GB2420152A

GB2420152A - Pressure-charged gasoline internal combustion engine

Info

Publication number: GB2420152A
Application number: GB0424845A
Authority: GB
Inventors: James William Griffith Turner; Richard John Pearson
Original assignee: Lotus Cars Ltd
Current assignee: Lotus Cars Ltd
Priority date: 2004-11-10
Filing date: 2004-11-10
Publication date: 2006-05-17
Also published as: WO2006051299A1; GB0424845D0

Abstract

An expander 220 is used to expand gases previously compressed in a compressor, eg of a turbocharger 207, and cooled in an intercooler 209 in order to reduce the temperature and pressure of the charge air while returning work to the crankshaft eg via a belt drive. This "turboexpansion", together with direct injection (GDI), reduces the end-of compression temperature in the engine by reducing the compression ratio. The engine may comprise combustion chambers 210, 211, 212 each having a pair of inlet valves and a pair of electronically controlled hydraulically actuated exhaust valves a, b. A duct 201 connects exhaust valves a to turbocharger turbine 207a the exhausted gases from which are combined with exhaust gas from exhaust valves b. Valves a and b are controlled independently thus enabling control of the turbocharger 207. Charge air may be drawn in via air filter 204 and pressurised by a supercharger 205 before further compression in the compressor 207b of the turbocharger 207. Supercharger 205 may be used only on start-up and/or at low speeds and bypassed otherwise so that only the turbocharger 207 is used. In a modification, fig.6, exhaust gases from exhaust valves a,b drive high- and low-pressure tubochargers, respectively. The engine may operate with controlled auto-ignition (CAI/ HCCI).

Description

A PRESSURE-CHARGED GASOLINE INTERNAL COMBUSTION ENGINE

The present invention relates to a pressure-charged gasoline internal combustion engine.

It is a known problem to provide improved fuel economy from gasoline internal combustion engines. One route to improve fuel economy is to reduce the swept volume of an engine and run the engine at a higher BMEP (Brake Mean Effective Pressure) for any given output. To achieve this and provide good fuel economy, particularly in part-load operating conditions, the expansion ratio of the engine should be kept as high as possible. In normal engines this also means that the compression ratio is similarly kept high. However, a high compression ratio is undesirable in a pressurecharged gasoline internal combustion engine because at high loads in such an engine the knock limit is a severe limitation. Indeed it is generally desirable to reduce the compression ratio of the engine at high loads and speeds of the engine, particularly when pressure charging is used; pressure charging being important to maintain high load engine performance. It has previously been proposed (e.g. by Saab) to provide an engine with a variable compression ratio (VCR) which can be varied with engine speed and load to meet the different requirements.

The present invention provides a pressure-charged gasoline internal combustion engine comprising: a combustion chamber; inlet valve means controlling admission of charge air into the combustion chamber; exhaust valve means for controlling exhaust of combusted gases from the combustion chamber; a compressor for compressing charge air prior to delivery of the charge air to the combustion chamber; an intercooler which receives compressed charge air from the compressor and cools the compressed charge air; an expander which receives cooled compressed charge air from the intercooler and expands the cooled compressed charge air to reduce both the temperature and pressure of the charge air prior to delivery of the charge air to the combustion chamber; and an injector which injects gasoline directly into the combustion chamber for mixing with the charge air conditioned previously by the compressor, the intercooler and the expander.

The concept of using an expander to expand and cool gases previously compressed in a compressor (e.g. turbo- charger) shall be referred to as "turboexpansion". The use of turboexpansion and gasoline direct injection (GDI) together is synergistic because both act to reduce the start of compression temperature in the engine. In contrast the VCR approach of the prior art (e.g. of SAAB) has aimed to reduce the end of compression temperature in the engine by reducing the compression ratio. Turboexpansion and GDI are charge-air conditioning concepts which are complementary and synergistic since they occur in successive parts of the induction process.

Preferred embodiments of the present invention will now be described with reference to the accompanying drawings, in which: Figure 1 is a schematic illustration of a pressure- charged gasoline internal combustion engine according to the present invention; Figure 2 is a schematic illustration of a combustion chamber of a first variant of the engine of Figure 1; Figure 3 is a temperature/entropy diagram illustrating operation of the engine of Figures 1 and 2; Figure 4 is a schematic illustration of a combustion chamber of a second variant of the engine of Figure 1; Figure 5 is a schematic illustration of a first modification of the induction system of the engine of Figure 1; and Figure 6 is a schematic illustration of a second modification of the induction system of Figure 1.

