WO2015071149A1

WO2015071149A1 - High-pressure pump for feeding fuel to an internal-combusion engine

Info

Publication number: WO2015071149A1
Application number: PCT/EP2014/073813
Authority: WO
Inventors: Benedetto Loiacono; Adriano SCIUSCO; Alessandro De Luca
Original assignee: Robert Bosch Gmbh
Priority date: 2013-11-15
Filing date: 2014-11-05
Publication date: 2015-05-21
Also published as: ITMI20131903A1

Abstract

A high-pressure pump for feeding fuel to an internal-combustion engine is provided with at least one cylinder (8), a piston (9) sliding inside the cylinder (8), and a spring unit (34) coupled with the piston (9); the spring unit (34) comprises a spring (35) and a disc (36) which, during use, is arranged abutting against one end (56a) of the spring (35); the disc (36) is provided with an eyelet (50) engaged, during use, by the piston (9); the eyelet (50) extends substantially along an axis (C) and is provided with a constriction (60) in the direction perpendicular to the axis (C), which divides up the eyelet (50) into a first lobe (61) and a second lobe (62), having a maximum width (L2) smaller than the maximum width (L1) of the first lobe (61); the disc (36) is provided with at least one first locking element (53; 54) configured to prevent the relative sliding of the disc (36) and the piston (9) along the axis (C) when the piston (9) is engaged with the second lobe (62).

Description

DESCRIPTION

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

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

A high-pressure pump for feeding fuel to an internal- combustion engine is known, said pump comprising a pump body provided with at least one pumping element; the pumping element comprises a cylinder, a piston sliding inside the cylinder, and a spring unit coupled with the piston; the spring unit comprises a spring and a disc provided with an eyelet which is engaged, during use, by the cylinder; the eyelet extends substantially along an axis and has a constriction in the direction perpendicular to the axis, which defines two differently sized lobes.

In particular, the piston is usually defined by a main body and by a head which extends radially with respect to the main body. The particular configuration of the piston head and the disc eyelet is such that the disc may be coupled with the piston even when the piston is already inserted inside the cylinder head. Owing to the particular shape of the eyelet, in fact, the disc may be coupled with the piston substantially in two stages: a first stage during which the head and the main body of the piston are inserted inside the larger lobe; and a second stage during which the piston is moved along the axis of extension of the eyelet beyond the constriction so that the main body of the piston engages with the smaller lobe and the head prevents extraction of the piston along the direction of sliding of the piston. A solution of this type is described for example in patent application MI2012A000270 filed in the name of the present Applicant.

However, the high-pressure pumps of this type have a drawback .

During assembly of the pump, and in particular during assembly of the spring unit and prior to housing the tappet set inside the respective cylinder, any relative movements of the piston and the disc along the axis of the extension of the eyelet may cause accidental disengagement of the disc from the piston, complicating the assembly operations.

An object of the present invention is therefore to provide a high-pressure pump which does not have the drawbacks of the prior art mentioned here and in particular it is an object of the present invention to provide a pump formed so that the assembly operations may be carried out in a rapid and simple manner, preventing accidental disengagement. In accordance with these objects the present invention relates to a high-pressure pump for feeding fuel to an internal-combustion engine comprising at least one cylinder, a piston sliding inside the cylinder, and a spring unit coupled with the piston; the spring unit comprising a spring and a disc which, during use, is arranged abutting against one end of the spring; the disc being provided with an eyelet engaged, during use, by the piston; the eyelet extending substantially along an axis and being provided with a constriction in a direction perpendicular to the axis, which divides up the eyelet into a first lobe and a second lobe, having a maximum width smaller than the maximum width of the first lobe; the disc being provided with at least one first locking element configured to prevent the relative sliding of the disc and the piston along the axis when the piston is engaged with the second lobe. Owing to the invention, accidental disengagement of the piston and the disc is substantially reduced. In particular, the piston is coupled with the disc when it is engaged with the second lobe. The disengagement of the piston and the second lobe is favoured by the relative movements along the axis of extension of the eyelet which cause the displacement of the piston inside the first (larger) lobe. The first locking element by preventing the relative movements of the piston and the disc along the axis of the eyelet prevents the relative disengagement of disc and piston, resulting in the assembly operations being simpler and faster .

