IT201600114815A1 - PUMP ASSEMBLY TO SUPPLY FUEL, PREFERABLY GASOIL, TO AN INTERNAL COMBUSTION ENGINE - Google Patents

Description

"PUMP GROUP TO FEED FUEL, PREFERABLY DIESEL, TO AN INTERNAL COMBUSTION ENGINE"

The present invention relates to a pump unit for supplying fuel, preferably diesel, to an internal combustion engine.

In particular, the present invention relates to a pumping unit of the type comprising a high pressure pump, in this case a piston pump, for feeding fuel to the internal combustion engine, and a low pressure or pre-feeding pump. to feed fuel from a holding tank to the piston pump.

Even more in detail, the present invention refers to the area exposed to air and the surrounding environment of the threaded coupling that joins the pump head to the relative closing cap of the supply chamber.

As is known, the piston pump comprises a pump body on which at least one head is mounted. Inside the head there is a cylinder in which a pumping piston is engaged in a sliding manner. An actuation device, for example a camshaft, is provided for moving the piston with a stroke of suction of the fuel in the cylinder and with a stroke of compression of the fuel contained in the cylinder itself.

The cylinder is open at the top at a hole that connects the compression chamber located at the top of the cylinder to the fuel intake chamber. In particular, the suction chamber is fed by a feeding channel and is delimited on one side by the head and on the other side by a sealing cap.

The intake chamber is connected to the cylinder through an intake valve.

The cap is coupled to the cylinder head by means of a threaded coupling. In particular, the head comprises an annular wall protruding outwards equipped with an external threaded surface coupled with a corresponding internal threaded surface of an annular portion of the cap. The cap can be made in one piece comprising a roof portion and joined to the aforementioned annular portion or it can comprise a lid held in position by a ring nut. In this last case, the ring nut acts as an annular portion of the cap, presenting the internal threaded surface for coupling with the external threaded surface of the annular wall of the head.

As known, the lower part of the threaded coupling, or the portion of the threaded coupling facing the head from which the annular wall protrudes, is freely exposed to the surrounding external environment.

In the event of the presence of water drops on the head, the latter can therefore reach the lower exposed portion of the threaded coupling under certain conditions. This circumstance can especially occur when the pump is mounted inclined with respect to the vertical with a "critical" inclination, or an inclination such as to spontaneously favor the accumulation of water by gravity in correspondence with the lower portion of the threaded coupling exposed to the surrounding external environment.

As is known, the lower portion of the annular wall of the cap, either in the form of a ring nut or in the form of an annular wall of a lid, for mechanical reasons has a lower edge internally provided with a lower surface inclined upwards in the direction of the annular wall of the cylinder head.

In other words, the internal and external surfaces of the annular edge of the cap are joined together not by a single lower edge orthogonal to the annular wall of the head. This inclined lower surface has the purpose of realizing a portion of the threaded surfaces that are invited and correctly screwed, which otherwise could jam and compromise correct screwing.

A similar inclined surface is in fact also obtained on the upper external portion of the annular wall of the head with a direct inclination from top to bottom, meaning with the bottom the direction that leads to the head.

Although therefore the inclined portion of the lower edge of the annular wall of the cap is necessary and useful for coupling the cap to the head, in this way a cavity is formed between the annular wall of the cap and the annular wall of the head.

Therefore, unfortunately, not only the lower portion of the threaded coupling is naturally exposed to water droplets but locally a potential water storage chamber is created precisely in this area.

Currently, the aforementioned inclined surface extends substantially along the entire length of the lower edge of the annular wall of the cap, thus creating a large chamber of potential water accumulation in correspondence with the exposed area of the threaded coupling between the cap and the head.

Since this threaded coupling is made between two steel elements, the presence of water could lead to the formation of rust not only externally but also internally to the coupling with consequent loss of strength of the threaded coupling itself.

Starting from this known technique, an object of the present invention is to provide an alternative pumping unit for feeding fuel, preferably diesel oil, to an internal combustion engine which is free from the drawbacks described above and which is simple and economical to implement. .

In particular, the purpose of the present invention is to implement a cap for the suction chamber which on one side allows correct screwing on the head and on the other is capable of avoiding or minimizing the accumulation of drops of water. in correspondence with the lower portion exposed to the air of the threaded coupling between the cap and the head and consequently avoid the local formation of rust.

