US3897764A

US3897764A - Liquid fuel injection pumping apparatus

Info

Publication number: US3897764A
Application number: US361845A
Authority: US
Inventors: Istvan Bakti
Original assignee: CAV Ltd
Current assignee: CAV Ltd
Priority date: 1973-05-18
Filing date: 1973-05-18
Publication date: 1975-08-05
Anticipated expiration: 1992-08-05

Abstract

A fuel pumping apparatus includes a feed pump which supplies fuel to an injection pump through a control device. Associated with the injection pump is a device which is responsive firstly to the pressure intermediate the control device and the injection pump, and secondly to a pressure derived from the outlet of the feed pump and controlled by a valve which carries the pressure in accordance with the speed at which the apparatus is driven.

Description

United States Patent Bakti LIQUID FUEL INJECTION PUMPING APPARATUS Aug. 5, 1975 3,552,366 1/1971 Kemp .1 123/139 AQ Primary Ei\'mniner-Churles .l. Myhre Assistant E.\'uminerDaniel J. OConnor Attorney, Agent or Firm-Holman & Stern 1571 ABSTRACT A fuel pumping apparatus includes a feed pump which supplies fuel to an injection pump through a control device Associated with the injection pump is a device which is responsive firstly to the pressure intermediate the control device and the injection pump. and secondly to a pressure derived from the outlet of the feed pump and controlled by a valve which carries the pressure in accordance with the speed at which the apparatus is driven.

3 Claims, 4 Drawing Figures E n skewer PATENTEDAUE 51% SHEET a mm @M mm m @N E 3 mm NQE Om M 2&7 m L a 2 mm O E mm E \m 8 Q Q mm km 3 h HI, Q N. Q

PATENTED B 5 I975 SHEET LIQUID FUEL INJECTION PUMPING APPARATUS This invention relates to liquid fuel injection pumping apparatus for supplying fuel to internal combustion engines and has for its object to provide such an apparatus in a simple and convenient form.

A liquid fuel injection pumping apparatus in accordance with the invention comprises in combination, an injection pump including a plunger operable by a cam, the injection pump being driven in timed relationship with the engine to which fuel is to be supplied, a feed pump for supplying fuel to the injection pump during the filling stroke thereof, a fuel control device for controlling the quantity of fuel supplied to the injection pump during the filling strokes thereof, the pressure of fuel intermediate the injection pump and the control device increasing as the quantity of fuel supplied to the injection pump is increased, a fluid pressure operable piston for controlling the timing of delivery of fuel to the engine, a servo valve for controlling the application ofliquid under pressure to one end of the piston, means for deriving a fluid pressure which varies in accordance with the speed of the engine, said fluid pressure being applied to the servo valve to cause movement thereof against the action of a spring thereby to allow liquid under pressure to act on the piston and fuel pressure operable means acting on said servo valve in addition to the action of the spring, said fuel pressure operable means being supplied with fuel under pressure from intermediate the injection pump and the control device whereby the position of the fluid pressure operable pis ton and thereby the timing of injection of fuel to the engine will vary in accordance with the speed of the engine and also in accordance with the quantity of fuel which is being supplied to the engine.

One example ofa liquid fuel injection pumping appa ratus in accordance with the invention will now be described with reference to the accompanying drawings in which:

FIG. 1 is a schematic layout of the apparatus,

FIG. 2 is a sectional side elevation of part of the apparatus shown in FIG. 1, and

FIGS. 3 and 4 show modifications of the portion of the apparatus shown in FIG. 2.

Referring to FIG. 1 of the drawings there is provided a feed pump which supplies fuel through a quantity control device 11 to a fuel injection pump 12. The fuel injection pump is driven in timed relationship with an engine 13 and supplies fuel thereto during the injection strokes thereof. It will be appreciated that the injection pump may be of the rotary distributor type. The quantity control device determines the amount of fuel supplied to the injection pump and hence the amount of fuel supplied at each injection stroke. Such a device is well known and may comprise a throttle valve such as is shown at 14 in the specification of U.S. Pat. No. 3,552,366.

The injection pump is provided with a fluid pressure operable device 14 which controls the timing of injection of fuel to the engine 13 and this is supplied with three fluid pressures. The first of these pressures is derived from a point intermediate the control device 11 and the injection pump 12. This pressure varies in accordance with the quantity of fuel which is supplied to the injection pump during the filling periods thereof and as the quantity of fuel supplied to the injection pump increases so also does this pressure. The second pressure is derived from the outlet of the feed pump 10 by way of a control valve 15 which modifies the feed pump pressure so that it varies in accordance with the square of the speed at which the engine is driven. The third pressure supplied to the device 14 is obtained directly from the outlet of the feed pump 10.

