been assembled their respective liners 12A, 12B, 12C, 12D. The clearance C between each of the liners 12A, 12B, 12C, 12D and their bores 11A, 11B, 11C, 11D is sealed in similar fashion to Figure 2 (seals not shown) to form respective hydraulic chambers 18A, 18B, 18C, 18D. In Figure 3, the coolant chambers 19 are omitted for convenience.

A hydraulic supply means is shown in the form of an oil feed 300 which is supplied with engine oil at pressure by the engine oil pump (not shown).

A hydraulic supply passage in the form of upper oil galleries 301A, 301B, 301C, 301D connects the uppermost part of each hydraulic chamber 18A, 18B, 18C, 18D to adjacent chambers and to the oil feed 300. A lower oil gallery 302A, 302B, 302C interconnects the lowermost part of the hydraulic chambers 18A, 18B, 18C, 18D to adjacent chambers. A restrictive oil bleed 303 connects the uppermost part of the hydraulic chamber 18D (furthest from the oil feed 300) to an oil return 304 to an engine sump (not shown).

The hydraulic chambers 18A, 18B, 18C, 18D are shown filled with engine oil.

When an engine having a block 10 according to the invention is first assembled, the hydraulic chambers 18A, 18B, 18C, 18D are full of air.

When the engine is first started, it bleeds the air out through the oil bleed 303 and the air will be displaced by engine oil at engine oil temperature and pressure.

When the engine is operated after the bleeding is complete, the liners will be hydraulically supported by the thin film oil jacket in the chambers 18A, 18B, 18C, 18D. The engine oil is supplied by the oil feed 300 at the pressure available to the engine lubrication system and all the time the engine is operating, the oil jacket will exist. In between engine running cycles, the oil jacket will be substantially retained by surface tension and the high position of the oil supply 301A and restrictive oil bleed 303.

Subsequent engine running re-establishes the oil film in similar fashion to that described above.

Movement or distortion of the liners 12A, 12B, 12C, 12D caused, for example, by mechanical or combustion forces, is damped by the oil film support provided by the oil jacket in the hydraulic chambers 18A, 18B, 18C, 18D. The resistance to liner movement and distortion results from the squeeze film effect created as a liner 12A, 12B, 12C, 12D moves sideways and tries to force the oil around to the opposite side via the narrow cavity C forming the chambers 18A, 18B, 18C, 18D. The incompressible nature of the oil opposes the movement and distortion by a squeeze film effect.

Cooling of the liners 12A, 12B, 12C, 12D is improved over conventional dry-liners by the provision of a direct contact between the liners 12A, 12B, 12C, 12D and coolant in the coolant chambers 19 and direct contact with the cylinder block 10 on the upper flange faces 14. This is particularly advantageous since such contact is at the cylinder head end of the liners and is in the hottest region of the liner above the top ring travel of the piston (not shown).

Heat transfer from the liners 12A, 12B, 12C, 12D into the block 10 over the piston ring travel area is also improved by the provision of a heat path through the oil film.

The filling of the chambers 18A, 18B, 18C, 18D could be done by methods different from that disclosed herein. The chambers 18A, 18B, 18C, 18D could be filled from a bottom feed into the lower oil gallery 302A, in which case it would be advantageous to include a non-return valve in the lower oil gallery 302A at the take off from the oil feed 300 and it would be possible to delete the take off from the oil feed 300 to the upper gallery 301A or to use it as the bleed passage. Retention of oil in the chambers 18A, 18B, 18C, 18D could be further improved by specific oil pump design, for example by using a positive displacement oil pump to reduce drain-back. It would also be possible to pre-fill the chambers 18A, 18B, 18C, 18D on assembly of the cylinder block 10.

Claims

1. A cylinder block assembly for an internal combustion engine comprising a cylinder block defining a cylinder liner housing bore and a cylinder liner, in which the cylinder liner is fitted into the cylinder liner housing bore with a radial clearance therebetween sealed at both ends to form a hydraulic support chamber which contains a hydraulic fluid providing a thin film support jacket for the cylinder liner.

2. A cylinder block assembly according to Claim 1 further comprising a hydraulic supply passage through which the hydraulic fluid is supplied to the hydraulic support chamber.

3. A cylinder block assembly according to Claim 1 or Claim 2 wherein the hydraulic fluid is the engine lubricating oil.

4. A cylinder block assembly according to Claim 3 wherein the hydraulic fluid is supplied by an engine oil pump through the supply passage.

5. A cylinder block assembly according to any preceding Claim further comprising additional cylinder liner housing bores and liner assemblies with hydraulic support chambers all hydraulically connected to the engine oil pump through further supply passages.

6. A cylinder block assembly according to Claim 5 further comprising plural supply passages between two hydraulic support chambers.

7. A cylinder block assembly according to any preceding Claim wherein the cylinder liner is supported by the cylinder block at the top of the cylinder liner housing bore.

8. A cylinder block assembly according to any preceding Claim wherein the liner is sealed to the cylinder liner housing bore by a sealing means to form the hydraulic support chamber.

9. A cylinder block assembly according to Claim 8 wherein the sealing means comprises a bead of sealing compound.

10. A cylinder block assembly according to Claim 8 or Claim 9 wherein the sealing means is applied to the cylinder liner housing bore before the assembly of the liner into the cylinder liner housing bore.

11. A cylinder block assembly according to Claim 8 or Claim 9 wherein the sealing means is applied to the cylinder liner before the assembly of the cylinder liner into the cylinder liner housing bore.

12. A cylinder block assembly according to any preceding claim wherein part of the cylinder liner is in direct contact with an engine cooling fluid.

13. A cylinder block assembly according to claim 12 wherein said part of the cylinder liner is in use immediately adjacent the cylinder head of the engine.

14. A cylinder block assembly according to claim 13 wherein said part of the cylinder liner comprises a flange which in use is interposed between the cylinder head and an upper flange face of a recess in the cylinder block.

15. A cylinder block assembly substantially as described herein with reference to the accompanying drawings.