Internal combustion engines for hybrid powertrain

Abstract

The hybrid powertrain includes an internal combustion engine, a regenerative brake/motor and an electric energy storage device such as a battery. Preferably the internal combustion engine is a diesel engine with programmable injection events and programmable intake and exhaust valve events. The regenerative brake/motor is capable of operating as both an electric generator and as an electric motor. The battery receives electric energy from the regenerative brake. In additional to supplying electricity to the motor, the battery drives the engine accessories. The battery also supplies electric energy to keep the exhaust aftertreatment systems (Lean NOx, NOx absorber, PM Filter) at optimal temperature to improve conversion efficiency. A powertrain controller schedules the energy distribution and driving forces associated with both the diesel engine and the motor to maximize the vehicle fuel economy and to minimize the vehicle exhaust emissions.

Description

FIELD OF THE INVENTION

[0002] The invention relates to internal combustion engines for use in hybrid powertrains to improve fuel economy and to reduce exhaust emissions.

BACKGROUND OF THE INVENTION

[0003] The recent development of hybrid powertrains in the automotive industry has demonstrated encouraging results for reductions in fuel consumption and exhaust emissions. A vehicle with a hybrid powertrain usually includes an internal combustion engine, an electric generator, an electric motor, a battery and other equipment. In series hybrid vehicles, the generator is driven by the mechanical output of the internal combustion engine. The output of the generator is then combined with the output of the battery to drive the electric motor, such that the mechanical output of the motor drives the vehicle. In contrast, the parallel hybrid vehicle includes an internal combustion engine, a regenerative brake/motor and an electric energy storage device such as a battery and other equipment. PHVs are usually driven directly by the mechanical output of the internal combustion engine. However, when the vehicle must be accelerated or decelerated at a rate that cannot be accomplished by the internal combustion engine alone, or if the drive efficiency of the engine would be degraded if only the internal combustion engine were used, the regenerative brake/motor, which is mechanically connected to the internal combustion engine, operates as an electric motor (on acceleration) or as a regenerative brake (on deceleration) to meet the required rate of acceleration or deceleration through the combined output of the internal combustion engine and the regenerative brake/motor.

[0004] The internal combustion engine of hybrid powertrain has narrow operating range. In series hybrid vehicles, the internal combustion engine is not mechanical connected to the driving wheels. In parallel hybrid vehicles, the regenerative brake/motor provides rapid acceleration or deceleration. Therefore, the internal combustion engine used in hybrid powertrains can be optimized for better fuel economy and less exhaust emissions compared to conventional internal combustion engines.

[0005] Examples of hybrid vehicle and their operating modes have been described in detail in several patents: For example, in U.S. Pat. No. 5,656,921, a parallel hybrid vehicle is disclosed having power sources from a SI engine and an electric motor. It employs fuzzy logic rules to adjust the entries in the tables determining the power splitting between the SI engine and the electric motor. The performance measure used to adjust the entries is given by the weighted ratio between the battery current and fuel flow rate. In U.S. Pat. No. 5,943,918, granted to Reed and U.S. Pat. No. 6,164,400 granted to Jankovic, a hybrid powertrain is described which uses power delivered by both the internal combustion engine and the electric motor. A shifting schedule was developed for a multiple ratio transmission to establishing a proportional relationship between accelerator pedal movement and the torque desired at the wheel. U.S. Pat. No. 6,223,106 granted to Toru Yano et al. and U.S. Pat. No. 6,318,487 granted to Yanase et al. each describe a hybrid vehicle control system operable to prevent the battery from being overcharged during regenerating braking. U.S. Pat. No. 5,725,064, describes a control system operable to open the intake and exhaust valves to reduce the pumping loss when the vehicle is operating in reverse or its electric motor driving mode without using a clutch device to disconnect the internal combustion engine from the transmission. Finally, U.S. Pat. No. 6,266,956 describes an exhaust emission control system for a hybrid car using a separate combustion device to heat the catalyst and to provide hydrocarbons as the reducing agent to the lean NOx catalyst.

