GB2105784A - Low-noise-level internal combustion engines - Google Patents

Abstract

Crankcase 5 is connected to internal components of the engine, particularly in the region of big end 10 by means of vibration damping and to some extent torque transmitting mountings 4. These consist of elastomeric material 15 protected from the adverse effects of hot oil by impervious flexible membrane 21,24. <IMAGE>

Description

SPECIFICATION Low-noise-level internal combustion engines The invention relates to internal combustion engines of the kind in which an engine power-unit comprising those parts of the engine which produce or transmit noise, namely cylinders, cylinder head, pistons, connecting rods, crankshaft bearings and crankshaft, connected to the crankcase in an oilwetted region of the engine by a plurality of vibration-damping and, at least partially, torquetransmitting elements. The vibration damping elements comprise elastic material which insulates the crankcase in respect of directly transmitted noise producing vibrations. The vibration-damping elements which support the power unit for torquetransmission relative to the crankcase are secured on one side to the crankcase walls and on the other side to the power unit substantially in the region of the crankshaft axis on the main bearing walls.

In low-noise-level engines of this kind since the torque-transmitting vibration-damping elements are arranged substantially in the region of the crankshaft axis and exposed to the hot mist of lubricating oil which develops in operation of the engine, the choice of material for the torque-transmitting vibration-damping elements is restricted to those elastic materials which have the required degree of resistance to hot lubricating oil. Such an oil-resisting property, particularly in the case of rubber elements, also directly affects the elastic properties of such an element, and therefore, its vibration-damping characteristics. The essential requirement of inherent oil-resistance therefore imposes a restriction in regard to the freedom of choice concerning the elements to be used, which amounts to a certain disadvantage in this known construction.

It is the aim of the present invention to avoid the above-described drawback and, more particularly, to enable an internal combustion engine of the kind specified to be designed in such a way as to allow a free choice of materials for the vibration-damping elements irrespective of their oil-resistance properties.

The present invention consists in an internal combustion engine of the kind in which an engine power-unit comprising those parts of the engine which produce or transmit noise, namely cylinders, cylinder head, pistons, connecting rods, crankshaft bearings and crankshaft, is connected to the crankcase in an oil-wetted region of the engine by a plurality of vibration-damping and at least partially torque-transmitting elements comprising elastic material which insulates the crankcase in respect of directly transmitted noise producing vibrations, where the vibration-damping elements, by which the power unit is supported for torque-transmission relative to the crankcase, are secured on one side to the crankcase walls and on the other side to the power unit substantially in the region of the crankshaft axis on the main bearing walls, characterised in that the torque-transmitting, vibration-damping elements are provided on that side thereof which is directed towards the oil-wetted region of the engine with an oil-resistant flexible covering.

The oil-resistant covering must of course be made of a flexible material but as it is not in use subject to particularly high demands in regard to its elastic properties and its main purpose is to keep all deleterious effects of the hot lubricating oil mist away from the vibration-damping elements themselves, the choice of materials for the damping elements may be governed solely by criteria relating to their most important function, namely that of torque transmission and at the same time assuring relative isolation of the power unit and crankcase in respect of direct transmission of noise-producing vibrations through solid bodies.

At least one of the vibration damping elements may comprise an elastic cushioning member mounted between confronting surfaces substantially parallel to a transverse axis at right angles to the vertical axis of the engine.

Such a vibration damping element may be a cylindrical vibration-damping bush having inner and outer sleeves secured one to the power unit and the other to the crankcase.

The oil-resistant flexible covering may be provided by a membrane secured between an outer retaining ring and an inner retaining ring, the retaining rings being secured one to the power unit and the other to the crankcase.

In an internal combustion engine in which, as is known for example from German OS 29 20 081 (G.B.

published Specification 2 046 356), the torquetransmitting, vibration-damping insulation elements are cylindrical vibration-damping connectors, each secured to the power unit by means of an intermediate piece and axially secured together with an associated connector outer mounting ring in a corresponding bore in the crankcase, a special advantage is obtained, if, according to a further development of the present invention, the oilresistant flexible covering is provided by a membrane, preferably a rubber membrane, vulcanised in place and secured between an outer retaining ring and an inner retaining ring, the outer retaining ring being axially secured, together with the outer connector mounting ring of the connector element; in the bore in the crankcase and the inner retaining ring being secured, together with an inner connector mounting ring of the vibration damper connector element, to the engine power unit. In this case the oil-resistant flexible covering is of similar configuration to the vibration-damping connector element itself, the essential difference residing in that the covering has no torque-transmitting function whatsoever and is required to be elastic only to such a degree as to ensure that the freedom of relative movement between the engine power unit and the crankcase afforded by the torque-transmitting vibration-damping connector elements is not impaired.

