GB2442794A

GB2442794A - I.c. engine turbocharger with electric motor drive

Info

Publication number: GB2442794A
Application number: GB0620114A
Authority: GB
Inventors: Timothy Peter Kelly
Original assignee: Bentley Motors Ltd
Current assignee: Bentley Motors Ltd
Priority date: 2006-10-11
Filing date: 2006-10-11
Publication date: 2008-04-16
Anticipated expiration: 2026-10-11
Also published as: GB2442794B; GB0620114D0

Abstract

An internal combustion engine has a turbocharger comprising a turbine 1 and compressor 2 mounted on a common shaft 3. The shaft 3 is extended at 5 to provide a driving connection between the shaft 3 and an electric motor 4. The provision of the electric motor 4 eliminates the normal driving dependency of the compressor 2 on the turbine 1 and the disposition of the compressor 2 between the electric motor 4 and the turbine 1 shields the motor 4 from the high temperatures in which the turbine normally operates. With appropriate ducting and solenoid valve control, the arrangement may also be used to dispense with airpumps and simplify the operation of catalytic converters. The arrangement of ducts 30, 31, 32, fig.4, enables air to be supplied by the compressor 2 to the air inlet 23 of the engine and/or the engine exhaust under the control of valves 33, 34 and wastegate 29. Air is supplied to the exhaust to augment the exhaust flow to thereby bring the exhaust catalyst 38 more quickly to its operating temperature.

Description

IMPROVEMENT IN OR RELATING TO TURBOCHARGERS

The present invention relates to a turbocharger for an internal combustion engine.

In conventional turbocharger operation, the turbine of the turbocharger under the action of exhaust gases from the engine drives a compressor through a common shaft to feed more air to the engine to increase its performance. More recently, it has been proposed to eliminate the driving dependency of the compressor on the turbine by positioning an electric motor between them drivably connected to the common shaft so that the compressor may be driven by the motor rather than by the turbine.

This positioning of the motor in the high temperature hostile environment of the turbine leads to operational problems with the motor and in serious cases to breakdown. It is an object of the invention to eliminate or mitigate these disadvantages.

According to one aspect of the present invention there is provided a turbocharger comprising a turbine and a compressor mounted on a common shaft and an electric motor drivably connected to the shaft and disposed in relation to the turbine so as to be thermally insulated therefrom.

In a preferred embodiment of the invention the electric motor is disposed on that side of the compressor remote from the turbine. For that purpose the common shaft is extended to provide a driving connection between shaft and motor. The compressor then acts as a thermal barrier between turbine and motor.

According to another aspect of the invention, there is provided an internal combustion engine having a turbocharger comprising a turbine and a compressor mounted on a common shaft, drive means connected to the t shaft and duct means enabling air to be supplied by the compressor to the air inlet to the engine and/or to the engine exhaust.

In a preferred embodiment of the invention, the drive means comprises an electric motor. The electric motor is disposed on that side of the compressor remote from the turbine. For that purpose the common shaft is extended to provide a driving connection between shaft and motor. The compressor then acts as a thermal barrier between turbine and motor. A catalytic converter having a catalyst is disposed in the engine exhaust downstream of the turbocharger. At engine startup air from the compressor is directed via the duct means to the converter to augment exhaust air from the exhaust manifold to bring the catalyst more quickly up to operating temperature. The duct means comprise a duct from the engine air inlet to the compressor, a duct from the engine exhaust to the turbine, and a duct connecting these two first mentioned ducts. A further duct leads from the turbine to the exhaust. Solenoid valves are advantageously disposed respectively in the duct between engine inlet and the compressor and in the connecting duct. The conventional wastegate, conventionally operable, is disposed in the exhaust duct connecting the exhaust manifold of the engine to the turbine. Operation of the valves and wastegate is controlled to enable the compressor to feed air to the catalytic converter at startup in order to reduce emissions.

In order that the invention may be more clearly understood embodiments thereof will now be described, by way of example, with reference to the accompanying drawings, in which:-.