[0006] The primary focus of the above patents is the drivability of the hybrid vehicle. Unfortunately, little efforts have been applied to the development and integration of the internal combustion engines to optimize the benefits of the hybrid powertrain for lower cost, better fuel economy and lower exhaust emissions, especially, for the heavy-duty diesel engines for the urban and on-highway truck and bus applications.

SUMMARY OF THE INVENTION

[0007] The present invention relates to advanced development of internal combustion engines for hybrid powertrain applications and its exhaust emissions controls for urban and on-highway vehicles. The hybrid powertrain includes a diesel engine, a regenerative brake/motor and an electric energy storage device such as a battery. The regenerative brake/motor is capable of operating as both an electric generator as a result of the regenerative braking to decelerate the vehicle and an electric motor. The battery supplies electric energy to and receives electric energy from the regenerative brake/motor. A powertrain controller schedules the driving forces supplied from at least one of the internal combustion engine and the electric motor.

[0008] The present invention also features a turbocharged diesel engine with capabilities of multiple fuel injection events and rate shaping, variable valve timing, an exhaust aftertreatment system, engine braking, and battery powered accessories, such as water pump and cooling fan etc.

[0009] The electric motor is used to supply supplemental torque to the drivetrain during acceleration and peak torque operating conditions and further acts as the sole power source during low load conditions. The electric motor will also serve as a regenerative brake during the vehicle decelerations. The regenerating brake, in combination with the engine exhaust brake or compression release brake, will provide sufficient retarding power to maintain a proper vehicle speeds on a down slope road. The electricity generated by the regenerating brake will be used to charge the battery.

[0010] The powertrain controller schedules fuel delivery to the diesel engine, monitors the battery power, and schedules the battery power delivery to the electric motor. The diesel engine is calibrated so that the combined power of the drivetrain will deliver sufficient power to the wheels and maintain drivability of the vehicle. Since the engine speed can be measured, the desired engine torque is equal to the engine power divided by engine speed Likewise, the desired motor torque is equal to the power desired from the electric motor divided by the electric motor speed. The power at the wheels is approximately equal to the sum of the power delivered from each of the power sources. The desired power at the wheels is the sum of the desired engine power and the desired electric motor power.

[0011] This strategy requires a fuel-scheduling map for steady state and transient operations of the diesel engine, as well as the functional relationship maps between the diesel engine and the electric motor. The fuel injection system of the diesel engine has multiple injection event capability such as, for example, pilot injection, main injection, post injection, and rate shaping capabilities, (i.e., triangle, boot, square etc.). The fuel schedule map will specify the injection timing, rate shaping, injection pressure and quantity for best engine fuel economy, emission control, and drivability.

[0012] One aspect of the present invention is to power the engine accessories with the battery of the hybrid powertrain. The accessories of current diesel engines are driven by the engines crankshaft which reduces its power output and fuel economy. The present invention uses the battery power, which is generated during the vehicle deceleration, to drive various engine accessories such as, for example, the cooling fan, water pump, engine control module, alternator, air compressor, power steering pump, and air conditioning compressor, etc.

[0013] Another aspect of the present invention is to apply the variable valve timing capability of the diesel engine to reduce the pumping work during the electric motor only mode, to perform cylinder cut-out, and to re-circulate EGR internally by delaying the exhaust valve closing and/or by early intake valve opening to reduce exhaust emissions (variable intake valve closing for increased compression ratio and/or Miller cycle operation).

[0014] A further aspect of the invention is to use the battery power to heat the catalytic converter to increase the catalyst efficiency. Efficiency of the after treatment device such as, for example, an NOx absorber and active lean NOx, are temperature dependent. The converter efficiency is decreased during partial load operation and at start up of the engine due to lower exhaust temperature. By externally heating the catalyst through a battery-powered heater, the catalyst maintains at its optimal conversion efficiency to reduce exhaust emissions.

