US3465733A

US3465733A - Liquid fuel supply systems for internal combustion engines

Info

Publication number: US3465733A
Authority: US
Inventors: John Charles Powell Thornber
Original assignee: CAV Ltd
Current assignee: CAV Ltd
Priority date: 1966-11-11
Filing date: 1967-10-31
Publication date: 1969-09-09
Anticipated expiration: 1986-09-09
Also published as: SE329297B; DE1576515A1; GB1190919A; ES347489A1

Description

Sept. 9, 1969 I J, c. THORNBER 3,465,733

LIQUID FUEL SUPPLY SYSTEMS FOR INTERNAL COMBUSTION ENGINES Filed Oct. 31, 1967 El 8 [I I /I9 ZZZ 5%" I FIG]. 4 \5 M4 lll oooogo United States Patent "ice US. Cl. 12332 6 Claims ABSTRACT OF THE DISCLOSURE A fuel supply system for an internal combustion engine including a pump and a nozzle there being associated with the nozzle a device including a flow controller and valve member slidable within a cylinder, the valve member being arranged to uncover a by-pass port after it has moved a predetermined extent thereby to allow unrestricted flow of fuel to the nozzle.

This invention relates to liquid fuel supply systems for compression ignition internal combustion engines and of the kind including an injection nozzle which is mounted on the body of the engine and through which fuel can be delivered to a combustion space on the engine and a fuel pump for supplying fuel to the nozzle in timed relationship to the engine, the nozzle incorporating a pressure responsive valve for controlling the flow of fuel therethrough.

The object of the invention is to provide such a fuel system in an improved form.

According to the invention a fuel system of the kind specified includes in association with or adjacent to the nozzle, a device comprising in combination, a cylinder one end of which is in communication with the nozzle, a flow controller including a variable restriction and through which the other end of the cylinder is in communication with said pump, a valve member slidable within said cylinder and a by-pass passage including a by-pass port in the wall of the cylinder, the by-pass port being arranged to be uncovered by said valve member after the latter has moved a predetermined extent under the action of fuel entering said one end of the cylinder and serving to allow fuel to flow to the nozzle without passing through the variable restriction of the flow controller.

In the accompanying drawings;

FIGURE 1 is a diagrammatic view of one example of a device in accordance with the invention, and

FIGURES 2, 3 and 4 show modifications of the device of FIGURE 1.

Referring to the drawings there is provided a cylinder one end of which is connected to a flow controller indicated at 11 and the other end of the cylinder is connected in use, by way of a passage 12 to an injection nozzle 9. The injection nozzle is of the conventional type and includes a spring loaded valve member for controlling the flow of fuel to an orifice. The nozzle is mounted so as to direct fuel into a combustion space of a compression ignition internal combustion engine. Moreover, the device is mounted adjacent to or may be formed integrally with the nozzle.

3,465,733 Patented Sept. 9, 1969 Within the cylinder 10 is mounted a slidable valve member 13 and this is loaded towards said one end of the cylinder 10 by means of a coiled compression spring 14. Within the valve member is formed an orifice 15 the action of which will be described later in the specification, the orifice 15 serving to place the opposite ends of the cylinder in communication with each other.

The flow controller comprises a bore 16 in the Wall of which and intermediate its ends, is formed a port 17 which communicates with said one end of the cylinder 10. Slidably mounted within the bore 16 is a valve element 18 and this is loaded towards one end of the bore by means of a coiled compression spring 19. Furthermore, said one end of the bore 16 is in communication by way of a passage 20 with the outlet of a fuel injection pump 8. In the valve element 18 is formed a further orifice 21 and the extent of movement of the valve element under the action of the spring 19 is limited by a stop 22. When the valve element is in contact with the stop the port 17 is partially closed by the valve element and this constitutes a variable restriction.

Formed in the wall of the cylinder 10 is a by-pass port 23 which is in communication with the passage 20 by means of a by-pass passage 24. Furthermore, a stop 25 is provided to limit the extent of movement of the valve member 13 under the action of the spring 14 and when the valve member is in contact with the stop the by-pass port 23 is covered.