Turning to Figure 1, there can be seen in the figure a pressure-charged internal combustion engine 10 having a turboexpansion charging system comprising a compressor in the form of a turbo-charger ii, having a compressor section hA and a turbine section 11B. The compressor section hA draws in charge air from atmosphere via an air filter 12.

The air compressed in the compressor section HA is then passed through an intercooler 13 to an expander 14. The expander 14 expands the compressed air, delivering work back to a crankshaft of the engine 10 via a belt drive 15. The expanded air is delivered to a plenum 16 from where it is delivered to the engine 10 where it undergoes combustion.

Combusted gases are then relayed from the engine 10 to the turbine section 11B of the turbocharger 11 to drive the turbine 11B. Afterwards they are exhausted to atmosphere.

Figure 2 shows a combustion chamber 1 of the engine 10, defined in a cylinder 2 by a piston 3 reciprocating in the cylinder. An inlet passage 4 leads charge air from the plenum 16 to the combustion chamber 1 with an inlet valve 5 operated by a cam 6 controlling flow of charge air into the chamber 1. An exhaust passage 7 allows flow of combusted gases out of the combustion chamber 1 to the turbine 11B, the flow being controlled by an exhaust valve 8 operated by a cam 9. A spark plug 17 can ignite fuel in the combustion chamber 1 and fuel is delivered directly to the chamber 1 by a gasoline direct injection (GDI) injector 18 (e.g. an air assist injector). The GDI injector 18 is vertically oriented to avoid bore wetting as much as possible and to give the largest possible spray angle. This maximises the amount of fuel which vaporises in the charge air and not on contact with internal surfaces of the engine 10. The GDI injector 18 produces an homogeneous fuel/air mixture rather than a stratified mixture to minimise NOx production and avoid the need for a lean NOx trap in the exhaust system.

The turboexpansion system operates (see Figure 3) by pressurising the charge air from atmospheric pressure (PAtm) to a pressure (Pupper) greater than the pressure (Pplenum) required in the plenum; the applicant refers to such compressing of the air in the turbocharger 11 as "overcompressing" since the pressure of the compressed air is greater than that needed in the plenum 16. The temperature of the charge air increases from atmospheric temperature T1, to a higher temperature T2 after compression in the compressor hA. The compressed air is then cooled to a temperature T3 by the intercooler 13 and then further cooled by expansion in the expander 14 to a temperature T4; ideally at full-load of the engine the temperature T4 of charge air in the plenum is less than atmospheric temperature.

The expanding of the compressed air in the expander 14 removes some work from the air (which is delivered to the crankshaft via the belt drive 15) and simultaneously reduces both pressure and temperature of the charge air. This makes it possible to achieve in the plenum a chosen air density at a temperature below that which can be achieved by use of an intercooler alone; theoretically twice atmospheric density is possible. The expander 14 could of any type and could delver output power mechanically, hydraulically or electrically.

The GDI injector 41 will inject fuel directly into the combustion chamber whilst the intake valve 24 is open and the vaporisation of the gasoline fuel in the charge air will reduce further the charge air temperature and increase inlet charge density and therefore increase volumetric efficiency. The use of a centrally located GDI injector 41 gives fewer constraints (when compared with a port-injected engine) in piston crown geometry and intake port profile since the GDI injector 41 can give a required fuel/air mixture characteristic without the need for flow control by features of the piston and/or intake port; the design of the piston and intake port can therefore be optimised for volumetric efficiency and full load performance.

Advanced injector designs currently available produce highly repeatable and controlled sprays and can be used to extend the range of lean burn operating conditions and produce improvements in hydrocarbon emissions. The GDI system will preferably be a spray-guided GDI system which generates less NOx than a port or wall guided system and thus avoids the need for a NOx trap in the exhaust system (the use of which reduces fuel efficiency by requiring the engine to run rich periodically to regenerate the NOx trap).

