US3547092A

US3547092A - Liquid fuel pumping apparatus

Info

Publication number: US3547092A
Application number: US796330A
Authority: US
Inventors: Basil Edward Knight
Original assignee: CAV Ltd
Current assignee: CAV Ltd
Priority date: 1968-02-07
Filing date: 1969-02-04
Publication date: 1970-12-15
Anticipated expiration: 1987-12-15
Also published as: DE1906135A1; GB1252437A; CH496170A; FR2001447A1

Description

United States Patent inventor Basil Edward Knight Eastcote, Pinner, England Appl. No, 796,330 f Filed Feb. 4, 1969 Patented Dec. 15, I970 Assignee C.A.V. Limited London, England Priority Feb. 7, 1968 Great Britain LIQUID FUEL PUMPING APPARATUS 15 Claims, 4 Drawing Figs.

[56] References Cited UNITED STATES PATENTS 1,919,601 7/1933 Simmen l23/l39.l4 2,291 ,939 8/1942 Amery 103/220 2,916,028 12/1959 Mansfield 123/139 3,143,104 8/1964 Cummings et al. l23/l39.11A

Primary Examiner-Laurence M. Goodridge Attorney-Holman, Glascock, Downing & Seebold ABSTRACT: A liquid fuel pumping apparatus for supplying fuel to an internal combustion engine and including an accumulator which is charged with fuel to a predetermined pressure, a stepped cylinder which accommodates a complementarily stepped piston, the narrower end of the piston being exposed to the pressure within the accumulator a valve for controlling the wider end of the cylinder to the accumulator thereby to achieve movement of the piston towards the narrower end of the cylinder and a valve or valves which can be opened when the valve is closed to allow fuel to flow from the wider end of the cylinder to an injection nozzle or nozzles mounted on an associated engine.

" PATENTEBnEmsmm A 35471192 SHEET 1 UF 3 BY MTM ATTOQN EYS PATENTEDDEEISIHTH 3541092 SHEETZUFS NVEN 0 a fi i ATT EN EYS LIQUID FUEL PUMPING APPARATUS apparatus in accordance with the invention; and

FIG. 4 is a sectional side elevation of a nozzle unit suitable for use with the apparatus of FIG. 3.

Referring to FIG. 1 there is provided an accumulator to which fuel is supplied under pressure from'any convenient source by way of a conduit 12. Intermediate the conduit 12 and the accumulator 10 is a nonreturn valve 1l. For controlling the pressure within the accumulator there is provided a control valve generally indicated at 13 and this includes a piston 14 one end of which is subjected tothe pressure within the accumulator to move it against the action of a coiled compression spring 15. A further piston 16 is provided and this is moved against the force developed by a fluid pressure applied to its end remote from the piston 14, by the piston 14 through the intermediary of a coiled compression spring 17. The piston 16 is slidable within a cylinder in the wall of which is formed a port which is in communication with the conduit 12. At a predetermined position of the piston 16 the-aforesaid port is brought into communication with a passage formed in the piston and which communicates with a drain. In operation as the accumulator pressure increases the piston 14 is moved against the action of the spring 15 and this movement is transmitted to the piston 16. At a predetermined pressure the aforesaid port is opened to the passageformed within the piston 16 and the conduit 12 is placed in communication with the drain so that no further fuel passes to the accumulator.

