Patent Application
20190211678
Internal combustion engines have had over 100 years of development and are clean, reliable, power dense where desired, and fuel efficient where desired. Piston engines have dominated automotive applications with gasoline engines being used more than diesel engines in the U.S. Automotive engines are undergoing rapid development to increase fuel efficiency to meet regulations. Longer ratios of the stroke relative to the bore, turbocharging, and use of the Miller or Atkinison cycles are technologies promoting efficiency. The goal of this invention is a more fuel efficient engine with inherently good pollution control properties.
Diesel engines are generally more fuel efficient than gasoline but are losing favor in automotive applications due to extra pollution control technology. Two-cycle engines have not been significant in automotive applications but have a long history of use in truck, locomotive, and large marine applications where their fuel efficiency had a good history. Pollution restrictions have particularly hurt fuel efficiency of these two cycle diesel engines and new designs now use four cycle engines. Turbocharging was critical to two-cycle diesel engine efficiency. The ElectroMotive Diesel Div. of Caterpillar (formerly ElectroMotive Div. GM) two-cycle locomotive engine designed an overrunning clutch mechanism which allowed a single turbocharger to operate coupled to the crankshaft at light loads and then uncouple from the crankshaft and operate much higher rpm once exhaust gas pressure built sufficiently. When gas pressure created more torque from the turbine than that applied by the shaft the overrunning clutch roller elements were moved to clearance positions and thus allowed the turbine to freewheel on the shaft. This EMD design of this successful overrunning clutch was essentially that of Dietrich Reister Herzgenaurach and Wolfgang Pfluenger in patent U.S. Pat. No. 3,537,555 (ref. 1). A similar overrunning clutch system, with an additional feature, is perhaps the most important mechanism for the concept of the Tangential Force Internal Combustion Engine (TFICE) of this patent.
Natural gas, propane, and landfill gas engines have been used in various applications for highly targeted reasons. Hydrogen is being used as a fuel for novel power sources in autos where pollution control laws are strictest. Battery fueled autos are gaining in numbers as are hybrid versions utilizing highly efficient gasoline engines. The Wankel engine is a rotary engine with no pistons or connecting rods and few moving parts. It has been successfully used in niche sports cars where light weight and good power density are beneficial (ref. 2). Emission challenges and low fuel efficiency kept this as a niche engine.
The jet engine was first used in airplanes late in WWII with the Messerschmitt ME262 in 1944. Frank Whittle of England was granted a patent for his turbo-jet engine in 1932. (ref 3). Today's gas turbine engines can have good fuel efficiency but at the high cost of multiple compressor and turbine stages. Gas turbine engines are used where weight and power density are prime concerns.
The present invention is hoped to have potentially significantly higher fuel efficiency than piston engines. The present invention couples force from the power cycle more directly to the output shaft as useable torque. A power vane is attached to the shaft through an overrunning clutch mechanism which allows 100% of the combustion force to be transmitted as usable torque to the shaft for essentially the entire duration of this power cycle. A piston engine design transmits only a fraction of the available connecting rod force into shaft torque because the force vectors need to be resolved to that which is tangential to the crankshaft. Such force vectoring is required at both the piston pin and crankpin. The remaining non-tangential load vectors lead to inefficiencies and unwanted localized forces which produce no desirable effect.
Piston thrust loading and high compressive forces directly into the crankshaft bearings are two unwanted but unavoidable forces in piston engines. The present invention eliminates such unwanted force vectors. Piston thrust loads are sometimes manifested as piston skirt seizures. The fact that the largest diesel piston engines use crossheads to avoid potential piston issues from such thrust loading recognizes this situation. The “piston” of the TFICE engine will have complexity of its own as it will need to locally match the overall torroid chamber shape and carry multiple sealing rings. But TFICE “pistons” operate on arms that transfer torque more directly to the shaft through a symmetrical OCS mechanism mentioned earlier. Said OCS mechanism clutches a multitude of symmetrically spaced roller elements between the vane (or an OCS “housing” securely fitted into the vane) and the shaft. This clutching action transmits torque directly instead of producing a compressive force onto an offset crankpin. Certainly the OCS produces highly localized compressive forces (creating contact stress on and around roller elements) but this is the mechanism for creating moments directly into the shaft. This clutching mechanism is an efficient means to create pure moments and is thought to be much more efficient at converting combustion forces into shaft torque than crankpin offsets and resolving forces.
Other unwanted forces in modern reciprocating piston engines produce crankshaft orbit as various reciprocating weights, crankpin throw angles, and various levels of balance weights produce sometimes unexpected forces on main and conrod bearings. Unit loading is typically high on conrod bearings, especially for the most highly fuel efficient diesel engines. Proper sizing and material choices are needed to avoid seizure or early wear out. Conrod bearings are commonly replaced at half the life of main bearings. The need to change crankshaft bearing increases with increased power and fuel efficiency and so designs are made for wear element components to be replaced instead of more expensive components. Similarly this TFICE invention would ultimately need roller elements and other local wear components designed-in to avoid replacement of higher cost components.
