The present invention relates to an arrangement in accordance with what is specified in the preamble of attached patent claim 1. The invention is applied advantageously to internal combustion engine units of the compound type for vehicles, comprising an internal combustion engine, a turbine driven by the engine's exhaust gases, and a transmission arranged between the turbine and a crankshaft issuing from the engine, which transmission comprises a hydrodynamic coupling flushed through with oil.

Prior art

10

Designers of internal combustion engines have for a long time attempted to obtain, to the greatest possible extent, from the engine's exhaust gases the llϊ-4 energy which would otherwise be lost. A customary way of doing this is to equip the engine with a so-called turbocharger consisting of a turbine which

15 is driven by the exhaust and is mechanically coupled to a compressor designed to compress the combustion air for supercharging the engine. Ever since their appearance 40 to 50 years ago, turbochargers have been developed and refined and have thereby attained a high leve ¹ _ ^•' adjustability and operational reliability. Nevertheless, a large amount of

20 energy still remains in the exhaust-gases after leaving the turbine.

A method for utilising at least some of this surplus energy is to arrange, in series with and downstream of this first turbine, a second turbine driven by the exhaust gases. If this turbine is in some way coupled so that it transmits 25 mechanically some of the surplus energy to the crankshaft of the engine or to transmissions connected thereto, a turbocompound system is obtained.

Such systems are previously known, for example from American Patent Specification 4,586,337 (US Cl. 60-605) and published international patent 30 application 86/00,665 (IPC4 Cl. F02B 41/10, 37/00, 67/00). These two specifications illustrate exhaust turbines which, via a long shaft and a hydrodynamic coupling, transmit the energy obtained from the exhaust to the front timing gears of a camshaft.

The hydrodynamic coupling is intended to isolate the torsional vibrations occurring in the exhaust turbine from those in the engine. In SAE Transactions Volume 62, pages 276-277, 1954, a turbocompound engine designed for aviation purposes and developed by Curtis-Wright is shown. This 18-cylinder engine has three exhaust gas turbine sections which, via a hydrodynamic coupling, obtain surplus energy and transmit it to a crankshaft. The coupling is fed from the lubricating oil system of the engine and is supplied with oil via its input shaft.

In these turbocompound systems it is important to minimize the losses in the transmission between the exhaust gas turbine and the crankshaft in order to ensure that the surplus energy obtained from the exhaust gases via the turbine will contribute a real additional driving force on the crankshaft. It is preferable to use the lubricating oil ofthe engine as the drive medium in the hydrodynamic coupling, since bearings in the hydrodynamic coupling can also be lubricated at the same time, and the engine's lubricating oil pump can be used to keep the hydrodynamic coupling filled and continuously flushed for carrying off heat generated in the coupling.

The main bearings in the hydraulic coupling bear, on the one hand, the turbine wheel in the pump wheel and, on the other hand, the stationary part ofthe coupling in either of the turbine wheel orthe pump wheel. Upon steady running, the bearings which bearthe turbine wheel in the pump wheel are subjected only to the slip prevailing in the hydraulic coupling between pump wheel and turbine wheel. These bearings which bearthe turbine wheel in the pump wheel can therefore be called low-speed bearings, which are subjected to higher speeds only in the event of transient phenomena, especially in the event of instantaneous torque changes on the input shaft to the pump wheel. The bearings which bear either ofthe pump wheel or turbine wheel in the stationary part of the coupling are continuously subjected, when running, to considerably higher speeds. These bearings can therefore be called high-speed bearings.

The principle of supplying lubricating oil/drive fluid to the working chamber of a hydrodynamic coupling through a stationary part in the coupling via main bearings is known per se from Patent Specifications US, A, 3,058,296, US,A,3,136,129 and FR,E,91671.

FR,E,91671 illustrates a solution where the coupling's low-speed bearings, bearing the turbine wheel in the pump wheel, are flushed through with oil, which is then conveyed to the working chamber of the coupling. The high¬ speed bearing, however, is completely without through-flowing lubrication.

