Indian Patents. 256828:"A CHARGE AIR SYSTEM FOR A FOUR-CYCLE INTERNAL COMBUSTION ENGINE"

Title of Invention	"A CHARGE AIR SYSTEM FOR A FOUR-CYCLE INTERNAL COMBUSTION ENGINE"
Abstract	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 that they are serially connected to supply air to said intake port and; an electric motor connected to drive one of said compressors.

Full Text	The present invention relates to a charge air system for a four-cycle internal combustion engine. 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, the 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 Accordingly, there is provided 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 that they are serially connected to supply air to said intake port; and an electric motor connected to drive one of said compressors. 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 outlet 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 er.gine performance due to the resulting lower exhaust back pressure. The pressure ratio of the motor-driven compressor need only be 13 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 method of improving the performance of naturally aspixated 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 b urned 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 method 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 the appended claims. The present invention, both a3 to its organization and manner of operation, together with further objects and advantages thereof, may be best underj;tood by reference to the following description. Brief Description of the Drawings Fig, 1 shows one of the 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 mc tor-driven compressor is placed in series with a turbocharger compressor. " """-" Fig. 2A shows a second preferred embodimenToTa 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 third preferred embodiment of a charge air system of this invention for a four-cycle engine where a motor-driven compressor is used to charge the 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 this 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 conprcssor can be used either in parallel or in series with 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 cass, the cylinder has an upright axis. Piston 16 reciprocates up and down within the cylinder under control of crank 18. The crank rotates around the crankshaft axis and is connected to the piston by means of connecting rod 20. The crankshaft and connecting rod are housed in crarikcase 22, which may contain oil for lubricating die lower part of the 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 the 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 the intake valve and exhaust valve for each cylinder is coordinated with die movement of the piston by mechanical interconnection of the cranksliaft with the cam shafts which control the valves. Fuel is introduced into the cylinder at the appropriate time through fuel injection nozzle 34. In some cases, the fuel may be delivered to the cylinder as a fuel-air mixture through the intake valve, By increasing the amount of air delivered to the cylinder and by corresponding increase of fuel, the power output of the engine 10 can be appreciably increased. At the same time, the engine efficiency can increase to yield more work per unit of fuel. To provide the additional air, centrifugal compressor 36 has its outlet tube 38 connected to tie intake port 26. However, if the engine 10 requires an intake manifold pressure of 4.5 times the atmospheric pressure, which is a 4,5 pressure ratio, such is beyond the 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 through a suitable air filter. The outlet tube 44 from compressor 40 is connected to the inlet of compressor 36, which thus becomes the second stage compressor. The use of series compressors results in the multiplying of the pressure ratio. As an example, for an engine which requires a 4.5 pressure raiio, the low pressure stage centrifugal compressor 40 would operate at a 2.1 pressure ratio, while the 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 through exhaust pipe 50 to the inlet of first stage turbine 46, The outlet of the first stage turbine 46 is connected by exhaust pipe 52 to the 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 the exhaust port, and this high back pressure increases the pumping loss of the engine. The exhaust gas turbine 46 is directly coupled to drive the centrifugal compressor 3(3, and the exhausl gas turbine 48 is directly coupled to drive the centrifugal compressor 40, The four-cycle internal combustion engine 54 illustrated in Fig, 2 is the same as the engine 10. Turbocharger 56 comprises an exhaust gas turbine 58 which is connected to receive hot exhaust gas from (he engine and expand it to atmosphere. The turbine 58 drives centrifugal compressor 60, which delivers air under pressure to the intake port of engine 54. The rotor in the exhaust gas turbine is directly connected to drive the rotor in the centrifugal compressor, In accordance with this invention, centrifugal compressor 62 has its compressed air outlet connected to the 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 throttle sensor. Thus, die compressor,} are arranged in scries, but the first stage compressor 62 is not driven by an exhaust gas turbine and, thus, does not raise the exhaust gas back pressure, If one of the series turbochargers is replaced with a motor-driven compressor, the result is a less complicated mechanical arrangement since only one turbocharger is mounted on the engine exhaust system and the back pressure on the engine is substantially reduced. 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 aUnospheric pressure. However, if a motor-driven compressor 62 is used in series with the turbocharger compressor, the required pressure ratio of 2,5 can be achieved by producing 1.3 from the motor-driven compressor 62 and 1,92 from the turbocharger compressor 60. Reducing the charging pressure ratio of the 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 significantly reduced, resulting in lower fuel consumption, higher power output, or both. The motor-driven compressor 60 is controlled by signals from demand, intake manifold pressure, engine speed and the like to yield these results, plus decreased exhaust gas pollution. The operation of the system shown in Fig. 2 can be enhanced by the 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 application, Serial No, 08/680,671, filed July 16, 1996. The turbocharger 156 shown in Fig. 2A (including turbine 158 and centrifugal compressor 160) has an internal motor-generator 156a that can be energized by the control means 67 in response to appropriate input signals. For example, a boost pressure sensor can be used to seM a signal to the control means 67 when the engine is operating at low speed and load. When the engine is called upon to accelerate, the boost pressure sensor or a throttle sensor can generate an input signal to control 67 and