The reduction of the temperature of the inlet charge by use of turboexpansion and GDI allows the engine to run at a compression ratio not possible normally without knock occurring. This is achieved in an engine with a compression ratio fixed for all speeds and loads.

Improved knock performance also provides an efficiency benefit by allowing the phasing of the combustion event to be advanced at the detonation borderline. This leads to improvements in thermal efficiency and enables a given torque level to be attained at lower boost pressures. A smaller turbo-charger may therefore be used so that low- speed torque and transient response are improved.

Advancing the combustion event also leads to lower exhaust temperatures and therefore reduces the degree of fuel enrichment necessary to limit the temperature of the gas entering the turbo-charger turbine. This can result in significantly reduced wide open throttle fuel consumption.

The ability to delay the addition of the fuel until the exhaust valve has closed eliminates, or dramatically reduces, the carry-over of fuel into the exhaust system during the valve overlap period. Such carried over fuel would give rise to exothermic reactions in the catalyst and require extra enrichment for catalyst substrate protection, which is fuel inefficient.

Rather than using conventional mechanical valve train, a fully variable valve train could be used. Turning to Figure 4, in the figure it can be seen that charge air from the plenum 16 is delivered to a combustion chamber 20 (formed by piston 21 reciprocating in a cylinder 22) via an inlet passage 23. Delivery of charge air into the chamber is controlled by an inlet valve 24 which is operated by a hydraulic actuator 25 (comprising a piston 28 movable in a cylinder 29), the piston 28 being mounted on a valve stern 27 of the valve 24). A spark plug 40 is operative in the combustion chamber 20. A GDI injector 41 is axially mounted in the head of the cylinder 22 to deliver gasoline directly into the combustion chamber 20 (e.g. with the use of compressed air assistance). Combusted gases leave the combustion chamber 20 via an exhaust passage 26 under the control of an exhaust valve 34 which is operated by a hydraulic actuator 35 (comprising a piston 36 movable in a cylinder 37, the piston 36 being mounted on a valve stem 38 of the valve 34). The combusted gases flow through the exhaust passage 26 to the turbine 11B of the turbo-charger 11.

The actuators 25 and 35 are controlled respectively by electro-hydraulic servo-valves 23 and 27 which control flow of hydraulic fluid to the actuators 25,35 from a pump 30 or to a sump 31. The servo-valves 23 and 27 are controlled by an electronic controller which controls the movement of the inlet valve 24 and the exhaust valve 34 in a closed loop feedback control arrangement which uses position feedback signals provided by two position sensors 32 and 33. The electronic controller 24 also controls operation of the spark plug 40 and the direct injector 41.

The use of valves controlled by actuators as in Figure 4 can allow throttleless operation of the engine, improving efficiency by dispensing with throttling losses in part-load conditions. Also the ability to vary all three of valve lift height, valve opening time and valve closing time allows greater efficiency. The use of a fully variable valve train allows optimisation of the expansion ratio in the engine in all conditions. The use of a fully variable valves as shown in Figure 4 could permit sparkless Controlled Auto-Ignition (sometimes called Homogeneous Charge Compression Ignition) in part-load Conditions. The recycling of exhaust gases in CAl operation would allow lean burn ignition without exceeding NOx limits for a 3-way oxidising catalyst.

Increased freedom to optimise valve events is permitted by the use of a GDI injector, which can be controlled to inject fuel only after the exhaust valve has closed and thus e.g. reduce carry-over of fuel into the exhaust system during valve overlap. This can allow significantly improved low-speed torque by suitable valve timing variation.

With fixed valve timing, the exhaust valve opening point is usually dictated by the trade-off between expansion work and pumping work at fullload. Again part-load operation is compromised by the full-load performance requirements. With a variable valve train, exhaust valve opening can be retarded at part-load relative to its full- load timing, increasing the effective expansion ratio.

The fully variable valve train described above also allows the engine to switch between 2 and 4 stroke operation, cylinder deactivation, conversion of one or more cylinders into compressors of air for storage in a tank and later expansion in the cylinders (such compression taking place e.g. during braking of a vehicle), or a Stop-at-idle fuel economy strategy.

The controllable valves of figure 4 also allow control of the charging system as will now be described with reference to Figures 5 and 6.

In Figure 5 there can be seen a multi-cylinder engine having three cylinders 210, 211, 212. Each cylinder has a pair of inlet valves "i" and two exhaust valves "a" and "b".