According to a preferred embodiment of the present invention, the first locking element is configured to prevent the sliding of the disc with respect to the piston along the axis in a first direction from the first lobe to the second lobe. In this way, the first locking element prevents the movement of the disc with respect to the piston which causes the displacement of the piston inside the first (larger) lobe, and therefore disengagement of the piston and the disc, making the assembly operations simpler and faster.

According to a preferred embodiment of the present invention, the first locking element is configured to cooperate in abutment against the spring.

In this way, the spring defines a locating surface for the locking element. The structure of the disc is simplified and easy and inexpensive to manufacture. According to a preferred embodiment of the present invention the disc has a top side arranged, during use, abutting against the end of the spring; the first locking element comprising at least one first projection, which extends from the top surface of the disc .

In this way, the locking element is defined by a projection which makes the structure of the disc easy and inexpensive to manufacture.

According to a preferred embodiment of the present invention the first projection extends along the top side along a second direction substantially transverse to the axis.

In this way, the projection abuts against the spring mainly along a direction transverse to the axis of the eyelet. In this way the locking element prevents not only the movements of the disc along the axis of the eyelet, but also the movements of the disc along directions which are transverse with respect to the axis of the eyelet, but in any case dangerous and able to favour disengagement of the disc from the piston.

According to a preferred embodiment of the present invention the disc is provided with at least one first auxiliary opening having a first perimetral edge; the first projection extending from the first perimetral edge .

In this way it is possible to simplify significantly the disc manufacturing operations. The fact that the projection extends from one edge of the auxiliary opening allows manufacture of the disc in two stages: a stage for pressing a provisional disc in which the projection extends in the same plane as the disc inside the auxiliary opening, and a stage for producing the definitive disc during which the projection is simply folded up so that it extends from the perimetral edge of the auxiliary opening. In this way manufacture of the disc according to the present invention is quick, simple and low-cost.

According to a preferred embodiment of the present invention the first projection has at least one curved side designed to cooperate in abutment against the end of the spring.

In this way the projection has a side formed so as to ensure reliable locking. The shape of the side, in fact, matches the shape of the spring portion against which it abuts.

According to a preferred embodiment of the present invention the disc comprises at least one second locking element configured to prevent sliding of the disc with respect to the piston along the axis in the direction from the first lobe to the second lobe.

In this way it is ensured that blocking of the movements of the disc with respect to the piston is even more stable and reliable owing to the presence of a second locking element.

According to a preferred embodiment of the present invention the first locking element and the second locking element are arranged on opposite sides of the axis .

In this way, each locking element acts on a respective portion of the disc, ensuring an overall optimum locking action. According to a preferred embodiment of the present invention the first locking element and the second locking element are arranged at the same distance from the centre of the disc. In this way, each locking element acts uniformly on a respective portion of the disc, ensuring a stable overall locking action.

According to a preferred embodiment of the present invention the first locking element and the second locking element are arranged symmetrically with respect to the axis. In this way, each locking element acts on a respective portion of the disc, ensuring stable overall locking. Since in most cases, the disc is also symmetrical with respect to the axis C, the locking elements act in a substantially identical manner on respective identical portions of the disc.

According to a preferred embodiment of the present invention the first locking element and the second locking element are substantially identical. In this way the locking action produced by the locking elements is uniform and the manufacture of the disc is simplified . According to a preferred embodiment of the present invention the disc has a top side arranged, during use, abutting against the end of the spring; the second locking element comprising at least one second projection which extends from the top side of the disc.

In this way, in a similar manner to that stated above for the first locking element, the fact that the second locking element is a projection results in manufacture of the disc structure being easy and low-cost.

According to a preferred embodiment of the present invention the disc is provided with at least one second auxiliary opening having a second perimetral edge; the second projection extending from the second perimetral edge .

In a similar manner to that stated for the first locking element, the fact that the projection extends from an edge of the auxiliary opening results in significant simplification of the disc manufacturing operations . According to a preferred embodiment of the present invention the width of the constriction is smaller than the maxim width of the first lobe and smaller than the maximum width of the second lobe. In this way the relative movements of the piston and the disc are greatly limited. In this way, in fact, the second lobe locks the piston in position, allowing the relative movement of the piston and the disc substantially only along the axis of the eyelet.

