HIGH - PRESSURE PUMP FOR SUPPLYING FUEL TO AN INTERNAL COMBUSTION ENGINE

The present invention relates to a high-pressure pump for supplying fuel to an internal combustion engine.

A known type of high-pressure pump comprises a pump body having at least one pump element; the pump element comprises a cylinder, a piston which can slide within the cylinder, and a resilient assembly coupled to the piston; the resilient assembly comprises a spring which, in use, is placed around the piston, and a plate having a central circular hole which, in use, is engaged by the piston.

In particular, the piston is usually formed by a main body and a head which extends radially relative to the main body.

The shape of the head of the piston and that of the central hole of the plate are such that, in order to assemble a pump of this type, the piston must first be coupled to the plate and the piston must then be inserted into the cylinder. In particular, the piston is fitted into the central hole of the plate until the head of the piston prevents the piston from sliding within the central hole, and the piston is then housed in the cylinder with one end inserted into the head of the pump body.

This method of assembly is particularly inconvenient because the piston must already be assembled on the plate before it is inserted into the cylinder.

Above all, in this type of pump the replacement of the plate or spring, which is often subject to wear, requires the removal of the piston from its seat. One object of the present invention is therefore to provide a high-pressure pump which is free of the aforementioned drawbacks of the prior art, and, in particular, one aim of the present invention is to provide a pump configured in such a way that the dismantling and mounting of the resilient assembly can be carried out regardless of whether the piston is or is not housed in the cylinder.

According to these objects, the present invention relates to a high-pressure pump for supplying fuel to an internal combustion engine comprising a pump body having at least one pump element; the pump element comprising a cylinder, a piston slidable within the cylinder, and a resilient assembly coupled to the piston, the piston having a main body and a head, which has a radial extension greater than the radial extension of the main body; the resilient assembly comprising a spring and a plate having a slot which is engaged, in use, by the cylinder; and the slot extending substantially along an axis and having a constriction in a direction orthogonal to the axis.

Further characteristics and advantages of the present invention will be made clear by the following description of a non-limiting examplary embodiment of the invention, with reference to the attached drawings, in which:

- Figure 1 is a schematic illustration of a high-pressure pump according to the present invention;

- Figure 2 is a sectional view, with parts removed for clarity, of a detail of the pump of Figure 1;

- Figure 3 is a perspective view of a first detail of Figure 1;

- Figures 4a, 4b and 4c are perspective views relating to three different assembly positions of some details of the pump of Figure 1;

- Figure 5 is a sectional view, with parts removed for clarity, of a second detail of the pump of Figure 1; - Figure 6 is a perspective view of a detail of the high-pressure pump according to an alternative embodiment;

- Figure 7 is a sectional view, with parts removed for clarity, of a detail of Figure 6.

In Figure 1, the reference numeral 1 indicates a high-pressure pump for supplying fuel, preferably diesel oil, to an internal combustion engine (which, for the sake of simplicity, is not shown).

The high-pressure pump 1 comprises a pump body 2 and a drive unit 3.

The pump body 2, indicated in Figure 1 by a dashed line, has at least one pump element 4, a feed circuit 6 and a delivery circuit 7.

In the non-limiting example described herein, the pump body 2 comprises a single pump element 4.

In variants of the present invention which are not shown, the pump body 2 comprises two pump elements or three or more pump elements.

The pump element 4 comprises a cylinder 8, extending along an axis Al, in which a corresponding piston 9 slides with a reciprocating motion. In the non- limiting example described and illustrated herein, the cylinder 8 is delimited by a cylindrical seat formed in the pump body 2.

With reference to Figure 2, the pump element 4 further comprises a head 10 having a compression chamber 11, which is coaxial with the axis Al and houses the piston 9 in an axially slidable way.

The head 10 is further provided with a delivery conduit 12 for feeding, in use, the compressed fuel to the delivery circuit 7 through a delivery valve 13, and with a feed conduit 14 for feeding, in use, the fuel received from the feed circuit 6 to the compression chamber 11 through an inlet valve 15. In use, the piston 9 moves in a direction substantially parallel to the axis Al between a first feed position and a second delivery position.