The exhaust valves "a" and "b" at least are each operated by a hydraulic actuator connected to the valve (as shown in Figure 4). Each exhaust valve "a" would be opened and closed independently of the exhaust valve "b" in the same cylinder.

Combusted gases flowing from the cylinders 210, 211, 212 flow through the exhaust valves "a" to a first exhaust duct 201. This exhaust duct 14 relays the combusted gases to the turbine stage 207a of a turbocharger 207.

The exhaust valves "b" are all connected to a second exhaust duct 202 through which combusted gases can flow from the cylinders 210, 211, 212 through the exhaust valves "b" to a catalytic converter 217.

The Combusted gases expanded in the turbine 207a are output from the turbocharger 207 via an exhaust duct 218,which is joined to the exhaust duct 202 at a joint 219.

At the joint 219 the combusted gases flowing from the turbo- charger 207 combine with the combusted gases flowing through the exhaust duct 202 and then the combined flow passes through the catalytic converter 217 to atmosphere.

The electronic controller can use its control of the actuators to control the opening and closing of the exhaust valves "a" to control what proportion of the total combusted gases flowing from each cylinder flow to the exhaust duct 201 and what proportion of the combusted gases flow through the exhaust duct 202. In this way the controller can control operation of the turbocharger 207. When greater boost is required then a greater proportion of the total combusted gases expelled from the cylinders 10, 11, 12 and 13 is fed through the turbo-charger 207 and vice versa.

Charge air is drawn into the engine via an air filter 204 and initially pressurisecj in a supercharger 205. The charge air pressurised in the supercharger 205 is then delivered to the turbocharger 207 to be further compressed.

The air leaving the turbocharger 207 is then cooled by - 10 - intercooler 209 and then expanded in expander 220 before delivery to a plenum 221 from where it is delivered into the engine via the inlet valves i.

A bypass valve 206 allows the supercharger 205 to be bypassed. it could be spring-loaded so that it opens automatically on the creation of a sufficient pressure differential across it. More likely it will be electrically controllable to allow bypass of the supercharger 205 under control of the engine management system; the supercharger will be used at low speeds and loads when boost provided by the supercharger alone is insufficient and not used at all at high speeds and loads (the supercharger could be clutched or electrically driven).

As described above the supercharger is used on start-up and/or at low speeds and with the supercharger bypassed otherwise so that only the turbocharger is used.

Alternatively the turbochargers could be set up for part- load operation and could be used with an axial flow supercharger switched on (e.g. via a clutch) for full load operation. A turbocharger which is electrically assisted at low speeds could also be used and the supercharger omitted altogether.

In Figure 6 a further variant of engine according to the present invention is shown. This engine has three cylinders 303, 304, 305 each cylinder having a pair of intake valves "i", an exhaust valve "a" and an exhaust valve "b". The exhaust valves "a" and "b" at least are operated by hydraulic actuators under the control of an electronic controller (as previously shown). Each exhaust valve "a" can be operated independently from the exhaust valve "b" in the same cylinder.

- 11 - The exhaust valves "a" of the cylinders 303, 304, 305 are all Connected to a first exhaust duct 306 which leads the combustecj gases to the turbine part 302a of a high pressure turbocharger 302. The exhaust valves "b" of the cylinders 303, 304, 305 are all connected to an exhaust duct 307 through which the combusted gases flow to a turbine section 301a of a low pressure turbocharger 301, bypassing the high pressure turbocharger 302.

Expanded combustecj gases exiting the turbine part 302a of the turbocharger 302 flow via an exhaust duct 318 to a joint 319 where the expanded combusted gases are fed into the flow of combusted gases passing along the exhaust duct 307. It is the combined flow of the combusted gases passing directly from the exhaust valves "b" and the combusted gases exiting the turbocharger 302 which are then fed to the turbine 301a of the low pressure turbocharger 301.

The combusted gases exiting the turbine 301a of the turbocharger 301 pass through an exhaust passage 312 to atmosphere via a catalytic converter 320.

Charge air drawn into the compressor part 301b of the turbocharger 301 is expelled through an intake duct 309 to be passed to the compressor part 302b of the high pressure turbocharger 302 or can pass along a bypass passage 314, bypassing the turbocharger 302 completely.