Figure 1 diagrammatically shows an existing turbocharger arrangement; Figure 2 diagrammatically shows a turbocharger arrangement according to the invention, Figure 3 diagrammatically shows a twin turbocharged engine arrangement suitable for utilizing the invention, and Figure 4 diagrammatically shows a modification of the arrangement shown in Figure 2 suitable for use with the engine of Figure 3.

Referring to Figure 1, the internal combustion engine turbocharger comprises a turbine 1, and a compressor 2 mounted on a common shaft 3.

Under normal operation, the turbine is driven by exhaust gases from the internal combustion engine (not shown) and this in turn drives the compressor 2 through the common shaft 3 to feed air to the cylinders of the internal combustion engine. An electric motor 4 is disposed between the turbine 1 and compressor 2 and is drivably connected to the shaft 3. The provision of the electric motor eliminates the driving dependency of the compressor 2 on the turbine 1. The turbine being driven, as it normally is, by exhaust gases from the engine operates in an extremely hostile environment. In particular, operational temperatures are extremely high.

The electric motor, being disposed adjacent the turbine is expected to operate in the same or a similar hostile environment. This can adversely effect the operation of the motor and in some cases leads to breakdown.

Referring to Figure 2, the internal combustion engine turbocharger arrangement of the invention has the same main elements of the arrangement described with reference to Figure 1. Equivalent parts on the two figures bear the same reference numerals. Thus, a turbine 1, in normal operation, drives a compressor 2 through a common shaft 3.

The electric motor 4, however, instead of being disposed between the compressor 2 and turbine 1, is disposed on that side of the compressor 2 remote from the turbine 1. For this purpose, the shaft 3 is extended at 5 to provide a drivable connection between the shaft 3 and the electric motor 4.

The compressor 2, which runs at a lower temperature than the turbine 1, therefore forms a thermal barrier between the turbine 1 and the motor 4 providing a lower temperature much less hostile environment in which to operate for the motor 4 and leading to a reduction in motor problems associated with that hostile environment. It would also be possible for the motor to be positioned to the other side of the turbine providing the spacing was such as to lead to a sufficient reduction in operating temperature for the motor 4. However, this is not as satisfactory an arrangement as that illustrated in Figure 2 because the length of the shaft 3 extension required to provide a sufficient spacing of the motor 4 from the turbine 1 may itself cause operational problems.

The facility to be able to drive the compressor reliably by means of an electric motor leads to a number of advantages. Reliance on exhaust gases to drive the turbine may lead to turbo lag. The ability to be able to spin the compressor up in advance of demand can eliminate this. Additionally, boost on demand, which may be beneficial under certain circumstances, can also be provided for. Furthermore, when the turbine is producing power which is not required the turbine can drive the motor as a generator and feed energy back into the system.

Figure 3 diagrammatically shows an existing twin turbocharged internal combustion engine. The cylinders are arranged in a "W" formation 20 made up of two six cylinder V's 21 and 22 placed together. The two V's have respective air inlets 23 and 24, exhaust manifolds 25 and 26, turbochargers 27 and 28 and wastegates 29 and 30. On engine starting, in order to comply with emission regulations, it is necessary to ensure that the catalysts in the catalytic converters in the exhausts reach a satisfactory operating temperature quickly, typically in under two minutes, and to achieve that additional air is supplied to the air inlets by respective electrically driven airpumps 31 and 32. These airpumps add a considerable weight penalty to the vehicle of which the engine forms part apart from the added complexity for what is an extremely short period in the overall operational time of the vehicle. The arrangement described with reference to Figure 2 enables the above mentioned airpumps 31 and 32 to be dispensed with. The manner in which this is done will now be described with additional reference to Figure 4 which diagrammatically shows the connection of the turbocharger of Figure 4 to an internal combustion engine.

As already described, in relation to Figures 1 and 2, in conventional turbocharger operation compression of the air in the airpump is dependant upon turning of the turbine which in turn is dependant upon flow of exhaust gasses. The provision of the electrically driven turbocharger as shown in Figure 2, eliminates this dependency. Referring to Figure 4, in which parts equivalent to parts in Figures 1, 2 and 3 are given the same reference numerals, the outlet from the airpump 2 is connected to the air inlet 23 of he engine 20 through a duct 30 and the inlet to the turbine 1 is connected to the exhaust manifold 25 of the engine 20 through duct 31.Ducts 30 and 31 are connected by a further duct 32. A solenoid valve 33 is disposed in duct between the junction between ducts 30 and 32 and the engine inlet 23.