The Wankel rotary engine uses an eccentric shaft and, like the piston engine, combustion forces do not vector directly to the shaft as torque. More combustion force is lost in Wankel engines compared to the TFICE engine being proposed. This engine is also thought to be inherently inferior to the piston engine in regards to fuel efficiency.
Jet engines or turbojet engines have combustion gas flow paths that efficiently resolve vectors into shaft torque via controlled gas flow paths. However the most basic gas sturbine engine does not have a simple, fully enclosed combustion process. Certainly modern jet engines are powerful and even fuel efficient with modern design utilizing multiple compressor and turbine stages and ever higher local temperatures. These design features precludes the use of fuel efficient gas turbines from any cost sensitive application.
Piston engines are fuel efficient via achieving relatively high combustion pressures that are contained in a fully enclosed combustion chamber. A reaction component to the force produced on the crankpin in a piston engine is the cylinder head and this fully encloses the combustion process. As the head is fixed via bolts to the block it thus serves as the torque reaction component. The torque reaction in the present invention is the reaction vane as it is pinned to the engine housing. In this manner the combustion torque has an effective reaction torque for mechanical equilibrium.
No forces in the TFICE invention create piston thrust forces or compressive forces into the support bearings. Pure tension or compression is not present in the vanes as combustion forces are tangential to the shaft and there is no reciprocating motion. Essentially, the vanes are either directly connected to the output shaft or the vane rides on roller elements on the shaft. Roller element bearings are envisioned in shaft support roles as these bearings have essentially no compressive or axial forces to contend with. Roller element bearings are another source of fuel efficiency compare to piston engines.
It is acknowledged that the design shown by example herein provides just 75 degrees of power duration cycle compared to the approximately 180 degrees in piston engines. Increasing this duration is possible with different timing and shaft gear ratios. However the TFICE invention is thought to provide much more useful work during the power duration such that small “cylinder (i.e. torroidal chamber) displacements” will produce relatively large torques.
The most pressing design challenge with the present invention is combustion sealing as the Power Vane leaves a growing inside gap as it rotates around the torroid. The invention shown herein explains basic operating principles and only a rudimentary combustion seal is proposed. The topic of combustion sealing will need to be addressed in more detail in the future. The seal shown herein is a series of sealing elements but it seems possible to use a continuous sealing assembly that would fit inside vanes that are locally hollow at this seal. If a continuous seal were developed then efficiency benefits could further develop as the use of longer power durations, beyond 180 degrees even could be envisioned.
The Tangential Force Internal Combustion Engine (TFICE) is imagined as a torque arm that applies torque directly to the output shaft through an Overrunning Clutch System (OCS). This OCS is a key mechanism needed in this engine as it allows nearly instantaneous torque application from the Power Vane (PV) to the shaft and simultaneously allows the Reaction Vane (RV) to freewheel relative to the shaft. This invention utilizes the common four cycle internal combustion process, i.e. an Otto Cycle. The invention forms combustion chambers via a torroidal housing chamber which is closed by two “pistons”, each “piston” having multiple ring type seals on each end, combined with seal elements that create an inside seal as one vane moves away or toward the other. Intake, compression, power, and exhaust cycles are spaced over the 360 degree housing torroid chamber in the present manifestation. Vanes move 360 degrees for a complete cycle while the shaft rotates more. The amount of shaft rotation for a complete cycle depends on key design features and an equation is developed herein that relates a complete cycle of the shaft to the 360 cycle of the Reaction Vane within the housing.
No pistons or connecting rods are utilized in the present invention. In place of these components are one Power Vane (PV) and one reaction vane (RV) with the ends of these vanes slip fitted to pistons having shapes that are overall form fitting to the torroid. The arms of the vanes serve as “connecting rods” but the arms extend across the shaft to produce symmetrical vanes and pistons across the centerline. The PV produces torque on a central shaft through the OCS mechanism when combustion occurs when either “piston” set has compressed the A/F mixture and the spark plug has fired. Power is taken at the exit end of the shaft in typical fashion.
At specific angles and for controlled angular durations the PV and VN are slowed, stopped, held to the housing, and then accelerated to essentially match speed and then re-couple with the shaft. Deceleration and acceleration of a vane is controlled by a gear, ramp, and pin mechanism shown herein. Each vane has a radial slot on one end which allows for the insertion of a pin in order to either accelerate or decelerate the vane. Vane hold mechanisms rely on pinning each vane to the housing for durations defined by a ramp in the timing gear that acts on the end of the pin. The power vane has no controlled acceleration; combustion serves to couple this vane to the shaft through the overrunning clutch system of this invention.