The compressed air supplied to the turbocharger 302 will be supplied at a first pressure and will then be pressurised to a higher second pressure by the turbocharger 302. The pressurised air leaving the compressor 302b passes through a duct 315 to be recombined with air flowing through the bypass passage 314. The combined air flow then passes through an intercooler 311 to be expanded in an expander 321 - 12 - and then to flow to a plenum 322 to be supplied to the intake valves i".

A bypass valve 310 is provided in the bypass passage 314. The bypass valve 310 is controlled by the electronic controller. Operation of the bypass valve 310 will enable the electronic controller to control how much of the intake air passes through the high pressure turbocharger 302.

An electronic controller controls opening and closing of the exhaust valves "a" and "b" (through control of the actuators connected to the exhaust valves) in order to control what proportion of the total flow of combusted gases exhausted from the cylinders 303, 304, 305 flows through the exhaust duct 306 and what proportion of the combusted gases flow through the exhaust duct 307. In this way, the electronic controller can control operation of the turbochargers 301 and 302.

In certain circumstances it will be preferable that all or at least the majority of the flow of combusted gases bypasses the turbocharger 302 completely. In this circumstance, the exhaust valves "a" are kept totally (or mostly) closed and the exhaust valves "b" are opened and closed on their own in each cycle. In this circumstance the electronic controller will also open fully the bypass valve 310 so that charge air does not pass through the turbocharger 302. For instance it is desirable on start-up of the engine to bypass the turbocharger 302 completely.

Since the turbocharger 302 is a high pressure turbocharger, it will provide a large restriction on the flow of combusted gases from the cylinders. On the other hand, the low pressure turbocharger 301 will place far less a restriction on the combusted gases and therefore it is preferable that - 13 - in start-up conditions the combusted gases flow only through the turbocharger 301.

The level of boost provided to the intake air supplied to the intake valves "i" can easily be controlled by electronic controller by varying the valve timing of the exhaust valves "a" and "b" in order to control the gas flow through the exhaust duct 306. Also, the controller can control boost by controlling the bypass valve 310.

The low pressure turbocharger 301 will be a turbocharger with a large turbine, giving a resistance to the flow of combusted gases much less than the high pressure turbocharger 302, which has a smaller turbine. However, the larger turbine size of the low pressure turbocharger 302 can lead to throttle response problems which are particularly problematic in the use of the engine in an automobile. This problem is ameliorated by the present invention by the electronic controller recognising times of acceleration of the engine and in such times diverting the majority of the flow of coinbusted gases to the high pressure turbocharger 302 which will react quickly when the throttle of the engine is open. Obviously, the bypass valve 310 is closed in such circumstances, in order that the intake air received by the inlet valves "1" is boosted to its maximum.

At high engine speeds the high pressure turbocharger 302 could provide an excess of boost if not suitably controlled by the electronic controller controlling the flow of combusted gases through the exhaust duct 306 and the flow of intake air through the bypass passage 314. Typically at full loads and high engine speeds in steady state conditions the high pressure turbocharger 302 will be in the main bypassed so that the majority of intake air will flow in the - 14 - bypass passage 314 and the majority of combusted gas flow will be through the exhaust duct 307.

Above the use of fully variable valve operating mechanisms with hydraulic actuators to permit CAl operation has been described. However, it would be possible to use variable mechanical valve operating systems (e.g. cam profile switching systems, can phasing systems, etc.) to facilitate limited CAl operation and to reduce throttling lenses at part-load. CAl operation can allow diluted operation at part-load conditions without exceeding the limits for NOx of a 3-way catalyst acting as an oxicat and still avoiding the need for a NOx trap.

The applicant expects a specific power output of 135- bhp/litre from the engines of the invention with an improvement in fuel economy over prior art engines of equivalent combustion chamber volumes.

Whilst above each described engine uses a turbo-charger as the or at least one of the compressors of charge air, it is possible to produce a system which does not use a turbo- charger at all and instead use one or more compressors of a different type. For instance a single supercharger could be used provided that the energy lost by inefficiencies in the supercharger and expander combination is more than offset by the increased efficiency of the engine arising from the use of an increased compression ratio. Use of twin superchargers is also possible, as is use of one or more electrically driven compressors.

