GB2459079A

GB2459079A - An air engine

Info

Publication number: GB2459079A
Application number: GB0800480A
Authority: GB
Inventors: Sean O'brien
Original assignee: Individual
Current assignee: Individual
Priority date: 2008-01-14
Filing date: 2008-01-14
Publication date: 2009-10-14
Also published as: GB0800480D0

Abstract

An air engine is characterised by an inline arrangement of pistons and cylinders. Compressed air is injected and exhausted by valves controlled by the engine electronic control unit (ECU). Air is injected during the compression stroke and shut off when the piston is at top dead centre (TDC), at which point the air expands and drives the power stroke. After reaching bottom dead centre (BDC) the exhaust valve opens allowing the expanded air to escape. The exhaust valve is held open depending on the speed of the engine. Also disclosed is a crank shaft having cranks positioned at 90 degree radial intervals about the axis of rotation.

Description

The 4 Cylinder Pneumatic Enciine

Introduction

This invention relates to a highly efficient engine that is powered by compressed air.

With the reality of global warming, the need for new means of powering vehicles is essential. There are many alternatives to fossil fuels on the market but they all have there disadvantages. For instance battery powered electric vehicles are plagued by large, heavy, toxic batteries that take a long time to recharge and consume lots of electricity. Hydrogen powered vehicles whether internal combustion or fuel cell are expensive and the hydrogen is highly volatile making it difficult to store safely on a road vehicle. There is even an air powered car, made by a company called MDI that uses compressed air to drive pistons inside an engine. This air engine uses unique connecting rods that allow the piston to be held at TDC (Top Dead Centre) for a percentage of its cycle, it does this so that it allows time for the air pressure that is being injected into the inside of the cylinder to build up. However there is disadvantages in this design, for a start it can only rev upto 3500rpm and the point in which the piston stops at TDC, the piston is not transmitting any torque through to the crankshaft, as it is relying on the other pistons in the engine to do this. This is making the engine less efficient and this is also limiting how fast the engine can rev.

To overcome this the four cylinder pneumatic engine uses various techniques to make it efficient. For a start it uses conventional connecting rods as opposed to articulated ones, as this makes it lighter and allows the piston to transmit power more efficiently through to the crankshaft, as it also allows the piston to move up and down from TDC to BDC without creating fluctuations in the torque curve. It uses electronic air injectors that are controlled by the ECU (electronic control unit). The use of these computer governed air injectors, enables the computer to decide when the air is to be injected. The use of electronic exhaust valves, that are also governed by the ECU allow the computer to decide when and which valve to open and close depending on engine speed and load. The use of the electronic exhaust valve does away with the need for a camshaft and tappets, thus taking strain off the engine and making it more efficient. The ECU receives the information on engine speed and load by the use of crankshaft position sensors and electronically variable throttle resistors, that send electrical signals regarding the position of the throttle pedal.

A unique crankshaft is fitted that I call the 4 way crankshaft, because it allows power to be transmitted in four places in one single revolution of the engine. This crankshaft design allows for smoother torque flow whilst keeping transmission fluctuations to a minimum.

The advantages of this engine compared to similar engines of this type, are that this engine is a lot more economical with the way it consumes compressed air. It is also a lot more powerful especially at higher engine speeds. Its also more energy efficient, due to the fact that it requires less compressed air to produce the same amount of power from similar engines. There is less internal friction due to the use of viscous components. Light weight materials are used throughout the construction.

The 4 Cylinder Pneumatic Enciine How it Works The Engine Cycle During very low rpm's the air is injected into the cylinder at TDC and the exhaust valve opens at BDC, this is done so that the engine can build momentum before beginning the mini compression stroke phase. As the revs increase the air is gradually injected before the piston reaches TDC, upto a point of no further than the last 1/3 of the exhaust stroke. At this point the piston is moving up towards TDC whilst the air is being injected, this upward motion of the piston increases the initial pressure of the injected air greatly. In order to achieve this compression the engine has to be running fast enough to achieve any decent momentum to be able to compress the air into a super highly compressed state. In order to be able to inject the air before the piston reaches TDC, the exhaust valve needs to close to stop air from escaping. This is done electronically by the use of electromagnetic exhaust valves. This process ends the exhaust stroke early and the rest of the stroke before the piston reaches TDC, becomes a compression stroke or mini compression stroke.

The faster the engine revs the larger the mini compression stroke gets and the more efficient the engine becomes, this produces more power at higher revs.

As soon as the piston passes TDC and enters the power stroke phase the air stops being injected and the piston is forced down by the rapidly expanding compressed air. After the piston gets to BDC the exhaust valve opens and the expanded air escapes. The exhaust valve stays open for as long as the computer deems necessary, depending on engine speed. Then the engine cycle starts again by closing the exhaust valve and injecting the air.