In particular, when the piston 9 moves in a first direction Dl between the delivery position and the feed position, the inlet valve 15 opens and the compression chamber 11 is filled with the fuel received from the feed circuit 6, and when the piston 9 moves in a second direction D2, opposite the first direction Dl, between the feed position and the delivery position, the inlet valve 15 closes, the delivery valve 13 opens, and the fuel in the compression chamber 11 is compressed and sent to the delivery circuit 7.

With reference to Figure 1, the feed circuit 6 is fed with fuel at low pressure from a feed conduit (not shown in the attached drawings) connected to a low-pressure pump (not shown), and feeds the feed conduit 14 of the pump element 4.

The delivery circuit 7 is configured to feed to a common rail (not shown in the attached drawings) the fuel at high pressure received from the pump element 4 through the delivery conduit 12.

The drive unit 3 comprises a shaft 17 rotatable about an axis A and a cam 19, which is coupled to the shaft 17 and rotates with the shaft 17. Preferably, the shaft 17 and the cam 19 are made in one piece, and the cam 19 is formed by an enlarged portion of the shaft 17.

The cam 19 preferably has three lobes, positioned symmetrically on opposite sides of the axis A. In a variant which is not shown, the cam 19 has two lobes.

Preferably, the shaft 17 and the cam 19 are housed in a seat 21 in the pump body 2 formed by a cylindrical wall 22.

The drive unit 3 further comprises a cam follower 23, which is positioned in contact with the cam 19 in order to convert, in use, the rotary motion of the cam 19 to the translational motion of the piston 9. The cam follower 23 is movable, with the corresponding piston 9, along the axis Al.

With reference to Figure 2, each cam follower 23 is formed by a roller 24, a cup 25 and a foot 26.

In particular, the roller 24 is rotatable about an axis B parallel to the axis A and perpendicular to the axis Al, and is housed rotatably in a semicylindrical seat 27 formed in the foot 26. In use, the roller 24 rotates without friction on the cam 19.

The cup 25 comprises a cylindrical wall 28 which extends along the axis Al, and is housed slidably along the axis Al in the cylinder 8.

The cylindrical wall 28 has an annular rib 30 which protrudes orthogonally from the inner lateral surface of the cylindrical wall 28 and divides the cylinder 8 into a housing portion 31 configured to house the foot 22 and a housing portion 32 configured to house the piston 9 and a resilient assembly 34.

Preferably, the annular rib 30 is made in one piece with the cylindrical wall 28. In a variant of the present invention which is not shown, the annular rib 30 is fixed to the inner lateral surface of the cylindrical wall 28.

The resilient assembly 34 comprises a helical spring 35 and a plate 36. In use, the spring 35 is positioned around the body of the piston 9, while the plate 36 is coupled to an end portion 37 of the piston 9.

With reference to Figure 2 and Figure 5, the end portion 37 of the piston 9 comprises a head 39 and an annular groove 40, positioned between the head 39 and a main body 41 of the piston 9.

The head 39 has a substantially cylindrical shape and preferably has a radial extension greater than the radial extension of the main body 41. In particular, the head 39 has an end face 42 which, in use, is positioned in contact with the foot 26. The end face 42 is preferably circular and has a diameter DF. Preferably, the diameter DF of the end face 42 is greater than the diameter DC of the main body 41 of the piston 9.

With reference to Figure 5, the annular groove 40 is at least partially engaged, in use, by the plate 36 and is delimited by a cylindrical base wall 44, which is annular and extends in a direction parallel to the axis Al, by an annular lateral wall 45, which extends orthogonally to the axis A and is delimited by the head 39, and by an annular lateral wall 46, which extends orthogonally to the axis Al and is delimited by the main body 41 of the piston 9.

The groove 40 has an axial height AP, understood as the height of the base wall 44 measured in a direction parallel to the axis Al. In the non-limiting example described and illustrated herein, the axial height AP is equal to 2.5 mm.

The diameter DS of the cylindrical base wall 44 is smaller than the diameter DC of the main body 41 of the piston 9 and smaller than the diameter DF of the end face 42.

With reference to Figure 2, the plate 36, as mentioned above, is coupled to the end portion 37 of the piston 9 and is designed so as to be housed without interference in the housing portion 32 in the cup 25.

