FIELD OF THE INVENTION

The present invention relates to a dosing system for supplying a fuel additive to the fuel tank of an internal combustion engine.

BACKGROUND OF THE INVENTION

Internal combustion engines require regular re-fueling with either petrol or diesel fuel. The quality of fuel can vary greatly and as a result of this and other factors, many engine operators choose to mix fuel additives with their fuel to increase performance or to modify certain parameters.

For example, chemical additives may include octane boosters to increase the octane level of the fuel for higher performance. Cleansing chemicals are also often used to ensure complex fuel injectors and

other components remain free from potential contaminants, thereby increasing maintenance intervals and enhancing reliability.

A common usage of internal combustion engines is in road going vehicles. Many vehicle operators, in particular trucking fleet operators, require the dosing of fuel with additives each time the vehicle is re-fueled. In the case of fleet operators, reliance must then be placed on the vehicle driver firstly to monitor the precise quantity of fuel added at each filling station and then to calculate and add the required amount of fuel additive in accordance with predetermined volumetric ratios. This is a time consuming task and many vehicle drivers, in particular professional contract drivers who drive many hundreds of kilometres daily, may not perform this task regularly, accurately or at all. As such, the technique is particularly susceptible to operator error.

Similar problems are encountered with stationary engines used in conjunction with, for example, generators and pumps. These engines may operate for very long periods of time and accordingly require frequent re-fueling. Once again, reliance must be placed on the operator to add the correct amount of additive.

In an attempt to overcome this reliance on

individual operators, it has been proposed automatically to add fuel additives to an engine's fuel tank upon re-fueling. In the past, this has been achieved by a float in the fuel tank which registers fuel addition in the tank and then actuates a mechanical apparatus coupled to the float to supply the required amount of fuel additive.

Problems with systems of this type have been high cost, mechanical complexity, inaccuracy of operation, and inability to adapt flexibly to different engines, different fuels and changes in fuel to additive ratios.

DISCLOSURE OF THE INVENTION

It is therefore an object of the present invention to overcome or ameliorate at least some of these deficiencies of the prior art.

According to a first aspect of the invention there is provided a dosing system for adding a fuel additive contained in an additive tank to the main fuel tank of an internal combustion engine, the system comprising: conduit means connecting said additive tank to the main fuel tank; detection means for generating a first signal indicative of a quantity of fuel added to the fuel tank; memory means for storing data indicative of a

predetermined ratio of additive to fuel for the engine; and supply means responsive to said first signal and said data to supply said fuel additive from said additive tank to said main fuel tank through said conduit substantially in proportion to the quantity of fuel added, thereby tending to maintain said predetermined ratio within said fuel tank.

Preferably, said detection means includes: means to generate a second signal indicative of quantity of fuel in the main fuel tank; comparator means for storing said second signal before and after a predetermined operating condition corresponding to a possible opportunity for adding fuel is detected and to generate said first signal if the second signals stored before and after said operating condition indicate the addition of fuel.

According to a second aspect of the invention there is provided a method for supplying fuel additive contained in an additive tank to the main fuel tank of an internal combustion engine, said method comprising the steps of:-

(a) generating a first signal indicative of a quantity of fuel added to the fuel tank;

(b) storing data in a memory means, said data being indicative of a predetermined ratio of additive to fuel required for said engine;

(c) supplying additive to said fuel tank from said additive tank substantially in proportion to the amount of fuel added in response to said first signal and said data; and

(d) thereby maintaining the predetermined ratio within the fuel tank.

Preferably, the method further comprises the steps of:

(e) generating a second signal indicative of the quantity of fuel in the tank;

(f) comparing said second signal before and after a predetermined operating condition corresponding to a possible opportunity for adding fuel is detected and generating said first signal if the second signals before and after detection of said operating condition indicate the addition of fuel.

