FUEL ADDITIVE METERING APPARATUS

Abstract: In a diesel engine fuel injection apparatus, a fuel injection pump (10) draws fuel from a reservoir, (12), delivers a portion of the fuel to the engine (20), and directs excess fuel through a return line (26) back to the reservoir. A supply pump (28) delivers fuel from a tank (30) to the reservoir to maintain a constant volume of fuel in the reservoir. A fuel metering unit (38) measures the rate of fuel delivery by the supply pump. An additive pump (64) feeds an additive through the return line to the reservoir where the additive mixes with the fuel. The fuel metering unit controls the additive pump to proportion the rate at which additive is fed to the reservoir to the rate at which fuel is delivered by the supply pump, and the amount of additive delivered to the engine is thereby proportioned to the amount of fuel consumed by the engine.

Description: This invention relates to a fuel additive metering apparatus in which an additive is mixed with fuel for delivery to an engine, and a method of operating the apparatus. The exhaust system of a diesel engine may be equipped with a trap to separate particulates from the engine exhaust gases and thereby reduce emission of particulates into the atmosphere. Such a trap must be regenerated periodically. Some proposals for trap regeneration involve use of an additive in the fuel consumed by the engine. When the additive passes to the trap in the engine exhaust gases, it catalyzes combustion of the particulates in the trap and thereby facilitates regeneration of the trap. An example of such an arrangement is shown in US patent No. 4,621,593. It is an object of the present invention to provide a fuel additive metering apparatus by which an additive is mixed with the fuel delivered to an engine in an amount proportional to the amount of fuel consumed by the engine. To this end, a fuel additive metering apparatus, and a method of operation thereof, in accordance with the present invention, is characterised by the features specified in the characterising portions of claims 1 and 6 respectively. In a preferred embodiment of the fuel additive metering apparatus provided by this invention, fuel is drawn from a reservoir, a portion of the fuel is delivered to the engine, excess fuel is directed back to the reservoir, fuel is supplied from a tank to the reservoir to maintain a constant volume of fuel in the reservoir, the amount of fuel supplied from the tank to the reservoir is measured, an additive is fed to the reservoir for mixing with the fuel, and the rate at which additive is fed to the reservoir is proportioned to the rate at which fuel is supplied from the tank to the reservoir, whereby the amount of additive consumed by the engine is proportioned to the amount of fuel consumed by the engine. The present invention will now be described, by way of example, with reference to the accompanying drawing, in which the sole figure is a schematic view of a preferred embodiment of the fuel additive metering apparatus provided by this invention. Referring to the drawing, a fuel apparatus for a diesel engine includes a fuel injection pump 10 that draws fuel from a reservoir 12 through a line 14, a filter 16 and a line 18, delivers a portion of the fuel to the engine 20, and directs excess fuel through a line 22, a fuel cooler 24 and a return line 26 back to the reservoir 12. A supply pump 28 delivers fuel from a tank 30 through a line 32, a water separator 34, a line 36, a fuel metering unit 38 and a line 40 to the reservoir 12. The inlet from line 40 to the reservoir 12 is controlled by a float valve 42 (admitting means) to maintain a constant volume of fuel in the reservoir 12. The fuel metering unit 38 has an inlet 44 that receives fuel through the line 36 from the supply pump 28, and an outlet 46 that directs fuel through the line 40 to the reservoir 12. A valve 48 alternately allows fuel to flow into the fuel metering unit 38 through the inlet 44, and to flow out of the fuel metering unit through the outlet 46. With the valve 48 in the position shown by solid lines, the supply pump 28 causes fuel to flow through the inlet 44 to a chamber 50 closed by a diaphragm 52. The fuel raises the diaphragm 52 against the bias of a spring 54 until a shaft 56 carried by the diaphragm 52 closes a switch 58. When a controller 59 senses closure of the switch 58, it energizes a solenoid 60 to move the valve 48 from the solid line position to the position shown by dotted lines. The bias of the spring 54 then lowers the diaphragm 52 and causes fuel to flow from the chamber 50 through the outlet 46 to the reservoir 12 until the shaft 56 closes a switch 62. When the controller 59 senses closure of the switch 62, it deenergizes the solenoid 60 to move the valve 48 from the dotted line position to the solid line position. The supply pump 28 then causes additional fuel to flow through the inlet 44 to the chamber 50. Movement of the diaphragm 52 from the position where the shaft 56 closes the switch 58 to the position where the shaft 56 closes the switch 62 displaces a calibrated amount of fuel to the reservoir 12. The float valve 42 in the reservoir 12 admits fuel to the reservoir only as the fuel injection pump 10 delivers fuel to the engine 20, and the frequency of operation of the diaphragm 52 and the switches 58 and 62 (which define switching means) accordingly indicates the rate at which fuel is delivered to the engine 20. A positive displacement pump or additive pump 64 feeds additive from a tank 66 through a line 68 and a check valve 70 into the return line 26 and thus to the reservoir 12 where the additive mixes with the fuel. A controller 72 (controlling means) operates the additive pump 64 in response to operation of the switch 62, proportioning the rate at which additive is fed to the reservoir 12 to the rate at which fuel is delivered by the supply pump 28 to the reservoir 12, and thereby proportioning the amount of additive delivered to the engine 20 to the amount of fuel consumed by the engine. The fuel additive metering apparatus provided by this invention thereby creates a precisely proportioned blend of additive and fuel for delivery to the engine. It will be noted that the fuel additive metering apparatus provided by this embodiment of the present invention also assures that the additive will not come into contact with fuel that contains water. Any water that may be present in the fuel delivered from the tank 30 is separated in the water separator 34 so the additive may be mixed with water-free fuel in the reservoir 12. It will be further noted that the fuel additive metering apparatus provided by this invention minimizes the time during which the additive must remain mixed with the fuel. By mixing the additive with the fuel in the reservoir 12 instead of the tank 30, the additive is mixed with fuel in a minimum volume portion of the fuel apparatus, and the residence time of the additive in the fuel is minimized accordingly.

