"HIGH-PRESSURE PUMP FOR FEEDING FUEL TO AN INTERNAL COMBUSTION ENGINE"

The present invention relates to a high-pressure pump for feeding fuel from a low-pressure hydraulic circuit to an internal combustion engine and to a method for manufacturing said pump.

Generally the high-pressure pump comprises at least one pump body; a head assembled on the pump body; a cylinder formed in the head; a pumping piston engaged slidably inside the cylinder; an intake valve for selectively controlling the fuel feed to the cylinder and a delivery valve for emitting the high-pressure fuel to the internal combustion engine.

The intake valve and the delivery valve are housed inside two respective seats formed in the head and are sealingly fixed to the walls of the head. Fixing is performed by means of threaded connections so as to withstand the high pressures inside the high-pressure pump .

The pump described above has long and costly manufacturing times because it requires numerous assembly operations and requires strong and costly materials. Moreover, the pump is prone to problems of wear and pressure losses.

The object of the present invention is to provide a high-pressure pump for feeding fuel, preferably diesel fuel, to an internal combustion engine, which limits at least one of the abovementioned drawbacks. According to the invention a high-pressure pump for feeding fuel, preferably diesel fuel, to an internal combustion engine is provided; the pump comprising a head; a cylinder; a pumping piston engaged with the cylinder; an intake valve having an intake valve body; and a delivery valve having a delivery valve body; and wherein the cylinder, the intake valve body and the delivery valve body are formed at least partly inside a single piece housed inside the head.

As a result of the present invention the high- pressure pump requires a smaller number of assembly operations and shorter production time and lower production costs compared to the prior art. Moreover, the pump according to the invention is prone to fewer problems relating to wear and pressure losses.

According to a preferred embodiment of the present invention, the head extends along an axis and has a seat which extends along the axis; the single piece being connected to the head inside the said seat.

According to another preferred embodiment of the present invention, the single piece comprises a first portion which extends along a second axis and in which the cylinder is formed, the second axis and the first axis preferably coinciding.

According to another preferred embodiment of the present invention, the single piece comprises a second portion which extends along a third axis and in which the delivery valve body is at least partly formed.

According to another preferred embodiment of the present invention, the second portion extends protruding radially with respect to the first portion; the head having a slot designed to allow insertion and seating of the second portion.

According to another preferred embodiment of the present invention, the delivery valve comprises a first closing member housed inside the second portion in contact with at least one portion of the delivery valve body . According to another preferred embodiment of the present invention, the pump comprises a further element connected to the second portion; and the further element and the second portion define the delivery valve body.

According to another preferred embodiment of the present invention, the intake valve body is formed at one end of the first portion of the single piece.

According to another preferred embodiment of the present invention, the intake valve comprises a second closing member which moves in a reciprocating manner into contact against the intake valve body.

According to another preferred embodiment of the present invention, the second closing member comprises a stem which is housed and guided inside the first portion of the single piece.

According to another preferred embodiment of the present invention, the intake valve comprises a resilient system and a disc mounted on one end of the first portion of the single piece.

According to another preferred embodiment of the present invention, the pump comprises a compression chamber arranged between the piston and the intake valve and connected to the intake duct by means of a through-hole which partly houses the stem.

According to another preferred embodiment of the present invention, the head has a cup-shaped form and comprises a contact face; and an opening opposite the contact face.

According to another preferred embodiment of the present invention, the single piece is gripped in contact against the head by means of a connector fixed to the head.

Owing to the present invention, the number of threaded connections and thus the wear, the power losses, the cost and the manufacturing time of the high-pressure pump are reduced. According to another preferred embodiment of the present invention the pump comprises a drainage duct and a sealing bush arranged between the opening in the head and the piston; the drainage duct extends from the intake duct to the sealing bush.

Another object of the present invention is to provide a method for manufacturing a fuel feed pump which overcomes the drawbacks of the prior art.

According to the present invention a method for manufacturing a pump for feeding fuel, preferably diesel fuel, to an internal combustion engine is provided; the pump comprising a head having a cup- shaped form and comprising at least one contact face and an opening opposite the contact face; a pumping piston; a delivery valve comprising a delivery valve body; an intake valve comprising an intake valve body; and a cylinder; and wherein the delivery valve body, the intake valve body and the cylinder are at least integrated in a single piece; the method comprising the step of: assembling the single piece on the head through the opening and in contact with the contact face .

According to a preferred embodiment of the present invention, the method comprises the step of fixing the single piece on the head by means of fixing means arranged along the opening.

The present invention will now be described with reference to the accompanying drawings which show non- limiting examples of embodiment thereof, in which:

- Figure 1 is a longitudinal view, with parts cross-sectioned and parts removed for clarity, of a high-pressure pump provided in accordance with the present invention;

- Figure 2 shows a side view, rotated through 90 degrees, with parts cross-sectioned, of the high- pressure pump according to Figure 1; and

Figure 3 is a longitudinal view, with parts cross-sectioned and parts removed for clarity, of an alternative embodiment of the invention according to Figure 1.

With reference to Figure 1, 1 denotes overall a high-pressure pump for feeding fuel, preferably diesel fuel, to an internal combustion engine (not shown) from a low pressure circuit (not shown) . The high-pressure pump 1 is of the pumping piston type.