motor-driven compressor and the motor in the turbocharger are both energized to provide an increased air supply during the acceleration period. When the turbocharger is running fast enough to provide an adequate air supply to the engine, a rotor speed signal from the motor 156a in motor-assisted turbocharger 156 is delivered to control 67, and both motors are de-energized to eliminate the need for external power. Additionally, at high engine speed and load, when maximum power output is required, the internal motor-generator 156a in the 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 the engine 10. In this case, a centrifugal compressor 68 is connected by intake manifold 70 to the inlet port. Compressor 68 is driven by electric motor 72 to supply charge air to the engine. A control system 57 is connected to the motor and to an electric power source 69 so that the compressor 68 is driven by the motor 72 when a quick engine accelerab'on is anticipated. The motor-driven compressor can be maintained at a predetermined minimum speed to provide boost pressure in the 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 The series connection of centrifugal compressors is shown in Fig. 2. A problem arises when the engine 54 is being started or is running at idle with either no exhaust gas flow to the turbine 58 or a minimum amount which does not run the turbocompressor sufficiently fast to provide enough air for acceleration. The employment of the compressor 62 at that point helps, but the air drag through compressor 60 when it is running at low speed sometimes does not permit rapid engine acceleration. Foi' this reason, the 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 the exhaust pipe and expands the exhaust gas to atmosphere. This drives the centrifugal compressor which delivers air under pressure out through tube 78 and reed valve 80 to the intake manifold 82. In parallel to this, centrifugal compressor 84 is driven by electric motor 86 to deliver air through reed valve 88 to manifold 82. This arrangement of parallel connected turbocompressor and electric motor compressor improves the performance of a rurbocharged four-cycle engine by compensating for the time lag of the turbochaigcr compressor 7(5 upon sudden throttle opening, by providing an electrically powered auxiliary compressor 84 which is connected direcdy to the engine intake duct between the turbocharger compressor and the engine. Backflow of compressed air from the electric compressor through the turbocharger is prevented by a pressure activated check valve 80. When sufficient speed is attained by the turbocompressor, its pressure output would overcome the check valve allowing its compressed air to enter the engine manifold, Backflow of air from die turbocompressor through the electric :ompressor is prevented by a second pressure activated check valve 88. A suitable motor controller with pressure sensors, speed sensor and a deirand sensor would be employed to provide timely motor switching, The engine 90 shown in Fig. 5 is the same as the engine 10. The use of an exhaust gas-drive turbine driving an engine driving centrifugal compressor, together with an electric motor-driven compressor connected in series with the turbocompressor has been described with respect to Fig. 2. The. use of an exhaust gas driven turbocompressor with 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 scries connection of the air system is desired and, in other operating conditions, a parallel connection is desired. Fig. 5 shows the manner in which ducting is connected so that the output of an electric motor-driven centrifugal compressor is .'selectively connected in parallel to or in series with an exhaust-driven turbocompressor. The exhaust pipe 92 is connected to the exhaust gas turbine portion 94 of turbocharger 96, The centrifugal compressor 98 of the turbocharger has its pressurized air outpu t connected to intake manifold 100 of engine 90. The intake manifold is connected to the intake port in conventional manner. Reed valve 102 is positioned in the intake manifold to permit air flow from the compressor 98 only in die downstream direction toward the intake port. Rate sensor 104 is positioned in the manifold to determine the flow rate of air from the compressor 98. This rate sensor is used in the 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 the wye is connected from air cleaner 108 through inlet tube 110 to die wye, Butterfly valve 112 is positioned in inlet tube 110 so thai 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 through inlet tube 118, which is connected by a tee to inlet tube 110. The compressed air output of compressor 114 is directed to outlet tube 120 which has a reed valve 122 therein and is connected by means of a tee connection to intake manifold 100 downstream of reed valve 122. Thus, the compressors 98 and 114 can operate in parallel in providing their outputs to intake manifold 100. In addition, outlet tube 124 is connected as a tee to the outlet tube 120 and is connected to the other branch of the wye 106. Butterfly valve 126 is positioned in outlet tube 124 to selectively close that tube. The two butterfly valves 112 and 126 are connected together and are operated by the same actuator 128 so that, when one butterfly valve is closed, the other 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 the like to control the amount of power to motor 116 and to control air actuator 128. With the actuator and the butterfly valves 112 and 126 in the position shown in Fig..'>, the compressor 98 receives its suction from the air cleaner and the two compressors are operating in parallel. With the actuator 128 m the opposite position, with valve 112 closed and valve 126 open, the 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 thus seen that, with additional ducting and valves, the flow path of the motor-driven compressor is directed into the intake of the turbocharger compressor 98 at the moment when turbocharger pressure output exceeds the electric motor compressor pressure output, In this way, the pressure output from the electric motor-driven compressor is used to compound the turbocharger pressure for a short time in order to sustain the enhancement of charging pressure from the electric motor-driven compressor. At some pressure rise rate, the rate sensor 104 will signal the motor control 130, and the air actuator 128 will set lhe synchronized valves 112, 126 to block backflow into the electric motor-driven compressor and switch off power to the motor 116 so that die turbocharger will operate in a normal unassisted mode. In the.ne several ways, an electric motor-driven compressor 114, often in combination with a turbocompressor 96, enhances the operating conditions of a four-cycle internal combustion engine. It is desirable to place the system shown in Fig. 5 in Q\v 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 with a significant amount of boost pressure. Thus, the 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 the