According to a preferred embodiment of the present invention the first lobe and the second lobe are substantially circle-shaped and intersect each other. In this way the second lobe "embraces" the piston, allowing the relative movement of the piston and the disc substantially only along the axis of the eyelet. As a result, the assembly operations are simplified and not affected by accidental disengagement. According to a preferred embodiment of the present invention the centre of the second lobe coincides with the centre of the disc. In this way the piston acts substantially in the centre of the disc, ensuring that there is a uniform stress acting on the disc, thus resulting in the pump being reliable and long-lasting.

Further characteristic features and advantages of the present invention will become clear from the description below of a non-limiting example of embodiment thereof, with reference to the figures in the accompanying drawings, in which: - Figure 1 is a diagrammatic representation of a high-pressure pump according to the present invention ;

Figure 2 is a cross-sectioned perspective view, with parts removed for greater clarity, of a detail of the pump according to Figure 1 ;

Figure 3 is a perspective view of a first detail of the pump according to Figure 1 ;

Figures 4a, 4b and 4c are perspective views, with parts removed for greater clarity, relating to three different stages during assembly of a few parts of the pump according to Figure 1.

In Figure 1 the reference number 1 indicates a high- pressure pump for feeding fuel, preferably diesel fuel, to an internal-combustion engine (not shown for greater simplicity) .

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

The pump body 2, which is indicated in Figure 1 by a dot-dash line, is provided with at least one pumping element 4, a feed circuit 6 and a delivery circuit 7.

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

According to variants (not shown) of the present invention, the pump body 2 comprises two pumping elements or three or more pumping elements. The pumping element 4 comprises a cylinder 8 extending along an axis Al, inside which a respective piston 9 slides with an alternating movement. In the non- limiting example described and illustrated here the cylinder 8 is defined by a cylindrical seat formed in the pump body 2.

With reference to Figure 2, the pumping element 4 comprises, moreover, a cylinder head 10 provided with a compression chamber 11 which is coaxial with the axis Al and houses the piston 9 in an axially slidable manner . The cylinder head 10 is provided, moreover, with a delivery duct 12 for feeding, during use, the compressed fuel to the delivery circuit 7 via a delivery valve 13; and a feed duct 14 for feeding, during use, the fuel from the feed circuit 6 to the compression chamber 11 via an inlet valve 15.

During use, the piston 9 moves along a direction substantially parallel to the axis Al between a first feeding position and a second delivery position.

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

With reference to Figure 1, the feed circuit 6 is supplied with low-pressure fuel from a supply duct (not shown in the accompanying figures) connected to a low- pressure pump (not shown) and feeds the feed duct 14 of the pumping element 4. The delivery circuit 7 is configured to feed to a common rail (not shown in the accompanying figures) the high-pressure fuel from the pumping element 4 via the delivery duct 12. The actuating unit 3 comprises a shaft 17 rotatable about an axis A, and a cam 19, which is connected to the shaft 17 and rotates together with the shaft 17. Preferably the shaft 17 and the cam 19 are formed as one piece and the cam 19 is defined by an enlarged portion of the shaft 17.

The cam 19 preferably has three lobes arranged symmetrically on opposite sides of the axis A. According to a variant (not shown) the cam 19 has two lobes.

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

The actuating unit 3 further comprises a tappet set 23 which is arranged in contact with the cam 19 so as to convert, during use, the rotary movement of the cam 19 into the translational movement of the piston 9.

The tappet set 23 is movable, together with the respective piston 9, along the axis Al .

With reference to Figure 2, each tappet set 23 is defined by a roller 24, a cup element 25 and a shoe 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, inside a semi-cylindrical seat 27 formed in the shoe 26. During use, the roller 24 rolls 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 inside the cylinder 8.

The cylindrical wall 28 is provided with an annular rib 30 which extends perpendicularly from the inner side surface of the cylindrical wall 28 and divides the cylinder 8 into a housing portion 31 configured to house the shoe 22 and into a housing portion 32 configured to house the piston 9 and a spring unit 34.

