CHARGE AIR SYSTEMS FOR FOUR-CYCLE INTERNAL COMBUSTION ENGINES

Abstract: This invention is directed to an air-charging system for a four-cycle internal combustion engine (54, 66, 74, 90) wherein an exhaust gas-driven turbocharger (56, 156, 76, 96, 196) is connected to the exhaust and inlet air of the engine (54, 66, 74, 90). An electric motor-driven compressor (62, 68, 84, 114) has its outlet connected either to the inlet or outlet of the air compressor section of the turbocharger (56, 156, 76, 96, 196) to increase the amount of air in the parallel connection or increase the pressure inthe series connection. The use of an electric motor-driven compressor (62, 68, 84, 114) increases engine acceleration and decreases engine back pressure and unburned fuel.

Description: Description CHARGE AIR SYSTEMS FOR FOUR-CYCLE INTERNAL COMBUSTION ENGINES Technical Field This invention is directed to method and apparatus including both a turbocharger and an electric motor-driven compressor for delivering charge air to a four-cycle internal combustion engine. Background Art The use of turbochargers to increase power output and decrease fuel consumption in four-cycle internal combustion engines is common practice today. Both spark ignition and diesel engines, use turbochargers to advantage and, in the case of diesel engines, the power output of an engine of a given cylinder displacement can easily be doubled by the addition of turbocharging with aftercooling. The turbocharger has gone through decades of development, and modern turbochargers used on high-speed diesel and gasoline engines are low in manufacturing cost, high in efficiency, and very durable commercial products. Although the turbocharger utilizes exhaust gas energy that would otherwise be wasted, the imposition of an exhaust gas turbine in the engine exhaust system necessitates raising the average back pressure on the engine cylinders in order to generate sufficient pressure drop across the turbine to generate the power necessary to drive the turbocharger' s compressor. This back pressure acts against the upstroke of the piston as it forces residual products of combustion out of the cylinder through the exhaust valves and increases the pumping loss of the engine. The level of back pressure caused by high pressure turbocharging of four-cycle engines is very high, even with the use of turbochargers that have relatively high overall efficiency. Any means that might be employed to lower the back pressure caused by the turbocharger turbine can result in significant improvement in engine performance. For example, if a diesel engine requires a pressure ratio of 2.5 times atmospheric pressure to reach the desired rated engine power output, a single turbocharger would impose a back pressure in the exhaust system of approximately two times atmospheric pressure. The use of series turbochargers is common today on engines that are rated at high power output. If the two compressors are placed in series combination, the pressure ratio of the charge air is the product of the individual pressure ratios of the compressors. As previously described, die use of series compressors results in their pressure ratios multiplying, so that high supercharge pressure can be supplied to the engine beyond that which a single turbocharger could produce by itself. If, for instance, a highly rated engine requires 4.5 pressure ratio, which is beyond the capability of a single commercial turbocharger, series turbochargers would require the low pressure stage of 2.1 pressure ratio and the high pressure state of 2.15 pressure ratio, the product of which is 4.51 pressure ratio overall. This significantly raises the exhaust gas back pressure. Disclosure of the Invention In order to aid in the understanding of this invention, it can be stated in essentially summary form that it is directed to a charge air system including both a turbocharger and an electric motor-driven compressor for four-cycle internal combustion engines. The motor-driven compressor may deliver pressurized air to the inlet of the turbine-driven compressor or in parallel thereto to the oudet of the turbine-driven compressor to achieve higher pressure or higher flow, depending upon engine needs. One purpose and advantage of this invention is the lowering of engine exhaust back pressure levels by the use of a motor-driven compressor in series with the turbocharger compressor. It is another purpose and advantage of this invention to provide a motor-driven compressor which has the ability to reduce the cost of turbocharging highly rated engines by replacing one turbocharger by a motor-driven compressor, while at the same time improving engine performance due to the resulting lower exhaust back pressure. The pressure ratio of the motor-driven compressor need only be 1.5 if the pressure ratio of the turbocharger compressor as a second stage is 3.0. The product of the pressure ratios is 4.5, equalling the required pressure ratio of the highly rated engine. It is another purpose and advantage to provide a mediod of improving the performance of naturally aspirated four-cycle engines by the use of a motor-driven compressor. By utilizing an external power source to drive the compressor, the engine can be supercharged without imposing back pressure on the exhaust system as does a turbocharger. Thus, an increase in charge air density