[0015] The fourth aspect of the invention is to open the exhaust valve during the compression stroke to perform compression release braking in combination with the regenerative braking of the electric motor to control vehicle speed and to prevent overcharge of the battery.

[0016] The fifth aspect of this invention to use motor assisted turbocharger during acceleration to improve the turbo charger responsiveness. The motor is powered the battery of the hybrid powertrain.

[0017] Further areas of applicability of the present invention will become apparent from the detailed description provided hereafter. However, it should be understood that the detailed descript and specific examples, while indicating preferred embodiments of the present invention, are intended for purposes of illustration only since various changes and modifications within the fair scope of the present invention will become apparent to those skilled in this art.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] FIG. 1 is a schematic representation of a conventional hybrid vehicle;

[0019] FIG. 2 is a schematic of a hybrid powertrain according to the present invention with integration of various engine and vehicle components;

[0020] FIG. 3 is a schematic of an alternative hybrid powertrain equipped with clutch and with integration of the engine and vehicle components;

[0021] FIG. 4 is a schematic of an internal combustion engine for use in hybrid powertrain applications;

[0022] FIG. 5 is an illustration of the catalyst conversion efficiency of a hybrid powertrain;

[0023] FIG. 6 illustrates the capabilities of a diesel engine fuel injection system;

[0024] FIG. 7 illustrates the valve lift of variable valve actuation system associated with the internal combustion engine of the present invention;

[0025] FIG. 8 is a schematic of the ECU.;

[0026] FIG. 9 is an operating diagram of steady state torque map for a hybrid vehicle;

[0027] FIG. 10 is an operating diagram of transient operating control of a hybrid vehicle with motor assisted turbocharger;

[0028] FIG. 11 is a flow chart of a control strategy for a heavy-duty hybrid vehicle;

[0029] FIG. 12A is a flow chart for the regenerative brake control; and

[0030] FIG. 12B is a flow chart for catalyst temperature and valve timing control.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0031] A schematic of a conventional serial hybrid powertrain is shown in FIG. 1. The numeral 10 designates a turbocharged diesel engine for use in a vehicle drivetrain. A motor/regenerative brake is shown at 20. Both diesel engine 10 and motor/regenerative brake 20 are connected to a multiple ratio transmission 30. Transmission 30 is mechanically connected to a pair of vehicle driving wheels 40. A battery 50 serves as an energy storage device which is electrically connected to motor/regenerative brake 20. An electronic controller unit 60 controls the overall drivetrain.

[0032] Referring to FIG. 2, the conventional drivetrain of FIG. 1 is shown to be modified to incorporate the features of the present invention. Specifically, FIG. 2 shows an integrated internal combustion engine 10A with the hybrid powertrain. Engine 10A is shown to include various controllable systems including a fuel injection system 11, a throttle system 12, an engine retrading mechanism 13, an aftertreatment system 14, a turbocharger 15, an intake/exhaust valve actuation system 16 for cylinder cutout and variable valve timing, in addition to power-operated accessories 17. Likewise, ECU 60A is shown to include several control functions including a vehicle control function 61, an engine control function 62, a transmission control function 63, a motor-generator brake control function 64, and a battery control function 65.

[0033] FIG. 3 shows an alternative configuration for the integrated internal combustion engine 10A within the hybrid powertrain. Specifically, a clutch device 70 is placed in between internal combustion 10A engine and motor 20.

[0034] FIG. 4 shows more details of the integration of the internal combustion engine and the hybrid powertrain. The clean air passes through an air filter 100 to a compressor 102. Compressor 102, which is driven by a turbine 105, increases the pressure of the air. Air is cooled when it passes through a charge air cooler 104 to increase the air density before entering the intake manifold 106.

