GB2260374A

GB2260374A - Fuel pump

Info

Publication number: GB2260374A
Application number: GB9121711A
Authority: GB
Inventors: Mahesh Patel; Christopher Martin Dona Little
Original assignee: Lucas Industries Ltd
Current assignee: ZF International UK Ltd
Priority date: 1991-10-12
Filing date: 1991-10-12
Publication date: 1993-04-14
Also published as: GB9121711D0

Abstract

A reciprocating plunger fuel injection pump has a plunger 13 slidable in and extending from a bore 12 in a pump barrel 10. A groove 30 is formed in the wall of the bore and is fed through a supply passage 31 from a source of lubricant under pressure. A drain passage 34 also connects with the groove and in use a continuous controlled flow of lubricant takes place through the drain passage. <IMAGE>

Description

FUEL PUMP This invention relates to a fuel injection pump for supplying fuel to an internal combustion engine and of the kind comprising a pump barrel in which is formed a bore, a reciprocable plunger slidable in the bore, the plunger extending from the barrel at one end thereof, a control sleeve angularly movable about the barrel, the control sleeve having a connection with the extending portion of the plunger whereby the angular position of the plunger can be controlled by angular movement of the sleeve, means for moving the sleeve angularly, a tappet engagable with the extended end of the plunger to effect inward movement of the plunger in the bore thereby to displace fuel from the bore and resilient means connected to the plunger and operable to effect outward movement of the plunger, a port formed in the wall of the bore through which fuel can enter the bore during the outward movement of the plunger from a source of fuel under pressure and a helical control edge on the plunger which during the inward movement of the plunger uncovers said port or a further port to allow fuel to spill from the bore.

Such pumps are well known in the art and it is known to provide in the wall of the bore a groove which is connected to a supply of lubricant under pressure, the groove being disposed intermediate the port or ports and the end of the bore from which the plunger extends.

Since the plunger is reciprocated lubricant is picked up from the groove to provide lubrication of the working clearance between the plunger and the wall of the bore.

Some lubricant will also flow out of the working clearance and will lubricate the working surfaces of the tappet and sleeve. However, fuel due to the high fuel pressure which is developed in the pumping chamber of the pump, will also flow along the working clearance and will mix with the lubricant in the groove and will flow onto the working surfaces of the sleeve and tappet. If the fuel is a light fuel such as is used in diesel engines for vehicles, escape of fuel is not serious so far as the lubrication of the various surfaces is concerned although it is desirable that the escape of fuel should be as small as possible since it dilutes the engine lubricating oil.To this end it is known to provide a further groove intermediate the port or ports and the first mentioned groove, and to connect the further groove to the low pressure fuel source so that the majority of the fuel is collected and returned to the source. Even with the further groove some flow of fuel does occur. If the fuel is a heavy fuel for example of the type which requires to be heated before it is supplied to the pump, the leakage of fuel as described presents a number of problems.

Firstly the fuel will tend to accumulate in the grooves and the lubricating action as described will be impaired.

Secondly since the heavy fuel has blocked the intended flow of lubricant, the lubricant will due to the heat, tend to form a lacquer. Thirdly the fuel oil in the event that the engine is stopped, will tend to solidify making it difficult if not impossible for the means which controls the setting of the sleeve to function.

The object of the invention is to provide a fuel pump of the kind specified in a simple and convenient form.

According to the invention in a pump of the kind specified there is formed in the wall of the bore intermediate said port or ports and the end of the bore from which the plunger extends, a circumferential groove, a first passage formed in the pump barrel and which in use, is connected to a source of lubricant under pressure and a second passage in the pump barrel connected to the groove and through which a controlled flow of lubricant takes place in the use of the pump.

An example of a pump in accordance with the invention will now be described with reference to the accompanying drawing which shows a sectional side elevation of part of the pump.

Referring to the drawing the pump comprises a stepped pump barrel 10 which is located within a housing 11. Formed in the barrel is a bore 12 in which is formed a reciprocable plunger 13. The plunger extends from the end of the barrel and is provided with a pair of lateral pegs 14 which are located in grooves 15 respectively formed in an extension of a sleeve 16 which is mounted for angular movement about a cylindrical portion 17 of the barrel. The sleeve 16 is provided with teeth for engagement by a rack bar 18 in known manner. The plunger has a head 19 formed at its free end, the head being engaged by a spring abutment 20 and this in turn is engaged by one end of a coiled compression spring 21 the opposite end of which is in engagement with a flanged spring abutment 22 which additionally serves to retain the sleeve 16 against axial movement.