is achieved, allowing fuel to be burned more efficiently, with the desirable result of less harmful pollutants emitted into the atmosphere in the engine exhaust. It is another purpose and advantage of this invention to provide a memod of improving the performance of a turbocharger four-cycle engine by compensating for the time lag of the turbocharger compressor upon sudden throttle opening, by providing an electrically powered auxiliary compressor which is connected directly to the engine intake duct between the turbocharger compressor and the engine. The features of the present invention which are believed to be novel are set forth with particularity in die appended claims. The present invention, both as to its organization and manner of operation, togedier with further objects and advantages thereof, may be best understood by reference to the following description. Brief Description of me Drawings Fig. 1 shows one of d e conventional systems for series turbocharging of a four-cycle engine. Fig. 2 schematically shows a first preferred embodiment of a charge air system of this invention for a four-cycle engine where a motor-driven compressor is placed in series with a turbocharger compressor. Fig. 2A shows a second preferred embodiment of a charge air system of this invention for a four-cycle engine where a motor-driven compressor is placed in series with a motor-assisted turbocharger compressor. Fig. 3 shows a d ird preferred embodiment of a charge air system of diis invention for a four-cycle engine where a motor-driven compressor is used to charge die engine. Fig. 4 shows a fourth preferred embodiment of a charge air system of this invention for a four-cycle engine where a motor-driven compressor is placed in parallel with a turbocharger compressor. Fig. 5 shows a fifth preferred embodiment of a charge air system of d is invention for a four-cycle engine where a motor-driven compressor can be used either in parallel or in series with a turbocharger compressor. Fig. 6 shows a sixth preferred embodiment of a charge air system of this invention for a four-cycle engine where a motor-driven compressor can be used eidier in parallel or in series widi a motor-assisted turbocharger compressor. Best Mode for Carrying Out the Invention A conventional internal combustion engine is shown in schematic cross- section and is generally indicated at 10 in Fig. 1. The engine 10 has a cylinder block 12 in which is located cylinder 14. In this case, die cylinder has an upright axis. Piston 16 reciprocates up and down within the cylinder under control of crank 18. The crank rotates around die crankshaft axis and is connected to die piston by means of connecting rod 20. The crankshaft and connecting rod are housed in crankcase 22, which may contain oil for lubricating the lower part of die engine. There is usually a plurality of cylinders along the crankshaft axis. The cylinders in the cylinder block are covered by cylinder head 24. The cylinder head has an intake manifold 26 and carries intake valve 28, which controls flow of air or air plus fuel mix to die cylinder. The cylinder head 24 also has an exhaust port 30 for each cylinder. The exhaust port 30 is controlled by exhaust valve 32. The opening and closing of die intake valve and exhaust valve for each cylinder is coordinated with d e movement of the piston by mechanical interconnection of the crankshaft wid die cam shafts which control die valves. Fuel is introduced into die cylinder at d e appropriate time dirough fuel injection nozzle 34. In some cases, d e fuel may be delivered to die cylinder as a fuel-air mixture dirough the intake valve. By increasing the amount of air delivered to die cylinder and by corresponding increase of fuel, die power output of the engine 10 can be appreciably increased. At d e same time, the engine efficiency can increase to yield more work per umt of fuel. To provide d e additional air, centrifugal compressor 36 has its oudet tube 38 connected to the intake port 26. However, if die engine 10 requires an intake manifold pressure of 4.5 times die atmospheric pressure, which is a 4.5 pressure ratio, such is beyond die capability of a single centrifugal compressor. Two centrifugal compressors can be used in series. Centrifugal compressor 40 is a first stage compressor and has an inlet 42 from atmosphere dirough a suitable air filter. The oudet tube 44 from compressor 40 is connected to d e inlet of compressor 36, which dius becomes die second stage compressor. The use of series compressors results in the multiplying of die pressure ratio. As an example, for an engine which requires a 4.5 pressure ratio, the low pressure stage centrifugal compressor 40 would operate at a 2.1 pressure ratio, while die high pressure stage would operate at a 2.15 pressure ratio. This would result in a 4.51 total pressure ratio. The series-connected centrifugal compressors are driven by serially connected exhaust gas turbines 46 and 48. The exhaust port 30 is connected dirough exhaust pipe 50 to die inlet of first stage turbine 46. -6- The oudet of the first stage turbine 46 is connected by exhaust pipe 52 to die inlet of second stage exhaust gas turbine 48. The turbine 48 exhausts to atmosphere. These series-connected exhaust gas turbines impose a high back pressure on die exhaust port, and diis high back pressure increases d e pumping loss of die