In accordance with the present invention, a pump unit is provided for supplying fuel, preferably diesel oil, to an internal combustion engine, in which the pump unit comprises:

- a head inside which a housing cylinder is obtained for a sliding pumping piston;

- a through hole that extends from the cylinder to the outside of the head;

- a plug coupled to the head in correspondence with the hole to define a suction chamber in communication with the cylinder through the hole; in which

- the coupling between the cap and the head is a threaded coupling between an external threaded surface of an annular wall of the head and an internal threaded surface of an annular wall of the cap;

- the annular wall of the cap comprises a lower edge provided with an inclined surface for joining and connecting with the internal surface of the annular wall of the cap;

- the projection of the inclined surface along a plane orthogonal to the internal surface of the annular wall of the cap is less than double the height of the thread of the internal surface of the annular wall of the cap.

The terms "internal" and "external" refer to the suction chamber in the sense that the walls defined as "internal" are those closest to the suction chamber in a direction orthogonal to the axis of the pump.

The terms "lower" and "upper" refer to the base of the head from which the annular coupling wall with the cap protrudes. The “lower” walls or portions are therefore those closest to the base of the head from which the annular coupling wall with the cap protrudes.

According to what was mentioned above, the invention provides that the projection of the inclined surface of the lower edge of the annular wall of the cap along a plane orthogonal to the axis of the pumping element is less than double the height of the thread present on the internal surface of the annular wall of the plug.

In this way, when the cap is started on the head, a chamber exposed to air and potential accumulation of water of very reduced dimensions and smaller than the known art is created. With less local accumulation of water, the risk of rust formation at the threaded coupling between cap and head is reduced or completely avoided. This solution is extremely advantageous when the pump is mounted with a critical inclination that would spontaneously lead the water to accumulate in this chamber.

In particular, the projection of the inclined surface along a plane orthogonal to the internal surface of the annular wall of the cap is less than 1/3 of the thickness of the annular wall of the cap.

In this way, any drops present on the lower edge of the cap are forced to travel a long distance before reaching the inclined surface and therefore there is a greater probability that these drops will not be able to complete this path.

In particular, the cap comprises a ring nut for fixing a cover on the head, the internal surface of the annular wall of the cap being in this case the internal surface of the ring nut.

In this way, the invention can also be applied to caps made of two distinct cover and ring components without requiring design changes to the covers but only to the lower edge of the ring nuts.

In particular, the lower edge of the annular wall of the cap includes a lower surface connected to the lower end of the inclined surface. This lower surface has a development along the plane orthogonal to the internal surface of the annular wall of the cap at least equal to double the height of the thread of the internal surface of the annular wall of the cap.

In this way, only a minimal part of the drops present on the lower edge of the annular wall of the cap can be received inside the chamber between the internal surface of the annular wall of the cap and the external surface of the annular wall of the head.

In particular, the lower surface is substantially orthogonal to the inner surface.

In this way, at least in conditions in which the axis of the pumping element is vertical, the lower surface does not convey the water to the chamber between the internal surface of the annular wall of the cap and the external surface of the annular wall of the head.

In particular, the lower surface provides surface roughness configured to block the drops of water passing on the lower surface towards the inclined surface.

In this way, the accumulation of water in the exposed area of the thread coupling is avoided even with the pump tilted so that the drops of water passing on the lower surface would naturally be pushed by gravity towards this area.

In particular, the lower edge of the annular wall of the cap comprises a connecting surface between the lower surface and the external surface of the annular wall of the cap, in which this connecting surface can be curved or inclined in such a way as to define with the internal surface inclined and the lower surface a trapezoid profile of the lower edge of the annular wall of the cap.

In this way, at least in some conditions of inclination of the pump, the drops present on the connecting surface are directed towards the external surface of the annular wall of the cap.

In particular, the lower surface is inclined with respect to the orthogonal to the internal surface in such a way as to define with the inclined surface a V-shaped profile of the lower edge of the annular wall of the cap.

In this way, according to some conditions of inclination of the pump, the drops present on the lower surface are directed towards the vertex of the V-profile to achieve the detachment of the drops from the lower edge, while according to other conditions of inclination of the pump the drops present on the lower surface are directed towards the external surface of the annular wall of the cap.

Further characteristics and advantages of the present invention will appear clear from the following description of a non-limiting example of its implementation, with reference to the figures of the annexed drawings, in which:

Figure 1 is a schematic sectional view of an embodiment of a ring nut of a cap for a pump assembly according to the present invention;

Figure 2 is an enlarged view of a detail of the lower edge of the ring nut of Figure 1;

Figure 3 is a view of a pump unit in an enlarged inclined position provided with the ring nut of Figure 4; and - Figure 4 is an enlarged view of a detail of Figure 3 in correspondence with the area exposed to the air of the threaded coupling between the ring nut and the head.