With reference to Figure 3, the plate 36 has an upper face 47, a lower face 48, a circular perimetric edge 49, a main groove 50 and two auxiliary apertures 51, which are positioned laterally to the main groove 50 and are substantially kidney- shaped.

Along the upper face 47, the plate 36 has a central raised part 53 with a substantially circular surface 53a. The main groove 50 and the auxiliary apertures 51 are positioned along the raised part 53. With reference to Figure 5, the projection 53 has a height AR, understood as the distance between the lower face 48 and the surface 53a of the raised part 53. In the non-limiting example described and illustrated herein, the raised part 53 has a height AR which is greater than the height AP of the groove 40, and is preferably equal to 2.7 mm. As described more fully below, this feature prevents the incorrect coupling of the plate 36 to the piston 9, in other words coupling with the upper face 47 directed towards the foot 22 instead of towards the inside of the cylinder 8.

With reference to Figure 3, the raised part 53 defines an annular portion 54 of the upper face 50. In use, the annular portion 54 defines, together with the raised part 53 and the cup 25, a seat 55 for housing an end 56 of the spring 35 (see Figure 2). In particular, the annular portion 54 defines the base of the seat 55, while the raised part 53 and the cup 25 define the lateral walls of the seat 55.

With reference to Figure 2, the spring 35 has an end 56a housed in the seat 55 of the plate 36 and an end 56b positioned so as to bear on the head 10. The spring 35 is therefore compressed between the head 10 and the plate 36.

In use, during the step of filling the compression chamber 11 (the phase of the downward movement of the piston 9), the plate 36 is positioned so that one of its sides bears on the head 39 of the piston 9. During the compression phase of the compression chamber 11 (the phase of the upward movement of the piston 9), there is a degree of play between the piston 9 and the plate 36.

For its part, the head 39 of the piston 9, and in particular the end face 42, bears on the foot 26.

In particular, owing to the effect of the spring 35, during the downward movement phase of the piston 9, the perimetric edge 49 of the plate 36 is kept constantly bearing on the annular rib 30 of the cup 25, and the head 39 of the piston 9 is kept in constant contact with the foot 26. During the upward movement phase of the piston 9, however, the head 39 of the piston 9 is not in contact with the foot 26. With reference to Figure 3, the main groove 50 has a substantially oval shape and extends mainly along an axis C, and has a width L, understood as the dimension measured in a direction orthogonal to the axis C.

The width L of the main groove 50 is greater than the diameter DF of the base wall 42 of the head 39 of the piston 9.

The main groove 50 has a base wall 57 and a lateral wall 58.

The base wall 57 has a slot 59 which extends along the axis C and has a constriction 60 in a direction orthogonal to the axis C.

The width LS of the constriction 60 is greater than or equal to the diameter DS of the cylindrical base wall 44, thereby allowing at least the groove 40 of the piston 9 to pass through the constriction 60.

In particular, the slot 59 is formed by a first lobe 61 and a second lobe 62. The second lobe 62 has a maximum width L2 (where the width is considered to be the dimension measured in a direction orthogonal to the axis C) which is less than the maximum width LI of the first lobe 61.

The maximum width LI of the first lobe 61 is greater than the diameter DF of the head 39 of the piston 9, thereby allowing the head 39 to pass through the first lobe 61.

The maximum width L2 of the second lobe 62 is greater than the diameter DS of the cylindrical base wall 44 and less than the diameter DF of the head 39.

The second lobe 62 is positioned substantially in the centre of the plate 36. Preferably, the centre of the second lobe 62 coincides with the centre of the plate 36.

In the non-limiting example described and illustrated herein, the first lobe 61 and the second lobe 62 are substantially circular in shape and intersect each other. The diameter LI of the first lobe 61 is greater than the diameter L2 of the second lobe 62.

In the non-limiting example described and illustrated herein, the first lobe 61 has a diameter LI substantially equal to the width L of the groove 52, while the diameter L2 of the second lobe 62 is less than the width L of the groove 52. Consequently, the base wall 57 extends substantially around the second lobe 62 and partially around the first lobe 61. Thus the base wall 57 forms an edge of the second lobe 62.