engine. The exhaust gas turbine 46 is direcdy coupled to drive die centrifugal compressor 36, and d e exhaust gas turbine 48 is direcdy coupled to drive die centrifugal compressor 40. The four-cycle internal combustion engine 54 illustrated in Fig. 2 is die same as die engine 10. Turbocharger 56 comprises an exhaust gas turbine 58 which is connected to receive hot exhaust gas from die engine and expand it to atmosphere. The turbine 58 drives centrifugal compressor 60, which delivers air under pressure to die intake port of engine 54. The rotor in die exhaust gas turbine is direcdy connected to drive the rotor in the centrifugal compressor. In accordance wid d is invention, centrifugal compressor 62 has its compressed air oudet connected to die inlet of centrifugal compressor 60 to form a series connected compression system. The centrifugal compressor 62 is driven by electric motor 64. Electric motor 64 is controlled by a control 67, which applies power from source 69 in response to input signals (generally designated by reference no. 25), such as from a boost pressure sensor and/or a dirotde sensor. Thus, die compressors are arranged in series, but die first stage compressor 62 is not driven by an exhaust gas turbine and, tiius, does not raise the exhaust gas back pressure. If one of die series turbochargers is replaced wid a motor-driven compressor, die result is a less complicated mechanical arrangement since only one turbocharger is mounted on die engine exhaust system and die back pressure on die engine is substantially reduced. For example, if a diesel engine requires a pressure ratio of 2.5 times atmospheric pressure to reach d e desired rated engine power output, a single turbocharger would impose a back pressure in die exhaust system of approximately two times atmospheric pressure. However, if a motor-driven compressor 62 is used in series with die turbocharger compressor, die required pressure ratio of 2.5 can be achieved by producing 1.3 from die motor-driven compressor 62 and 1.92 from die turbocharger compressor 60. Reducing die charging pressure ratio of die turbocharger compressor 60 from 2.5 to 1.92 results in a reduction in exhaust back pressure to approximately 1.5 times atmospheric pressure. Thus, the engine's pumping loss is significandy reduced, resulting in lower fuel consumption, higher power output, or bodi. The motor-driven compressor 60 is controlled by signals from demand, intake manifold pressure, engine speed and die like to yield diese results, plus decreased exhaust gas pollution. The operation of die system shown in Fig. 2 can be enhanced by die addition of a motor-assisted turbocharger as illustrated in Fig. 2A. Motor- assisted turbochargers and their operation are described in a co-pending United States patent apphcation, Serial No. 08/680,671 , filed July 16, 1996. The turbocharger 156 shown in Fig. 2 A (including turbine 158 and centrifugal compressor 160) has an internal motor-generator 156a mat can be energized by die control means 67 in response to appropriate input signals. For example, a boost pressure sensor can be used to send a signal to die control means 67 when die engine is operating at low speed and load. When the engine is called upon to accelerate, d e boost pressure sensor or a d rotde sensor can generate an input signal to control 67 and motor-driven compressor and die motor in die turbocharger are bod energized to provide an increased air supply during die acceleration period. When die turbocharger is running fast enough to provide an adequate air supply to die engine, a rotor speed signal from die motor 156a in motor- assisted turbocharger 156 is delivered to control 67, and bodi motors are de-energized to eliminate die need for external power. Additionally, at high engine speed and load, when maximum power output is required, the internal motor-generator 156a in d e turbocharger can be de-energized by control 67, while the motor-driven compressor remains energized. This condition corresponds to the series compressor arrangement in Fig. 2 and described previously. Fig. 3 shows an internal combustion engine 66 which is die same as die engine 10. In diis case, a centrifugal compressor 68 is connected by intake manifold 70 to die inlet port. Compressor 68 is driven by electric motor 72 to supply charge air to the engine. A control system 67 is connected to d e motor and to an electric power source 69 so diat die compressor 68 is driven by die motor 72 when a quick engine acceleration is anticipated. The motor-driven compressor can be maintained at a pre- determined minimum speed to provide boost pressure in die engine intake manifold at engine idle, or at low load and speed conditions. Thus, a significant amount of air can be present in the cylinder before additional fuel is injected when an engine acceleration is called for. Due to the higher air charge at die beginning of acceleration, die transient time to reach high engine speed is significantiy reduced, die fuel is burned more completely, and die amount of harmful pollutants in the engine exhaust is substantially lessened. The motor-driven compressor 68 is controlled by signals from demand, intake manifold pressure, engine speed and die like to yield these results, plus decreased exhaust gas pollution. The series connection of centrifugal compressors is shown in Fig. 2. A problem arises when