[0035] The energy of the exhaust air is used to drive turbine 105 with variable geometric nozzles 108. A high-speed motor 110, which is powered by battery 50 of the hybrid powertrain, will be used to increase turbine's responsiveness at part load operating condition and during acceleration.

[0036] Harmful pollutants, such as NOx and particulate matters (PM), are removed from the exhaust gas before the discharging to the ambient. The efficiency of the after treatment system is temperature dependent. The conversion efficiency is lowered due to low exhaust temperature during low speed and part load and start up operating conditions. An electric heater 112 is used to heat the after treatment system at its optimum conversion temperature at all engine-operating conditions. Battery 50 of the hybrid powertrain provides the power to electric heater 112. The conversion efficiency comparison with and without electric heat is shown in FIG. 5.

[0037] The engine coolant is circulated to cool the engine by a water-pump 114. Hot coolant flows to a radiator 116, which is cooled by a fan 118. Instead of being driven by the engine crankshaft, water pump 114 and cooling fan 118 are powered by battery 50 of the hybrid powertrain.

[0038] The capability of diesel engine fuel injection system 11 is shown in FIG. 6. It has the multiple injection and rate shaping capabilities. The pilot injection reduces the combustion noise and the NOx emissions. The first post injection reduces PM emissions with minimum fuel economy penalty. The second post injection provides hydrocarbon species for catalytic converter to reduce NOx emissions.

[0039] Valve actuators associated with valve actuation mechanism 16 provide variable timing capabilities and its valve lift profile is shown in FIG. 7. The Valve actuators change the opening and closing timing of the intake and exhaust valves, as well as to reopen the valves. By reopening the intake and exhaust valves, it will reduce the pumping loss during the motor only operating mode of the hybrid powertrain. By pre-opening the intake valve during the exhaust blow down stroke, a small portion of the exhaust gas discharges to the intake manifold. This portion of the exhaust gas will be readmitted to the cylinder to mix with fresh air. It is called internal exhaust gas recirculation. It reduces the NOx formation during diesel engine combustion process. Another EGR configuration is to reopen the exhaust valve during the intake stroke. The exhaust gases will reentry from the exhaust manifold to the cylinder due to higher pressure of the exhaust manifold.

[0040] In combination of the diesel engine's injection capabilities and the valve actuation capabilities, one or more cylinders can be cut out during part load or the motor only operating modes to maximize the fuel economy.

[0041] FIG. 8 shows the inputs and outputs of electronic controller 60A. The inputs to the electronic controller include the vehicle torque requirements, vehicle speed, engine speed, engine boost pressure and temperature, battery power level, transmission gear and motor torque level etc. The outputs include engine speed, torque, engine fueling map, motor torque, transmission gear and retarding power etc.

[0042] FIG. 9 shows a steady state map with the engine torque output 130 from the diesel engine 10A and the motor torque output 120 from electric motor 20. The hybrid powertrain demonstrate that vehicle emissions can be effective reduced. For example, if the hybrid powertrain outputs 500 HP at 1200 engine rpm (in which the diesel engine outputs 300 HP at NOx emission level of 3.5 g/hp-hr and the electric motor outputs 200 hp) the hybrid powertrain emission will be equivalent to a 500 HP engine with NOx emission level of 2.1 g/hp-hr.

[0043] FIG. 10 shows time sequences for the hybrid powertrain's is transient responses. Step 150 shows a torque command of a vehicle. A command increases torque demand at time t1 and decreases at time t5. The motor output torque 160 reaches its maximum value at time t2. The engine output torque 170 reaches a specific value at time t4. The combined torque of the hybrid powertrain 180 reaches a specified value at time t3, which has shorter response time than the internal combustion engine alone. As seen, the hybrid powertrain also has fast response at the decrease of command torque.

