Power plants, such as automotive or marine engines, and engines driving stationary electrical generators or pumps, for example, are often required to operate over a wide range of output torque. An automobile engine, for example, must provide a significant amount of torque for accelerating the automobile from rest to a cruising speed. Once the automobile has reached the cruising speed, substantially less torque is generally required for maintaining the cruising speed. An engine that produces sufficient power for rapidly accelerating an automobile will generally be larger than would be required for maintaining cruising speed, and will operate inefficiently when throttled back to produce only the power required for maintaining the desired cruising speed. A stationary power plant driving a generator presents a similar challenge when electrical loads are imposed on, and removed from the generator.
One approach to improving the efficiency of power plants used in such applications is to utilize multi-engine power plants, having two or more engines, or two or more engine modules, with output shafts that are selectively coupled together when the demand for output torque is high, such as during acceleration of an automobile. Once a steady state condition is reached, and the torque requirement is reduced, such as during steady speed cruising of an automobile, the second engine is decoupled, and may actually be shut down to improve efficiency of the power plant. Commonly assigned U.S. Pat. No. 6,306,056 B1, to Moore, and U.S. Pat. No. 6,474,068 B1, to Abdel Jalil, et al, describe methods and apparatus for operating multi-engine power plants in this manner.
Both Moore, and Abdel Jalil, disclose individually controlling airflow to separate internal combustion engines of a multi-engine power plant. This approach works well, and is consistent with state of the art beliefs, as held by those having skill in the art, that airflow to each engine must be controlled with a separate throttle body, in order to achieve proper operation and torque sharing of the engines. It has been commonly accepted by those having skill in the art that a separate throttle body was required for each engine in a multi-engine power plant, to control the speed of an engine during the period of time when that engine was being started, so that the engine speed would not run away while the engine was being started and brought up to an operating speed that matched the speed of other engines in the power plant that were already running.
The inventor of the present invention has discovered, however, that in a multi-engine power plant, including a first internal combustion engine module having an air intake and an output shaft for delivering power, and a second internal combustion engine module having an air intake and an output shaft for delivering power, air flow can be controlled to the intakes of the engine modules at a common manifold absolute pressure (MAP) of both engine modules, during operation of one or both of the engine modules, with a single throttle body operatively connected to the air intakes of both the first and second engine modules.
By using only a single throttle body for controlling airflow to two or more engine modules of a multi-engine power plant, a number of duplicate components, that were required in prior multi-engine power plants, can be eliminated. The complexity, cost, weight and size of a power plant according to the invention are all reduced, and reliability is improved, in comparison to prior multi-engine power plants.
In one form of the invention, an apparatus for controlling a multi-engine power plant includes a single throttle body, and a controller operatively connected to the throttle body for controlling a flow of air through the throttle body. The throttle body includes an inlet for receiving a flow of air, and an outlet operatively connected to the air intakes of both a first and a second engine module for delivering the flow of air to the intakes of the engine modules at a common manifold absolute pressure (MAP) of both engine modules during operation of one or both of the engine modules. The apparatus may further include an inlet manifold defining a common internal plenum, having an inlet for receiving the flow of air from the throttle body, a first outlet for delivering a portion of the flow of air from the common internal plenum to the intake of the first engine module, and a second outlet for delivering a remainder of the flow of air from the common internal plenum to the intake of the second engine module.
A multi-engine power plant, according to the invention may include a first internal combustion engine module having an air intake and an output shaft for delivering power, a second internal combustion engine module having an air intake and an output shaft for delivering power, and a single throttle body operatively connected to the air intakes of both the first and second engine modules, for controlling a flow of air to the intakes of the engine modules at a common manifold absolute pressure (MAP) of both engine modules during operation of one or both of the engine modules. The power plant may also include a selectively engagable clutch for operatively coupling the output shaft of the second engine module to output shaft of the first engine module, to thereby produce a common output torque from the first and second engine modules.
In an apparatus or method, according to the invention, a flow of fuel to the first engine module may be controlled independently from a flow of fuel to the second engine module, and a flow of fuel to the second engine module may be controlled independently from a flow of fuel to the first engine module. Ignition in the first engine module may also be controlled independently from ignition in the second engine module, and ignition in the second engine module may be controlled independently from ignition in the first engine module. The flow of air through the throttle body may be controlled as a function of a desired torque output of the power plant.
The output shaft of the second engine module may be selectively operatively connected to the output shaft of the first engine module. The flow of air through the throttle body may be controlled as a function of whether the output shaft of the second engine module is operatively coupled to the output shaft of the first engine module. The output shaft of the second engine module may be selectively operatively connected to the output shaft of the first engine module, as a function of the desired torque output of the power plant.
The flow of air through the throttle body may be controlled according to a first function of desired torque output from the power plant when only the first engine module is operating, and controlled according to a second function of desired torque output when both the first and second engine modules are operating. When the speed of the output shaft of the second engine module does not substantially match the speed of the output shaft of the first engine module, as would be the case when the first engine module was operating but the second engine module was only idling or being started, for example, the throttle body may be controlled according to a third function of desired torque output from the power plant. The second engine module may also be started, by coupling its output shaft to the output shaft of the first engine module, while the first engine module is operating, and controlling the throttle body according to the third function of desired torque while the second engine module is being started.
The foregoing and other features and advantages of the invention will become further apparent from the following detailed description of exemplary embodiments, read in conjunction with the accompanying drawings. The detailed description and drawings are merely illustrative of our invention rather than limiting, the scope of the invention being defined by the appended claims and equivalents thereof.
Throughout the following description of exemplary embodiments of the invention, components and features that are substantially equivalent or similar will be identified in the drawings by the same reference numerals. For the sake of brevity, once a particular element or function of the invention has been described in relation to one exemplary embodiment, the description and function will not be repeated for elements that are substantially equivalent or similar in form and/or function to the components previously described, in those instances where the alternate exemplary embodiments will be readily understood by those skilled in the art from a comparison of the drawings showing the various exemplary embodiments in light of the description of a previously presented embodiment.