die engine 54 is being started or is running at idle widi eidier no exhaust gas flow to die turbine 58 or a minimum amount which does not run die turbocompressor sufficiendy fast to provide enough air for acceleration. The employment of die compressor 62 at diat point helps, but die air drag through compressor 60 when it is running at low speed sometimes does not permit rapid engine acceleration. For d is reason, d e internal combustion engine 74 shown in Fig. 4 has its turbocompressor and its electric motor-driven compressor connected in parallel. Turbocompressor 76 receives exhaust gas flow from he exhaust pipe and expands die exhaust gas to atmosphere. This drives d e centrifugal compressor which delivers air under pressure out dirough tube 78 and reed valve 80 to the intake manifold 82. In parallel to d is, centrifugal compressor 84 is driven by electric motor 86 to deliver air dirough reed valve 88 to manifold 82. This arrangement of parallel connected turbocompressor and electric motor compressor improves d e performance of a turbocharged four-cycle engine by compensating for d e time lag of the turbocharger compressor 76 upon sudden dirotde opening, by providing an electrically powered auxiliary compressor 84 which is connected direcdy to d e engine intake duct between die turbocharger compressor and d e engine. Backflow of compressed air from die electric compressor dirough die turbocharger is prevented by a pressure activated check valve 80. When sufficient speed is attained by die turbocompressor, its pressure output would overcome die check valve allowing its compressed air to enter die engine manifold. Backflow of air from d e turbocompressor dirough the electric compressor is prevented by a second pressure activated check valve 88. A suitable motor controller widi pressure sensors, speed sensor and a demand sensor would be employed to provide timely motor switching. The engine 90 shown in Fig. 5 is die same as die engine 10. The use of an exhaust gas-drive turbine driving an engine driving centrifugal compressor, togedier widi an electric motor-driven compressor connected in series widi die turbocompressor has been described widi respect to Fig. 2. The use of an exhaust gas driven turbocompressor widi a parallel connected electric motor-driven compressor has been described widi respect to Fig. 4. It can be understood that, in some operating conditions, a series connection of die air system is desired and, in odier operating conditions, a parallel connection is desired. Fig. 5 shows die manner in which ducting is connected so that die output of an electric motor-driven centrifugal compressor is selectively connected in parallel to or in series wid an exhaust-driven turbocompressor. The exhaust pipe 92 is connected to die exhaust gas turbine portion 94 of turbocharger 96. The centrifugal compressor 98 of d e turbocharger has its pressurized air output connected to intake manifold 100 of engine 90. The intake manifold is connected to d e intake port in conventional manner. Reed valve 102 is positioned in the intake manifold to permit air flow from die compressor 98 only in the downstream direction toward the intake port. Rate sensor 104 is positioned in die manifold to determine the flow rate of air from die compressor 98. This rate sensor is used in die control system described below. Inlet air to the turbocompressor 98 comes from either of two sources. Wye 106 is connected to the turbocompressor inlet. One branch of die wye is connected from air cleaner 108 through inlet tube 110 to d e wye. Butterfly valve 112 is positioned in inlet tube 110 so that it may be opened and closed. Centrifugal compressor 114 is driven by electric motor 116. The compressor 114 takes its suction from air cleaner 108 mrough inlet tube 118, which is connected by a tee to inlet tube 110. The compressed air output of compressor 114 is directed to oudet tube 120 which has a reed valve 122 tiierein and is connected by means of a tee connection to intake manifold 100 downstream of reed valve 122. Thus, die compressors 98 and 114 can operate in parallel in providing dieir outputs to intake manifold 100. In addition, oudet tube 124 is connected as a tee to die oudet tube 120 and is connected to die other branch of d e wye 106. Butterfly valve 126 is positioned in oudet tube 124 to selectively close diat tube. The two butterfly valves 112 and 126 are connected toged er and are operated by die same actuator 128 so mat, when one butterfly valve is closed, die odier one is open. Control system 130 receives power from power supply 132 and receives signals 25 including engine speed, intake and exhaust manifold pressures, air flow rates, demands and die like to control the amount of power to motor 116 and to control air actuator 128. Widi die actuator and die butterfly valves 112 and 126 in die position shown in Fig. 5, d e compressor 98 receives its suction from die air cleaner and die two compressors are operating in parallel. Widi die actuator 128 in die opposite position, widi valve 112 closed and valve 126 open, d e compressor 114 discharges into the intake of compressor 98 to place die compressors in series to provide a higher manifold pressure, as contrasted to a higher volume flow. It is tiius seen diat, widi additional ducting and valves, die flow patii of die motor-driven compressor is directed into die