In use, when delivery of fuel occurs from the injection pump since the by-pass port 23 is closed, the fuel flows into said one end of the bore 16 and through the orifice 21 formed in the valve element 18. The fuel flowing through this orifice passes through the port 17 into said one end of the cylinder 10. This fuel causes movementof the valve member 13 against the action of the spring 14 and a quantity of fuel is displaced from the other end of the cylinder 10 and flows to the injection nozzle for delivery to the engine. The flow of fuel through the orifice 21 causes a pressure drop and the valve element 18 is moved against the action of the spring 19. This movement restricts the size of the port 17 and consequently the rate at which fuel can flow to said one end of the cylinder is controlled.

After a predetermined quantity of fuel has entered said one end of the cylinder the end of the valve member 13 uncovers the by-pass port 23 with the result that fuel flows directly from the passage 20 into said one end of the cylinder at an unrestricted rate and the remaining quantity of fuel delivered by the injection pump flows to the injection nozzle at an unrestricted rate. At the end of the injection period and if the pump is of the kind in which a predetermined relief of the pressure within the pipe line which interconnects the pump and the nozzle is provided for, then the valve member 13 will move back a predetermined amount which may or may not close the by-pass port 23. However, both the valve member 13 and the valve element 18 are moved into contact with their respective stops by means of the springs, the purpose of the orifice 15 being to permit fuel to transfer from said one end to said other end of the cylinder 10 during this movement.

A modification of the above arrangement is shown in FIGURE 2 and this modification concerns the provision of a valve which positively prevents the flow of fuel through the orifice 15 Whilst the valve member 13 is moving towards said other end of the cylinder and before the by-pass port 23 is opened. As shown the cylinder is enlarged at said one end and there is provided in contact with the valve member 13, a plate 26 which is loaded away from the valve member 13 by means of a coiled compression spring 27. The plate 26 together with the adjacent annular end surface of the valve member 17 constitute sealing surfaces which can co-operate as will be described, to prevent the flow of fuel through the orifice 15.

In use, when fuel enters said one end of the cylinder the pressure thereof will urge the plate 26 into contact with the valve member 13 and these two components will move together against the action of the spring 14 as described above. At a predetermined position during this movement it is arranged that the plate 26 contacts the step in the cylinder 10 and when this occurs further movement of the plate 26 is prevented and the plate is moved in the opposite direction by means of the spring 27 into contact with a stop 28 mounted in the wider end of the cylinder. The valve member 13 will continue to move as described in the first example. The advantage of this arrangement is that no fuel can flow through the orifice until the plate 26 is lifted from the valve member and consequently the quantity of fuel which is supplied at the restricted rate of the injection nozzle is not affected by the small flow of fuel which is bound to occur through the orifice 15 of the device shown in FIGURE 1.

The arrangement shown in FIGURE 3 is very similar to that described with reference to FIGURE 2 except that in this case the plate 26 is loaded by a coiled tension spring 29 which is secured to the plate 26 at one end and which is secured to a transversely extending pin fixed within the bore 10. The action of the spring 29 is to move the plate 26 away from the valve member 13 as soon as the by-pass port 23 is opened.

In FIGURE 1 there is shown in dotted outline a passage 30 which at one end is in communication with the passage 12 and which at its other end opens into the cylinder 10 at a position such that it will be uncovered by the valve member 13 after the latter has uncovered the by-pass port 23. By this arrangement the movement of the valve member 13 against the action of the spring 14 will be limited and the main quantity of fuel supplied to the engine will flow through the by-pass passage 24, the by-pass port 23 and the passage 30 to the injection nozzle. This modification can be applied to the arrangements shown in FIGURES 2 and 3.

The addition of the passage 30 can present practical difficulties in the construction of the device in that additional width is required to accommodate the passage 30 by the side of cylinder 10. In order to overcome this problem the passage may be formed in the valve member 13 as is shown in FIGURE 4. In all other respects the devices of FIGURE 4 is the same as that of FIGURE 1. The valve member 13 is provided with a peripheral groove 30 which is in constant unrestricted communication with the end of the cylinder from which extends the passage 12. By this arrangement the valve member 13 will move during the injection stroke of the pump by an amount sufficient to expose the groove 30 to the port 23.

This modification may be applied to the devices of FIGURES 2 and 3 but it will be necessary to re-position the orifice 15.