There is also provided a rotary distributormember 20 which is adapted to be driven in timed relationship with the engine with which the apparatus is associated. Moreover, the distributor member is biased towards one end of the bore in which it is located by means of a coiled compression spring 21. In the periphery of the distributor member is formed a plurality of equiangularly spaced but axially extending grooves 22 and these are arranged to register in turn with a pair of ports 23, 24 formed in the wall of the bore in 'whichthe distributor member is mounted. The port 23 is in communication with the accumulator 10 and the port 24 is in communication with the wider end of a cylinder 25. Slidable within the cylinder 25 is a stepped piston 26 the narrower end of which is subjected to the pressure pertaining in the accumulator. Furthermore,'

formed in the wall of the wider portion of the cylinder 25 is a groove 27 which is in communication with a drain by way of a which extends from the free end thereof to a point on its wall intermediate its end. .In use, when one of the grooves 22 registers with the ports 23 and 24 the piston 26 will bemoved to the position in which it is shown by virtue of the differential pressure acting upon its end. During this time the passage portion 270 is out of register with the remainder of the passage. Also formed in the distributor member is a delivery passage 30 which is arranged to register in turn and as the distributor member rotates, with a plurality of outlet ports 31 which in use, communicate with the injection noules respectively of the associated engine. The delivery passage 30 is in communication with a plurality of outwardly extending inlet passages 32 formed in the distributor member and which are arranged to register in turn and as the distributor member rotates, with an inlet port 33 formed in the wall of the bore in which the dis with one end of a cylinder 34 which contains a spring loaded valve member 35. In the wall of the cylinder 34 is formed a port 36 which is in communication with the wider end of the cylinder 25 and for cooperation with the port 36, the valve member is provided with a groove 37 which is in constant communication with the end of the cylinder 34 which commu nicates with the port 33. v

The wall of the bore accommodating the distributor member is provided with a control port 38 with which registers in turn and as'the distributor member rotates, a plurality of control passages 39 communicating with the delivery passage and the inlet passages 30 and 32 respectively.

In use, asthe distributor member moves angularly from the position in which it is shown the groove 22 moves out of register with the ports 23 and 24 and the passages 30, 32 and 39 move into register with ports 31, 33 and 38 respectively. When this occurs the pressure of fuel acting on the narrower end of the piston 26 displaces the latter towards the wider end of its cylinder and fuel is displaced therefrom and flows by way of the port 36, the groove 37 and the passage within the valve member 35 to the port 33. The fuel then flows through this port into one of the inlet passages 32 and to an outlet port 31 by way of the delivery passage 30. This flow of fuel continues until the valve member 26 has attained a position at which the passage 29 formed in the wider portion thereof registers with the groove 27. When this occurs the pressure of fuel in the wider end of the cylinder 25 falls rapidly as also does the pressure of fuel in the passage in the distributor member and also the pipe line which interconnects the outlet port 31 with the nozzle. As a result of this the valve member within the nozzle closes quickly and the restrictor 28 acts to control the residual pressure within the aforesaid passages. Continued angular movement of the distributor member moves the passages 30, 32 and 39 out of register with the ports 31, 33 and 38 respectively the passage portion 27a out of register with the remainder of the passage and moves a groove 22 into communication with the ports 23 and 24. When this occurs the valve member 26 is moved to the position in which it is shown in the drawing by virtue of the differential action as explained.

Moreover, it will be appreciated that the volume of fuel which was used to effect injection is returned to the accumulator during the return motion of the piston 26.

The purpose of the valve member 35 is to control the rate of injection of fuel to the engine and this valve operates in conjunction with specially shaped end portions of the passages 32. The registration of a passage 32 with the port 33 is restricted in a manner which varies during the rotation of the distributor member 20. The pressure drop across the restriction is maintained at a substantially constant value by applying the pressure drop across the valve member 35. Should the pressure drop exceed the required value the valve is moved so as to increase the restriction at the port 36. In this manner the rate of supply of fuel to the engine varies with the area of the restriction between passages 32 and port 33. The cycle is repeated with the fuel being supplied to the engine cylinders in turn.