[0044] FIG. 11 is a flowchart showing the control strategy of the hybrid powertrain. The powertrain ECU 60A in FIG. 3 read the vehicle torque requirement and the engine operating parameters, such as speed, fuel injection rate, boost pressure and temperature etc. in step 210. The ECU 60A calculates the engine torque output in step 220. Step 230 compares the vehicle operating torque Tveh and the vehicle torque requirement Treq. If Treq is less than Tveh, then step 280 indicates that vehicle braking is required to reduce the powertrain torque output, and the motor brake regeneration is activated as indicated at step 270. If the required torque Treq is larger than Tveh, then step 240 indicates that the engine torque output is checked. If the engine torque Teng is less than Treq, the hybrid powertrain will switch to the motor/engine dual operating mode at step 250. Otherwise, the hybrid powertrain will operate in the engine only mode at step 260.

[0045] The powertrain regenerating brake control flowchart is shown in FIG. 12A. The ECU 60A reads a deceleration command input at step 310, and calculates the deceleration torque requirement (based on vehicle speed and other operating parameters, engine brake torque, and the motor brake torque) at step 320. If the required deceleration torque is greater than the motor regenerative brake torque, which is determined at step 330, then engine braking will be activated in combination with the motor regenerating brake, as shown at step 340. Otherwise, the vehicle will operate in the motor regenerating brake only mode at step 370. During the engine braking mode, the engine brake noise will be checked in order to comply with local noise regulations, as indicated by step 350. If the braking noise level is not acceptable, the engine valve timing can be varied to reduce the brake noise as shown in step 360.

[0046] FIG. 12B shows a control strategy related to catalyst temperature for reducing engine exhaust emissions. At step 400, the operating parameters of the diesel engine are read. Thereafter, step 430 compares the exhaust gas temperature with the temperature required for effective catalyst operation. If the exhaust gas temperature is lower than the required temperature, the exhaust valve timing will be adjusted through variable valve actuation (VVA) device to increase the temperature, as indicated in step 410. Step 440 determines the hydrocarbon concentration of the exhaust gas since a proper hydrocarbon concentration is required for effective NOx adsorption and lean NOx catalyst operations. If the hydrocarbon concentration is lower than specified, post injection or auxiliary exhaust manifold injection is required to add hydrocarbons into the exhaust gas stream in step 420. The catalyst temperature is determined in step 450 for optimum emissions reduction performance. If the catalyst temperature is lower than the optimum performance temperature, a battery powered catalyst heater will be turned on to increase the catalyst temperature in step 460.

[0047] Although a particular control strategy is disclosed, it will be apparent to persons skilled in the art that modifications may be made without departing from the scope of the invention. All such modifications as well as equivalents thereof are to be included within the scope of the following claims.

Claims

1. A hybrid powertrain for urban and on-highway vehicle comprising a diesel engine, an electronic controller, a transmission, an electric motor/regenerative brake, and a battery; said transmission having torque input from said diesel engine and said electric motor; said diesel engine having a turbo charger and a fuel scheduling means for regulating fuel delivery in response to the vehicle demand for speed and torque; said electrical motor can function as regenerating brake to retarding the vehicle during deceleration of the vehicle; said electric motor can function as generator to charge the batter during the regenerative brake process; said electronic controller having stored the fueling map as a function engine operating parameters, such as boost pressure, temperature, engine speed, etc. for steady state and transient operations of meeting the government emissions regulations; said electronic controller having stored the relationship of the electric motor speed and electric motor current; the relationship of the battery power and the current output; the relationship of battery charging current and the regenerative retarding power; said controller having stored the relationship between the output torque of diesel engine and the output torque of the electric motor for providing combined torque output to meet the vehicle torque requirement

2. The hybrid powertrain as set forth in claim 1 includes the torque input from both the said diesel engine and the said electric motor for steady state calibration;

3. The hybrid powertrain as set forth in claim 1 includes the torque input from both the said diesel engine and the said electric motor for transient state calibration;

4. The hybrid powertrain as set forth in claim 1 wherein said electric controller including means for scheduling the torque delivery for the diesel engine and the motor to meet the total torque demand.