In US,A,3,058,296 and US,A,3,136,129 both the high-speed and low-speed bearings are flushed through with all the oil/hydraulicfluid which is to be conveyed to the working chamber of the coupling. If the heat generated in the working chamber of the hydraulic coupling is to be carried off effectively, relatively large flows are required. This results in great losses being created in the high-speed bearings.

Object of the invention

An object of the present invention is to provide an effective oil supply to a working chamber in a hydrodynamic coupling flushed through with oil, which oil supply can be adjusted for carrying off the heat generated in the hydraulic coupling.

Another object is to obtain at the same time a lubrication ofthe bearings of the hydrodynamic coupling using the same oil supply system, which bearings are all designed to be lubricated by a flow of oil passing through them before the main oil flow reaches the working chamber of the hydrodynamic coupling, as a result of which the bearings are lubricated with cooler oil.

A further object is for each bearing to obtain a flow of oil passing through it, which is adapted to the different bearing types in such a way that the friction losses generated in the bearings are kept to the minimum possible level.

In these respects, the arrangement according to the invention is characterised by the features which emerge from the characterising part of patent claim 1.

Further features characterising the invention and advantages thereof will become apparent from an embodiment of the invention illustrated

hereinbelow and described in greater detail with reference to the attached figures.

Brief description of the figures

Figure 1 shows diagrammatically an internal combustion engine unit according to the invention.

Figure 2 shows in detail the hydrodynamic coupling according to one embodiment of the invention.

Description of a preferred embodiment

Figure 1 shows diagrammatically an internal combustion engine unit 1 of the turbocompound type comprising an internal combustion engine 2, a turbocharger 22 consisting of an exhaust turbine 23 and, driven by this, a turbo compressor 24 compressing the intake air of the engine 2, a second exhaust gas turbine 3, hereinafter called the power turbine, and a transmission 4 between the power turbine 3 and a crankshaft 5 in the internal combustion engine 2. The crankshaft 5 of the engine 2 drives, via a transmission 46 consisting of a coupling 43 and a gearbox 25, a load 6 in the form of, for example, a heavy land vehicle. The exhaust gases from the engine 2 drive in a first stage the exhaust turbine 23 and thereafter the series-coupled powerturbine 3.

Figure 2 shows in detail a hydrodynamic coupling 16 which forms part of the transmission 4. The primary side of the coupling 16 is driven by the power turbine 3 via a shaft 40 issuing from the latter and, arranged on this shaft 40, a gear wheel 41. The gear wheel 41 is in engagement with and drives a gear wheel 19 which is secured to and forms part of a pump wheel 8 arranged in the coupling 16. The gear wheel 19 and the pump wheel δ are journalled on the one hand by a ball bearing 9 in a stub axle 10 arranged securely in the coupling housing 37, and on the other hand in a ball bearing system 12, consisting of one or more ball bearings 12, on a sleeve 13 arranged in the coupling 16 on the output shaft 17 of the coupling 16. In the housing 37 and in the stub axle 10 there runs a channel 14 through which oil from the lubricating system of the engine 2 is conveyed, on the one hand, to bearings

(not shown) bearing the shaft 40 and, on the other hand, to the coupling 16. The channel 14 is adjustably throttled by means of a bearing holder washer 35 and holds the bearing 9 in place and at the same time forms an adjustable gap 21 between itself and the sleeve 13. The gap 21 is advantageously set so that the oil flow passing through the gap is sufficient to flush through the hydraulic coupling and carry off the heat generated. In an application of a hydrodynamic coupling in a compound system to a six-cylinder internal combustion engine of 400 hp and an oil lubricating system pressure of 3 bar, the necessary flushing is obtained, for carrying off the heat generated, at a flow of a couple of litres per minute. The greater part of this flow then passes the low-speed bearing 12 bearing the the turbine wheel in the pump wheel. After the gap 21, the channel 14 opens out into a space upstream of the low-speed bearing 12. The space is sealed off with respect to the high¬ speed bearing 9 by means of a sealing ring 36 which, however, leaks a sufficient amount of oil to lubricate the bearing 9.