Referring now to FIG. 2 the device 14 is shown therein in greater detail as also is a portion of the injection pump. The latter includes a plunger 16 which through the intermediary of a roller 17 is moved inwardly by the action of cam lobes 18 which are formed on the internal periphery of a cam ring 19 which is an gularly movable within a body part 20 of the apparatus.

The setting of the cam ring 19 determines the timing of injection of fuel to the engine 13 and the angular set ting of the cam ring 19 is determined by the device 14. This includes a piston 21 which is slidable within a bore formed in the body part. Each end of the bore is closed by a cap 22 and the piston 21 is coupled to the cam ring 19 by means of a tongue 23. Formed in the piston is a bore 24 the left hand end of which is closed by a plug 25. Slidable within the bore 24 is a servo valve 26 and the space intermediate the servo valve 26 and the plug 25 is supplied with fuel at a pressure which varies in accordance with the square of the speed at which the engine is driven. The pressure is applied to the servo valve by way of a passage 36 extending within the body part and piston 21. In other words this is derived from the control valve 15.

Formed in the wall of the bore 24 is a port 27 which communicates with the left hand end of the piston by way of a passage formed therein. The port 27 in an equilibrium position, is covered by a land of the servo valve. The left hand side of the land forms an end wall of a groove which is formed in the servo valve and this groove is in constant communication with the outlet of the feed pump 10 by way of a passage 37 in the body part and piston 21. In other words the land is subjected to the third pressure referred to in FIG. 1. The right hand side of the land is exposed to a low pressure such as that which exists within the body part of the apparatus.

The plug 22 includes an extension 28 and within the plug and extension is formed a recess 29 which is closed by a pipe connector 30. Within the recess 29 is located a spring 31 which acts on the flange of a push rod 32 which extends through a bore in the extension into contact with the right hand end of the servo valve. Formed in the wall of the extension is a restricted orifice 33 which communicates with the interior of the body part of the apparatus and formed in the pipe union is a further restricted orifice 34. The pipe union is connected to the pressure which exists intermediate the control device 11 and the injection pump 12.

In operation and considering only the effect of the pressure which is dependent on the square of the speed, as this pressure increases the servo valve 26 will be moved towards the right against the action of the spring 31. [n so doing the land will uncover the port 27 to the groove in the servo valve so that fuel from the outlet of the feed pump will flow to the left hand end of the piston and thereby cause movement thereof towards the right until the port 27 is again covered by the land. By this arrangement the movement of the servo valve is followed closely by the equivalent movement of the piston 21 and this results in angular movement of the cam ring 19. If the pressure of fuel should fall then the servo valve will move to the left to uncover the port 27 to the low pressure which exists within the body part of the apparatus. The servo valve may contact the plug 25 and the spring acting on the servo valve may move the piston towards the left, alternatively, the reaction due to the rollers engaging the cam lobes may effect the movement of the piston towards the left.

Considering now the effect of the pressure supplied through the pipe union 30. The pressure within the re cess 29 which is dependent upon the pressure intermediate the control device 11 and the injection pump 12, acts on the end area of the push rod 32 and assists the action of the spring 31 as a result the position of the servo valve and therefore the piston 2I, will depend both upon the speed at which the engine is operating and also upon the pressure intermediate the control device II and the injection pump which depends on the volume of fuel which is supplied to the injection pump during the filling stroke and therefore the quantity of fuel which is being supplied to the engine during the delivery strokes of the injection pump. The orifice 34 is provided to reduce the pressure which exists between the control device II and the injection pump and the size of this orifice is carefully chosen in relation to the effective area of the end of the push rod 32 so that the effect of variation of the quantity of fuel supplied to the engine does not over-shadow the effect of variations of speed of the engine. The orifice 33 is provided to ensure a continuous flow of fuel through the recess 29 and in addition it ensures that the variation in this pressure as will occur between the filling periods and delivery periods of the injection pump is reduced to an acceptable level.

In the arrangement shown in FIG. 3 the pipe union 30 is omitted and the end cap 22 and the surrounding body part are modified to allow the fuel pressure which is dependent upon quantity, to be supplied to the recess 29 it will be noted that in this case the orifice 34 is formed in the end cap 22.

