Lubrication of the piston member of a fuel injection pump

Abstract

 An improved lubrication arrangement for a piston member (2) arranged to be reciprocatingly movable in a cylinder element (1) of an injection pump for fuel or the like pressure medium, wherein lubricant is supplied under pressure into a lubrication groove (5) arranged in the cylinder element (1) and encircling the piston member (2). The flow-through of the lubricant is effected by providing the cylinder element (1) with at least one channel (6) extending in the longitudinal direction of the cylinder element, said channel (6) being connected with said lubrication groove (5) for leading lubricant continuously into another position on the mantle surface of the piston member (2) at a distance from said lubrication groove (5) further to be recovered and for possible recirculation.

Description

[0001] The invention relates to the lubrication of the piston member of an injection pump for fuel or the like pressure medium.

[0002] Feeding of fuel into a cylinder of an internal combustion engine by means of an injection pump takes place under high pressure. For this reason the clearance between the slide surfaces of the cylinder element and the piston member of the pump has to be very small, only some thousandths of millimetre, so that fuel cannot to any significant extent leak through the clearance into the inner parts of the pump. Generally the purpose of the lubrication system for the piston member of an injection pump is not only to provide lubrication of the piston member but also to reduce this clearance and, thus, to prevent for its part fuel leakages. In addition the lubrication provides cooling, protection against corrosion and wear and a cleansing of the slide surfaces.

[0003] In known lubrication systems the lubricating oil is pressure-fed into this clearance. Due to the narrowness of the clearance, however, the oil flow is slow, even when the feeding pressure for the oil is increased. In addition, the lubricating oil warms up in the narrow clearance so that its temperature exceeds desired values, about 110-115°C for mineral oils, whereby especially in a large diesel engine when heavy oil is used as fuel, the warmed-up lubricating oil reacts more easily with the fuel and forms a sticky lacquer and/or carbon deposit, which can make it more difficult for the piston member to move in the cylinder element and may cause the feeding ducts for the lubricating oil to become entirely blocked. It should be noted that the term "large diesel engine" as used herein refers to a diesel engine that is applicable for use as a main propulsion engine or auxiliary engine for a ship or in a diesel heating power plant etc..

[0004] One aim of the invention is to provide an improved lubrication system for the piston member of an injection pump, from which the drawbacks appearing in known systems especially in connection with large diesel engines using heavy oil as a fuel can essentially be eliminated.

[0005] By means of the lubrication arrangement according to the invention the flow of lubricating oil can be made more effective, whereby its temperature is lowered and impurities can be removed more effectively by the oil. The invention also allows improved lubrication even when using lower oil pressures than would be typical in a comparable system.

[0006] According to the invention an injection pump for fuel or the like pressure medium, having a piston member arranged to be reciprocatingly movable in a cylinder element and to pump said medium at a high pressure end of said piston member, the pump including means to supply lubricant under pressure, to a lubrication groove provided in the cylinder element and encircling the piston member, is characterised in that the flow-through of lubricant is effected by providing the cylinder element with at least one channel extending in the longitudinal direction of the cylinder element, said channel being in communication with said lubrication groove for leading lubricant to another position on the mantle surface of the piston member spaced from said lubrication groove in a direction away from the high pressure end.

[0007] Preferably said at least one channel extending in the longitudinal direction of the cylinder element is arranged at least substantially on the diametrically opposite side of the cylinder element to that at which the lubricating oil is supplied to the lubrication groove.

[0008] Suitably the cylinder element includes a separate lubrication channel encircling the piston member at said another position spaced from said lubrication groove, said lubrication channel being connected to said at least one channel and being arranged to spray the mantle surface of the piston member with oil to effect the lubrication.

[0009] Desirably said separate lubrication channel communicates with the mantle surface of the piston member through at least one nozzle orifice.

[0010] The nozzle orifices can secure splash lubrication in the lower part of the piston member.

[0011] Conveniently a space for recovering lubricant is provided in communication with the piston member and the space communicates with the separate lubrication channel via a clearance which is greater than that existing between the piston member and the cylinder element in the region between the lubrication groove and the separate lubrication channel, whereby lubricant can flow from said lubrication channel along the mantle surface of the piston member freely into the space where the lubricant can be recovered for possible re-use.

[0012] The invention will now be further described with reference to the accompanying drawing, in which

Figure 1 is a partially cross-sectioned view of the lubrication arrangement for a piston member in an injection pump in accordance with the invention, and

Figure 2 shows schematically the circulation of lubricating oil in the cylinder element of the pump shown in Figure 1.

[0013] In the drawing, a cylinder element 1 of a fuel injection pump encloses a reciprocatingly movable piston member 2. The invention does not relate to the actual feeding of fuel by means of the injection pump, but this can take place in some known way by making use of known constructional solutions. Therefore these constructions are not shown in detail in the drawing and they are not described here. It can be said that the fuel is pumped by the upper or high pressure end of the piston member 2 shown in Figure 1.

