The present invention relates to control systems, and, in particular, to control systems for internal combustion engines.

BACKGROUND OF THE INVENTION It has been proposed that a gas mixture in the form of ortho-hydrogen oxygen (HHO) gas (also known as polycell-hydrogen oxygen gas, or oxyhydrogen) is suitable for use in improving operating characteristics of internal combustion engines (ICEs, engines).

Ortho-hydrogen oxygen gas comprises hydrogen (H ₂ ) and oxygen (O ₂ ) in a molar ratio of 2:1 hydrogen:oxygen. HHO gas generators for vehicles and vessels are on-board electrolysis cells that generate hydrogen and oxygen, which is fed into the air intake system of an engine. The injection of HHO gas into an engine may improve the characteristics of the combustion leading to a greater horsepower output per unit of fuel consumed.

This translates into improving the fuel efficiency of the engine and reducing the C02 emissions per kilometre travelled. The electrical energy to power the electrolysis cells is taken from the vehicles battery, which in turn draws power from the alternator, which in turn draws power from the engine. Thus, the energy efficiency of an HHO generator and a control system are of vital importance to the energy efficiency of the vehicle or vessel as a whole. A HHO generator system is defined as an on-board vehicle or vessel system which operates to generate HHO gas. The gas generated by such a system is typically fed via a conduit system to the air inlet system of the internal combustion engine. Typically, such a HHO generator system comprises: an HHO generator (for example an electrolysis unit); an electrical connection to the vehicle's battery; an electrolyte solution reservoir; tube or tubes to replenish the electrolyte solution that has been converted to HHO gas connecting the electrolyte solution reservoir to the HHO generator; HHO gas output tubes conveying the HHO gas to the air inlet system of the engine, via a water bubbler system which acts as a safety mechanism preventing an engine backfire from igniting the gas any further along the tube. Numerous Universities have done research studies on this technology. In particular, studies have been carried out by the University of NW Ohio, Purdue University, and Fox Valley Technical College in the USA, and Cukurova University, of Adana, Turkey. University of NW Ohio and Cukurova University both concur in their conclusions that a system needs to devised that can control the rate of HHO gas into the engine to enable optimisation of the HHO injection rate and thereby achieve maximum fuel efficiency and minimise C02 emissions per kilometre travelled in the vehicle or vessel. Furthermore, the University of Cukurova research study measured the increase in engine torque at various RPM (engine revolutions per minute) when injecting a fixed amount of HHO gas in comparison to a variably controlled amount of HHO gas. The results showed the variably controlled HHO injection produced 25% - 40% more torque in the peak torque RPM range compared to a fixed rate of HHO injection. A snapshot of the results show RPM followed by percentage increase in torque:

1900 RPM 29%, 2000 RPM 31 %, 2100 RPM 25%, 2200 RPM 36%, 2300 RPM 40%, 2400 RPM 36%, 2500 RPM 33%, 2600 RPM 46%.

Numerous methods have been proposed to address the control issues, but none of them have achieved the desired level of control or the desired level of energy efficiency.

A typical HHO generator comprises a six cell electrolysis unit which is connected to a vehicle's 12 volt electrical system. An electrolyte reservoir is connected to the HHO generator via tubing and serves to replenish water consumed by the electrolysis process. HHO gas produced by the HHI generator is fed into the engine air inlet system via a bubbler system which is a protection system against a backfire from the engine. Many if not most HHO generators use KOH (Potassium hydroxide) and distilled water as an electrolyte solution and use 316L stainless steel for the electrode plates. Many HHO generator systems include a pulse width modulation (PWM) circuit in their connection to the vehicle electrical power. The limitations and problems with pulse width modulation as a power control system are discussed further in the examples of systems 1 , 2 and 3 below.

Current control using a PWM assumes a fixed or steady resistance in the electrolysis cell unit. If the resistance within the electrolysis unit changes, then the PWM cannot control the desired current flow. Assuming all electrical connections are good, there are three factors that affect the internal resistance of the cell unit: the ratio of KOH to water in the electrolyte solution; the internal resistance of the electrode plates; the temperature of both the solution and the electrode plates. As temperature in the electrolysis cell increases, the resistance of the steel electrode plates increase, the resistance of the electrolyte solution decreases. In practice, the overall resistance decreases.