In the arrangement shown in FIG. 4 a spring 35 is interposed between the push rod 32 and the servo valve 26. This spring is a relatively light spring and ensures that the servo valve 26 and therefore the piston 21 are maintained in the fully retarded position for starting purposes. As soon as the pressure which is dependent upon speed increases sufficiently the servo valve 26 moves into contact with the push rod 32 and thereafter the spring 35 has no effect, the embodiment working in the same manner as the embodiments shown in FIGS. 2 and 3.

I claim:

I. A liquid fuel injection pumping apparatus for supplying fuel to internal combustion engines which apparatus comprises in combination: an injection pump including a plunger operable by a cam, the injection pump being driven in timed relationship with an engine to which fuel is to be supplied; feed pump means for supplying fuel to the injection pump during the filling stroke thereof; fuel control device means for controlling the quantity of fuel supplied to the injection pump during the filling strokes thereof, the pressure of fuel intermediate the injection pump and the control device means increasing as the quantity of fuel supplied to the injection pump is increased; fluid pressure operable piston means for adjusting the setting of said cam thereby to control the timing of delivery of fuel to an engine; pressure responsive servo valve means for controlling the application of liquid under pressure to one end of the piston means; fluid pressure means which varies in accordance with the speed of an engine; said fluid pressure means being applied to the servo valve means to cause movement thereof against the action of a spring thereby to allow liquid under pressure to act on the piston means, and fuel pressure operable means acting on said servo valve means in addition to the action of the spring; passage means through which said fuel pressure operable means is sujbected to fuel under pressure from intermediate the injection pump and the control device means whereby the position of the fluid pressure operable piston means and thereby the timing of injection of fuel to an engine will vary in accordance with the speed of that engine and also in accordance with the quantity of fuel which is being supplied to that engine; said fuel pressure operable means comprising a push rod slidable in a plug serving to close one end of a cylinder containing the piston means, a spring chamber defined in said plug, said spring being located in said chamber, one end of said push rod being located in said chamber and serving as an abutment for said spring, and the fuel under pressure intermediate the injection pump and control device being supplied to said chamber, whereby the push rod transmits the spring force to the servo valve means and also the force generated by the pressure intermediate the injection pump and control device means acting on the push rod.

2. The apparatus as claimed in claim 1 including a further spring acting intermediate the push rod and the servo valve means, said further spring, in the absence of fuel or fluid pressure, acting to effect movement of the piston means its maximum extend in the direction opposite to that in which it is moved by the fluid pressure.

3. The apparatus as claimed in claim 2, including a restricted passage leading from said chamber; said restricted passage opening to a drain; and a restrictor interposed in said passage means conveying fuel pressure to said spring chamber.

Claims

1. A liquid fuel injection pumping apparatus for supplying fuel to internal combustion engines which apparatus comprises in combination: an injection pump including a plunger operable by a cam, the injection pump being driven in timed relationship with an engine to which fuel is to be supplied; feed pump means for supplying fuel to the injection pump during the filling stroke thereof; fuel control device means for controlling the quantity of fuel supplied to the injection pump during the filling strokes thereof, the pressure of fuel intermediate the injection pump and the control device means increasing as the quantity of fuel supplied to the injection pump is increased; fluid pressure operable piston means for adjusting the setting of said cam thereby to control the timing of delivery of fuel to an engine; pressure responsive servo valve means for controlling the application of liquid under pressure to one end of the piston means; fluid pressure means which varies in accordance with the speed of an engine; said fluid pressure means being applied to the servo valve means to cause movement thereof against the action of a spring thereby to allow liquid under pressure to act on the piston means, and fuel pressure operable means acting on said servo valve means in addition to the action of the spring; passage means through which said fuel pressure operable means is sujbected to fuel under pressure from intermediate the injection pump and the control device means whereby the position of the fLuid pressure operable piston means and thereby the timing of injection of fuel to an engine will vary in accordance with the speed of that engine and also in accordance with the quantity of fuel which is being supplied to that engine; said fuel pressure operable means comprising a push rod slidable in a plug serving to close one end of a cylinder containing the piston means, a spring chamber defined in said plug, said spring being located in said chamber, one end of said push rod being located in said chamber and serving as an abutment for said spring, and the fuel under pressure intermediate the injection pump and control device being supplied to said chamber, whereby the push rod transmits the spring force to the servo valve means and also the force generated by the pressure intermediate the injection pump and control device means acting on the push rod.