intake of die turbocharger compressor 98 at the moment when turbocharger pressure output exceeds die electric motor compressor pressure output. In diis way, die pressure output from die electric motor-driven compressor is used to compound die turbocharger pressure for a short time in order to sustain die enhancement of charging pressure from die electric motor- driven compressor. At some pressure rise rate, the rate sensor 104 will signal die motor control 130, and the air actuator 128 will set die synchronized valves 112, 126 to block backflow into d e electric motor- driven compressor and switch off power to d e motor 116 so diat die turbocharger will operate in a normal unassisted mode. In tiiese several ways, an electric motor-driven compressor 114, often in combination with a turbocompressor 96, enhances d e operating conditions of a four-cycle internal combustion engine. It is desirable to place die system shown in Fig. 5 in die parallel operating mode when die engine 90 is required to accelerate from low speed to high speed under load. At low engine speed, such as engine idle, the turbocharger 96 is incapable of supplying the engine wid a significant amount of boost pressure. Thus, d e motor-driven compressor 114 is energized from control 130 by a low engine speed signal or a low boost pressure signal to provide boost pressure to die engine intake manifold 100 dirough valve 122. When die engine 90 accelerates to a speed where die turbocharger compressor 98 is capable of charging the engine sufficiendy, d e turbocharger compressor oudet pressure opens valve 102 and provides high boost pressure to the engine. At diis time, a boost pressure signal from sensor 104 tells the control 130 to de-energize die motor 116 driving compressor 114 and air back flow dirough die motor-driven compressor 114 is prevented by check valve 122. During die acceleration period, the butterfly valves 126 and 112 remain in die position shown in Fig. 5, depicting parallel operation of he compressors. When die engine is required to operate at maximum power output, it is desirable to change die system over to a series arrangement of the compressors. An engine load signal sent to the control 130 causes die butterfly valve 126 to open and simultaneously causes butterfly valve 122 to close. The engine intake air flow pati is tiien from the air cleaner 108 dirough duct 118 to compressor 114. The compressed air from compressor 114 flows through duct 120, dirough butterfly valve 126 to die intake of the turbocharger compressor 98. Super-compressed air then flows from die turbocharger compressor 98 dirough check valve 102 to duct 100, leading to die engine intake manifold. Check valve 122 prevents backflow of die super-compressed air into duct 120. Upon deceleration of d e engine from high speed and power operation to low-speed, low-load conditions, a low boost pressure signal from sensor 104 sends a signal to d e control 130 and moves die butterfly valves back to die position shown in Fig. 5, which places die compressors in a parallel arrangement in preparation for die next engine acceleration. The parallel arrangement of compressors 114 and 98 provides die engine 90 with an increase in boost pressure during acceleration periods above diat which could be supplied by d e turbocharger 96 along. This reduces acceleration time, reduces smoke during acceleration, and reduces harmful exhaust emissions. The change-over to series operation of die compressors 114 and 98 provide die engine wid high boost pressure due to die multipUcation of die compressor pressure ratios. The series compression of e intake air provides high boost pressure to die engine so diat higher power output can be produced, compared wid diat which could be provided by die single turbocharger alone. Fig. 6 is die same as the system of Fig. 5 except diat turbocharger 196 having turbine 194 and compressor 198 has an internal motor- generator 196a diat is operable from power supply 132 by control 130 to enhance the operation of die turbocharger 196. For example, during periods of low engine speed and boost, a signal from sensor 104 activates control 130 to provide sufficient power to d e internal motor-generator 196a to maintain a predetermined turbocharger speed and boost pressure. Upon receiving an input signal indicating a demand for an acceleration in excess of some predetermined acceleration, control 130 supplies higher power to die motor 196a to increase d e turbocharger speed and boost to provide die internal combustion engine 90 with die demanded acceleration. Turbocharger rotor speed signals can be provided to control 130 from motor 196a to de-energize the motor 196a when d e turbocharger 196 is providing sufficient compressed air boost from d e exhaust energy of die internal combustion engine. Thus, die provision and operation of a motor-assisted turbocharger, as set forth above, can further enhance, and contribute further flexibihty in die operation of die multiple compressor, series-parallel system of Fig. 5. This invention has been described in its presentiy contemplated best modes, and it is clear diat it is susceptible to numerous modifications, modes and embodiments within die ability of tiiose skilled in die art and widiout d e exercise of d e inventive faculty. Accordingly, d e scope of d is invention is defined by die scope of die following claims.