engine intake manifold 100 through valve 122, When the engine 90 accelerates to a speed where the turbocharger compressor 98 is capable of charging the engine .sufficiently, the turbocharger compressor outlet pressure opens valve 102 and provides high boost pressure to the engine. At this time, a boost pressure signal from sensor 104 tells the control 130 to de-energize the motor 116 driving compressor 114 and air back flow through the motor-driven compressor 114 is prevented by check valve 122. During the acceleration j«riod, the butterfly valves 126 and 112 remain in the position shown in Fig. 5, depicting parallel operation of the compressors. When the engine is required to operate at maximum power oulputj it is desirable to change the system over to a series arrangement of the compressors, An engine load signal sent to the control 130 causes the butterfly valve 126 to open and simultaneously causes butterfly valve 122 to close. The engine intake air flow path is then from the air cleaner 108 through duct 118 to compressor 114, The compressed air from compressor 114 flows through duct 120, through butterfly valve 126 to the intake of the turbocharger compressor 98. Super-compressed air then flews from tlve turbocharger compressor 98 through check valve 102 to duct ICO, leading to the engine intake manifold. Check valve 122 prevents backfl.ow of die super-compressed air into duct 120. Upon deceleration of the 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 the control 130 and moves the butterfly valves back to the position shown in Fig. 5, which places the compressors in a parallel arrangement in preparation for the next engine acceleration. The parallel arrangement of compressors 114 and 98 provides the engine 90 with an increase in boost pressure during acceleration period s above that which could be supplied by the turbocharger 96 along. This reduces acceleration time, reduces smoke during acceleration, and reduces harmful exhaust emissions, The change-over to series operation of the compressors 114 and 98 provide the engine with high boost pressure due to ihe multiplication of the compressor pressure ratios. The series compression of the intake air provides high boost pressure to the engine so that higher power output can be produced, compared with that which could be provided by the single turbocharger alone. Fig. 6 is the same as the system of Fig. 5 except that turbocharger 196 having turbine 194 and compressor 198 has an internal moi.or- generator 196a that is operable from power supply 132 by control 130 to enhance the operation of the turbocharger 196. For example, during periods of low engine speed and boost, a signal from sensor 101 activates control 130 to provide sufficient power to the 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 supplier higher power to the motor 196a to increase the turbocharger speed and boost to provide me internal combustion engine 90 with the demanded acceleration. Turbocharger rotor speed signals can be provided to control 130 from motor 196a to de-energize the motor 196a when the turbocharger 196 is providing sufficient compressed air boost from the exhaust energy of the internal combustion engine. Thus, the provision and operation of a motor assisted turbocharger, as set forth above, can further enhance, and contribute further flexibility in the operation of the multiple compressor, series-parallel system of Fig. 5. This invention has been described in its presently conterrplated best modes, and it is clear that it is susceptible to numerous modifications, modes and embodiments within the ability of those skilled in tho art and without the exercise of the inventive faculty, Accordingly, the scope of this invention is defined by the scope of the following claims, WE CLAIM: 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 that 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 as claimed in claim 1 wherein said first compressor is driven by said electric motor. 3. The charge air system for a four-cycle internal combustion engine as claimed in 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 as claimed in claim 3 wherein said four-cycle internal combustion engine has an exhaust port and there is ducting connecting said exhaust port to said exhaust gas turbine so that 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 as claimed in claim 4 wherein said first compressor is driven by said electric motor. 6. The charge air system for a four-cycle internal combustion engine as claimed in 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 as claimed in claim 6 wherein said air tube is also connected to said intake manifold so that 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 as claimed in claim 7 wherein there 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 as claimed in claim.8 wherein said valve is a check valve. 10. The charge air system for a four-cycle internal combustion engine as claimed in claim 8 wherein there 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 that said compressors operate in parallel. 11. The charge air system for a four-cycle internal combustion engine as claimed in 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 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 as claimed in claim 11 wherein said second compressor is connected to an air inlet and there is an actuatable valve in said air inlets, said actuatable valves being connected together so that when one is open the other is closed so that said second compressor is selectively connected to said air inlet or to said air tube from said first compressor. 13. A charge air system as claimed in claim 1, 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 outlet, 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 outlet, said outlet 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 outlet 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 the other 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 that 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 there 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 as claimed in claim 13 wherein said first centrifugal compressor is electric motor-driven. 15. The charge air system for a four-cycle internal combustion engine as claimed in 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 as claimed in claim 15 wherein said first centrifugal compressor is electric motor-driven. 17. The charge air system for a four-cycle internal combustion engine as claimed in claim 13 having control means connected to supply power to said electric motor and control said electric motor and control the output of said electric motor-driven centrifugal charge air compressor so that said electric motor-driven compressor supplies adequate charge air in preparation for fast acceleration of said four-cycle internal combustion engine when the output of said exhaust gas turbine-driven centrifugal compressor is inadequate. 18. The charge air system for a four-cycle internal combustion engine as claimed in claim 17 wherein said first centrifugal compressor is electric motor-driven. 