The HHO generator has an electrolyte reservoir. As the water portion of the electrolyte is converted to HHO gas, the volume of water decreases and the volume of KOH remains constant, thereby increasing the ratio of KOH to water in the solution, which decreases the resistance of the electrolysis unit.

Thus, any control system that relies on a constant resistance within the electrolysis cell would be highly impractical. Gas production is controlled by the flow of current, according to Faraday's 1 st Law of

Electrolysis - the mass of a substance altered at an electrode during electrolysis is directly proportional to the quantity of electricity transferred at that electrode. Later scientific study has shown that the gas production, for a fixed controlled flow of current, increases in relation to the temperature of the electrolyte solution. The chemical process is utilising energy from the heat energy within the electrolyte solution.

Various techniques have been implemented and documented to control or adapt the current flow in the HHO generator. The following 3 systems which are described below are largely energy inefficient and or lack sufficient control of the HHO generator system current. Figure 1 of the accompanying drawings illustrates an example of a first previously- considered system (system 1), that shows direct connection between an automotive battery 3 and an HHO generator 4.

In this illustration a switch 1 is used to control the production of HHO gas by turning the current on and off. The current 2 is only limited by the internal resistance of the battery 3, the HHO generator 4 and the circuit wiring 5.

In electrical circuit theory, the resistance of the circuit wiring is deemed to be zero. A voltage generation device such as a battery also has a theoretical resistance of zero. Once electrical current has passed through an electrolysis cell, the electrode plates become polarized and the state of the electrolysis cell changes and it acts more like a battery than a resistance in the circuit. With the electrolysis cell disconnected from any power source, a voltage can be measured across the terminals of the electrolysis cell. Therefore the electrolysis cell is also a voltage generation device albeit a very small voltage, and it has a theoretical resistance of zero. The calculation of the theoretical current flowing through this circuit is 12 volts divided by zero resistance which, in theory, would have an infinite current flowing through this circuit. In system 1 of Figure 1 , the resistance of the circuit varies according to the heat generated in the electrolysis cell 4 and in the circuit wiring. The resistance of the metal electrode plates increases with heat, and the resistance of the electrolyte decreases with heat. In most cases the overall resistance of the electrolyte cell decreases, which in turn, causes a greater current to flow through the circuit, which in turn, causes less resistance. This can create an effect whereby the electrolyte cell draws greater and greater current until it becomes a current 'run-away' situation. A 'current run-away' describes a situation whereby the only limiting factor on the volume of current flowing is the maximum current that can be drawn from the battery, or the maximum current that can be drawn from the alternator at those engine revolutions. The increased current draw on the alternator, increases the 'drag' load on the engine, effectively subtracting power from the engine and reducing the overall efficiency.

Figure 2 of the accompanying drawings illustrates a second example of a system (system 2) that improves on system 1 of figure 1 by introducing time-domain control of the switch 1 known as Pulse Width Modulation (PWM). The duty cycle (on to off time ratio) is altered using a controller 6 in order to reduce the average current over time. This system (system 2) has large improvements on the previous system (system 1) since the current can be accurately adjusted with use of a timer in the controller 6.

Figure 3 illustrates a graph with the vertical Y axis indicating a current 2, the horizontal X axis indicates time 7. In this illustration, the 'on cycle' is roughly equal in time to the 'off cycle' and the peak current 10 is roughly double the average current 8. This is probably what the designers of this circuit aimed to achieve. Although the average current, /, can be adjusted to the required value, by adjusting the length of time of the On cycle' in relation to the Off cycle' the peak current is still only governed by the internal resistance of the battery, of the HHO generator and the circuit wiring, which, as described previously, is a very low and fluctuating resistance. This system is probably only approximately 50% energy efficient. It also has no means of dynamic variation of current whilst the vehicle is driving.