It will be appreciated that the distances moved by the

valve members

13 and 18 during the injection stroke determines the shape of the delivery curve of the nozzle unit. The distance moved by the valve member 13 before the bypass port is opened determines the amount of fuel which will be injected into the engine at the restricted rate although a small movement of the valve member 13 will be required to pressurize the column of fuel between the device and the valve member of the nozzle unit to the opening pressure of the latter. If the flow controller is set such that control occurs quickly and the flow is small then it is possible that the pressurization of the aforesaid column of fuel will be so slow that the injection pump completes its injection stroke before the bypass port is opened. Such an arrangement of course would be useless. In a less extreme case it is possible for an appreciable delay of the start of injection to occur. The flow controller in order to overcome this problem, should be set such that flow control does not occur until the amount of fuel required to pressurize the aforesaid column of fuel has passed through the controller. This may be achieved by positioning the stop 22 of the flow controller such that the volume of fuel required to move the valve member 18 to its controlling position is substantially equal to the volume of fuel required to achieve pressurization of the aforesaid volume. In this manner there will be a minimum delay of the start of injection of fuel.

In order to ensure accuracy of control the residual pressure in the pipe line connecting the pump and the device together with the aforesaid volume at the end of the injection stroke should be at a predetermined value for each engine speed and delivery quantity since it is the residual pressure which determines the amount of pressurization required before the opening of the valve in the nozzle unit is attained. For example, in a conventional in-line injection pump where a plurality of nozzles respectively, each injection pump may have incorporated therewith a residual pressure valve which controls the pressure in the pipe line when injection of fuel has finished. In a distributor type fuel pump where a single injection pump serves a plurality of nozzles a single residual pressure valve may be employed which is brought into communication with the pipe lines in turn to determine the residual pressure. Alternatively unloading delivery valves may be employed which unload a specific volume of fuel from the pipelines at the end of the injection stroke.

Having thus described my invention what I claim as new and desire to secure by Letters Patent is:

1. A liquid fuel supply system for a compression ignition engine and comprising an injection nozzle including a pressure responsive valve mounted on the body of the engine and through which fuel is delivered to a combustion space of the engine, a fuel pump for supplying fuel to the nozzle in timed relationship with the engine, a conduit interconnecting the pump and the nozzle, a device mounted between the downstream end of the conduit and the nozzle, the device comprising a first cylinder one end of which i in communication with the nozzle, a flow controller through which the other end of the cylinder is connected to the downstream end of the conduit, a variable restriction in the flow controller and through which fuel can flow between the downstream end of the conduit and the other end of the cylinder, a by-pass port formed in the Wall of the cylinder, a by-pass passage connecting said port with the downstream end of the conduit, 21 valve member slidable in said cylinder and resilient means acting to urge the valve member towards said other end of the cylinder whereby fuel entering the other end of the cylinder at a controlled rate through the flow controller will urge the valve member against the action of the resilient means until the by-pass port is uncovered Whereafter further movement of the valve member will be unrestricted, fuel being supplied to the nozzle during movement of the valve member against the action of the resilient means.

2. A fuel system as claimed in claim 1 in which the flow controller comprises a bore, one end of said bore communicating With the downstream end of the conduit, a port formed in the wall of said bore and communicating with said other end of the cylinder, a valve element slidable in said bore, resilient means acting to bias the valve element towards said one end of the bore and in which position the port is uncovered by the valve element, and a restricted flow path through which the ends of the bore are in communication with each, whereby the pressure drop across said flow pat-h moves the valve element against the action of the resilient means thereby to reduce the effective size of said port, the latter constituting said variable restriction.

3. A fuel system as claimed in claim 2 in which said position of the valve element is determined by a stop.

4. A fuel system as claimed in claim 3 in which the movement of the valve member under the action of fuel entering said other end of the cylinder is limited after the bypass port has opened, by the opening of a passage which places said one end of the cylinder in direct communication with said by-pass port.

5. A fuel system as claimed in claim 4 including a further restricted flow path between the ends of said cylinder.

References Cited UNITED STATES PATENTS 3,387,597 6/1968 Wirsching 123-32 3,392,715 7/1968 Thoma 123-139 3,394,891 7/1968 VOit 239533 LAURENCE M. GOODRIDGE, Primary Examiner US. Cl. X.R.