19. The charge air system for a four-cycle internal combustion engine as claimed in 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 as claimed in claim 19 wherein said first centrifugal compressor is electric motor-driven. 21. The charge air system for a four-cycle internal combustion engine as claimed in claim 13 wherein an outlet 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 as claimed in claim 21 wherein said first centrifugal compressor is electric motor-driven. 23. The charge air system for a four-cycle internal combustion engine as claimed, in 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 with claim 21 wherein said valving has an actuatable valve to selectively open and close said duct between the outlet of said first centrifugal compressor and the inlet of said second centrifugal compressor. A charge air system as claimed in claim 1, 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 outlet 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 outlet, said outlet 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 that said motor-driven first centrifugal compressor is powered separately from exhaust as so that it can provide high charge air volume for the purpose of reducing levels of harmful pollutants in the engine exhaust gas when the engine is called upon to accelerate from low to high operating speeds. 26. The charge air system for a four-cycle internal combustion engine as claimed in claim 25 wherein there is a valve in the outlet 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 as claimed in claim 25 wherein there is a valve in the outlet of said second centrifugal compressor to prevent backflow of air through said second compressor when said first compressor provides higher pressure. 28. The charge air system for a four-cycle internal combustion engine as claimed in claim 27 wherein said valve is a check valve. 29. The charge air system for a four-cycle internal combustion engine as claimed in claim 26 wherein said valve is a check valve. 30. The charge air system for a four-cycle internal combustion engine as claimed in claim 25 wherein there is a check valve in the outlet of each of said compressors to prevent backflow of air. 31. The charge air system for a four-cycle internal combustion engine as claimed, in claim 25 wherein a duct connected between said outlet 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 as claimed in claim 31 wherein said duct connecting said outlet of said first centrifugal compressor to said inlet of said second centrifugal compressor includes a selectively operable valve so that 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 as claimed in claim 1 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 outlet, said outlet 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 as claimed in claim 33 wherein said control means is connected to energize said electric motor, said control means receiving signals corresponding to engine operating conditions. 35. The charge air system for a four-cycle internal combustion engine as claimed in 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 as claimed in claim 1 comprising: a four-cycle internal combustion engine having an intake port and an exhaust port, a turbocompressor connected to both 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 the engine 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. 37. The charge air system for a four-cycle internal combustion engine as claimed in 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 as claimed in 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 the engine exhaust. 39. The charge air system for a four-cycle internal combustion engine as claimed in 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 method of supplying charge air to a four-cycle internal combustion engine utilizing the charge air system as claimed in claim 1 comprising the steps of: connecting an exhaust gas-driven turbocompressor to both 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 charge air system as claimed in claim 3 wherein said second compressor is part of a motor-assisted turbocharger. 42. The charge air system as claimed in claim 13 wherein an electric motor is connected to assist said exhaust gas turbine in driving said other compressor. 43. The charge air system as claimed in 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 other compressor, (b) is controlled and de-energized when said exhaust gas turbine can provide a predetermined high level of charge air from the internal combustion engine exhaust, and (c) is controlled and super-energized when a predetermined acceleration load is demanded of said internal combustion engine. 44. The charge air system as claimed in claim 33, comprising: an electric motor-assisted turbocharger connected with said engine exhaust and operable in conjunction with 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 thereby to provide, with the energy of said engine exhaust, a predetermined minimum level of charge air to said intake port. 45. The charge air system as claimed in claim 46 wherein said electric motor is super-energized when the engine is called upon to accelerate from low to high operating speeds. 46. The charge air system as claimed in 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. 47. The charge air system as claimed in claim 36 wherein said additional electric powered air supply means is an electric motor within said turbocompressor. 48. The method of supplying charge air to a four-cycle internal combustion engine as claimed in claim 40 wherein the 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 the engine exhaust when the engine is called upon to accelerate from low to high operating speeds. 49. The method of supplying charge air to a four-cycle internal combustion engine as claimed in claim 40 wherein the electric motor-driven centrifugal compressor is connected in series with the turbocompressor to supply higher pressure to the intake port of the engine when the 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 the engine exhaust when the engine is called upon to accelerate. 50. The method as claimed in claim 40 wherein the step of connecting an electric motor to the exhaust driven turbocompressor to assist the turbocompressor in supplying charge air to the internal combustion engine. 51. The method as claimed in claim 50 wherein maintaining a predetermined minimal level of charge air from said turbocompressor by the application of electric power to said electric motor. 52. The method as claimed in claim 51 wherein de-energizing said electric motor when said turbocompressor can provide a predetermined level of charge air without the assistance of said electric motor. 53. The method as claimed in claim 50 wherein 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. 54. A charge air system for a four-cycle internal combustion engine substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