Claims: 1. A fuel additive metering apparatus for an engine (20) having a fuel injection pump (10), the fuel additive metering apparatus comprising a fuel supply including a reservoir (12) and an additive pump (64) for delivering an additive to the reservoir for mixing with the fuel therein, the fuel injection pump being capable of drawing fuel from the fuel supply, delivering a portion of the fuel to the engine, and directing excess fuel back to the fuel supply, characterised in that the fuel additive metering apparatus further comprises admitting means (42) for controlling admission of additional fuel to the reservoir to maintain a constant volume of fuel therein, a fuel metering unit (38) measuring the rate at which such additional fuel is admitted to the reservoir, and controlling means (72) for controlling the additive pump to proportion the rate at which additive is fed to the reservoir to the rate at which such additional fuel is admitted to the reservoir, whereby the amount of additive delivered to the engine is proportioned to the amount of fuel consumed by the engine. 2. A fuel additive metering apparatus as claimed in claim 1, comprising a return line (26) for directing excess fuel from the fuel injection pump (10) back to the reservoir (12), the additive pump (64) delivering the additive through the return line to the reservoir. 3. A fuel additive metering apparatus as claimed in claim 1 or claim 2, wherein the fuel metering unit (38) comprises an inlet (44) that receives such additional fuel from a source (28,30) of fuel under pressure, an outlet (46) that directs such additional fuel to the reservoir (12), and a valve (48) that alternately allows such additional fuel to flow into the fuel metering unit through the inlet and to flow out of the fuel metering unit through the outlet, the fuel metering unit also having a chamber (50) closed by a diaphragm (52) and a spring (54) biasing the diaphragm in a direction for discharging fuel from the chamber, the diaphragm being displaced against the bias of the spring by the pressure of the source of fuel when the valve allows fuel to flow through the inlet, the diaphragm carrying a shaft (56) that operates switch means (58,62) when said diaphragm is fully displaced against the bias of the spring, a solenoid (60) responsive to the operation of the switch means for causing the valve to allow fuel to flow through the outlet and thereby allowing the spring to displace the diaphragm in the fuel discharging direction, the shaft further operating the switch means when the diaphragm is fully displaced in the fuel discharging direction, the solenoid being responsive to the further operation of the switch means for causing the valve to allow fuel to flow through the inlet, and wherein the controlling means (72) is responsive to operation of the switch means. 4. A fuel additive metering apparatus as claimed in any one of the preceding claims, comprising a tank (30) and a supply pump (28) for delivering the additional fuel from the tank to the reservoir. 5. A fuel additive metering apparatus as claimed in any one of the preceding claims, comprising a water separator (34) through which the additional fuel passes before admission to the reservoir. 6. A method of operating a fuel additive metering apparatus for an engine, the method comprising the steps of drawing fuel from a reservoir (12), delivering a portion of the fuel to the engine (20) and directing excess fuel back to the reservoir, delivering additional fuel to the reservoir, and delivering an additive to the reservoir for mixing with the fuel therein, characterised by controlling admission of the additional fuel to the reservoir to maintain a constant volume of fuel therein, measuring the rate at which such additional fuel is admitted to the reservoir, and proportioning the rate at which additive is fed to the reservoir to the rate at which such additional fuel is admitted to the reservoir, whereby the amount of additive delivered to the engine is proportioned to the amount of fuel consumed by the engine. 7. A method as claimed in claim 6, wherein the additonal fuel is delivered to the reservoir (12) through a water separator (34).

Inventors: HOFFMAN, MARK BARRETT, RYAN, PAUL DANIEL
Applicants: GENERAL MOTORS CORPORATION
Application year: 1987
Main classification: F02B47
IPC codes: F01N3, F02D19, F02M25, F02B3, F02B47