Figure 4 illustrates a similar graph to figure 3, with the vertical Y axis indicating a current 2, the horizontal X axis indicates time 7. Figure 4 illustrates the time-domain controlled current which, when the duty cycle is switched on, is climbing to a very high peak current flow. When the duty cycle is switched off, the current flow 9 is zero. The graph shows a much more likely scenario than in figure 3, in which during the 'on cycle' the peak current 10 is only limited by the internal resistance of the battery, of the HHO generator and the circuit wiring and the peak current 10 climbs towards infinity. The 'off cycle' is a much greater time period than the 'on cycle' to adjust the average current 8 to the required value. Although the average current 8 can be adjusted to the required value, the peak current 10 is still only governed by the internal resistance of the battery, of the HHO generator and the circuit wiring, which in total is a very low and fluctuating resistance. This system is probably far lower than 50% energy efficient. It also has no means of dynamic variation of current whilst the vehicle is driving.

Figure 5 illustrates system 3 which is similar to the previous circuit illustrated in figure 2, and adds known (and possibly variable) resistance to the circuit, to lower the current and therefore heating effect within the HHO generator. In figure 5, a shunt resistor 12, could be used to monitor the current in the HHO generator.

In this illustration, the voltage measured across the shunt resistor 12, is fed into a control operational amplifier (op-amp) 13, which in turn sets the resistance on the variable resistor 1 1. This control loop allows the system to self-regulate.

In this illustration, if the input from battery 3 is 12V, the current 2 is 12A, the voltage drop across the variable resistor 11 is 5.9 V, the voltage drop across the shunt resistor 12 is 0.1V, we can see that one half of the circuit voltage is present across the shunt resistor 12 and the variable resistor 11. The output getting to the HHO generator 4, is 6V. The same circuit current passes through the HHO generator 4, the shunt resistor 12 and the variable resistor 11. It means 144 Watt input power for 72 Watt output power and this gives an efficiency of about 50% for the system. This is still largely inefficient. It can be seen that only one half of the system power is dissipated within the HHO generator.

Whilst this system greatly improves on the control of current in the HHO generator and allows closed-loop control it is very inefficient in operation.

US patent number 4,424,105 discloses a HHO gas generator comprising a solid state current limiting circuit which uses national grid line (mains) current as a power source, which makes it a non-portable device that cannot be easily adapted to be used in a vehicle. US patent number 4,424, 105 also discloses that the current limiting circuit incorporates a series transistor operated in a variable-resistance, current limiting mode which is energy inefficient. This invention relies on manual operation of a calibrated dial to vary the gas output which would be totally impractical if not downright dangerous whilst driving.

Chinese patent 101949341 discloses a polycell hydrogen and oxygen HHO gas generator which claims throttle control of the amount of electrical voltage through the electrolysis cell. The description has no mention of current-mode power conversion and the drawings have no illustration of current-mode power conversion electronic circuitry. The description of the control is of a monolithic chip which cannot, by definition contain a large copper wound inductor which is necessary in any current mode power conversion circuitry, thus as the description is extremely vague it must be assumed it does not have it and it uses a form of pulse width modulation which is inherently energy wasteful. Throttle control for controlling the hydrogen and oxygen is not satisfactory as the throttle pedal is not in direct relation to the engine revolutions. In an example, using only one gear ratio and the engine starting at 800 rpm, full throttle pedal, the engine increases revolutions from 800 rpm to 4000 rpm. The amount of hydrogen and oxygen required for combustion optimisation at 800 rpm is very different to the amount of hydrogen and oxygen required at 4000 rpm, yet CN 101949341 would supply the same amount of hydrogen and oxygen at 800 rpm and at 4000 rpm because the control reference is the throttle pedal. A second example is full throttle at 800 rpm reaching a plateau with half throttle at 3000 rpm. CN 101949341 would provide gas input in totally the reverse amounts to what is required. The throttle control is a driver input signal, our patent is based on an engine's sensors analogue signal input.