Full Text

The present invention relates to a charge air system for a four-cycle internal
combustion engine.
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, the 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
Accordingly, there is provided 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
that they are serially connected to supply air to said intake port;
and
an electric motor connected to drive one of said compressors.
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 outlet 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 er.gine performance due to the resulting lower exhaust back pressure. The pressure ratio of the motor-driven compressor need only be 13 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 method of improving the performance of naturally aspixated 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 b urned 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 method 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 the appended claims. The present invention, both a3 to its organization and manner of operation, together with further objects and advantages thereof, may be best underj;tood by reference to the following description.
Brief Description of the Drawings
Fig, 1 shows one of the 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 mc tor-driven
compressor is placed in series with a turbocharger compressor. " """-"
Fig. 2A shows a second preferred embodimenToTa 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 third preferred embodiment of a charge air system of this invention for a four-cycle engine where a motor-driven compressor is used to charge the 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 this 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 conprcssor can be used either in parallel or in series with 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 cass, the cylinder has an upright axis. Piston 16 reciprocates up and down within the cylinder under control of crank 18. The crank rotates around the crankshaft axis and is connected to the piston by means of connecting rod 20. The crankshaft and connecting rod are housed in crarikcase 22, which may contain oil for lubricating die lower part of the 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 the 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 the intake valve and exhaust valve for each cylinder is coordinated with die movement of the piston by mechanical interconnection of the cranksliaft with the cam shafts which control the valves. Fuel is introduced into the cylinder at the appropriate time through fuel injection nozzle 34. In some cases, the fuel may be delivered to the cylinder as a fuel-air mixture through the intake valve,
By increasing the amount of air delivered to the cylinder and by corresponding increase of fuel, the power output of the engine 10 can be appreciably increased. At the same time, the engine efficiency can increase to yield more work per unit of fuel. To provide the additional air, centrifugal compressor 36 has its outlet tube 38 connected to tie intake port 26. However, if the engine 10 requires an intake manifold pressure of 4.5 times the atmospheric pressure, which is a 4,5 pressure ratio, such is beyond the 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 through a suitable air filter. The outlet tube 44 from compressor 40 is connected to the inlet of compressor 36, which thus becomes the second stage compressor. The use of series compressors results in the multiplying of the pressure ratio. As an example, for an engine which requires a 4.5 pressure raiio, the low pressure stage centrifugal compressor 40 would operate at a 2.1 pressure ratio, while the 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 through exhaust pipe 50 to the inlet of first stage turbine 46,

The outlet of the first stage turbine 46 is connected by exhaust pipe 52 to the 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 the exhaust port, and this high back pressure increases the pumping loss of the engine. The exhaust gas turbine 46 is directly coupled to drive the centrifugal compressor 3(3, and the exhausl gas turbine 48 is directly coupled to drive the centrifugal compressor 40,
The four-cycle internal combustion engine 54 illustrated in Fig, 2 is the same as the engine 10. Turbocharger 56 comprises an exhaust gas turbine 58 which is connected to receive hot exhaust gas from (he engine and expand it to atmosphere. The turbine 58 drives centrifugal compressor 60, which delivers air under pressure to the intake port of engine 54. The rotor in the exhaust gas turbine is directly connected to drive the rotor in the centrifugal compressor,
In accordance with this invention, centrifugal compressor 62 has its compressed air outlet connected to the 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 throttle sensor. Thus, die compressor,} are arranged in scries, but the first stage compressor 62 is not driven by an exhaust gas turbine and, thus, does not raise the exhaust gas back pressure, If one of the series turbochargers is replaced with a motor-driven compressor, the result is a less complicated mechanical arrangement since only one turbocharger is mounted on the engine exhaust system and the back pressure on the engine is substantially reduced. 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 aUnospheric pressure. However, if a motor-driven compressor 62 is used

in series with the turbocharger compressor, the required pressure ratio of 2,5 can be achieved by producing 1.3 from the motor-driven compressor 62 and 1,92 from the turbocharger compressor 60. Reducing the charging pressure ratio of the 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 significantly reduced, resulting in lower fuel consumption, higher power output, or both. The motor-driven compressor 60 is controlled by signals from demand, intake manifold pressure, engine speed and the like to yield these results, plus decreased exhaust gas pollution.
The operation of the system shown in Fig. 2 can be enhanced by the 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 application, Serial No, 08/680,671, filed July 16, 1996.
The turbocharger 156 shown in Fig. 2A (including turbine 158 and centrifugal compressor 160) has an internal motor-generator 156a that can be energized by the control means 67 in response to appropriate input signals. For example, a boost pressure sensor can be used to seM a signal to the control means 67 when the engine is operating at low speed and load. When the engine is called upon to accelerate, the boost pressure sensor or a throttle sensor can generate an input signal to control 67 and motor-driven compressor and the motor in the turbocharger are both energized to provide an increased air supply during the acceleration period. When the turbocharger is running fast enough to provide an adequate air supply to the engine, a rotor speed signal from the motor 156a in motor-assisted turbocharger 156 is delivered to control 67, and both motors are de-energized to eliminate the need for external power.
Additionally, at high engine speed and load, when maximum power
output is required, the internal motor-generator 156a in the 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 the engine 10. In this case, a centrifugal compressor 68 is connected by intake manifold 70 to the inlet port. Compressor 68 is driven by electric motor 72 to supply charge air to the engine. A control system 57 is connected to the motor and to an electric power source 69 so that the compressor 68 is driven by the motor 72 when a quick engine accelerab'on is anticipated. The motor-driven compressor can be maintained at a predetermined minimum speed to provide boost pressure in the 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 The series connection of centrifugal compressors is shown in Fig. 2. A problem arises when the engine 54 is being started or is running at idle with either no exhaust gas flow to the turbine 58 or a minimum amount which does not run the turbocompressor sufficiently fast to provide enough air for acceleration. The employment of the compressor 62 at that point helps, but the air drag through compressor 60 when it is running at low speed sometimes does not permit rapid engine acceleration. Foi' this reason, the 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 the exhaust pipe and expands the exhaust gas to atmosphere. This drives the centrifugal compressor which delivers air under pressure out through tube