Due to the provision of additional, that is separate, elements for the covering, the vibration-damping connector elements themselves may safely continue to be used in the form of conventional massproduced and therefore inexpensive vibrationdamping connectors.

In a modified arrangement the end parts of the outer and inner retaining rings are bonded respectively to the adjacent end parts of the outer and inner sleeves or connector retaining rings so that the damper element together with the membrane assembly forms a single unit. In a further modification the flexible membrane is secured directly to the inner and outer sleeves or connector retaining rings.

According to another embodiment of the invention at least that part of the torque-transmitting vibration-damping elements which consists of an elastic material may be provided, on that end thereof which faces the oil-wetted region of the engine, with a coating of oil-resistant elastic material, such as for example Teflon (Registered Trade Mark). Such a provision obviates all additional constructional outlay in respect of the engine itself. Vibration-damping elements which have been rendered oil-resistant in this particular manner may be used and fitted in exactly the same way as otherwise similar but uncoated elements, thus achieving a considerable simplification in the practical application of the present invention.

The invention will be hereinafter more particularly described with reference to examples of embodiments shown in the drawings.

Figure 1 is a vertical section showing the arrangement of a torque-transmitting, vibration-damping connector element in an internal combustion engine according to the present invention, and Figure 2 is a view corresponding to Figure 1 showing another embodiment of the invention.

The engine power unit of an internal combustion engine, a part of which is shown in Figure 1, comprises the main bearings 2, the crankshaft 3 mounted therein and also the remaining parts of the engine which are subject to direct noise producing vibrations, namely cylinders, cylinder head, pistons and connecting rods, none of which are shown in the drawing, and is connected by means of a plurality of vibration-damping, torque-transmitting elements 4 to the crankcase 5 which is thereby insulated in respect of the direct structural transmission of noise producing vibrations. The main bearings 2 are in each case constructed in two parts and secured by means of bolts 6 to the main bearing walls 7 which extend downwards from the cylinder block.

In this embodiment the vibration-damping elements 4 of the invention are constructed as cylindrical vibration-damping connectors which are secured by means of an intermediate piece 8 to a lug 9 on the upper part 10 of the main bearings 2 and axially secured in bores 11 provided in bosses 12 on the crankcase 5. A rubber element 15 is secured, by vulcanising, between an outer sleeve or mounting ring 13 and an inner sleeve or mounting ring 14, its elastic properties being such as to ensure relative isolation of the power unit 1 and crankcase 5 as far as direct structural transmission of noise producing vibrations is concerned whilst at the same time permitting transmission of torque between these parts.

The inner mounting ring 14 of the vibrationdamping connector element 4 is slipped over the intermediate piece 8 and secured relative to the power unit 1 by means of a clamping bolt 18 adapted to be screwed into a threaded bore 17 in the lug 9 and a corresponding clamping plate 16. The intermediate piece 8 is centred relative to the lug 9 on the upper part 10 of the main bearing 2 by means of a sleeve 19.

Along the upper edge, not shown, the crankcase 5 is provided with an oil-tight seal applied to a mating flange or the like on the power unit 1 which prevents leakage of lubricating oil from the interior of the crankcase 5.

In orderto provide protection forthevibrationdamping connector elements 4 which are mounted in the crankcase walls in the region of the crankshaft axis, and thus in a region which has a very high concentration of hot lubricating oil mist when the internal combustion engine is in operation, from chemical attack by such hot oil mists which normally have a highly deleterious effect on all those rubber compounds which have the required vibrationdamping properties, there is provided an oilresistant flexible covering 21. In the embodiment according to Figure 1 the flexible covering consists of a membrane 24, for example a rubber membrane secured by vulcanising, between an outer retaining ring 22 and the inner retaining ring 23.The outer retaining ring 22 of this covering 21 is mounted together with the corresponding outer mounting ring 13 of the vibration-damping connector element 4 in a bore 11 formed in the wall of the crankcase 5, abutting a shoulder 25 in said bore 11 on the inwardly directed side thereof. The inner retaining ring 23 of the covering 21 is secured together with the corresponding inner mounting ring 14 of the vibration-damping connector element 4 by means of the clamping bolt 18 and clamping plate 16 against a shoulder 26 on the intermediate piece 8.