With reference to Figure 3, 1 indicates, as a whole, a pump unit for supplying fuel, preferably diesel oil, to an internal combustion engine (not shown).

The pump unit 1 in its entirety comprises a high pressure pump with pumping pistons (shown in part) suitable for supplying fuel to the aforementioned internal combustion engine (not shown) and a pre-supply pump, not shown and for example with gears, suitable for feeding fuel to the high pressure pump. The high pressure pump and the gear pump are driven by a shaft (not shown in the attached figures).

Pump 1 comprises a pump body (not shown) and a head 2 assembled to the pump body. A cylinder 3 is obtained in the head 2 and extends along an axis A1. A pumping piston (not shown) extends along the axis A1 and is coupled in a sliding manner to the cylinder 3. An intake duct 16 is obtained laterally in the head 2 to supply an intake chamber 6 for partial housing of an intake valve (not shown) to control the passage of fuel from intake chamber 6 to cylinder 3.

The upper portion of the cylinder 3 defines a compression chamber in communication on one side with the intake chamber 16 and laterally with a delivery duct 17.

The head 2 has a hole 4 passing along the axis A1, which places one end of the cylinder 3 in communication with the intake chamber 6. In particular, the hole 4 extends from the cylinder 3 towards the outside of the head 2. In greater detail, the hole 4 extends in the head 2 from the intake chamber 6 to the compression chamber and houses part of the intake valve.

The pumping piston is moved by an actuation device (not shown in the attached figures) along the cylinder 3 with a reciprocating rectilinear motion comprising an intake stroke for the fuel in the cylinder 3 and a compression stroke for the fuel contained inside the cylinder 3 itself to compress the fuel drawn into the compression chamber by the intake chamber.

The suction chamber 16 is limited on one side by the head 2 and on the other side by a cap 5. In particular, the cap 5 is coupled to the head 2 on the opposite side to the pumping piston with respect to the hole 4. The cap 5 is schematized in figure 3 in the form of a ring nut 18 which acts on a cover (not shown) fixing it against the head 2. According to an alternative form, the ring nut and the cover can also be a single element.

The ring nut 18 is shown separated from the head in figure 1 and its lower edge is schematized in figure 2.

The ring nut 18 is coupled along an external threaded surface 8 of an annular wall 7 which protrudes from the head 2. The internal surface 10 of the ring nut 18 is also threaded so that the coupling between the cap 5, in this case the ring nut 18 is shown 2 takes place in a threaded manner by coupling the threaded external surface 8 of an annular wall 7 from the head 2 and the internal surface 10 of the ring nut 18.

The annular wall 9 of the ring 18 comprises a lower edge 12, where by bottom is meant close to the base of the head 2, which acts as a lower connection between the internal 10 and external 11 walls of the ring 18.

In particular, the lower edge 12 comprises an inclined surface 13 connected to the internal surface 10 of the ring 18. As visible in figure 3 and in the enlargements of figures 2 and 4, the lower edge 12 of the annular wall 9, and in particular in correspondence with the inclined surface 13, is exposed to the air and in general to the surrounding environment. Consequently, the lower area of the threaded coupling between ring nut 18 and head 2 is in turn exposed to the air and the surrounding environment. As shown in figure 3, it is sometimes possible that the pump 1 is mounted in such a way that the axis A1 of the pumping element is not aligned with the vertical defined by the force of gravity but has an inclination. In such a scenario it may happen that the inclination presents a value such that any drops of water present on the lower edge 12 tend spontaneously by gravity to move towards the inclined surface 13 and accumulate in the chamber between said inclined surface 13 and the external surface 8 of the annular wall 7 of the head 2, i.e. in correspondence with the exposed part of the threaded coupling between the cap 5 and the head 2.

To avoid excessive accumulation of water precisely in this area which, as shown in Figure 4, the projection H of the inclined surface 13 along a plane orthogonal to the internal surface 10 of the ring 18 is less than double the height of the thread h of the ring 18 itself. This necessarily leads to the fact that any water accumulation chamber comprised between this inclined surface 13 and the external surface 8 of the annular wall 7 of the head 2 has an inlet less than the height of the thread h of the ring nut 18. By virtue of such geometric proportions an accumulation of water such as to allow it to enter the threaded coupling is prevented and therefore the possible local formation of rust is prevented.