Claims: Claims 1. A charge air system for a four-cycle internal combustion engine comprising: a first centrifugal compressor; a second centrifugal compressor; a four-cycle internal combustion engine having an intake port; ducting interconnecting said first and second compressors so diat they are serially connected to supply air to said intake port; and an electric motor connected to drive one of said compressors. 2. The charge air system for a four-cycle internal combustion engine of claim 1 wherein said first compressor is driven by said electric motor. 3. The charge air system for a four-cycle internal combustion engine in accordance wid claim 1 wherein said second compressor is driven by an exhaust gas turbine. 4. The charge air system for a four-cycle internal combustion engine in accordance widi claim 3 wherein said four-cycle internal combustion engine has an exhaust port and tiiere is ducting connecting said exhaust port to said exhaust gas turbine so diat exhaust from said four- cycle internal combustion engine drives said exhaust gas turbine and said exhaust gas turbine drives said second compressor. 5. The charge air system for a four-cycle internal combustion engine of claim 4 wherein said first compressor is driven by said electric motor. 6. The charge air system for a four-cycle internal combustion engine in accordance wid claim 1 wherein said engine has an intake port and said second centrifugal compressor is connected to said intake port by an intake manifold and said first centrifugal compressor is connected to said second centrifugal compressor by means of an air tube. 7. The charge air system for a four-cycle internal combustion engine in accordance widi claim 6 wherein said air tube is also connected to said intake manifold so d at said first centrifugal compressor is connected to deliver air to said second centrifugal compressor and to said intake manifold. 8. The charge air system for a four-cycle internal combustion engine in accordance with claim 7 wherein mere is a valve in said tube to prevent air in said inlet manifold from passing into said air tube. 9. The charge air system for a four-cycle internal combustion engine in accordance with claim 8 wherein said valve is a check valve. 10. The charge air system for a four-cycle internal combustion engine in accordance widi claim 8 wherein tiiere is a valve in said tube between said first centrifugal compressor and said second centrifugal compressor to selectively cut off air from said first centrifugal compressor to said second centrifugal compressor to cause said first centrifugal compressor to deliver air to said intake manifold so diat said compressors operate in parallel. 11. The charge air system for a four-cycle internal combustion engine in accordance widi claim 10 wherein said valve in said air tube from said first centrifugal compressor to said intake manifold is a check valve and said valve in said tube between said first compressor and said -16- second compressor is an actuatable valve actuatable between an open position and a closed position. 12. The charge air system for a four-cycle internal combustion engine in accordance widi claim 11 wherein said second compressor is also connected to an air inlet and tiiere is an actuatable valve in said air inlets, said actuatable valves being connected togetiier so tiiat when one is open die odier is closed so diat said second compressor is selectively connected to said air inlet or to said air tube from said first compressor. 13. A charge air system for a four-cycle internal combustion engine comprising: a four-cycle internal combustion engine having an intake port and an exhaust port; a first centrifugal charge air compressor having an inlet and an oudet, said inlet of said first charge air compressor being connected to receive atmospheric air; a second centrifugal charge air compressor, said second centrifugal compressor having an inlet and an oudet, said oudet of said first centrifugal compressor being connected to said inlet of said second centrifugal compressor, an intake manifold, said intake manifold being connected to said oudet of said second centrifugal compressor and to said inlet port of said four-cycle engine, an electric motor connected to drive one of said centrifugal compressors; an exhaust gas turbine connected to drive die odier of said centrifugal compressors and an exhaust pipe connected to said exhaust port of said four-cycle engine and to said exhaust gas turbine so tiiat said electric motor-driven compressor can be driven to provide a high level of charge air to said four-cycle internal combustion engine in preparation for fast acceleration of said engine when tiiere is low flow of exhaust gas and said exhaust gas-driven charge air compressor by itself delivers inadequate charge air for fast acceleration. 14. The charge air system for a four-cycle internal combustion engine in accordance widi claim 13 wherein said first centrifugal compressor is electric motor-driven. 15. The charge air system for a four-cycle internal combustion engine in accordance widi claim 13 wherein said second centrifugal charge air compressor is connected to said exhaust gas turbine to be driven by said exhaust gas turbine. 16. The charge air system for a four-cycle internal combustion engine in accordance with claim 15 wherein said first centrifugal compressor is electric motor-driven. 17. The charge air system for a four-cycle internal combustion engine in accordance with claim 13 further including control means connected to supply power to said electric motor and control said electric motor and control die output of said electric motor-driven centrifugal charge air compressor so tiiat said electric motor-driven compressor supplies adequate charge air in preparation for fast acceleration of said four-cycle internal combustion engine when die output of said exhaust gas turbine-driven centrifugal compressor is inadequate. 