In order to control the amount of fuel delivered to the engine at each injection stroke the return motion of the piston 26 is controlled by a stop in the form of an axially slidable rod 40. The setting of the rod 40 is determined by the axial setting of a control member 41 and the axial setting of this member is in part determined by an operator adjustable member 42 which acts upon the member 41 through the intermediary of a governor spring 43 and in part by a speed sensitive mechanism generally indicated at 44. This mechanism comprises a pair of pivotal governor weights 45 which are mounted within a cage which is driven in timed relationship with the engine through a shaft 46. The shaft 46 is loaded in one direction by the action of a coiled compression spring 47 and the arrangement is such that as the speed rotation increases the weights 45 move outwardly and compress the spring 47 as well as compressing the spring 43. Movement of the member 41 towards the left against the action of the spring 43 results in movement of the tributor member is mounted. The port 33is in communication rod 40 in a direction to reduce the permitted travel of the piston 26. In the event that the force exerted by the governor spring 43 is increased then the member 41 is moved in the reverse direction and the piston 26 is allowed an increased travel so as to increase the quantity of fuel supplied to the engine. The combination of the weights 45 and the governor spring 43 act as a mechanical governor to control the speed of the engine. In order to effect a control over various other elements of the system two fluid pressures are provided one of which is responsive to the speed of the engine and the other of which is responsive to the load on the engine. The axial position of the shaft 46 is dependent upon the speed of the engine and a groove formed on this shaft controls the effective size of an orifice 48. The axial setting of the member 41 is dependent upon the load on the engine and a groove formed on this member controls the effective size of an orifice 49. The pressure upstream of the orifices is obtained from any convenient source at constant pressure.

The pressure downstream of the orifice 48 is dependent upon the speed at which the engine is operating and this pressure is applied to said one end of the distributor member to move it against the action of the spring 21. By this arrangement the axial setting of the distributor member is dependent upon the speed at which the apparatus is driven. Furthermore; the pressure downstream of the orifice 49 which pressure is responsive to the load on the on the engine is applied to the other end of the distributor member to assist the action of the spring 21. By this arrangement the axial setting of the distributor member is responsive both to the speed of and the load on the engine. The outer ends of the passages 32 communicate with helically disposed grooves and by this arrangement as the axial setting of the distributor member varies, so the timing of injection of fuel to the engine is varied.

In order to control the emission of smoke by the engine a maximum fuel stop is provided and this is in the form of a pressure responsive piston 50 which is subjected to the pressure downstream of the orifice 48. The piston 50 is disposed at right angles to the member 41 and the latter bears upon a cam form which is machined upon the periphery of the piston 50. By this arrangement as the speed at which the engine is operating increases the permitted excursion of the piston 26 is also decreased.

The pressure downstream of the orifice 48 is also applied to the free end of the piston 16 to move it in opposition to the action of the spring 17. In this manner the pressure within the accumulator is also dependent upon the speed at which the apparatus is driven. in order to ensure a flow of fluid through the orifices 48 and 49 restrictors 51 and 52 are provided between the opposite ends of the bore containing the distributor member respectively and a drain.

The return stroke of the stepped piston 26 in the system described is determined by an adjustable stop 40 and this controls the quantity of fuel which is delivered to the engine at each injection stroke. Moreover, the interspace between the wider portion of the piston and the adjacent end of the wider portion of the cylinder is in communication with a drain.

In a modification shown in FIG. 2 the drain connection is provided in the narrower part of the cylinder which accommodates the stepped piston 126. Furthermore, in the wall of the narrower portion of the stepped piston is a groove 127 which is in constant communication with the interspace between the narrower and wider portions of the piston. When the drain connection is in communication with the groove the piston can move without hinderance but as soon as the drain connection is covered by the piston then an hydraulic lock is created in the interspace and further movement of the piston is prevented. In order to vary the permitted movement the angular setting of the narrower part of the piston is adjustable by means of a rack bar 128 which is engaged with teeth formed in a recessed portion of the narrower portion of the piston. The rack bar 128 is arranged to be operated in the same manner as the stop 40 of the first example.

Alternatively flow through the drain connection of the first example may be controlled by an electromagnetic valve the operation of which can be controlled by a transducer responsive to the position of the piston 26, and by a signal obtained from the member 41. The valve would be closed to create the hydraulic lock when the piston attains the desired position.