78 and reed valve 80 to the intake manifold 82. In parallel to this, centrifugal compressor 84 is driven by electric motor 86 to deliver air through reed valve 88 to manifold 82.
This arrangement of parallel connected turbocompressor and electric motor compressor improves the performance of a rurbocharged four-cycle engine by compensating for the time lag of the turbochaigcr compressor 7(5 upon sudden throttle opening, by providing an electrically powered auxiliary compressor 84 which is connected direcdy to the engine intake duct between the turbocharger compressor and the engine. Backflow of compressed air from the electric compressor through the turbocharger is prevented by a pressure activated check valve 80. When sufficient speed is attained by the turbocompressor, its pressure output would overcome the check valve allowing its compressed air to enter the engine manifold, Backflow of air from die turbocompressor through the electric :ompressor is prevented by a second pressure activated check valve 88. A suitable motor controller with pressure sensors, speed sensor and a deirand sensor would be employed to provide timely motor switching,
The engine 90 shown in Fig. 5 is the same as the engine 10. The use of an exhaust gas-drive turbine driving an engine driving centrifugal compressor, together with an electric motor-driven compressor connected in series with the turbocompressor has been described with respect to Fig. 2. The. use of an exhaust gas driven turbocompressor with 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 scries connection of the air system is desired and, in other operating conditions, a parallel connection is desired. Fig. 5 shows the manner in which ducting is connected so that the output of an electric motor-driven centrifugal compressor is .'selectively connected in parallel to or in series with an exhaust-driven turbocompressor. The exhaust pipe 92 is connected to the exhaust gas turbine portion 94 of turbocharger 96, The centrifugal compressor 98 of the turbocharger has its pressurized air outpu t connected

to intake manifold 100 of engine 90. The intake manifold is connected to the intake port in conventional manner. Reed valve 102 is positioned in the intake manifold to permit air flow from the compressor 98 only in die downstream direction toward the intake port. Rate sensor 104 is positioned in the manifold to determine the flow rate of air from the compressor 98. This rate sensor is used in the 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 the wye is connected from air cleaner 108 through inlet tube 110 to die wye, Butterfly valve 112 is positioned in inlet tube 110 so thai 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 through inlet tube 118, which is connected by a tee to inlet tube 110. The compressed air output of compressor 114 is directed to outlet tube 120 which has a reed valve 122 therein and is connected by means of a tee connection to intake manifold 100 downstream of reed valve 122. Thus, the compressors 98 and 114 can operate in parallel in providing their outputs to intake manifold 100. In addition, outlet tube 124 is connected as a tee to the outlet tube 120 and is connected to the other branch of the wye 106. Butterfly valve 126 is positioned in outlet tube 124 to selectively close that tube. The two butterfly valves 112 and 126 are connected together and are operated by the same actuator 128 so that, when one butterfly valve is closed, the other 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 the like to control the amount of power to motor 116 and to control air actuator 128. With the actuator and the butterfly valves 112 and 126 in the position shown in Fig..'>, the compressor 98 receives its suction from the air cleaner and the two compressors are operating in parallel. With the actuator 128 m the
opposite position, with valve 112 closed and valve 126 open, the 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 thus seen that, with additional ducting and valves, the flow path of the motor-driven compressor is directed into the intake of the turbocharger compressor 98 at the moment when turbocharger pressure output exceeds the electric motor compressor pressure output, In this way, the pressure output from the electric motor-driven compressor is used to compound the turbocharger pressure for a short time in order to sustain the enhancement of charging pressure from the electric motor-driven compressor. At some pressure rise rate, the rate sensor 104 will signal the motor control 130, and the air actuator 128 will set lhe synchronized valves 112, 126 to block backflow into the electric motor-driven compressor and switch off power to the motor 116 so that die turbocharger will operate in a normal unassisted mode. In the.ne several ways, an electric motor-driven compressor 114, often in combination with a turbocompressor 96, enhances the operating conditions of a four-cycle internal combustion engine.
It is desirable to place the system shown in Fig. 5 in Q\v 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 with a significant amount of boost pressure. Thus, the 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 the engine intake manifold 100 through valve 122, When the engine 90 accelerates to a speed where the turbocharger compressor 98 is capable of charging the engine .sufficiently, the turbocharger compressor outlet pressure opens valve 102 and provides high boost pressure to the engine. At this time, a boost pressure signal from sensor 104 tells the control 130 to de-energize the motor 116 driving compressor 114 and air back flow through the motor-driven compressor