Claims

- 15 - CLAIMS: 1. A pressure-charged gasoline internal combustion engine

comprising: a combustion chamber; inlet valve means controlling admission of charge air into the combustion chamber; exhaust valve means controlling exhaust of combusted gases from the combustion chamber; a compressor for compressing charge air prior to delivery to the combustion chamber; an intercooler which receives compressed charge air from the compressor and cools the compressed charge air; an expander which receives cooled compressed charge air from the intercooler and expands the cooled compressed charge air to reduce both the temperature and pressure of the charge air prior to delivery of the charge air to the combustion chamber; and an injector which injects gasoline directly into the combustion chamber for mixing with the charged air conditioned previously by the compressor, the intercooler and the expander.

2. A pressure-charged gasoline internal combustion engine as claimed in claim 1 wherein the compressor is a turbo- charger driven by combusted gases expelled from the combustion chamber.

3. A pressure-charged gasoline internal combustion engine as claimed in claim 2 comprising a second charge air pressurising device in addition to the turbo-charger, wherein the exhaust valve means comprises a first exhaust - 16 - valve controlling flow of combusted gases to the turbocharger and a second exhaust valve controlling flow of combusted gases to a bypass passage which bypasses the turbocharger, and the exhaust valve means is operated by a valve operating mechanism which controls operation of the first and second exhaust valves to control in degree boost provided by the turbocharger.

4. A pressure-charged gasoline internal combustion engine as claimed in claim 3 wherein the second charge air pressurising device is a second turbo-charger which is driven by the coinbustecj gases flowing through the bypass passage.

5. A pressure-charged gasoline internal combustion engine as claimed in claim 3 wherein the second charge air pressurising device is a supercharger.

6. A pressure-charged gasoline internal combustion engine as claimed in claim 1 wherein the compressor is a supercharger 7. A pressure-charged gasoline internal combustion engine as claimed in any one of the preceding claims wherein the combustion chamber is defined by walls of a cylinder in the engine and a piston reciprocating in the cylinder and the injector is centrally located in an upper surface of the cylinder to deliver fuel axially into the cylinder.

8. A pressure-charged gasoline internal combustion engine as claimed in any one of the preceding claims wherein the injector delivers gasoline to the combustion chamber in a - 17 - manner which creates a homogeneous mixture of fuel and air therein.

9. A pressure-charged gasoline internal combustion engine as claimed in any one of the preceding claims wherein the injector is a part of a sprayguided gasoline direct injection system.

10. A pressure-charged gasoline internal combustion engine as claimed in any one of the preceding claims comprising a valve operating mechanism for operating the inlet valve means which can vary operation of the inlet valve means with variation in engine speed and load, wherein in selected part load operating conditions of the engine the inlet valve means is used to control in amount the charge air delivered to the combustion chamber and the engine operates without throttling of the charge air prior to delivery of the charge air via the inlet valve means to the combustion chamber.

11. A pressure-charged gasoline internal combustion engine as claimed in any one of the preceding claims comprising a valve operating mechanism for operating the exhaust valve means which can vary operation of the exhaust valve means with variation in engine speed and load, wherein in selected part load operating conditions the exhaust valve means is closed early in each exhaust intake to trap combusted gases in the combustion chamber for mixing with the charge air next delivered to the combustion chamber and the fuel next injected into the combustion chamber to create a homogeneous mixture of air, combusted gases and fuel which is ignited by compression ignition.

- 18 - 12. A pressure-charged gasoline internal combustion engine as claimed in any one of the preceding claims wherein the expander outputs work via a transmission system.

13. A pressure-charged gasoline internal combustion engine substantially as hereinbefore described with reference to and as shown in the accompanying drawings.