5. The hybrid powertrain as set forth in claim 1 said electronic controller could sense the battery power level.

6. The said battery in claim 1 will be charged during regenerating braking and delivery power to the motor to provide torque to the drivetrain.

7. The hybrid powertrain as set forth in claim 1 said electronic controller could schedule power delivery by the diesel engine and the motor if the battery power level is too low.

8. A hybrid powertrain for urban and on-highway vehicle comprising a diesel engine, an electronic controller, a transmission, an electric motor/regenerating brake, and a battery; said transmission having torque input from said diesel engine and said electric motor/regenerating brake. A internal combustion engine used in a hybrid powertrain consists of engine compression release device and/or engine exhaust brake,

9. Said diesel engine have auxiliary brake system such as exhaust engine brake, the compression release engine brake in addition to the regenerating brake.

10. The hybrid powertrain as set forth in claim 7, said electric motor can function as regenerating brake to retarding the vehicle during deceleration of the vehicle.

11. The hybrid powertrain as set forth in claim 7 said electric motor can function as generator to charge the batter during the regenerating brake process.

12. The hybrid powertrain as set forth in claim 7 said electronic controller could estimate the retarding torque requirement to maintain proper vehicle speed.

13. The hybrid powertrain as set forth in claim 7 said electronic controller could schedule the retarding torque delivery by the engine brake if the retarding torque required by the vehicle is larger than the torque available by the regeneration braking.

14. The hybrid powertrain as set forth in claim 7 said electronic controller could sense the battery power to avoid over charging and the effectiveness of the regenerating brake.

15. A hybrid powertrain for urban and on-highway vehicle comprising a diesel engine, an electronic controller, a transmission, an electric motor/regenerating brake, and a battery; said transmission having torque input from said diesel engine and said electric motor/regenerating brake. A internal combustion engine used in a hybrid powertrain consists of: a. A engine have at least one cylinder with at least one intake and one exhaust valve; b. A fuel injection system, which is able to deliver fuel in multiple injection events per cycle and in different rate shaping. c. A motor assisted turbocharger system. d. An exhaust aftertreatment device with battery powered electric heater. e. A variable valve timing device which is capable of controlling the valve opening events and timing; f. Battery powered accessory device such as cooling fun, water pump, engine control module etc. g. Engine compression release device and/or engine exhaust brake

16. The hybrid powertrain as set forth in claim 1 wherein said diesel engine is characterized by with NOx and PM exhaust emissions for each engine speed value and torque value.

17. Said diesel engine has its accessories, such as water pump, cooling fan etc is powered by the battery of the hybrid powertrain.

18. Said diesel engine has variable valve timing capability to hold both intake and exhaust valve open to reduce the pumping loss when the hybrid powertrain is at motor only operation mode.

19. Said diesel engine has cylinder cut-out capability to reduce fuel consumption when the hybrid powertrain is at engine only or at engine and motor combined operating mode.

20. Said diesel engine has variable valve timing capability to open the intake valve during blow down stroke or delay the intake valve closing to induce exhaust gas re-circulation internally for NOx emissions reduction.

21. Said diesel engine will have exhaust aftertreatment systems (Lean NOx, NOx absorber, PM Filter) to reduce exhaust emissions. The heater power by the said battery is used to maintain the aftertreatment temperature to achieve optimum conversion efficiency.

22. Said diesel engine will have multiple injection capabilities to control the exhaust species for optimum catalyst conversion efficiency.

23. The said diesel engine will have variable timing capability to control the exhaust temperature to allow the catalyst at its optimum conversion level.

24. The said diesel engine will have variable timing capability to control the braking noise when the engine compression release brake is used.

25. The said diesel engine will have variable timing capability to reduce warm up period for cold whether operations.