114 is prevented by check valve 122. During the acceleration j«riod, the butterfly valves 126 and 112 remain in the position shown in Fig. 5, depicting parallel operation of the compressors.
When the engine is required to operate at maximum power oulputj it is desirable to change the system over to a series arrangement of the compressors, An engine load signal sent to the control 130 causes the butterfly valve 126 to open and simultaneously causes butterfly valve 122 to close. The engine intake air flow path is then from the air cleaner 108 through duct 118 to compressor 114, The compressed air from compressor 114 flows through duct 120, through butterfly valve 126 to the intake of the turbocharger compressor 98. Super-compressed air then flews from tlve turbocharger compressor 98 through check valve 102 to duct ICO, leading to the engine intake manifold. Check valve 122 prevents backfl.ow of die super-compressed air into duct 120.
Upon deceleration of the 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 the control 130 and moves the butterfly valves back to the position shown in Fig. 5, which places the compressors in a parallel arrangement in preparation for the next engine acceleration. The parallel arrangement of compressors 114 and 98 provides the engine 90 with an increase in boost pressure during acceleration period s above that which could be supplied by the turbocharger 96 along. This reduces acceleration time, reduces smoke during acceleration, and reduces harmful exhaust emissions, The change-over to series operation of the compressors 114 and 98 provide the engine with high boost pressure due to ihe multiplication of the compressor pressure ratios. The series compression of the intake air provides high boost pressure to the engine so that higher power output can be produced, compared with that which could be provided by the single turbocharger alone.
Fig. 6 is the same as the system of Fig. 5 except that turbocharger 196 having turbine 194 and compressor 198 has an internal moi.or-

generator 196a that is operable from power supply 132 by control 130 to enhance the operation of the turbocharger 196. For example, during periods of low engine speed and boost, a signal from sensor 101 activates control 130 to provide sufficient power to the 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 supplier higher power to the motor 196a to increase the turbocharger speed and boost to provide me internal combustion engine 90 with the demanded acceleration. Turbocharger rotor speed signals can be provided to control 130 from motor 196a to de-energize the motor 196a when the turbocharger 196 is providing sufficient compressed air boost from the exhaust energy of the internal combustion engine.
Thus, the provision and operation of a motor assisted turbocharger, as set forth above, can further enhance, and contribute further flexibility in the operation of the multiple compressor, series-parallel system of Fig. 5.
This invention has been described in its presently conterrplated best modes, and it is clear that it is susceptible to numerous modifications, modes and embodiments within the ability of those skilled in tho art and without the exercise of the inventive faculty, Accordingly, the scope of this invention is defined by the scope of the following claims,

WE CLAIM:
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
that 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 as claimed in claim 1 wherein said first compressor is driven by said electric motor.
3. The charge air system for a four-cycle internal combustion engine as claimed in 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 as claimed in claim 3 wherein said four-cycle internal combustion engine has an exhaust port and there is ducting connecting said exhaust port to said exhaust gas turbine so that 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 as claimed in claim 4 wherein said first compressor is driven by said electric motor.
6. The charge air system for a four-cycle internal combustion engine as claimed in 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 as claimed in claim 6 wherein said air tube is also connected to said intake manifold so that 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 as claimed in claim 7 wherein there 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 as claimed in claim.8 wherein said valve is a check valve.
10. The charge air system for a four-cycle internal combustion engine as claimed in claim 8 wherein there 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 that said compressors operate in parallel.
11. The charge air system for a four-cycle internal combustion engine as claimed in 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 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 as claimed in claim 11 wherein said second compressor is connected to an air inlet and there is an actuatable valve in said air inlets, said actuatable valves being connected together so that when one is open the other is closed so that said second compressor is selectively connected to said air inlet or to said air tube from said first compressor.
13. A charge air system as claimed in claim 1, 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 outlet, 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 outlet, said outlet 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 outlet 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 the other 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 that 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 there 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 as claimed in claim 13 wherein said first centrifugal compressor is electric motor-driven.
15. The charge air system for a four-cycle internal combustion engine as claimed in 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 as claimed in claim 15 wherein said first centrifugal compressor is
electric motor-driven.
17. The charge air system for a four-cycle internal combustion engine as claimed in claim 13 having control means connected to supply power to said electric motor and control said electric motor and control the output of said electric motor-driven centrifugal charge air compressor so that said electric motor-driven compressor supplies adequate charge air in preparation for fast acceleration of said four-cycle internal combustion engine when the output of said exhaust gas turbine-driven centrifugal compressor is inadequate.
18. The charge air system for a four-cycle internal combustion engine as claimed in claim 17 wherein said first centrifugal compressor is electric motor-driven.
19. The charge air system for a four-cycle internal combustion engine as
claimed in 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 as claimed in claim 19 wherein said first centrifugal compressor is electric motor-driven.
21. The charge air system for a four-cycle internal combustion engine as claimed in claim 13 wherein an outlet 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 as claimed in claim 21 wherein said first centrifugal compressor is electric motor-driven.
23. The charge air system for a four-cycle internal combustion engine as claimed, in 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 with claim 21 wherein said valving has an actuatable valve to selectively open and close said duct between the outlet of said first centrifugal compressor and the inlet of said second centrifugal
compressor.
A charge air system as claimed in claim 1, 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 outlet 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 outlet, said outlet 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 that said motor-driven first centrifugal compressor is powered separately from exhaust as so that it can provide high charge air volume for the purpose of reducing levels of harmful pollutants in the engine exhaust gas when the engine is called upon to accelerate from low to high operating speeds.
26. The charge air system for a four-cycle internal combustion engine as claimed in claim 25 wherein there is a valve in the outlet 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 as claimed in claim 25 wherein there is a valve in the outlet of said second centrifugal compressor to prevent backflow of air through said second compressor when said first compressor provides higher pressure.
28. The charge air system for a four-cycle internal combustion engine as claimed in claim 27 wherein said valve is a check valve.
29. The charge air system for a four-cycle internal combustion engine as claimed in claim 26 wherein said valve is a check valve.
30. The charge air system for a four-cycle internal combustion engine as claimed in claim 25 wherein there is a check valve in the outlet of each of said compressors to prevent backflow of air.
31. The charge air system for a four-cycle internal combustion engine as
claimed, in claim 25 wherein a duct connected between said outlet 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 as claimed in claim 31 wherein said duct connecting said outlet of said first centrifugal compressor to said inlet of said second centrifugal compressor includes a selectively operable valve so that 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 as claimed in claim 1 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 outlet, said outlet 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 as
claimed in claim 33 wherein said control means is connected to
energize said electric motor, said control means receiving signals
corresponding to engine operating conditions.
35. The charge air system for a four-cycle internal combustion engine as claimed in 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 as claimed in claim 1 comprising:
a four-cycle internal combustion engine having an intake port and an exhaust port, a turbocompressor connected to both 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 the engine 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.
37. The charge air system for a four-cycle internal combustion engine as claimed in 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 as claimed in 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 the engine exhaust.
39. The charge air system for a four-cycle internal combustion engine as claimed in 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 method of supplying charge air to a four-cycle internal combustion engine utilizing the charge air system as claimed in claim 1 comprising the steps of:
connecting an exhaust gas-driven turbocompressor to both 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 charge air system as claimed in claim 3 wherein said second compressor is part of a motor-assisted turbocharger.
42. The charge air system as claimed in claim 13 wherein an electric
motor is connected to assist said exhaust gas turbine in driving said
other compressor.
43. The charge air system as claimed in 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 other compressor, (b) is controlled and de-energized when said exhaust gas turbine can provide a predetermined high level of charge air from the internal combustion engine exhaust, and (c) is controlled and super-energized when a predetermined acceleration load is demanded of said internal combustion engine.
44. The charge air system as claimed in claim 33, comprising:
an electric motor-assisted turbocharger connected with said engine exhaust and operable in conjunction with 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 thereby to provide, with the energy of said engine exhaust, a predetermined minimum level of charge air to said intake port.
45. The charge air system as claimed in claim 46 wherein said electric motor is super-energized when the engine is called upon to accelerate from low to high operating speeds.
46. The charge air system as claimed in 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.
47. The charge air system as claimed in claim 36 wherein said additional electric powered air supply means is an electric motor within said turbocompressor.
48. The method of supplying charge air to a four-cycle internal combustion engine as claimed in claim 40 wherein the 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 the engine exhaust when the engine is called upon to accelerate from low to high operating speeds.
49. The method of supplying charge air to a four-cycle internal combustion engine as claimed in claim 40 wherein the electric motor-driven centrifugal compressor is connected in series with the turbocompressor to supply higher pressure to the intake port of the engine when the 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 the engine exhaust when the engine is called upon to accelerate.
50. The method as claimed in claim 40 wherein the step of
connecting an electric motor to the exhaust driven turbocompressor to