588866; AWP; DMR Amendments to the claims have been filed as follows CLAIMS: 1. A pressure-charged gasoline internal combustion engine comprising: a combustion chamber; inlet valve means controlling admission of charge air into the combustion chamber; exhaust valve means controlling exhaust of combusted gases from the combustion chamber; a compressor for compressing charge air prior to delivery to the combustion chamber; an intercooler which receives compressed charge air from the compressor and cools the compressed charge air; an expander which receives cooled compressed charge air from the intercooler and expands the cooled compressed charge air to reduce both the temperature and pressure of the charge air prior to delivery of the charge air to the combustion chamber; and an injector which injects gasoline directly into the combustion chamber for mixing with the charged air conditioned previously by the compressor, the intercooler and the expander wherein: the compressor is a supercharger.
2. A pressure-charged gasoline internal combustion engine as claimed in claim 1 comprising a turbocharger in addition to the supercharger, wherein the exhaust valve means comprises a first exhaust valve controlling flow of combusted gases to the turbocharger and a second exhaust valve controlling flow of combusted gases to a bypass passage which bypasses the turbocharger, and the exhaust

2. A pressure-charged gasoline internal combustion engine as claimed in claim 1 comprising a turbocharger in addition to the supercharger, wherein the exhaust valve means comprises a first exhaust valve controlling flow of combusted gases to the turbocharger and a second exhaust valve controlling flow of combusted gases to a bypass passage which bypasses the turbocharger, and the exhaust * * ** I *IS * S S S S S S S * S I IS *SS S S S S. * S S S S S S

S S S S S S I S S

555 5 S S S 2o valve means is operated by a valve operating mechanism which controls operation of the first and second exhaust valves to control in degree boost provided by the turbocharger.

3. A pressure-charged gasoline internal combustion engine as claimed in claim 1 or claim 2 wherein the combustion chamber is defined by walls of a cylinder in the engine and a piston reciprocating in the cylinder and the injector is centrally located in an upper surface of the cylinder to deliver fuel axially into the cylinder.

4. A pressure-charged gasoline internal combustion engine as claimed in any one of the preceding claims wherein the injector delivers gasoline to the combustion chamber in a manner which creates a homogeneous mixture of fuel and air therein.

5. A pressure-charged gasoline internal combustion engine as claimed in any one of the preceding claims wherein the injector is a part of a sprayguided gasoline direct injection system.

6. A pressure-charged gasoline internal combustion engine as claimed in any one of the preceding claims comprising a valve operating mechanism for operating the inlet valve means which can vary operation of the inlet valve means with variation in engine speed and load, wherein in selected part load operating conditions of the engine the inlet valve means is used to control in amount the charge air delivered to the combustion chamber and the engine operates without throttling of the charge air prior to delivery of the charge air via the inlet valve means to the combustion chamber.

* * ** S 555 * S S S S S S S * S S ** 555 * S S 5 S S S S S S * S S S S * * S S 5*5 S S S S 7. A pressure-charged gasoline internal combustion engine as claimed in any one of the preceding claims comprising a valve operating mechanism for operating the exhaust valve means which can vary operation of the exhaust valve means with variation in engine speed and load, wherein in selected part load operating conditions the exhaust valve means is closed early in each exhaust intake to trap combusted gases in the combustion chamber for mixing with the charge air next delivered to the combustion chamber and the fuel next injected into the combustion chamber to create a homogeneous mixture of air, combusted gases and fuel which is ignited by compression ignition.

8. A pressure-charged gasoline internal combustion engine as claimed in any one of the preceding claims wherein the expander outputs work via a transmission system.

9. A pressure-charged gasoline internal combustion engine substantially as hereinbefore described with reference to and as shown in the accompanying Figure 5.

588866; AWP; Ctf * S *S * S.s * S S S S * S S * S * 55 *55 S S * ** * S S * S S *

S S S S S S S S S

555 5 S S S Amendments to the claims have been filed as follows CLAIMS: 1. A pressure-charged gasoline internal combustion engine comprising: a combustion chamber; inlet valve means controlling admission of charge air into the combustion chamber; exhaust valve means controlling exhaust of combusted gases from the combustion chamber; a compressor for compressing charge air prior to delivery to the combustion chamber; an intercooler which receives compressed charge air from the compressor and cools the compressed charge air; an expander which receives cooled compressed charge air from the intercooler and expands the cooled compressed charge air to reduce both the temperature and pressure of the charge air prior to delivery of the charge air to the combustion chamber; and ::.: an injector which injects gasoline directly into the S...

combustion chamber for mixing with the charged air 2O conditioned previously by the compressor, the intercooler : and the expander wherein: the compressor is a supercharger, that is a compressor driven by power output by the engine rather than by exhaust a.. . gas flow.