Patent Application
20050284444
The present invention relates to improvements in 4-stroke internal combustion engines (gasoline, diesel, etc.) used for transportation, generation of energy, or powering of different mechanisms.
Internal combustion engines to which the present invention is related are based mostly on Otto or Diesel thermodynamic cycles, or on their variations. These engines are widely described in literature. They are inexpensive, have high power-to-weight ratios, and are relatively economical. But their efficiency is still substantially less than the thermodynamically possible theoretical limit.
One of their problems is that the length of the compression stroke is equal to the length of the power stroke. Therefore, the gases during the power stroke (which obviously have higher pressure) cannot expand enough to expend all of their energy within the cylinder. As a result, they exhaust at too high a pressure, so that their energy is not fully utilized for mechanical work. In terms of thermodynamics it means that the cycle of conventional engines is symmetrical, i.e. the volume of fuel-air mixture taken in (and then compressed) is equal to the volume to which combustion gases expand within an engine after combustion. Their unused power goes to the exhaust.
An additional adverse factor in known engines is that adjusting their power output is done by changing the amount of fuel fed to a cylinder while the amount of air taken in remains unchanged equal to the full capacity of the cylinder(s). This means that the engine works generally at a non-optimal fuel-to-air ratio. This fact additionally increases fuel consumption and aggravates environmental pollution.
Attempts to cope with these problems by controlling the movements of intake valve(s) alone (U.S. Pat. No. 6,679,207) cannot fully solve the problem because this measure only allows control of the amount of fuel fed into the cylinders at the expense of reducing the actual pre-combustion pressure and thus reducing the efficiency of the engine.
Attempts to cope with the above problem by varying the volume of the combustion chamber as per U.S. Pat. No. RE23,307 cannot be successful either. This patent allows the engine to compensate for the reduction of ambient air pressure at highly increased altitude (for instance, in aircraft) by increasing the compression ratio well beyond the values acceptable for operation at standard sea level. Thus for automobiles operating mostly at standard sea level, this invention is not applicable.
The problem of the efficiency of internal combustion engines operating mostly at standard sea level is addressed in the present invention.
The present invention relates in general to a method and device for improving the efficiency of the internal combustion engine which work mostly at sea level and, more specifically, to a method and device for achieving a more efficient thermodynamic cycle in the internal combustion engine by providing the following:
The above control devices can be either mechanical cams, or electronically/computer controlled mechanisms to control both the intake and/or exhaust valve(s); and the effective volume of the combustion chamber(s).
The devices in group (a) allow part of the air taken in during the intake stroke to escape during the compression stroke through the still open intake/exhaust valve(s) until the amount of air left in the cylinder is exactly enough for the consumption of all of the fuel to be injected to the cylinder at the particular throttle setting. After reaching this point, the valve(s) close, compression begins and the fuel is actually injected into the cylinder. But used only by themselves, these devices (in group a) reduce the compression ratio at which ignition is being initiated, thus reducing the efficiency of the engine.
The devices of group (b) control the compression ratio at the peak of the compression stroke (the ratio is fixed per this invention depending on the design of the engine and octane of the fuel). For this purpose, a conditioning piston is provided to adjust the effective volume of the combustion chamber to the amount of air being compressed. This conditioning piston is driven either via mechanical linkages, or is electronically controlled. Its movements, however, are the part of adjustments and are not part of the cycle. But by themselves, if not combined with adjustment of the beginning of compression, the movements of the conditioning piston change the compression ratio, either reducing the efficiency of the engine, or causing detonation of the fuel.
The devices of the group (c) tune the combustion chamber to the particular octane of the fuel by setting the position of conditioning piston. Only the unique combination of variable compression stroke and variable effective volume of combustion chamber(s) both controlled in dependence of the amount of fuel fed to keep the compression ratio permanent, conditions the engine for extracting more power from the same amount of fuel used (or using less fuel for the same power delivered). As a result, fuel consumption is reduced.
Because of more complete combustion, the level of pollution is reduced too. In addition, since exhaust gases in the inventive engine leave the cylinders at substantially lower pressure and temperature, the losses of power in the process of muffling, are also reduced.
With all of these features, in the range of 15 to 300 Hp, the efficiency of the inventive engine can be as much as 35 to 45% which is substantially better than the efficiency of regular internal combustion engines (usually under 25%).
The novel features of the present invention are set forth in particular in the appended claims. The invention itself, however, will be best understood from the description of the preferred embodiment which is accompanied by the following drawings.
The inventive method of achieving complete combustion of fuel and oxygen within engine's cylinders is explained in the pressure-volume diagram in
In contrast to the method used in standard engines, the inventive method adjusts the volume of air to be compressed in accordance with the current amount of the fuel fed (that is, with the current throttle setting) to achieve full combustion of both the fuel and the oxygen of the air compressed to the optimum controllable compression. This is done by adjusting both the beginning points of the compression 7, 8, and 9 in
At all throttle settings, the continuation of the stroke due to the expansion of combustion gases beyond the positions at which the original volume of the air was compressed 11, 12 and 13 in
The above method is implemented in the engine schematically shown in
Here, the lifting of pushrod 26 is timed by both the main cam 29 and the auxiliary cam 30 which is mounted on an axle 27. The main cam 29 has a profile typical of conventional engines. The auxiliary cam 30, however, has the shape of a wedge. It does not rotate but can be moved in either of the directions indicated by arrows 35 and 36. Advancement of cam 30 in the direction indicated by arrow 35 increases the duration of the intake valve in the open position while movement of cam 30 in the opposite direction indicated by arrow 36 results in a corresponding decrease in the duration of the intake valve 32 in the open position.
To make the engine work at full throttle and, therefore, with maximum amounts of both fuel injected and air compressed, cam 30 is moved in the direction indicated by arrow 36 (as shown in the
In order to keep the compression ratio constant and optimal, the above control of the amounts of air and fuel taken in is combined with the control of the effective volume of the combustion chamber 38. Here, the conditioning piston 24 within the auxiliary cylinder 22 controls the effective volume of the combustion chamber 38. To this end, the screw 25 moves the conditioning piston 24 up and down as shown by arrows 39 and 40. An electro-mechanical connection between the screw 25 and the gas pedal turns the screw 25 to lift the piston 24 in accordance with the depression of the gas pedal. The advantage of an electro-mechanical (or computerized) connection over the use of pure mechanical devices is the capability of switching from fuel of one octane to another without loosing efficiency. Here, optimal conditions are kept by controlling circuitry that adjusts the compression ratio.
Upon injection of the fuel at the second stroke and subsequent ignition, combustion gases expand during the third (power) stroke producing useful shaft work similarly to the power stroke of conventional engines. The difference here is that the inventive engine works, in all the ranges of power output at optimum air-to-fuel ratio and at increased combustion gas expansion. Since the initial pressure of gases is greater than in conventional engines, while the pre-exhaust pressure is less than in the conventional engines, the power developed by the inventive engine is greater than the power developed by the conventional engine at the same fuel consumption (or, fuel consumption is less at the same power output).
The fourth stroke differs from the same stroke in conventional engines by the fact that because of greater expansion during the third (power) stroke, the pressure of exhausting gases is less than in conventional engines. As a result, the inventive engine waists less energy muffling exhaust noise to the same decibel level.
This invention is not limited to the details shown since various modifications and structural changes are possible without departing from the spirit of the present invention. What is desired to be protected is set forth in particular in the appended claims.