The present invention is named a Tangential Force Internal Combustion Engine (TFICE) and it utilizes the typical four OTTO cycles over the 360 degrees of the torroid chamber. Typical intake and compression cycles of approximately 9:1 are utilized and the power duration is 90 degrees shaft or less in the present manifestation. Intake and exhaust flows into the torroidal combustion chambers are thru ports that are covered and uncovered by piston motions. A one way flow valve may be used at each port to prevent wrong gases from entering the wrong port.
The best description of the TFICE begins with Section A-A of
The seal elements for the torroid found in
An Overrunning Clutch System (OCS) is integral to the operation of this engine. Vane movement must be controlled so that vanes can move fixed with the shaft, as during power transfer or for other cycles needs. At various times a vane will need controlled deceleration and then holding to the housing for fixed lengths of time. The OCS allows these events but cannot perform all above mentioned requirements.
A complete development of the steady state engine operation is seen in overview in
The present invention will need proper sizing and metallurgy of the shaft and OCS components for adequate life against contact fatigue. It's thought that the detail design will incorporate pressing together 180 degree sectional assemblies containing the OCS mechanism while bolting together vane halves, akin to crushing a rod bearing on the conrod assembly. Hardened (or surface hardened) shafts, roller elements, and OCS housing will be needed. Assembly of the shaft, vanes, and OCS subassembly will need to be done outside the housing. There will need to be temporary means of holding roller pin elements, perhaps grease that could be flushed before running. Torroidal shaped “pistons” could be fitted that are slotted to accept the fitting of vane ends that are essentially tabs. Excess axial clearance is needed in each piston so as to prevent axial loading of the pistons thru thermal growth of vanes. This engine will bring new thought patterns to the details of component design and assembly. The most basic principles of good engine design will still apply but in unique ways. It cannot be the goal of this first patent to foresee and design in detail for all possibilities.
This TFICE engine will need a strategy for starting since designed steady state operation relies on combustion alone for movement of the PV for a small portion of its travel. Detailed drawings have not been made but the thought process is to have a starter motor that turns the shaft and another starting only system that moves the Power Vane via a pin in slot similar to that of the three acceleration/deceleration mechanisms. Alternatively the PV could be moved via liner actuator to put it on the ramp of the OCS pin prior to turning the shaft.
There is a possible concern with the PV loosing timing as it has a portion of its cycle left uncoupled and relying on combustion to lock it to the shaft. In realty this portion does not need to exist for any significant length as inserting the OCS pin in a timed manner with the start of ignition should be possible. Thus each change of event would be controlled essentially by the shaft and then starting could be in the usual manner. The changeover from being held to full shaft motion at ignition is a concern as it has no acceleration control. Good materials for contact stress (carburized shaft and roller element housing, 52100 pins) and a minimum of excess clearance should provide adequate life. This changeover during starting will be using a low speed, low torque starter motor and so should be less concern. Overlap of a hold and move mechanism occurring coincidently could be a possibility depending on tolerences, this must be considered in every case. As a safety the various pins could have a tapered end design and/or chamfered holes that prevent pin breakage at maximum material conditions.
Other mechanisms for safety, cooling, lubrication, other sealing functions, fuel and air mixture and delivery, ignition and noise suppression are generally not shown since standard design methodology can be applied. Additional features for facilitating assembly (ie ports and covers) are generally not shown. Fasteners have not been generally shown for this patent but should follow good Engineering practices.
The present application does not allow for unequal length cycles (ie Atkinson cycle equivalent). However the concept of an Atkinson cycle applied to a TFICE type engine could have huge efficiency benefit gains, perhaps more than that provided to piston engines. It is conceptual that a near 360 degree “tangential force power stroke” is possible but the current limitation is ability to seal the inside of the torroid chamber over those angles.
Reference
Reference
Note that the PV gear will theoretically need to hold an extra 90(5/6)−27=48 degrees since the RV moves 27 degrees during its gear-controlled acceleration as the shaft moves 90 degrees (with this particular 5:6 ratio of timing gear to shaft gear). This movement during its acceleration lets the RV get ahead of the PV from cycle to cycle. There is an assumed instantaneous acceleration of the PV from combustion.
Reference
Reference
Reference
1. Items 6, roller elements, are shown in operation for two cases: 1. where the vane is not making torque and 2. the case where the vane is making torque.
Steady State Operation Cycle
Steady state operation is shown in
RVC=2xr+2y Eqn 1.
Where
r=RVC/360 (this follows from the definition of r) Eqn 2.
Thus for the designs depicted in the present invention:
360r=180r+2y
y=90r Eqn 3.
Equation 3 is plotted in
The designs depicted herein utilize a single shaft gear and three timing gears driven directly from said gear. No intermediate gears are shown but these could be useful to limit the angular displacement of the vanes during acceleration or deceleration.