18. The charge air system for a four-cycle internal combustion engine in accordance widi claim 17 wherein said first centrifugal compressor is electric motor-driven. 19. The charge air system for a four-cycle internal combustion engine in accordance widi claim 17 wherein said second centrifugal charge air compressor is connected to said exhaust gas turbine to be driven by said exhaust gas turbine. 20. The charge air system for a four-cycle internal combustion engine in accordance widi claim 19 wherein said first centrifugal compressor is electric motor-driven. 21. The charge air system for a four-cycle internal combustion engine of claim 13 further including an oudet tube connected from said first centrifugal charge air compressor to said intake manifold and valving between said first and second charge air compressors to selectively connect said first and second charge air compressors in series and in parallel. 22. The charge air system for a four-cycle internal combustion engine in accordance witii claim 21 wherein said first centrifugal compressor is electric motor-driven. 23. The charge air system for a four-cycle internal combustion engine in accordance widi claim 21 wherein said second centrifugal charge air compressor is connected to said exhaust gas turbine to be driven by said exhaust gas turbine. 24. The charge air system for a four-cycle internal combustion engine in accordance widi claim 21 wherein said valving includes an actuatable valve to selectively open and close said duct between die oudet of said first centrifugal compressor and the inlet of said second centrifugal compressor. 25. A charge air system for a four-cycle internal combustion engine comprising: a four-cycle internal combustion engine having an intake port and an exhaust port, an intake manifold connected to said intake port and an exhaust manifold connected to said exhaust port; a first centrifugal charge air compressor, said first compressor having an inlet and an outlet, said oudet of said first centrifugal charge air compressor being connected to said intake manifold, an electric motor connected to drive said first centrifugal charge air compressor; a second centrifugal charge air compressor, said second compressor having an inlet and an oudet, said oudet of said second centrifugal charge air compressor being also connected to said intake manifold; an exhaust gas turbine connected to drive said second centrifugal compressor and an exhaust pipe connected from said exhaust port to said exhaust gas turbine to supply exhaust gas from said four-cycle internal combustion engine to said exhaust gas turbine to drive said second centrifugal compressor so diat said motor-driven first centrifugal compressor is powered separately from exhaust as so diat it can provide high charge air volume for die purpose of reducing levels of harmful pollutants in die engine exhaust gas when die engine is called upon to accelerate from low to high operating speeds. 26. The charge air system for a four-cycle internal combustion engine in accordance widi claim 25 wherein tiiere is a valve in die oudet of said first centrifugal compressor to prevent backflow of air through said first centrifugal compressor when it is unpowered. 27. The charge air system for a four-cycle internal combustion engine of claim 25 wherein there is a valve in the oudet of said second centrifugal compressor to prevent backflow of air dirough said second compressor when said first compressor provides higher pressure. 28. The charge air system for a four-cycle internal combustion engine in accordance widi claim 27 wherein said valve is a check valve. 29. The charge air system for a four-cycle internal combustion engine in accordance widi claim 26 wherein said valve is a check valve. 30. The charge air system for a four-cycle internal combustion engine in accordance with claim 25 wherein mere is a check valve in die oudet of each of said compressors to prevent backflow of air. 31. The charge air system for a four-cycle internal combustion engine of claim 25 further including a duct connected between said oudet of said first centrifugal compressor to said inlet of said second centrifugal compressor so that said compressors can selectively be connected in series. 32. The charge air system for a four-cycle internal combustion engine of claim 31 wherein said duct connecting said oudet of said first centrifugal compressor to said inlet of said second centrifugal compressor includes a selectively operable valve so diat said valve can be opened to permit series connection and can be closed to inhibit series connection of said first and second compressors. 33. A charge air system for a four-cycle internal combustion engine comprising: a four-cycle internal combustion engine having an intake port and an exhaust port, a centrifugal charge air compressor having an inlet and an oudet, said oudet of said centrifugal charge air compressor being connected to said intake port; an electric motor driving said centrifugal charge air compressor; and control means connected to said electric motor to drive said centrifugal charge air compressor to provide high charge air density for the purpose of lowering levels of harmful pollutants in the engine exhaust when the engine is called upon to accelerate from low to high operating speeds. 34. The charge air system for a four-cycle internal combustion engine in accordance wid claim 33 wherein said control means is connected to energize said electric motor, said control means receiving signals coπesponding to engine operating conditions. 35. The charge air system for a four-cycle internal combustion engine in accordance widi claim 34 wherein signals to said control means for controlling said electric motor driving said centrifugal air compressor include intake manifold pressure, engine rpm and engine demand. 