BRIEF DESCRIPTION OF THE DRAWINGS

A preferred embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings in which:

Figure 1 is a schematic diagram of a dosing system according to the invention; and

Figure 2 is a flow diagram representing the computer program controlling the dosing system of Figure 1.

PREFERRED EMBODIMENT OF THE INVENTION

The example below is described in relation to an engine powering a motor vehicle. However, it will be appreciated by those skilled in the art that a dosing system according to the invention is equally applicable to stationary engines and other applications.

With reference to Figure 1, the invention provides a dosing system 10 for adding a fuel additive contained in additive tank 12 to the main fuel tank 14 of a vehicle powered by an internal combustion engine (not shown) . Additive tank 12 is connected by a conduit indicated generally at 16 to the main fuel tank 14. In the preferred embodiment shown, the conduit 16 includes a first pipe 18 extending between the additive tank 12 and supply assembly 20 and a further pipe 22 leading from the supply assembly 20 to a manifold 24. The manifold distributes additive via pipes 26 to the fuel tank 14. More than one distribution pipe 26 is shown, since many vehicles have more than one fuel tank. However, only one fuel tank is shown in this example for the sake of clarity.

The supply assembly 20 in the embodiment shown is comprised of an electric pump 20a and an electric solenoid valve 20b connected by pipe 28.

A microcomputer, indicated generally at 30, includes memory means 30a, computation means 30b and

comparator means 30c. Electrical power is provided for the microcomputer from the vehicle's electrical system via electrical input 34.

The microcomputer 30 is adapted to issue a first signal which is indicative of a quantity of fuel added to the fuel tank. The memory means 30a stores data representative of the predetermined ratio of the additive to fuel, as required for the particular engine. Supply assembly 20 in conjunction with microcomputer 30 is responsive to the first signal and the stored data in order to control the flow of fuel additive from the additive tank 12 to the main tank 14 through conduit 16 in proportion to the amount of fuel added. This may be conveniently achieved by controlling the period of time for which solenoid valve 20b remains open. Alternatively, a controlled dosage pump may be used.

Fuel tank 14 is provided with sensing means 32 to generate a second signal indicative of quantity of fuel in the tank 14. In a highly preferred embodiment, the sensing means is the existing tank level indicator. However, other devices could of course be substituted if desired.

The second signal is inputted to microcomputer 30 via input 36 and is continuously stored in the memory means 30a of the microcomputer before and after a predetermined operating condition of the engine or

vehicle is satisfied. If the "after" second signal is found to be greater than the "before" second signal by comparator means 30c, then the first signal is generated.

One predetermined operating condition, in the case of a motor vehicle, is whether or not the vehicle is stationary. Various methods are available to detect this operating condition including a current/voltage sensor on the engine's ignition circuit, an electronic sensor on the vehicles speedometer or tachometer, or a proximity sensor on a wheel or other rotary component of the vehicle. Such a proximity sensor could be optical or magnetic such as a Hall effect generator. The advantage of a device such as a Hall effect generator is its ability to function in dirty environments. The signal generated by the sensor is sent to the microcomputer via input 38.

In the embodiment shown in Figures 1 and 2 , the mode of operation of the engine is detected by an electronic sensor on the vehicle's speedometer. Thus, the sensor provides a "YES" signal if the vehicle is stationary and a "NO" signal if the vehicle is moving.

The logic of the dosing system will now be described in reference to the flow chart of Figure 2 , the reference numerals in which corresponds to the following features or procedures

50 System start.

52 Detect ignition on.

54 Check calibration required.

56 Calibration.

58 Load calibration and tank data.

60 Check calibration data error free?

62 Error indicator.

64 Detect vehicle stationary?

66 Calibration.

68 Tank data error free?

70 Generate second signal.

72 Correct second signal for tank shape.

74 Compare before and after second signals, additive required?

76 Generate first signal (supply additive) .

78 Generate second signal.

80 Correct second signal for tank shape.

82 Store corrected second signal.

The flow chart begins at 50 when the system is started and an electrical sensor detects at 52 when the ignition is turned on. This also ensures electrical power is provided from the engine's alternator to microcomputer 30 via input 34 (as shown in Figure 1) . The microcomputer then checks if calibration of the dosing system is required at 54, and supplies a "YES" or "NO" signal accordingly.