SUMMARY OF THE INVENTION

According to one aspect of the present invention, there is provided a closed-loop control system for regulating an input of a variable amount of HHO gas into an air inlet system of an internal combustion engine, the system comprising: a closed-loop controller operable to monitor a state of an internal combustion engine by using the analogue values of outputs of engine sensors analogue signals, the closed loop controller comprises a hardware state or a software state algorithm operable to develop a control reference signal; a current mode controller operable to produce regulated current mode electrical input power to an HHO generator; wherein said closed-loop controller provides said control reference signal to said current mode controller; an HHO generator operable to produce a variable and regulated amount of HHO gas for injection into an air inlet system of an internal combustion engine; and wherein said closed-loop controller is operable to use a single or multiples of sensor analogue signals of an internal combustion engine to compute and adjust the control reference signal.

In one example, said current mode controller comprises a Buck converter electronic circuit operable to produce regulated current-mode electrical input power to said HHO generator.

In one example, said current mode controller comprises a Boost converter electronic circuit operable to produce regulated current-mode electrical input power to said HHO generator.

In one example, said HHO generator is operable to produce a substantially instantaneous and optimised amount of HHO gas for injection into such an air inlet system during a start-up phase of such an internal combustion engine.

In one example, said HHO generator is operable to produce a substantially instantaneous adjustment to an amount of HHO gas injected into such an air inlet system in response to an adjustment of the said control reference signal. In one example, the closed loop controller will monitor the sensor analogue signal of an internal combustion engine which senses RPM (revolutions per minute), said closed-loop controller is operable to compute and adjust the control reference signal.

In one example, the closed loop controller will monitor the sensor analogue signals of an internal combustion engine which senses RPM (revolutions per minute) and which senses a MAP (Manifold absolute pressure), said closed-loop controller is operable to compute and adjust the control reference signal.

In one example, the closed loop controller will monitor the sensor analogue signals of an internal combustion engine which senses RPM (revolutions per minute) and which senses a Mass Airflow sensor, said closed-loop controller is operable to compute and adjust the control reference signal.

According to another aspect of the present invention, there is provided a system for providing an oxyhydrogen gas mixture to an internal combustion engine, the control system comprising: an oxyhydrogen gas mixture generator operable to output an oxyhydrogen gas mixture for supply to an air inlet of an internal combustion engine; a closed-loop controller operable to receive a measurement signal relating to an operating parameter of an internal combustion engine, and to generate a control signal in dependence on such a received measurement signal and on a predetermined control scheme; and a current mode controller operable to receive such a control signal from the closed-loop controller, and operable to produce regulated current mode electrical input power to the oxyhydrogen gas mixture generator so as to control output of oxyhydrogen gas mixture from the generator independence upon such a received control signal. The current mode controller may comprise a Buck controller or a Boost controller.

In such a system, the operating parameter of the internal combustion engine may be one or more of the engine speed, mass airflow, manifold absolute pressure, throttle position, fuel flow rate, turbo boost pressure, ignition timing, and fuel injection timing.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a circuit diagram illustrating an example of a prior art system that shows direct connection between an automotive battery and an HHO generator;

Figure 2 is a circuit diagram illustrating an example of a prior art system that improves on that in figure 1 by introducing time-domain control of the switch 1 known as Pulse Width Modulation; Figure 3 is a graph illustrating prior art current control using Pulse Width Modulation with a 50% duty cycle. ;

Figure 4 is a graph illustrating prior art current control using Pulse Width Modulation whereby the peak current is extremely high because it is only limited by the internal resistances of the battery, the HHO generator and the wiring; Figure 5 is a circuit diagram illustrating prior art current control using an op-amp in which only one half of the energy is utilised to power the HHO generator;

Figure 6 is a circuit diagram and schematic diagram illustrating one embodiment of the present invention;

Figure 7 is a circuit diagram and schematic illustrating another embodiment of the present invention; and