The housing 11 defines a cylindrical guide surface 23 for a cup shaped tappet 24 which in use, is driven inwardly by the action of an engine cam either directly or indirectly through a rocker mechanism. During inward movement of the tappet the base wall thereof engages with the head of the plunger to impart inward movement of the plunger against the action of the spring. The spring returns the plunger and also the tappet when so allowed by the cam.

In known manner there is provided in the wall of the bore a pair of ports 26 which communicate with a fuel supply gallery 27 defined between the housing and the pump barrel. The ports 26 are arranged to be covered by the plunger 13 after a predetermined inward movement and thereafter fuel will be expelled from the pumping chamber 28 defined in part by the end of the plunger and the wall of the bore to an associated engine. The plunger is also provided with a groove which is in communication with the pumping chamber 28, the groove having a helical control edge 29 which uncovers one of the ports 26 to the groove after a further inward movement of the plunger and when the port is uncovered to the groove fuel spills from the pumping chamber and is returned to the supply gallery 27.

The angular setting of the sleeve and plunger determines the point during the inward movement of the plunger at which spill takes place and therefore the amount of fuel supplied to the associated engine.

Formed in the wall of the bore at a position intermediate the ports 26 and the end of the barrel 10 from which the plunger extends, is a first circumferential groove 30. This groove communicates by way of a passage 31 in the barrel and a cooperating passage 32 in the housing, with an inlet 33 which in use is connected to a source of lubricant under pressure.

Conveniently the source of lubricant is the oil pump of the associated engine. Extending from the groove 30 is a further passage 34 and this opens into a circumferential groove 35 which is formed in the periphery of the extension 17 of the pump barrel about which the sleeve 16 is located. Holes 36 and 37 are formed in the sleeve and the spring abutment respectively to allow the lubricant to escape from the groove 35 into the tappet chamber. In use, the lubricating oil will flow into the groove 30 and will provide for lubrication of the working surfaces of the plunger and the bore. In addition, oil will leave the groove by way of the passage 34 and will flow into the groove 35 where it will provide for lubrication of the contacting surfaces of the sleeve and barrel extension. The oil will then flow through the passages 36 and 37 to provide for lubrication of the tappet.The flow of oil is restricted and this can be effected either by an external restriction or by suitable sizing of for example the passage 34 or the passage 36.

In the use of the pump fuel oil from the pumping chamber will flow down the working clearance due to the high pressure in the pumping chamber and will mix with the lubricating oil in the groove 30. Even though the fuel oil may be heavy, the accumulated fuel oil will tend to be washed out of the groove 30 and the various passages by the flow of lubricating oil. In this way the lubrication by the lubricating oil of the various surfaces can take place as described and the risk of blockage of the various passages by solidified fuel oil is minimised. The mixture of fuel oil and lubricating oil whilst it would normally be returned to the engine lubricating system, may if required be collected in a suitable tank for disposal.

In order to minimise the quantity of fuel oil which collects in the groove 30, a further groove 38 may be formed in the wall of the bore at a position intermediate the ports and the first mentioned groove 30.

The groove 38 is connected to the gallery 27 so that substantially all the fuel oil which leaks from the pumping chamber due to the high pressure therein, will be collected in the groove 38 and returned to the fuel supply gallery.

Claims

1. A fuel injection pump for supplying fuel to an internal combustion engine comprising a pump barrel in which is formed a bore, a reciprocable plunger slidable in the bore, the plunger extending from the barrel at one end thereof, a control sleeve angularly movable about the barrel, the control sleeve having a connection with the extending portion of the plunger whereby the angular position of the plunger can be controlled by angular movement of the sleeve, means for moving the sleeve angularly, a tappet engagable with the extended end of the plunger to effect inward movement of the plunger in the bore thereby to displace fuel from the bore and resilient means connected to the plunger and operable to effect outward movement of the plunger, a port formed in the wall of the bore through which fuel can enter the bore during the outward movement of the plunger from a source of fuel under pressure and a helical control edge on the plunger which during the inward movement of the plunger uncovers said port or a further port to allow fuel to spill from the bore, a circumferential groove formed in the wall of the bore intermediate said port or ports, and the end of the bore from which the plunger extends, a supply passage in the pump barrel for connection in use to a source of lubricant under pressure, said supply passage communicating with said circumferential groove and a drain passage in the pump barrel through which a continuous controlled flow of lubricant can flow from the groove in the use of the apparatus.

2. An apparatus according to Claim 1, in which said drain passage leads into an annular space defined between the pump barrel and the control sleeve.

3. An apparatus according to Claim 2, including a further drain passage from said annular space said further drain passage conveying lubricant to the working surfaces of the tappet.

4. An apparatus according to Claim 3, in which one of said drain passages is a restricted passage.