The pump 1 comprises a pump body (not shown) ; a head 2 which extends along an axis Al and is assembled on the pump body; a cylinder 3 which extends along an axis A2 ; a pumping piston 4 engaged with the cylinder 3 so as to slide in a reciprocating manner inside the cylinder 3; an intake valve 5 for feeding fuel to the piston 4 and having an intake valve body 36; and a delivery valve 6 for releasing fuel pumped by the piston 4 and having a delivery valve body 22. In a preferred and non-limiting version shown in the accompanying figures, the axis A2 and the axis Al coincide .

The head 2 is provided with a seat 7 which extends along the axis Al and has an opening 11 at the base of the seat 7. The head 2 has a cup-shaped form comprising a side wall 9, which is preferably but not necessarily cylindrical; and a contact face 10 opposite the opening 11. In a preferred non-limiting version of the present invention, the contact face 10 is perpendicular to the side wall 9. Furthermore, the head 2 comprises a slot 12 formed in a portion of the side wall 9.

The cylinder 3, the intake valve body 36 and the delivery valve body 22 are formed at least partly in a single piece 8 housed inside the head 2 and formed by a monobloc preferably made of steel or other material highly resistant to stresses.

The single piece 8 is housed inside the seat 7 of the head 2 and extends along the axis A2.

The single piece 8 is inserted inside the head 2 passing through the opening 11. Furthermore, the single piece 8 is arranged in contact against the contact face 10 of the head 2 by means of a connector 19 fixed to the head 2.

The single piece 8 comprises a portion 13 inside which a hole 16 is formed along the axis A2 and a portion 14 having a hole 17 formed along an axis A3. The portion 14 extends protruding radially with respect to the portion 13 and is inserted and housed inside the slot 12.

With reference to Figures 1 and 2, the portion 14 defines the delivery valve body 22 of the delivery valve 6. The delivery valve 6 comprises a closing member 18 which moves inside the delivery valve body 22 and is in contact with at least one portion of the delivery valve body 22. Furthermore, the delivery valve body 6 comprises a delivery duct 27 for feeding fuel under pressure.

The delivery valve 6 comprises a fixed element 23 and a resilient element 25 arranged between the closing member 18 and the fixed element 23. The closing member 18 moves along the axis A3 in a reciprocating manner so as to allow or prevent the exit of the fuel under pressure from the piston 4.

With reference to Figure 1, the cylinder 3 is defined by the hole 16 of the single piece 8, which is formed with a cylindrical shape and depending on the piston 4 which it must house. The piston 4 performs a reciprocating rectilinear movement along the cylinder 3.

The pump 1 comprises an intake channel 30 for feeding fuel to the intake valve 5.

Furthermore, the single piece 8 comprises a through-hole 26 for housing part of the intake valve 5 and a compression chamber 21 arranged between the piston 4 and the through-hole 26.

The intake valve body 36 is formed in the single piece 8. In particular the intake valve body 36 is formed at one end of the portion 13. The intake valve 5, consequently, extends along the axis A2 in the portion 13 and comprises an intake duct 31 which extends radially with respect to the axis A2 ; a disc 32 mounted externally on the end of the portion 13 of the single piece 8; a resilient system 33, in particular a - preferably helical - spring 33; a closing member 34 comprising a stem 34a and a foot 35; and the intake valve body 36 formed in the end of the portion 13 of the single piece 8. The stem 34a is housed inside the through-hole 26. The spring 33 is arranged between the disc 32 and the end of the portion 13 of the single piece 8 so as to exert an axial resilient force relative to the axis A2. The disc 32 is connected to the stem 34a so as to keep the foot 35 in contact with the intake valve body 36. The intake valve body 36, consequently, is defined by the end of the portion 13 of the single piece 8 and the closing member 34 moves in a reciprocating manner into contact with the intake valve body 36.

Furthermore, the pump 1 comprises a sealing bush 47 arranged between the opening 11 in the head 2 and the cylinder 3 and connected to the cylinder 3 by means of the connector 19. The single piece 8 comprises a drainage duct 46 which extends parallel to the cylinder 3 and which connects the intake duct 31 to the sealing bush 47.

During assembly, the single piece 8 is assembled on the head 2 through the opening 11 and is positioned in contact with the contact face 10 and fixed by means of the connector 19 to the opening 11.

According to an alternative embodiment of the present invention, the delivery valve 6 is replaced by the delivery valve 106. Moreover, the single piece 8 is replaced by the single piece 108. The single piece 108 comprises the portion 13 (as in the preceding embodiment) and a portion 114. The portion 114 comprises an external threaded surface 150 along one side end. The delivery valve 106 comprises a cylindrical element 115 connected to the portion 114. In particular, the cylindrical element 115 and the portion 114 define a delivery valve body 122 of the delivery valve 106. The delivery valve 106 comprises a closing member 118 which moves inside the delivery valve body 122. The delivery valve body 122 comprises a closing member 118, a fixed element 123 and a resilient element 125 arranged between the fixed element 123 and the closing member 118. In the closed position, the closing member 118 is in contact with part of the delivery valve body 122, in particular with the portion 114. During assembly of the pump 1, the single piece 108 is assembled together with the head 2 of the pump 1 and fixed to the slot 12 of the head 2 with the connector 19. Moreover the closing member 118 is housed inside the cylindrical element 114 and fixed by means of the threaded means to the portion 114.

It is moreover evident that the present invention also embraces embodiments not described in the detailed description, and equivalent embodiments which fall within the scope of protection of the accompanying claims .