Figure 8 is a circuit diagram and schematic diagram illustrating another embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Example of embodiments of the present invention that seek to provide respective control systems to improve the combustion characteristics of fuels used in internal combustion engines by regulating an input of a variable amount of ortho- hydrogen and oxygen gas into the air inlet system of said internal combustion engine, using a closed-loop control of an energy efficient current mode power conversion electronic circuitry to regulate, both dynamically and variably, the input power to the on-board ortho-hydrogen and oxygen gas generator using multiple various analogue data signals from the said internal combustion engine as inputs to a closed-loop control reference signal are disclosed herein. The energy efficient current mode power conversion electronic circuitry or apparatus can be a Buck converter or a Boost converter

Figure 6 of the accompanying drawings illustrates, schematically and by way of example only, a current mode control system having a vehicle or vessel battery 3 connected to a current-mode controller 15. A HHO generator cell device 4 is connected to the current- mode controller 15. The current-mode controller 15 utilizes an energy efficient power conversion circuit 31 , in series with a monitored shunt resistor 14.

The battery 3 is operable to supply electrical power to the current-mode controller 15. The current-mode controller 15 utilizes an energy efficient power conversion circuit to maintain constant controlled current or substantially constant controlled current flowing through the HHO generator 4. Since HHO gas generation is proportional to the amount of current flowing in the cell, direct control of the current allows direct control of HHO gas generation. The current mode controller 15 is illustrated in more detail in Figure 7.

Figure 7 of the accompanying drawings illustrates schematically one embodiment of the present invention, by way as example only, which includes an energy efficient power conversion circuit using a Buck converter circuit.

The embodiment of Figure 7 includes an inductor 20, an input capacitor 16, an output capacitor 17, a diode 23, a high-side MOSFET-(Metal Oxide Semiconductor Field Effect Transistor) 19, a resistor 24, a shunt resistor 21 , an earth connection 22, a current mode controller 18, a battery 3 and an HHO generator 4. The Buck Converter has two modes of operation: a first mode when the MOSFET switch 19 is closed, and a second mode when the MOSFET switch 19 is open. In the first mode of operation, when the MOSFET switch 19 is closed, voltage out minus voltage in is applied across the inductor 20 and this consequently causes a linearly increasing current that flows through the inductor 20. Then, in the second mode of operation when the MOSFET switch 20 is open, current continues to flow, with the diode 23 now conducting, allowing circulation of current from the inductor 20.

The output capacitor17 stabilises the circuit output as well as providing smoothing for the saw tooth ripple caused by the conversion process. Since the voltage across the inductor 20 is now voltage out minus 0.6V this then causes the current to decrease linearly.

The control will normally compare the current output through the shunt resistor 21 , to a reference voltage and in turn change the pulse width created by the current mode controller 18.

In HHO gas generation the Buck Converter will be run in continuous mode which means the load current never falls to zero and instead just constantly rises and falls above this point. Whilst the switch is on the rise in current can be described with the following equation d is delta current indicating changing current, d is delta time indicating changing time, L is the inductor value, V _£ is the input voltage and v ₀ is the output voltage.

Then whilst the MOSFET switch 19 is off, the fall in current is determined by the following equation: d_ ₌ Vo +Vp

d L '

V _D is the voltage drop across the diode 23.

Energy stored in the inductor 20 can be stated as E = - L · I _L

Since this is the case it can therefore be said that the energy in the inductor 20 increases and decreases whilst the switch is on and the switch is off, retrospectively.

Note that the duty cycle for this Buck Converter is D =—— . Knowing that whilst the MOSFET switch 19 is closed, the voltage across inductor 20l/ _L ,thenF _L = Vi ~ V ₀ and when the switch is open the two following equations can be stated

AI _L = C° ÷ ^V d = ⁽ ^ t _Q , t ₀ = D

M _Lo = j ^{= t} ° ^+t ° d = =^ t ₀ , t ₀ = (1 - D)T

Note that T is the time period.

Then from these equations it can be stated that

L L

Using earlier definitions it can also then be said that (Vi - V ₀ )D - V ₀ (l - D)T = 0

Since in this situation voltage does not particularly matter to the circuit, but the current does.

Current-mode regulators adjust the peak current output of the circuit through use of a control reference signal. The origin of the control reference signal is illustrated in figure 8.