This valve 33 may be valve 33 of the existing arrangement. An on/off solenoid valve 34 is disposed in duct 32 and a temperature sensor 35 is disposed in the duct 31 adjacent exhaust 25. The existing turbocharger wastegate 35 is disposed in duct 31 and is operative to control flow of exhaust gas from exhaust manifold 25 to the turbine 1 by moving between two extreme positions. In one extreme position, all of the exhaust gas flows through the turbine 1 and in the other extreme position all of the exhaust gas bypasses the turbine 1 before exhausting via a catalytic converter 38.

At engine start up, the compressor 2 is driven by the electric motor 4 to supply air via ducts 30, 32 and 31 to the catalytic converter thus to increase the flow of oxygen thereto augmenting exhaust gas flow from exhaust manifold 25 to bring the catalyst in the converter more quickly to its operating temperature in order to reduce emissions. Valve 33 is wholly or partially closed, valve 34 is open and the wastegate 29 is set in the turbine bypass position. Airflow is in the direction shown by the arrows in Figure 4.

Following start up, the turbine may then revert to its "normal" operating position. Valve 33 will be open and valve 34 closed. With the wastegate 29 "open" exhaust gas flow bypasses the turbine and exhausts through the converter 38. With the wastegate 29 "closed" exhaust gas flow goes through the turbine to drive the turbine 1 and through it the airpump 2 to exhaust via duct 37 and the converter 38.

It will be appreciated that the above embodiment has been described by way of example only and that many variations are possible without departing from the scope of the invention.

Claims

1. A turbocharger comprising a turbine and a compressor mounted on a common shaft and an electric motor drivably connected to the shaft and disposed in relation to the turbine so as to be thermally insulated therefrom.

2. A turbocharger as claimed in claim 1, in which the electric motor is disposed on that side of the compressor remote from the turbine.

3. A turbocharger as claimed in claim 2, in which the common shaft is extended to provide a driving connection between shaft and motor.

4. A turbocharger substantially as hereinbefore described with reference to Figure 2, or to Figure 3, or to Figure 2 with the modification of Figure 4 of the accompanying drawings.

5. An internal combustion engine having a turbocharger comprising a turbine and a compressor mounted on a common shaft, drive means connected to the shaft and duct means enabling air to be supplied by the compressor to the air inlet to the engine and/or to the engine exhaust.

6. An internal combustion engine as claimed in claim 5, in which the drive means comprises an electric motor.

7. An internal combustion engine as claimed in claim 6, in which the electric motor is disposed on that side of the compressor remote from the turbine.

8. An internal combustion engine as claimed in claim 6 or 7, in which the common shaft is extended to provide a driving connection between shaft and motor.

9. An internal combustion engine as claimed in any of claims 5 to 8, in which a catalytic converter having a catalyst is disposed in the engine exhaust, downstream of the turbocharger.

10. An internal combustion engine as claimed in any of claims 5 to 9, in which the duct means comprises a first duct from the engine air inlet to the compressor, a second duct from the engine exhaust to the turbine and a third duct connecting the first and second ducts.

11. An internal combustion engine as claimed in claim 10, in which a further duct leads from the turbine to the engine exhaust.

12. An internal combustion engine as claimed in claim 10 or 11, in which solenoid valves are disposed respectively in the first duct and in the third duct.

13. An internal combustion engine as claimed in any of claims 5 to 12, in which a wastegate is disposed in the exhaust duct connecting the exhaust manifold of the engine to the turbine.

1 4. An internal combustion engine as claimed in claim 1 3, when C' appendant to claim 12, in which control means are provided to control operation of the solenoid valves and wastegate to enable the compressor to feed air to a catalytic converter of the engine at engine startup to reduce emissions.

15. An internal combustion engine substantially as hereinbefore described with reference to Figure 2, or to Figure 3, or to Figure 2 with the modification of Figure 4 of the accompanying drawings.