36. A charge air system for a four-cycle internal combustion engine comprising: a four-cycle internal combustion engine having an intake port and an exhaust port, a turbocompressor connected to bodi said intake port and exhaust port to be driven by expansion of exhaust gas and to supply air to said intake port; and additional electric powered air supply means for supplying additional air to said intake port to provide adequate charge air to said intake port at engine idle and low load in preparation for fast acceleration of die engine for the purpose of lowering levels of harmful pollutants in d e engine exhaust when the engine is called upon to accelerate from low to high operating speeds. 37. The charge air system for a four-cycle internal combustion engine of claim 36 wherein said additional electric powered air supply means is in an electric motor-driven charge air compressor. 38. The charge air system for a four-cycle internal combustion engine of claim 37 wherein a control means is connected to said electric motor of said electric motor-driven compressor, said control means receiving signals to energize said motor and drive said compressor when required to supplement said turbocompressor for the purpose of lowering levels of harmful pollutants in d e engine exhaust. 39. The charge air system for a four-cycle internal combustion engine of claim 38 wherein said control means receives signals from engine operating conditions, including engine rpm, intake manifold pressure and engine demand to power said electric motor. 40. The mediod of supplying charge air to a four-cycle internal combustion engine comprising the steps of: connecting an exhaust gas-driven turbocompressor to boui an exhaust port and an inlet port of a four-cycle internal combustion engine to supply charge air thereto; and connecting an electric motor-driven centrifugal compressor to supply additional air to the four-cycle internal combustion engine as required to lower levels of harmful pollutants in the engine exhaust when the engine is called on to accelerate from low to high operating speeds. 41. The mediod of supplying charge air to a four-cycle internal combustion engine of claim 40 wherein die electric motor-driven centrifugal compressor is connected in parallel to the exhaust gas-driven turbocompressor to deliver additional volume of air to lower levels of harmful pollutants in die engine exhaust when die engine is called upon to accelerate from low to high operating speeds. 42. The mediod of supplying charge air to a four-cycle internal combustion engine in accordance with claim 40 wherein the electric motor- driven centrifugal compressor is connected in series with die turbocompressor to supply higher pressure to die intake port of the engine when die turbocompressor is running at low speed due to low exhaust gas flow to provide adequate air for fast acceleration of the engine and lower levels of harmful pollutants in die engine exhaust when die engine is called upon to accelerate. 43. The charge air system in accordance widi claim 3 wherein said second compressor is part of a motor-assisted turbocharger. 44. The charge air system in accordance widi claim 13 wherein an electric motor is connected to assist said exhaust gas turbine in driving said odier compressor. 45. The charge air system in accordance wid claim 44 wherein said electric motor (a) is controlled and energized to assist said exhaust gas turbine in maintaining a predetermined minimum level of charge air from said odier compressor, (b) is controlled and de-energized when said exhaust gas turbine can provide a predetermined high level of charge air from die internal combustion engine exhaust, and (c) is controlled and super- energized when a predetermined acceleration load is demanded of said internal combustion engine. 46. The charge air system in accordance widi claim 33, further comprising: an electric motor-assisted turbocharger connected widi said engine exhaust and operable in conjunction widi said centrifugal charge air compressor to provide charge air to said intake port of said internal combustion engine, said electric motor being connected to said control and operated tiiereby to provide, wid die energy of said engine exhaust, a predetermined minimum level of charge air to said intake port. 47. The charge air system in accordance widi claim 46 wherein said electric motor is super-energized when die engine is called upon to accelerate from low to high operating speeds. 48. The charge air system in accordance with claim 46 wherein said motor-assisted turbocharger provides a rotor speed signal to said control and said control de-energizes said electric motor at rotor speeds above a predetermined high level. 49. The charge air system in accordance with claim 36 wherein said additional electric powered air supply means is an electric motor widiin said turbocompressor. 50. The mediod in accordance widi claim 40 further comprising die step of connecting an electric motor to die exhaust driven turbocompressor to assist die turbocompressor in supplying charge air to die internal combustion engine. 51. The mediod in accordance wid claim 50 further comprising maintaining a predetermined minimal level of charge air from said turbocompressor by die apphcation of electric power to said electric motor. 52. The mediod in accordance widi claim 51 further comprising de-energizing said electric motor when said turbocompressor can provide a predetermined level of charge air witiiout die assistance of said electric motor. 53. The mediod in accordance with claim 50 furdier comprising applying a higher level of electric power to said electric motor when acceleration in excess of a predetermined level is demanded of said internal combustion engine.

Inventors: HALIMI EDWARD M, MALOOF RALPH P, WOOLLENWEBER WILLIAM E, HALIMI, EDWARD, M., MALOOF, RALPH, P., WOOLLENWEBER, WILLIAM, E.
Applicants: HALIMI EDWARD M, MALOOF RALPH P, TURBODYNE SYS INC, WOOLLENWEBER WILLIAM E, HALIMI, EDWARD, M., MALOOF, RALPH, P., TURBODYNE SYSTEMS, INC., WOOLLENWEBER, WILLIAM, E.
Application year: 1996
Main classification: F02B37
IPC codes: F02B33, F02B37, F02B39