As regards the high-speed bearing 9, it is important that the oil flow should not become so great that the friction losses in the bearing begin to increase. For a typical spherical ball bearing, a minimum required oil flow for effective lubrication may be about one centilitre per minute. This corresponds to a continuous damping of the bearing. For this spherical ball bearing, a maximum permissible oil flow may be about 1 litre per minute, and, in the event of the flow exceeding this value, the bearing becomes heavier and hotter and causes great friction losses. The sealing ring 36, which is preferably a steel ring, is ground on its radial inside, leaving a calibrated gap between the sealing ring 36 and the bearing holder washer 35. This gap is dimensioned in such a way that a limited oil flow leaks from the space upstream of the low-speed bearing 12 to the high-speed bearing 9. The main part of the oil flow first passes the low-speed bearing 12 and lubricates the latter and then reaches the working chamber 34, while a limited subsidiary flow is conveyed to the high-speed bearing 19. The subsidiary flow to the high-speed bearing is suitably adapted so that the high-speed bearing obtains a flow which lies within the permissible minimum and maximum flow range for the bearing type in question, with margins in respect of both the minimum and maximum flow limits.

The pump wheel 8 forms a unit together with the gear wheel 19, a bearing holder 15, a blade holder 18 and a casing 20. The gearwheel 19, the bearing holder 15 and the blade holder 18 are held together by a bolted joint 7. The blade holder 18 is made up of a ring with a half-toric form, in which the blades 28 ofthe primary side are arranged. The casing 20 is secured to the blade holder 18 by bolt connection 23 mounted in holes 38 arranged in flanges 24 and 26, respectively, on the periphery of the casing 20 and blade holder 18, respectively. The casing 20 is arched in such a way that a narrow gap 27 is formed between it and the sleeve 13. There is thus formed in the pump wheel 8 a chamber 29 in which is arranged the secondary side of the coupling 16 in the form of a turbine wheel 30. The turbine wheel 30 consists of said sleeve 13 and a blade holder 31 which is secured in a flange 33 on the sleeve 13 by means of a bolted joint 32. The blade holder 31 is shaped as a ring with an almost half-toric form, in which the blades ofthe secondary side are arranged. The blade holder 31 is turned towards the blade holder 18 in such a way that together they form a torus-shaped working chamber 34.

Oil is thus conveyed to the coupling 16 through the channel 14 and is forced onwards through the bearing 12 to the working chamber 34. In the pump wheel 8, the oil is set in a circular motion. On account ofthe centrifugal force, the oil is forced outwards towards the perimeter of the pump wheel 8 and flows from there at a higher speed across to the turbine wheel 30. The flow energy of the oil is converted in the turbine wheel 30 to a mechanical movement of rotation. The oil is maintained in the working chamber 34 on account of the centrifugal force in the coupling, but, when new cool oil is supplied, the heated oil flows round the perimeter ofthe turbine wheel 30 and sprays out through an overflow drain/ the gap 27 which lies radially inside of the working chamber 34 and its pump wheel and turbine wheel 8, 30. The size ofthe gap 27 determines the rigidity ofthe coupling. If the gap is made large, with a large internal diameter in the recess in the casing 20, the degree of filling in the working chamber 34 is reduced and the coupling then becomes more flexible. The rigidity of the coupling can thus be adapted simply by dimensioning of the size ofthe gap. When the coupling is enclosed in a housing 37, the oil is collected in the housing from, on the one hand, the gap 27 and, on the other hand, from the high-speed bearing 9. The oil is the conveyed onwards to an oil sump (not shown) through a drainage hole 39 in the housing 37.

By means of these arrangements, oil can be supplied to the coupling 16 as working medium and to the bearing system 12 of the coupling 16 for lubrication and cooling of the latter. The supply is effected through parts of the coupling 16/coupling housing 37 which do not rotate, and this improves the possibilities of creating leakproof flows of oil to the coupling 16.