[0014] As a consequence of the normal operation of an injection pump fuel tends to flow, because of the high pressure, into a clearance 3 between the sliding surfaces of the cylinder element 1 and the piston member 2 away from the fuel injection chamber into the inner parts of the pump, i.e. downwards in Figure 1. Especially in the case of a large diesel engine, when heavy oil is used as the fuel, mixing of the fuel and the oil used for lubricating the clearance 3 tends to create a sticky lacquer or to form carbon deposits due to the high temperature created in the clearance 3. In accordance with the invention the prevention of these phenomena is accomplished by effecting the lubrication oil flow so that the temperature of the lubricating oil is lowered and any carbon deposits which are formed can be removed.

[0015] As shown in Figure 1 the lubricating oil is fed along a longitudinally extending channel 4 into an annular lubrication groove 5 formed in the cylinder element which encircles the piston member 2. From the annular lubrication groove 5, the lubricating oil is led along a further longitudinally extending channel 6 in the cylinder element into a lubrication channel 7, which also encircles the piston member 2 and which is located at a distance spaced from the annular lubrication groove 5 in the direction away from the high pressure chamber of the pump. Provided around the lubrication channel 7 are a number of nozzle orifices 8, through which the channel 7 communicates with the mantle surface of the piston member 2. Because the cross-sectional area of the nozzle orifices 8 are suitably restricted in comparison with the cross-section of the channel 7, the mantle surface of the piston member 2 is subjected to splash lubrication. Sprays of lubricating oil provide more effective lubrication and aid in removal of impurities. At the same time the nozzle orifices 8 act to restrict excessive flow-through of lubricating oil allowing the lubricating oil to effectively lubricate the mantle surface of the piston member via the contact achieved between the oil and the piston member in the lubrication groove 5.

[0016] After leaving the nozzle orifices 8, the lubricating oil flows through a clearance 9 into a space 10 inside the pump, from which it can be recovered and after filtering, or other purifying techniques, can be recirculated back into the channel 4. The clearance 9 is greater than that existing between the piston member and the cylinder element in the region between the lubrication groove 5 and the channel 7.

[0017] Figure 2 shows the circulation of lubricating oil according to the embodiment of Figure 1 although this view shows only the lubricating oil channels and flows of lubricating oil.

[0018] In practice the nozzle orifices 8 can be formed in a variety of different ways, but providing each orifice with a circular aperture has proved to be an optimum arrangement for removing larger impurity particles. Instead of a ring of circular apertures for instance, one slot encircling the piston member or several slots each partially encircling the mantle of the piston member are equally feasible but the breadth of such a slot or slots, which allows a comparable volume of flow through it to that flowing through nozzle orifices with a certain diameter, is considerably smaller than the diameter in question, so that the use of slots only allows impurity particles having correspondingly smaller cross-section, to pass out of the channel 7.

[0019] Locating the longitudinally extending channel 6 on the diametrically opposite side of the cylinder element 1 with regard to the feed channel 4 provides a particularly favourable flow-through of lubricating oil around the entire mantle surface of the piston member 2. The location of the channel 6, however, can be changed according to need. It is also feasible to provide the cylinder element 1 with more than one channel 6 as well as with more than one feed channel 4, provided the aggregate dimensions of the channels are selected to provide proper circulation and lubrication.

[0020] The invention is not limited to the embodiment shown in the drawing, since several modifications of the illustrated arrangement are feasible within the scope of the following claims.

Claims

1. An injection pump for fuel or the like pressure medium, having a piston member (2) arranged to be reciprocatingly movable in a cylinder element (1) and to pump said medium at a high pressure end of said piston member, the pump including means (4) to supply lubricant under pressure, to a lubrication groove (5) provided in the cylinder element (1) and encircling the piston member (2), characterised in that the flow-through of lubricant is effected by providing the cylinder element (1) with at least one channel (6) extending in the longitudinal direction of the cylinder element, said channel (6) being in communication with said lubrication groove (5) for leading lubricant to another position on the mantle surface of the piston member (2) spaced from said lubrication groove (5) in a direction away from the high pressure end.

2. An injection pump according to claim 1, characterised in that said at least one channel (6) extending in the longitudinal direction of the cylinder element is arranged at least substantially on the diametrically opposite side of the cylinder element (1) to that at which the lubricating oil is supplied to the lubrication groove (5).

3. An injection pump according to claim 1 or claim 2, characterised in that the cylinder element (1) includes a separate lubrication channel (7) encircling the piston member (2) at said another position spaced from said lubrication groove (5), said lubrication channel (7) being connected to said at least one channel (6) and being arranged to spray the mantle surface of the piston member (2) with oil to effect the lubrication.

4. An injection pump according to claim 3, characterised in that said separate lubrication channel (7) communicates with the mantle surface of the piston member (2) through at least one nozzle orifice (8).

5. An injection pump according to claim 3 or claim 4, characterised in that a space (10), known per se for recovering lubricant, is provided in communication with the piston member (2) and in that the space (10) communicates with the separate lubrication channel (7) via a clearance (9) which is greater than that existing between the piston member (2) and the cylinder element (1) in the region between the lubrication groove (5) and the separate lubrication channel (7), whereby lubricant can flow from said lubrication channel (7) along the mantle surface of the piston member (2) freely into the space (10) where the lubricant can be recovered for possible re-use.

Drawing