Due to this arrangement of the flexible oil-resistant covering 21 the demands imposed on the quality of the rubber element 15 in the vibration-damping connectors 4 are reduced purely to the elastic properties thus affording much wider freedom in regard to the optimisation of vibration-damping mountings for mounting the engine power unit 1 in the crankcase 5.

The embodiment of the invention illustrated in Figure 2 differs from that according to Figure 1 only in regard to the actual construction of the oilresistant covering 21. In the embodiment according to Figure 2 the oil-resistant flexible covering is provided by a coating 27 of an oil-resistant elastic material, such as for instance Teflon (Registered Trade Mark), applied to that end of the vibration damping connector elements 4 which faces the oil-wetted region of the engine. Instead of the complete coating on the end of the outer retaining ring 13, inner retaining ring 14 and rubber element 15 on that end thereof which is directed towards the interior of the crankcase 5 as shown in Figure 2, the provision of a coating layer on the rubber element 15 alone would also suffice for the purposesofthe present invention.

In both illustrated examples of embodiments of the invention, the end of bore 11 which is remote from the interior of the crankcase is provided with a cover 28, consisting, for example, of a thermoplas tics material which inhibits noise emission by radiation from the vibration-damping connector elements 4 and their mountings.

In one modified arrangement the outer end parts of the outer 22 and inner 23 retaining rings are bonded to the adjacent end parts of the outer mounting rings 13 and inner mounting ring 14 respectively so that the damping element 4 together with the membrane assembly 21 forms a single unit.

This bonding operation is carried out subsequent to the manufacture of the vibration damper elements 15 and membranes 24 so that flexible or elastic materials having the required individual characteristics can be used.

Claims (11)

1. An internal combustion engine of the kind in which an engine power-unit comprising those parts of the engine which produce or transmit noise, namely cylinders, cylinder head, pistons, connecting rods, crankshaft bearings and crankshaft, is connected to the crankcase in an oil-wetted region of the engine by a plurality of vibration-damping and at least partially torque-transmitting elements comprising elastic material which insulates the crankcase in respect of directly transmitted noise producing vibrations, wherein the vibration-damping elements, by which the power unit is supported for torquetransmission relative to the crankcase, are secured on one side to the crankcase walls and on the other side to the power unit substantially in the region of the crankshaft axis on the main bearing walls, characterised in that the torque-transmitting, vibration-damping elements are provided on that side thereof which is directed towards the oil-wetted region of the engine with an oil-resistant flexible covering.

2. An internal combustion engine according to claim 1 wherein at least one of the vibration damping elements comprises an elastic cushioning member mounted between confronting surfaces substantially parallel to a transverse axis at right angles to the vertical axis of the engine.

3. An internal combustion engine according to claim 1 wherein at least one of the torquetransmitting, vibration-damping elements is a cylindrical vibration-damping connector having inner and outer sleeves secured one to the power unit and the other to the crankcase.

4. An internal combustion engine according to claim 3 wherein the oil-resistant flexible covering is provided by a membrane secured between an outer retaining ring and an inner retaining ring, the retaining rings being secured one to the power unit and the other to the crankcase.

5. An internal combustion engine according to claim 1, in which the torque-transmitting, vibrationdamping elements are cylindrical vibration-damper connectors each secured by means of an intermediate piece to the power unit and axially secured together with an associated connector outer mounting ring in a corresponding bore in the crankcase, wherein the oil resistant flexible covering is provided by a membrane secured between an outer retaining ring and an inner retaining ring, the outer retaining ring being axially secured together with the outer connector mounting ring of the vibration-damper element in the corresponding bore in the crankcase and the inner retaining ring being secured together with an inner connector mounting ring of the vibration damping element to the power unit.

6. An internal combustion engine according to claim 4 or claim 5 wherein the membrane is of rubber and secured to the inner and outer retaining rings by vulcanising.

7. An internal combustion engine according to any of claims 4 to 6 wherein the end parts of the outer and inner retaining rings are bonded respectively to the adjacent end parts of the outer and inner sleeves or connector mounting rings so that the damper element forms a single unit.

8. An internal combustion engine according to claim 1 or claim 3, wherein at least that part of each torque transmitting vibration-damping element which consists of elastic material is provided on that side thereof which faces the oil-wetted region of the engine with a coating of oil resistant flexible material.

9. An internal combustion engine according to claim 3 wherein the flexible covering is provided by a membrane secured directly to the inner and outer sleeves.

10. An internal combustion engine substantially as hereinbefore described with reference to and as shown in Figure 1 of the accompanying drawings.

11. An internal combustion engine substantially as hereinbefore described with reference to and as shown in Figure 2 of the accompanying drawings.