assist the turbocompressor in supplying charge air to the internal combustion engine.
51. The method as claimed in claim 50 wherein maintaining a predetermined minimal level of charge air from said turbocompressor by the application of electric power to said electric motor.
52. The method as claimed in claim 51 wherein de-energizing said electric motor when said turbocompressor can provide a predetermined level of charge air without the assistance of said electric motor.
53. The method as claimed in claim 50 wherein 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.
54. A charge air system for a four-cycle internal combustion engine substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

Documents:

2329-del-1996-abstract.pdf

2329-del-1996-claims.pdf

2329-del-1996-complete-spacition(granted).pdf

2329-DEL-1996-Correspondence-Others.pdf

2329-del-1996-correspondence-po.pdf

2329-del-1996-description (complete).pdf

2329-del-1996-drawings.pdf

2329-del-1996-form-1.pdf

2329-del-1996-form-13.pdf

2329-del-1996-form-19.pdf

2329-del-1996-form-2.pdf

2329-del-1996-form-29.pdf

2329-del-1996-form-4.pdf

2329-del-1996-form-6.pdf

2329-del-1996-gpa.pdf

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Patent Number

256828

Indian Patent Application Number

2329/DEL/1996

PG Journal Number

31/2013

Publication Date

02-Aug-2013

Grant Date

31-Jul-2013

Date of Filing

28-Oct-1996

Name of Patentee

TURBODYNE SYSTEMS, INC.,

Applicant Address

6155 CARPINTERIA, CALIFORNIA 93013, U.S.A.

Inventors:

#	Inventor's Name	Inventor's Address
1	EDWARD M. HALIMI.	163 HOT SPRINGS ROAD, MONTECITO, CALIFORNIA 93108, U.S.A.
2	RALPH P. MALOOF	4527 PARK MONACO, CALABASAS, CLIFORNIA 91302, U.S.A.
3	WILLIAM E. WOOLLENWEBER	3169 CAMINO DEL ARCO, CARLSBAD, CALIFORNIA 92009, U.S.A.

PCT International Classification Number

F02B0 37/10

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	08/559,424	1995-11-15	U.S.A.