In a further alternative the ports 23 and 24 and the groove 22 may be omitted and replaced by an electromagnetic valve operable in synchronism with the engine at the appropriate time. As in the previous alternative a transducer would be provided to monitor the position of the piston 26 and the signal derived from the transducer would be compared with a control signal derived from a speed and demand sensitive electrical circuit. By halting the flow of fuel from the accumulator the piston 26 will stop moving at the required position.

In a further arrangement the distributor member per se is replaced by a plurality of cam operated valves or electromagnetic valves, the latter being operated in proper sequence and in timed relationship. FIG. 3 shows such an arrangement with a valve 222 controlling the flow of fuel from the accumulator to the wider end of the cylinder which accommodates the piston 26. This valve replaces the ports 23, 24 and grooves 22. For controlling the flow to the injection nozzles valves 223 are provided there being one valve per nozzle. These valves replaced ports 31 and passage 30, and for closing the spill passage 27 a valve 225 is provided. For controlling the rate of injection of fuel a device 224 may be provided between the cylinder containing the piston 26 and the valve 223. This device can be of the type described in our copending British Pat. application No. 50,655/66. Instead of the valves 223 used in conjunction with conventional nozzles electromagnetically operable nozzles as shown in FIG. 4 may be used.

The nozzle shown in FIG. 4 comprises a body portion 60 at one end of which is mounted a nozzle head 61 having an orifice through which in use, liquid fuel passes into a combustion space of the associated engine. Within the nozzle head is a seating 62 with which cooperates the shaped end of an elongated rod like valve element 63. The other end of the valve element of enlarged diameter and is slidably mounted within a bush 64 and a light spring 65 is provided to urge the valve element into contact with the seating. The chamber in which the spring is mounted is in communication with a fuel inlet 66 and this chamber also communicates with a space defined between the valve element and the wall of the bore in which it is mounted. The operation of the portion of the nozzle so far described is very well known however, since the spring 65 is a light spring only a small increase in fuel pressure at the inlet 66 would be required to move the valve element to the open position. The extent of movement of the valve element is limited by a stop member 67 which is contacted by the enlarged portion of the valve element.

The inlet 66 is connected to the wider end of the cylinder containing the piston 26 and will therefore be subjected to a high pressure for a substantial proportion of the time during which the apparatus is in use. It is therefore necessary to cause a force to be exerted on the valve element which opposes the force exerted, by the high fuel pressure in the inlet 66. This force is provided by causing the fuel pressure to act upon the end of a small piston thereby to produce a force which is applied to the valve element. ln the drawing the small piston is referenced 68 and it is slidably mounted within a bore formed in a cap 69. The outer end of the bore is in communication with a further fuel inlet 70 and in use, the

inlets

66 and 70 are connected together. The piston 68 is provided with a stem 71 and this is coupled to the valve element 63 through the intermediary of a solenoid armature 72. The area of the piston 68 exposed to the fuel pressure is slightly less than effective area of the valve element which is exposed to the fuel pressure and the valve element is maintained in the closed position by the action of the spring 65.

In order to move the valve element tothe open position the aforesaid armature 72 is moved by the action of a solenoid 73. The solenoid is mounted within the cap 69 and a hollow cylindrical extension 74 which is retained relative to the body of the nozzle. The stem 71 passes with clearance through the solenoid and the free space within the cap 69 and the extension 74 is vented to atmosphere through event 75. If desired the inlet 70 may be connected directly to the accumulator.

