Proposal For Piezo Electric Pistons in Internal Combustion Engines
Copyright Jon Snell, April. 2004, firstname.lastname@example.org
This proposal is to suggest using piezoelectric materials in order to move a piston and also extract energy from an internal combustion engine. In most current configuration, pistons are connected to a cam shaft in order to provide energy for gas compression as well as to extract mechanical energy.
Piezoelectric materials bend when current is induced in them and produce current when bent. They can be stacked in such a manner where opposite ends of strips are tied together and the voltage inverted in order to provide a linear motion. Doing so would form a stack capable of several inches of linear movement. This linear motion would be used to push the cylinder to provide compression. A compressed mixture of gasoline and air would be ignited as in current internal combustion engines. When the compressed gas mixture is ignited it will explod and push linearly against the stack like a regular piston, and generate a current. This current would be used to power a device as well as to charge a battery (possibly capacitors). The valves would have to be run electrically since there would be no mechanical linkage as is present in common internal combustion engines.
The advantages of such a setup would be:
- variable engine displacement as cylinder positions can be controlled by software
- variable compression to provide the highest efficiencies and power possible
- direct electrical energy extraction
- no need to place multiple engine cylinders in the same phase, allowing them to be enabled and disabled at any time, depending on demand
Another alternative with nearly the same characteristics would be a linear electrical motor or solenoid used in the same manner.
One such configuration would function in the following manner:
A piston would be directly connected to a magnet by a stright shaft. The magnet would travel within a housing which had two coils on it in order to form a solenoid. The coils would cover the same area, but one would have more windings than the other (a center tap for a single coil would be another alternative). The two coils would be used to both transform movement of the magnet into electrical energy, as well as apply force to the magnet. Two coils would be used in order to reduce the usage of external transformers or power electronics. A single coil could be used, but this may require the use of high current DC-DC voltage converters. The cylinder would also have an intake valve controlled by a small solenoid, an exhaust valve controlled by another solenoid, and a spark plug. In most scenarios engine operation would be controlled electronically, so a position sensor of some sort would also be necessary. An optical sensor would probably work the best. The cylinder would operate like a typical 4 cycle engine in some ways. The cycle would start with the piston closest to the wall of the cylinder. The intake valve would be opened. The controlling electronics would then apply current to a set of windings, causing the piston to move away from the cylinder wall and pull in the air and fuel ratio. When the piston has pulled in enough of the air and fuel mixture, current will be removed and it will stop travelling away from the opposite cylinder wall. It need not stop at the same position every time, and it does not need to be the same end of travel reached after detonation. The intake valve will then be closed. After the intake cycle is complete, the controller will once again apply current to the coils. This current will move the piston towards the opposite wall until the desired compression is achieved. Once the desired compression is achieved, the computer will connect a huge load such as a battery at lower voltage to the coils. High voltage will then be applied to the spark plug, causing the air/fuel mixture to detonate. The detonation will apply a large force to the piston, which will be resisted by the high load in the coils. The load will have to be high enough to stop the piston entirely at a desired position before it hits the end of its travel limits and be used as generated electricity. It may be used to charge the battery which up until this time has been powering the coils, solenoids, and spark plug. Once the piston is stopped, the exhaust valve will be opened by applying current to the exhaust solenoid. Current will then be applied to the coils to move the piston towards the cylinder wall in order to drive the exhaust gasses out. The exhaust valve will be closed, and then the cycle can be repeated. No mechanical energy is produced, only electrical.