4 Way Crankshaft A crankshaft on a 4 stroke, 4 cylinder, inline internal combustion engine allows 2 pistons to be at TDC at once and the other 2 to be at BDC. This typical layout would be unsuitable for a 4 cylinder pneumatic engine as it is a 2 stroke engine and fitting this kind of crankshaft to this type of engine would result in unsmooth operation and jerky acceleration at the very least. So to compensate for this I have designed a crankshaft that enables the torque to be transmitted smoothly over 4 offset points around the axis of the crankshaft. This design allows a power stroke to be transmitted once every quarter of an engine revolution. This makes the engine run in the smoothest possible way whilst minimising transmission shock.

The ECU (Electronic Control Unit) The ECU is the heart of this engine without it, the engine would not be able to operate. The ECU controls all of the engines main components such as the electromagnetic exhaust valve and electronic air injectors, as well as receiving and processing electrical signals from devices such as the crank position sensor and throttle resistor as well as other electrical components relating to the engines operation. The ECU will consist of a series of micro-processors and transistors programmed to operate the various electrical components.

The 4 Cylinder Pneumatic Enciine How it Works Solenoid Air Valve The solenoid air valve is a device fitted before the expansion chamber to control the quantity of air flowing into the engine. This device consists of an air tight plunger that slides back and forth by the force of electromagnetism in a solenoid. This device is connected to the ECU via a relay and it acts as the throttle, allowing air into the engine under the operators control also the ECU can adjust the air flow automatically when sensors around the engine detect extra strain being put upon it.

Expansion Chamber The expansion chamber is a volume chamber that equalizes the air pressure coming from the solenoid air valve. Without this device the air entering the different cylinders will be at different pressures to each, other resulting in uneven displacement of torque through the crankshaft which could cause damage and premature engine wear.

Materials Used and Possible Manufacturing Techniques The pneumatic engine will use many modern, light weight materials that I deem will be suitable for this application. Below I have listed the main components and the materials they could be made from:-Engine Block = Sand Casted Aluminium Alloy Cylinder Head = Sand Casted Aluminium Alloy Pistons = Heat Resistant Nylon, Aluminium Connecting Rods = Forged aluminium alloy 4 Way Crankshaft = Pressure Die Cast Aluminium, Tempered Cast Steel High Pressure Air Pipes = Aluminium Tubbing, Zinc Galvanized Steel Tubbing Expansion Chamber =Rolled Sheet Aluminium Oil Sump = Pressed Sheet Aluminium Bushes and Bearings = Nylon, Steel Roller Bearings, Soft Bronze Solenoid Valves = Soft Iron, Copper Wire, Machined Brass Air Injectors = Mild Steel, Copper Wire, Nylon, Soft Iron ECU = Glass Fibre, Copper, Silicon, Solder, Aluminium

KEY

1-Solenoid Air Valve 2-Expansion Chamber 3-Electro-Magnetic Exhaust Valves 4-Electronic Air Injectors 5-Nylon/Aluminium Pistons 6-Crank Position Sensor 7-Four Way Crankshaft 8-Compressed Air Storage Cylinder tNDEX & 9-l2volt Lithium Battery 10-Electronic Control Unit (ECU) 1 5 11-Aluminium Alloy Engine Block SCANNUG 12-Connecting Rods 13-Oil Sump 14-Standard 4 Cylinder Internal Combustion Crankshaft 15-Exhaust Air Outlet Pipe Standard 4 cvi Crankshaft A crankshaft on a four stroke four cylinder inline internal combus engine looks alot like this. itis et1kientfor that t eofengine asit allows torque to be transmitted evenly through four points on the crankshaft This design caters fr the four strokes intake, compressk)n, combustjon exhaast in the smoothest possible way as it allows a power stroke to be transmitted every single stroke.

4Way Crankshaft S.'.. If the above crankshaft was to befitted to a 4 cnderpnemce * : : there would be two power strokes at once transmitted through the crankshaft because the Pneumatic Engine is 2 stoke and the standard crank . : is not designed to take 2 power strokes at any I time.

* . This effect will most probably.dage the crankshaft and ithe engine did * ;m it would be teznbley unsmooth and would generate alot itransnhissjon1 * shock. To get around this dilennna I have designed a crankshf that cai * .: rnsrnit torque smoothly and evenly. It is a standard crankshaft but the :. middle two points are split horizontally to allow a power stroke to be transmitted once every half stroke of the engines two stroke cvlcle I have nauetj this the 4 way crankshzft because ityou where to look straight down It, it would look Eke it has four arms extending from the center.