Motor vehicles – With fluid or mechanical means to accumulate energy to power...
Reexamination Certificate
1998-06-15
2001-05-01
Vanaman, Frank (Department: 3611)
Motor vehicles
With fluid or mechanical means to accumulate energy to power...
C180S302000, C123S090120
Reexamination Certificate
active
06223846
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to vehicle systems capable to accumulate energy derived from vehicle motion during its deceleration or obtained from operation of the vehicle engine, and use the accumulated energy to assist in vehicle acceleration and propulsion at a later time.
BACKGROUND OF THE INVENTION
Most automotive vehicles are propelled by internal combustion engines consuming hydrocarbon fuels. Burning these fuels produces exhaust gas containing harmful air-pollutants, such as carbon monoxide, nitrogen oxides, and unburned hydrocarbons. It also contains substantial amount of carbon dioxide which, if produced in large quantities worldwide over long period of time, can contribute to an undesirable increase in average global temperature. Concern for clean air and a desire to prevent adverse consequences of man-made global warming dictate a need to substantially improve fuel efficiency of automotive vehicles.
By itself, the internal combustion engine is a reasonably efficient machine. Unfortunately, the driving pattern of most automotive vehicles is such, that a substantial fraction of energy produced by their engines is wasted. Typically, the driving pattern involves frequent accelerations, each followed by a deceleration. Each acceleration involves a significant increase in fuel consumption needed to produce the additional energy necessary to increase the vehicle speed. Then, during a subsequent deceleration, this added energy is absorbed by vehicle brakes and dissipated as heat.
Attempts to overcome such waste of energy led to development of systems in which the energy of vehicle motion is not dissipated during braking, but converted into a form in which it can be temporarily stored and, then, used again to accelerate the vehicle at a later time. Typically, such system includes an internal combustion engine, an energy storage, and a second machine absorbing the energy of vehicle motion and placing it into the storage during braking. During subsequent acceleration, the second machine receives energy from the energy storage and uses it to supplement the work of the internal combustion engine. Such systems are known as hybrid vehicle systems. An electric hybrid includes an electric generator/motor as a second machine, and an electric battery for energy storage. A fluid-power hybrid includes a pump/motor and a pressurized-fluid accumulator. A flywheel hybrid includes a variable-ratio transmission and a flywheel.
A disadvantage, common to all of the above mentioned hybrids, is added cost and complexity associated with the need for the second machine and associated mechanisms needed to connect it to vehicle wheels in-parallel to or in-line with the internal combustion engine. Added complexity also increases probability of failures, thus contributing to a reduction in overall system reliability.
Another significant disadvantage is a substantial increase in vehicle weight, which is especially pronounced in hybrids using electric batteries for energy storage. Electric batteries are excellent energy storage devices, but the weight of their electrode-plates and electrolyte often adds so much to the mass of the vehicle that it requires a larger engine to drive it. In addition, a heavier vehicle is likely to cause more damage in traffic accidents.
Another deficiency of hybrids using a second machine is that the process they use for energy conversion is often inefficient. For example, one-way energy conversion efficiency of many conventional electric generators and motors does not exceed 50%, and therefore, at best, only a quarter of braking energy can be reclaimed for acceleration. More advanced generators and motors have higher efficiency, but their cost is often prohibitive.
A very significant drawback of electric batteries is a relatively slow rate at which they can be efficiently charged. This limits their ability to absorb the vehicle braking energy during a strong deceleration.
In view of the above, it is clear that it is highly desirable to have a vehicle system which does not suffer from the above disadvantages, while retaining all the fuel economy advantages of other hybrid systems. A properly conceived hybrid system using compressed-air for energy storage can meet these requirements. Such a system is the subject of the present invention.
BACKGROUND ART
The concept of saving kinetic energy of a vehicle during braking, storing it as compressed-air, and later using it for vehicle acceleration has been proposed before. A U.S. Pat. No. 5,529,549 to Moyer describes one such concept. A review of the differences between the present invention and its advantages over the above patent is given below.
(1) The above patent is limited to a case of saving the energy of braking and using it for later acceleration. The present invention, in addition to saving the braking energy, includes charging the air-reservoir with compressed-air during periods other than vehicle braking, whenever the pressure in the air-reservoir drops below a predetermined level. This is accomplished by operating the engine partly as a compressor charging the air-reservoir and, at the same time, partly as an internal combustion engine propelling the vehicle and driving the compressor. Preventing a complete discharge of the air-reservoir is a significant advantage, since it assures availability of compressed-air whenever it is needed for acceleration or for assist in constant speed operation.
(2) Moyer's patent describes an internal combustion operation limited to a four-stroke cycle. The present invention, on the other hand, describes an engine which can selectively operate as a four-stroke, or as a two-stroke internal combustion engine, quickly switching from one cycle to another whenever needed. Ability to switch from the four-stroke to the two-stroke internal combustion operation permits a substantial increase in engine torque. It is especially useful during acceleration from low engine speed, when torque produced by a four-stroke engine is often inadequate.
(3) The present invention includes, in its preferred embodiment, a third type of a valve in each engine cylinder. This valve, the charging valve, is dedicated to connecting the cylinder to the air-reservoir, whenever needed. Thanks to the charging valves, the engine can receive air partly from the air-reservoir through the charging valves, and partly from an intake manifold through intake valves. This permits the engine to receive fuel into its cylinders via injection into the intake ports rather than via direct injection into the compressed air in the cylinders. Port fuel injection is much less expensive than direct fuel injection. Currently, most automobiles use port fuel injection. In addition, the charging valves permit recharging the air-reservoir with compressed-air during normal internal combustion operation. This is accomplished by selectively opening the charging valve during each compression stroke. The charging valve also eliminate the need for distribution valves. The above patent does not provide for the charging valves and therefore does not offer the above described advantages of the present invention.
(4) Moyer proposes to control the flow of air from the cylinder to the pressure tank and back by flowing the air through a variable restriction. As it is well known, throttling an air-flow in a restriction inevitably leads to a substantial loss of energy. The present invention avoids this type of energy loss. It envisions flowing the air through unrestricted passages and controlling the magnitude of the braking force by varying the volume of the air-charge received into the engine cylinder, as well as varying the volume and the degree of compression of the air discharged from the cylinder into the air-reservoir. This is accomplished by varying the timings of the valves openings and closings.
(5) The above patent includes a supercharged engine function. Supercharging an internal combustion engine involves filling its cylinders with pressurized air so that, at the beginning of the compression stroke, the cylinder pressure
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