Figure 8 illustrates schematically preferred features of an embodiment of the present invention, by way of an example only, and shows a closed-loop control system intended to improve the combustion characteristics of fuels used in internal combustion engines by regulating an input of a variable amount of HHO gas into the air inlet system of said internal combustion engine. In this illustration, the system includes a closed-loop controller 26, which is operable to generate a control reference signal 25, one or more analogue engine sensors operable to generate respective analogue signals 27, an internal combustion engine 28, an HHO generator 4, an HHO gas conduit system 30, an engine air inlet system 29, an inductor 20, an input capacitor 16, an output capacitor 17, a diode 23, a high-side MOSFET-(Metal Oxide Semiconductor Field Effect Transistor) 19, a resistor 24, a shunt resistor 21 , an earth connection 22, a current mode controller 18, and a battery 3. The closed-loop controller 26 is operable to control the supply of electrical current to the HHO generator 4 in accordance with a predetermined method. The method may embody a control algorithm and a set or sets of parameters, said algorithm can be provided as a hardware state algorithm or for reasons of convenience, software may be used to contain the algorithm.

The closed-loop controller 26 is operable to receive analogue signals 27 from one or more engine sensors, and to monitor the state of the engine 28 by mapping such received analogue signals 27. The closed-loop controller 26 uses a hardware state algorithm or an algorithm within software and set of parameters to develop and adjust a control reference signal 25 to provide a control reference for the current mode controller 18 to adjust the peak current output and thereby adjust the HHO gas output of the HHO generator 4 which optimises the combustion characteristics of the fuel and improves the thermal efficiency of the engine.

The HHO generator 4 produces HHO gas which is injected into the engine air inlet system 29 via an HHO gas conduit system 30. The HHO gas conduit system 30 may contain one or more bubbler systems which act as a dryer and as a flash back arrestor. As a greater or lesser amount of HHO gas is injected into the internal combustion engine 28, and as the vehicle or vessel driver provides input via the throttle control mechanism, the internal combustion engine 28 will have changing states which will be monitored by multiple engine sensors, said sensors adjusting the analogue values of the multiple sensor analogue signals 27 of said internal combustion engine supplied to said closed- loop controller 26.

In one embodiment of the invention, the closed loop controller 26 operates to monitor the sensor analogue signal 27 of said internal combustion engine which senses RPM (revolutions per minute), said closed-loop controller is operable to compute and adjust the control reference signal. In this example, an engine sensor is provided that outputs a signal relating to the engine speed (revolutions per minute, RPM). This signal is supplied to the closed-loop controller 26 and is used to adjust the control reference signal 25.

In one embodiment of the invention, the closed loop controller 26 operates to monitor the sensor analogue signals 27 of said internal combustion engine which sense RPM

(revolutions per minute) and which sense MAP (Manifold absolute pressure), said closed- loop controller is operable to compute and adjust the control reference signal. In this example, two engine sensors are provided: a first that outputs a signal relating to the engine speed (revolutions per minute, RPM), and a second that outputs a signal relating to the manifold absolute pressure (MAP) of the engine 28. These signals are supplied to the closed-loop controller 26 and are used to adjust the control reference signal 25.

In one embodiment of the invention, the closed loop controller 26 operates to monitor the sensor analogue signals 27 of said internal combustion engine which sense RPM

(revolutions per minute) and which sense a Mass Airflow sensor, said closed-loop controller is operable to compute and adjust the control reference signal. In this example, two engine sensors are provided: a first that outputs a signal relating to the engine speed (revolutions per minute, RPM), and a second that outputs a signal relating to the mass airflow of the engine 28. These signals are supplied to the closed-loop controller 26 and are used to adjust the control reference signal 25.

The sensors provided to monitor the engine 28 and to provide the signals 27 can be of any type appropriate to the application of the system. For example, the sensors may produce signals relating to the engine speed (RPM), manifold absolute pressure (MAP), mass airflow, throttle position, fuel flow rate, turbo boost pressure, ignition timing, and fuel injection timing. The signals may be used singly, or in any suitable combination.