With reference to Figures 4a, 4b and 4c, the particular shape of the slot 59 in the plate 36 allows the plate 36 to be coupled to the piston 9 even when the piston 9 has already been inserted into the head 10. Because of the particular shape of the slot 59, the plate 36 can be coupled to the piston 9 substantially in two phases, namely a first phase in which the head 39 of the piston 9 is inserted into the first lobe 61 (Figures 4a and 4b), and a second phase in which the piston 9 is moved along the axis C past the constriction 60 in such a way that the groove 40 of the piston 9 is engaged by the base wall 57.

The particular shape of the slot 59 in the plate 36 thus facilitates the mounting of the pump element 4 and also simplifies the operations of replacing the plate 36 or the spring 35. This is because the plate 36 or the spring 35 can be replaced without any need to remove the piston 9 from its seat.

Above all, the presence of a raised part 53 with a height AR greater than the height AP of the groove 40 of the piston 9 makes the plate 36 non-symmetrical and allows the user to mount the plate 36 in one direction only.

The plate 36 can only be coupled to the head 39 of the piston with its upper face 47 directed towards the inside of the cylinder 8 and with its lower face 48 directed towards the foot 26. The plate 36 is preferably made by milling and turning.

In a variant of the high-pressure pump, a plate 136 shown in Figures 6 and 7 is used. The plate 136 has an upper face 147, a lower face 148, a circular perimetric edge 149, a slot 159 and two auxiliary apertures 151, positioned laterally relative to the slot 159.

Along the upper face 147, the plate 136 has a central raised part 153 with a substantially circular surface 153a. The slot 159 and the auxiliary apertures 151 are positioned along the raised part 153.

The slot 159 extends substantially along an axis C and has a constriction 160 in a direction orthogonal to the axis C.

The width LS' of the constriction 160 is greater than or equal to the diameter DS of the cylindrical base wall 44 of the piston 9, thereby allowing at least the groove 40 of the piston 9 to pass through the constriction 160.

In particular, the slot 159 is formed by a first lobe 161 and a second lobe 162. The second lobe 162 has a maximum width L2' (where the width is considered to be the dimension measured in a direction orthogonal to the axis C) which is less than the maximum width LI' of the first lobe 161.

The maximum width LI' of the first lobe 161 is greater than the diameter DF of the head 39 of the piston 9, thereby allowing the head 39 to pass through the first lobe 161.

The maximum width L2' of the second lobe 162 is greater than the diameter DS of the cylindrical base wall 44 and less than the diameter DF of the head 39.

The second lobe 162 is positioned substantially in the centre of the plate 136. Preferably, the centre of the second lobe 162 coincides with the centre of the plate 136.

In the non-limiting example described and illustrated herein, the first lobe 161 and the second lobe 162 are substantially circular in shape and intersect each other. The diameter LI' of the first lobe 161 is greater than the diameter L2' of the se- cond lobe 162. The second lobe 162 has an edge 157, which, in use, engages with the groove 40 of the piston 9.

With reference to Figure 7, the edge 157 has a height which is less than the height of the raised part 153, and the raised part 153 has a height AR' which is greater than the height AP of the groove 40 of the piston 9. The height AR' is considered to be the distance between the lower face 148 and the surface 153a of the raised part 153.

These features make the plate 136 non-symmetrical, thereby requiring the user to mount the plate 136 in one direction only.

This is because the plate 136 can only be coupled to the head 39 of the piston with its upper face 147 directed towards the inside of the cylinder 8 and with its lower face 148 directed towards the foot 26.

The mounting of the plate 136 is similar to the mounting of the plate 36 of Figures 1 - 5.

In a similar way to what has been described in respect of the plate 36, the particular shape of the slot 159 in the plate 136 allows the plate 136 to be coupled to the piston 9 even when the piston 9 has already been inserted into the head 10. Because of the particular shape of the slot 159, the plate 136 can be coupled to the piston 9 substantially in two phases, namely a first phase in which the head 39 of the piston 9 is inserted into the first lobe 161, and a second phase in which the piston 9 is moved along the axis C past the constriction 160 in such a way that the groove 40 of the piston 9 is engaged by the edge 157 of the second lobe 162.

Preferably, the plate 136 is made by shaping and stamping.

Finally, the present invention evidently covers embodiments not described in the detailed description and equivalent embodiments which lie within the scope of protection of the attached claims.