If a "YES" signal is supplied, the dosing system is calibrated at 56. This would be required if, for example, the memory means 30a were erased or a new dosing system was installed. If a "NO" signal is supplied the calibration and tank data is loaded into the microcomputer memory at 58.

It will be appreciated that the first time the system is operated a range of fuel volume levels and corresponding second signals are required to be entered into the microcomputer via a keypad or such device (not shown) . These calibration details are utilized by the dosing system's computation means 30b. When calibration is complete, a check is performed to see if the calibration data is complete or corrupted in any way. If any problems arise, the dosing system indicates an error at 62. This will normally be in the form of a visual indicator signifying to the operator that the system is not functioning correctly and will not automatically dose the fuel tanks with additive upon addition of fuel. An example of such a visual indicator is a red light on the dashboard of the vehicle.

If the calibration data is complete and error free, the system checks the engine's operating condition at 64. In the embodiment shown, a sensor on the vehicle speedometer indicates whether the vehicle is moving or stationary.

If the vehicle is moving a "NO" result is issued and the system at 68 checks if the tank data is complete. If there is no stored second signal indicative of the quantity of fuel in the tank the system will return a "NO" result and progresses to 78 to measure the quantity of fuel in the fuel tank and issue a second signal. The second signal is corrected for the tank shape at 80 and then the corrected second signal is stored at 82 in the memory means 30a.

The system then returns to 64 if calibration option 66 issues a "NO" signal. This option will be described in more detail later. The system again checks at 64 whether the vehicle is stationary or moving. If vehicle motion is indicated a "NO" result is issued and the system again checks the tank data is complete at 68. As a second signal was stored previously at 82, the tank data will be complete. This ensures a "YES" result is issued at 68 and the system progresses to 70 and subsequently remeasures the quantity of fuel in the fuel tank. Again this is corrected for tank shape at 72 (a step identical to the correction performed at 80) .

Comparator 74 then compares the second signal issued and corrected after the vehicle being stationary was indicated with the second signal issued and corrected before the vehicle being stationary was indicated. If the "after" second signal is greater

than the "before" second signal, the system recognises that fuel has been added and a first signal is calculated using computation means 30b. At 76 supply assembly 20 adds the required additive to the fuel tank in response to the first signal and stored data. The system then returns to 78 and repeats the above process. As long as vehicle motion is continuously indicated the system will step through the following path, 78-80-82-66-64-68-70-72-74 and again to 78.

Calibration option 66 provides, if the vehicle is stationary, an opportunity to alter the calibration data. Whilst the vehicle is stationary, the sensor at 64 issues a "YES" signal. The system will then alternate between 64 and 66 to allow recalibration.

The calibration function at 66 allows the operator to adjust any of the calibration values in the system when the vehicle is stationary. Conveniently, the vehicle and dosing system does not have to be powered down and any memory does not have to be erased when calibrating. If no calibration is required, the system merely alternates between 64 and 66 waiting for either an indication of movement or else further calibration.

It will be appreciated that by continuously checking for a change in the level in the tank whenever the vehicle stops, and then automatically adding the required amount of fuel additive from a

secondary tank in accordance with precisely predetermined volumetric ratios, the possibility for operator error is almost entirely eliminated. This in turn leads to enhanced engine reliability, longer maintenance intervals, and quicker fuel stops. Moreover, the system can easily and cost-effectively be retro-fitted to existing vehicles. Thus, the invention represents a commercially significant improvement over the prior art.

Although the invention has been described with reference to specific examples, it will be appreciated by those skilled in the art that the invention may be embodied in many other forms.