Preferably the annular rib 30 is formed as one piece with the cylindrical wall 28. According to a variant (not shown) of the present invention the annular rib 30 is fixed to the inner side surface of the cylindrical wall 28.

The spring unit 34 comprises a helical spring 35 and a disc 36. During use, the spring 35 is arranged around the body of the piston 9, while the disc 36 is coupled with 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 arranged between the head 39 and a main body 41 of the piston 9.

The head 39 has a substantially cylindrical shape and has, preferably, a radial width greater than the radial width of the main body 41.

In particular, the head 39 has a bottom side 42 which, during use, is arranged in contact with the shoe 26. The bottom side 42 is preferably circular and has a diameter DF. Preferably, the diameter DF of the bottom side 42 is greater than the diameter DC of the main body 41 of the piston 9. The annular groove 40, during use, is at least partly engaged by the disc 36 and is defined by a cylindrical base wall 44, which is annular and extends in a direction parallel to the axis Al, by an annular side wall 45, which extends at right angles to the axis A and is defined by the head 39, and by an annular side wall 46, which extends at right angles to the axis Al and is defined by the main body 41 of the piston 9.

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

The disc 36, as already mentioned above, is coupled with the end portion 37 of the piston 9 and has dimensions such that it is able to be housed without interference in the housing portion 32 inside the cup element 25. With reference to Figure 3, the disc 36 has a top side 47, a bottom side 48, a circular perimetral edge 49, an eyelet 50, a first auxiliary opening 51 and a second auxiliary opening 52 which are arranged laterally in relation to the main groove 50, and a first locking element 53 and a second locking element 54.

With reference to Figure 2, the spring 35 has an end 56a arranged abutting against the top side 47 of the disc 36 and an end 56b arranged abutting against the cylinder head 10. Consequently the spring 35 is compressed between the cylinder head 10 and the disc 36. With reference to Figure 3, the eyelet 50 extends substantially along an axis C and has a constriction 60 in a direction perpendicular to the axis C which divides the eyelet 50 into a first lobe 61 and a second lobe 62.

The second lobe 62 has a maximum width L2 smaller than the maximum width LI of the first lobe 61, where "width" is understood as meaning the dimension measured in a direction perpendicular to the axis C.

The maximum width LI of the first lobe 61 is greater than the diameter DF of the head 39 of the piston 9 so as to allow 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 smaller than the diameter DF of the head 39.

The width LS of the constriction 60 is substantially the same as, or at the most slightly bigger than, the diameter DS of the cylindrical base wall 44 so as to allow the groove 40 of the piston 9 to pass through the constriction 60.

Preferably, the width LS of the constriction 60 is smaller than the maximum width LI of the first lobe 61 and smaller than the maximum width L2 of the second lobe 62.

The second lobe 62 is arranged substantially in the centre c of the disc 36. Preferably, the centre of the second lobe 62 coincides with the centre c of the disc 36.

In the non-limiting example described and shown here, the first lobe 61 and the second lobe 62 are substantially circle-shaped and intersect each other. The diameter LI of the first lobe 61 is greater than the diameter L2 of the second lobe 62. With reference to Figures 4a, 4b and 4c, owing to the particular shape of the eyelet 50 of the disc 36, the disc 36 may be coupled together with the piston 9 even when the piston 9 is already inserted inside the cylinder head 10. Owing to the particular shape of the eyelet 50, in fact, it is possible to couple the disc 36 with the piston 9 substantially in two stages: a first stage, during which the head 39 of the piston 9 is inserted in the first lobe 61 (Figures 4a and 4b) ; and a second stage, during which the piston 9 is moved along the axis C beyond the constriction 60 in the direction D3 which extends from the first lobe 61 to the second lobe 62 so that the groove 40 of the piston 9 is engaged by the edges of the second lobe 62. The particular shape of the eyelet 50 of the disc 36 therefore facilitates the assembly of the pumping element 4 and furthermore simplifies the operations for replacement of the disc 36 or the spring 35. The replacement of the disc 36 or the spring 35 may, in fact, be performed without necessarily removing the piston 9 from its seat.

