Electronic Valve Actuation in Combustion Engine
The aim of this project is to actuate the valves of an internal combustion engine electronically instead of mechanical methods. The advantage of having electronically actuated valves instead of the mechanical ones is that it helps to improve the engine performance by reduced fuel consumption and improved power output.
The electronic valve actuation helps to vary the valve timings infinitely in internal combustion engines which provide desired open and close intervals of intake and exhaust valves at variable engine speeds. Once the valve timings are perfected, it leads to reduced fuel consumption and greater engine efficiency.
The project covers the modeling and software for implementing an electronically actuated valve with the development of a hardware model which can be developed for future practical applications. But the project does not involve running the valve in an actual engine.
This thesis provides a method for electronically actuating valves used in an internal combustion engine. This method for valve actuation looks at utilising the expected change to a 42V standard in motor vehicles. It also provides a simplified model detailing how this principle works.
The advantage of electronic valve actuation is that it provides an easy method of infinitely varying the valve timing in internal combustion engines. The relationship between the desired open and shut intervals of the intake and exhaust valves vary with respect to engine speed. While some car manufacturers have developed methods of varying valve timing, most of these are still mechanical methods, and don’t allow for an infinitely variable timing profile. Improved timing will result in reduced fuel consumption and improved power in motor vehicles. Characteristics of solenoids are examined. These characteristics are used to design different mechanical layouts of the valve in order to reduce the required force by the solenoids.
With the use of the electronics from James Kennedy’s PUMA arm control board, the working of the simplified model is explained. The software is currently written to generate a PWM signal for driving the solenoid, and to modify that signal in response to an encoder input.
1.1 Thesis Overview
The aim of this thesis is to provide a method for electronically actuating valves used in an internal combustion engine. A simplified model of an engine valve has been built to demonstrate the principal behind this, and to provide a platform to demonstrate the functionality of the software. The electronics to be used have been taken from James Kennedy’s board used in the Control of the PUMA 560 arm and detailed in his thesis, Design and Implementation of a Distributed Digital Control System in an Industrial Robot.
The reason behind electronically actuating valves is to allow for easy and infinitely variable valve timing to improve engine performance. Current mechanical methods used are difficult to change and when they are changed they don’t allow more then a few possibilities for valve timing.
The valve controller explained in this thesis uses the Texas Instruments TMS320F241 to run a full bridge power converter to drive the DC solenoid used to actuate the valve.
1.2 Scope of Work for this Thesis
This thesis covers the modelling and software for an electronically actuated valve. It also provides a concept and a basic hardware model that can be further developed for use in practical applications. The model provides a starting point for future development towards a design robust enough to run inside an internal combustion engine, while the software provides position control and as more becomes known about what is required by the actuation system, it can be further developed to encompass this. This thesis does not deal with running the valve in an engine, as, at this stage, that is too complex a step to go to. This thesis looks at running the bench top model at speeds of up to 3000rpm. This is close to what is needed for everyday driving but for practical use, it would need to be increased a little.
1.3 Research Justification
Current internal combustion motors used in motor vehicles rely on an outdated system for opening and closing the intake and exhaust valves to the engine. This system involves using a camshaft that is attached by pulleys to the crankshaft. The trouble with this system is that it is a purely mechanical system and therefore the timing of the valve openings cannot be readily modified. This mechanical system also eliminates the possibility of an upgrade without a complete overhaul.
This mechanical system does not optimize fuel economy and performance for the full range of engine revs. Electronic valve actuation will allow for these criteria to be optimized. With the increasing price of petrol and the increasing awareness of problems caused by vehicle emissions, these optimizations are important. Attempts at electronically actuating valves have been limited by the power that is supplied by the 12V standard currently used in motor vehicles. This thesis will look at utilizing the expected change to a 42V standard to overcome some of the problems inherent with this lack of power. Other problems present have been getting the valve to run at the required speeds and generating enough force from solenoids to meet these speeds. The use of a DSP chip should help to overcome the speed problems, while careful modeling and analysis will look at reducing the force required by the solenoids.
Source of Information: The University of Queensland