The lower edge 12 of the ring 18 comprises a lower surface 14 connected to the lower end of the inclined surface 13 and orthogonal to the internal surface 10 of the ring 18 itself.

This lower surface 14 has a development L along the plane orthogonal to the annular wall 9 of the ring 18 at least equal to double the height of the thread h of the ring 18 itself.

This lower surface 14 may provide surface roughness (not shown) to block the drops of water transiting towards the inclined surface 13 and the exposed area of the threaded coupling.

As can be seen in Figure 4 or Figure 2, on the opposite side with respect to the inclined surface 13 the lower edge 12 comprises a curvilinear connecting surface 15 which joins the lower surface 14 to the outer surface 11 of the ring 18. Alternatively, this connecting surface 15 can also be inclined rectilinear so as to make a lower edge 12 with a trapezoid profile.

According to another embodiment, not shown, the lower edge 12 can be shaped V where the internal branch of the threaded coupling is made from the inclined surface 13 and the external branch connects the lower edge 12 to the external surface 11 of the ring nut.

It is clear that modifications and variations can be made to the invention described here without departing from the scope of the attached claims.

Claims (10)

CLAIMS 1. A pump unit for feeding fuel, preferably diesel, to an internal combustion engine; the pump unit (1) comprising: - a head (2) inside which a housing cylinder (3) is obtained for a sliding pumping piston; - a through hole (4) that extends from the cylinder (3) towards the outside of the head (2); - a plug (5) coupled to the head (2) in correspondence with the hole (4) to define a suction chamber (6) in communication with the cylinder (3) through the hole (4); wherein the coupling between the plug (5) and the head (2) is a threaded coupling between an external threaded surface (8) of an annular wall (7) of the head (2) and an internal threaded surface (10) of an annular wall (9) of the cap (5); wherein the annular wall (9) of the cap (5) comprises a lower edge (12) provided with an inclined surface (13) connected to the inner surface (10); in which the projection (H) of the inclined surface (13) along a plane orthogonal to the internal surface (10) of the annular wall (9) of the cap (5) is less than double the height of the thread (h) of the cap (5 ). Pump assembly as claimed in claim 1, wherein the projection (H) of the inclined surface (13) along a plane orthogonal to the internal surface (10) of the annular wall (9) of the cap (5) is less than 1.5 times the height of the thread (h) of the cap (5). 3. Pump unit as claimed in claim 1, wherein the projection (H) of the inclined surface (13) along a plane orthogonal to the internal surface (10) of the annular wall (9) of the cap (5) is less than 1/3 of the thickness (S) of the annular wall (9) of the cap (5). Pump assembly as claimed in any one of the preceding claims, wherein the cap (5) comprises a ring nut (18) for fixing a cover on the head (2), the inner surface (10) of the annular wall (9) of the cap (5) being the internal surface (10) of the ring nut (18). Pump assembly as claimed in any one of the preceding claims, wherein the lower edge (12) of the annular wall (9) of the plug (5) comprises a lower surface (14) connected to the lower end of the inclined surface (13) ; the lower surface (13) presenting a development (L) along the plane orthogonal to the internal surface (10) of the annular wall (9) of the cap (5) at least equal to double the height of the thread (h) of the cap (5) . Pump assembly as claimed in claim 5 wherein the lower surface (14) is substantially orthogonal to the inner surface (10) of the annular wall (9) of the cap (5). 7. Pump assembly as claimed in claim 5 or 6 wherein the lower surface (14) comprises surface roughness to block the water drops transiting on the lower surface (14) towards the inclined surface (13) of the lower edge (12) of the annular wall (9) of the cap (5). Pump assembly as claimed in claim 5 or 6 or 7, wherein the lower edge (12) of the annular wall (9) of the plug (5) comprises a curvilinear connecting surface (15) between the lower surface (14) and the external surface (11). Pump assembly as claimed in claim 5 or 6 or 7, wherein the lower edge (12) of the annular wall (9) of the plug (5) comprises an inclined connecting surface between the lower surface (14) and the outer surface (11) configured to define with the inclined surface (13) and the lower surface (14) a trapezoid profile of the lower edge (12) of the annular wall (9) of the cap (5). 10. Pump assembly as claimed in claim 5 wherein the lower surface (14) is inclined with respect to the orthogonal to the inner surface (10) of the annular wall (9) of the cap (5) in such a way as to define with the inclined surface (13 ) a V-shaped profile of the lower edge (12) of the annular wall (9) of the cap (5).