Method of controlling engine stop-start operation for heavy-duty hybrid-electric and hybrid-hydraulic vehicles

#The field of the invention relates to the stop-start operation of a hybrid-electric or hybrid-hydraulic heavy-duty vehicle with a gross vehicle weight rating of 10,000 lbs or higher.

#In typical heavy-duty vehicle applications, including those with hybrid drive systems, a rotating internal combustion engine includes multiple gear and/or pulley and belt power take-offs (PTOs) that operate the vehicle subsystems and accessories. As a result, turning off the engine causes the vehicle subsystems and accessories to be turned off.

#It is desirable to eliminate engine idling at vehicle stops to, among other things, increase fuel economy, minimize noise, and minimize engine exhaust emissions pollution to improve the quality of the operating environment. This is especially true for transportation and delivery vehicles such as, but not limited to, urban transit buses and local package freight pick up and delivery vans that may experience hundreds of stops during daily operation.

#The accompanying drawings, which are incorporated in and form a part of this specification, illustrate the logic flow of the invention and its embodiments, and together with the description, serve to explain the principles of this invention.

#FIG. 1A is an block diagram of an embodiment of a series hybrid-electric drive system with electrically powered accessories.

#FIG. 1B is a block diagram of an embodiment of a parallel hybrid-electric drive system with electrically powered accessories.

#With reference to FIG. 1A, an embodiment of a series hybrid-electric drive system 100 with electrically powered accessories 110 will be described. An engine 120 can be turned off because both the high voltage requirements and the low voltage requirements are met by respective energy storages 130, 140. A generator 150 is operated as a motor to spin the engine 120 during frequent restarts. A low-voltage engine starter 160 may be used infrequently with the generator 160 whenever the high-voltage energy storage 130 can not deliver enough power to the generator 150 for spinning the engine 120 during engine start. For example, in an implementation of this embodiment where ultracapacitors are used for energy storage, the low voltage starter 160 is used at the beginning of the day when the ultracapacitors are empty. The engine 120 may be any internal combustion engine that would be used to produce enough power to provide traction for propelling the vehicle.

#With reference to FIG. 1B, an embodiment of a parallel hybrid-electric drive system 200 with electrically powered accessories 110 will be described. Again, the engine 120 can be turned off because both the high voltage requirements and the low voltage requirements are met by the respective energy storages 130, 140. FIG. 1B conceptually depicts that the electric motor mechanical output and the engine mechanical output operate in parallel and are coupled together to add power and torque to the traction propulsion drive train 210. In a typical implementation, a motor 220 is located in front or behind a transmission 230 and turns the same mechanical torque shaft as the engine and transmission. In the Stop-Start method of the present invention, the engine 120 and the electric motor 220 must be able to decouple from the vehicle propulsion drive train 210 to allow the electric motor 220 to spin the engine 120 during engine startup. Turning off and restarting of the vehicle internal combustion engine does not cause engine damage and can be performed a multiplicity of times without causing degradation of the starting mechanism. Alternatively, in place of, or in addition to a standard low voltage starter, a separate generator/starter 240 capable of hundreds of restarts per day is provided for the engine 120.

#As illustrated in FIGS. 1A and 1B, an air conditioning (A/C) compressor 250 is assumed to include its own electric motor drive 265 similar to the air conditioning units used in fixed buildings. In the embodiments shown, the hydraulic pump and air compressor units 270, 280 are driven by the single electric motor 260, but in an alternative embodiment, each may have its own electric motor. The low-voltage requirements are supplied by either a Power Take-Off (PTO) alternator or generator 270, a DC-to-DC converter 280 from the high voltage distribution bus, or an AC-to-DC power supply 285 from the AC inverter bus. The low-voltage energy storage 140 is also shown in the diagrams, but may be unnecessary if the DC-to-DC converter 280 were used and there was always sufficient energy available to start the engine 120.