I claim:

l. A liquid fuel pumping apparatus for supplying fuel to an internal combustion engine and comprising an accumulator, a fuel pump for charging the accumulator to a predetermined pressure, a stepped piston accommodated within a complementary cylinder, a first conduit interconnecting the narrower end of the cylinder with the accumulator, a second conduit interconnecting the wider end ofthe cylinder with'the accumulator, first valve means for controlling the flow of fuel through the second conduit said valve means when opened serving to cause movement of the piston towards the narrower end of the cylinder, control means for limiting the movement of the piston towards the narrower end of the cylinder, a third conduit extending from the wider end of thecylinder for connection to the discharge orifice of a fuel injection nozzle and a timing valve for controlling the flow of fuel through said third conduit the arrangement being such that when said timing valve is opened the piston will move towards the wider end of the cylinder to discharge fuel therefrom through the third conduit. i

2. An apparatus as claimed in claim 1 including a spill port formed in the wall of the wider portion of the cylinder and acooperating spill passage formed in the piston and in communication with the wider end of the cylinder, the arrangement being such that at a predetermined position in the movement of the piston towards the wider end of the cylinder, the spill port and spill passage will communicate with each other to reduce the pressure in the wider end of the cylinder and thereby terminate the flow of fuel through the third conduit.

3. An apparatus as claimed in claim 2 including a second valve means closable to prevent flow through said spill port when the first valve means is operated.

4. An apparatus as claimed in claim 3 in which the movable portions of said first and second valve means and said timing valve are formed in a rotary member adapted to be driven in synchronism with the engine with which the apparatus is associated. g

- 5. An apparatus as claimed in claim 4 including an injection control device for controlling the rate of flow of fuel through said third conduit.

6. An apparatus as claimed in claim 5 in which said injection control device includes a piston controlled variable orifice in said third conduit and a further variable orifice controlled by the rotary member in said third conduit, the piston being subject to the pressure drop across the further variable orifice and moving in a direction to adjust the flow of fuel through the piston controlled variable orifice so as to maintain the aforesaid pressure drop substantially cons tag 7. An apparatus asclaimed in claim 3 in which one or all of the first and second valve means and the timing valve are valves the operation of which is controlled by a cam shaft adapted to be driven in time relationship with the associated engine.

8'. An apparatus as claimed in claim 7 in which the valves are electromagnetic valves which are operated in time relationship.

9. 'An apparatus as claimed in claim 3 in which a plurality of timing valves are provided for controlling the flow of fuel through respective discharge orifices, said timing valves being electromagnetic valves and each valve including a valve element movable away from a seating to permit flow through the associated discharge orifice, a spring for loading the valve element into contact with the seating, means for substantially balancing the fuel pressure acting on the valve element, and a solenoid armature movable by the action of a solenoid when the latter is supplied with electric current to allow movement of the valve element away from the seating and thereby to permit flow of fuel through the orifice.

10. An apparatus as claimed in claim 3 in which the control means for limiting movement of the piston comprises a mechanical stop the setting of the stop being determined by an engine speed sensitive governor.

11. An apparatus as claimed in claim 3 in which the control means comprises a device which controls the open period of said first valve means thereby to control the movement of the piston towards the narrower end of the cylinder.

12. An apparatus as claimed in claim 3 in which said control means comprises a device for creating an hydraulic lock in the annular space defined between the end of the wider end of the cylinder adjacent the narrower end thereof and the piston, thereby to halt the movement of the piston towards the narrower end of the cylinder.

13. An apparatus as claimed in claim 12 in which said device comprises an electromagnetic valve operable by an electric circuit to which a first signal derived from a trans ducer responsive to the position of the piston is applied together with a control signal dependent upon speed and demand.

14. An apparatus as claimed in claim 12 in which the piston is provided with a helical groove in constant communication with said annular space and there is provided in the wall of the cylinder a drain connection through which the fuel from said annular space flows until the connection is covered by the piston, the angular setting of the piston being adjustable to determine the instant at which the hydraulic lock is created.

15. An apparatus as claimed in claim 14 in which the angu-- lar setting of the piston is controlledsby a rack which cooperates with teeth formed in thfi'ston, the rack bar being adjustable by'aspeed sensitive governor.