With reference to Figure 3, the first locking element 53 and the second locking element 54 are configured to prevent the relative sliding of the disc 36 and the piston 9 along the axis C when the piston 9 is engaged with the second lobe 62. In particular, the first locking element 53 and the second locking element 54 are configured to prevent sliding of the disc 36 with respect to the piston 9 along the axis C in the direction D3 extending from the first lobe 61 to the second lobe 62, as indicated by the arrow shown in the figure . In the non-limiting example described and illustrated here, the first locking element 53 and the second locking element 54 are configured to cooperate in abutment against the spring 35.

In particular, the first locking element 53 and the second locking element are substantially identical, are arranged symmetrically with respect to the axis C and extend from the top side 47 of the disc 36.

Preferably the first locking element 53 and the second locking element 54 are defined respectively by a first projection 63 and a second projection 64 which have a curved face 67 designed to cooperate in abutment against the end 56a of the spring 35 (Figure 2) .

According to a variant (not shown) the first locking element 53 and the second locking element 54 are pins.

Preferably the first projection 63 extends along the top side 47 in a first direction Tl substantially transverse to the axis C, while the second projection 64 extends along the top side 47 in a second direction T2 substantially transverse to the axis C.

In the non-limiting example described and illustrated here, the first locking element 53 and the second locking element 54 are arranged at the same distance from the centre c of the disc 36.

Preferably, the first locking element 53 and the second locking element 54 are arranged along the portion of the top side 47 lying between the perimetral edge 49 and the edge of the second lobe 62. In this way the first locking element 53 and the second locking element 54 block the movements of the disc 36 along the direction D3. In the non-limiting example described and illustrated here, the first locking element 53 and the second locking element 54 extend respectively from a first perimetral edge 65 of the first auxiliary opening 51 and from a second perimetral edge 66 of the second auxiliary opening 52.

Preferably the first auxiliary opening 51 and the second auxiliary opening 52 are substantially identical and arranged symmetrically with respect to the axis C.

In the non-limiting example described and illustrated here, the first auxiliary opening 51 and the second auxiliary opening 52 are substantially shaped as a circular rim segment.

Advantageously, the disc 36 may be made by means of pressing .

In particular, in order to manufacture the disc 36 according to the present invention, two stages are sufficient : producing, by means of pressing, a provisional disc in which the locking elements 53 and 54 are arranged aligned along the plane of the disc 36 inside the auxiliary openings 51 and 52; producing the definitive disc 36 by simply folding up towards the top side 47 the first locking element 53 and the second locking element 54 so that they extend from the top side 47 in order to prevent relative sliding of the disc 36 and the piston 9 along the axis C when the piston 9 is engaged with the second lobe 62.

Finally it is clear that the present invention also covers other embodiments not described in the detailed description and equivalent embodiments which fall within the scope of protection of the accompanying claims .

Claims

High-pressure pump for feeding fuel to an internal-combustion engine comprising at least one cylinder (8), a piston (9) sliding inside the cylinder (8), and a spring unit (34) coupled with the piston (9); the spring unit (34) comprising a spring (35) and a disc (36) which, during use, is arranged abutting against one end (56a) of the spring (35) ; the disc (36) being provided with an eyelet (50) engaged, during use, by the piston (9); the eyelet (50) extending substantially along an axis (C) and being provided with a constriction

(60) in a direction perpendicular to the axis (C) , which divides up the eyelet (50) into a first lobe

(61) and a second lobe (62), having a maximum width (L2) smaller than the maximum width (LI) of the first lobe (61); the disc (36) being provided with at least one first locking element (53; 54) configured to prevent the relative sliding of the disc (36) and the piston (9) at least along the axis (C) when the piston (9) is engaged with the second lobe ( 62 ) .

Pump according to Claim 1, wherein the first locking element (53; 54) is configured to prevent the sliding of the disc (36) with respect to the piston (9) at least along the axis (C) in a first direction (D3) .

Pump according to Claim 2, wherein the first locking element (53; 54) is configured to cooperate in abutment against the spring (35) .

Pump according to Claim 3, wherein the disc (36) has a top side (47) arranged, during use, abutting against the end (56a) of the spring (35) ; the first locking element (53; 54) comprising at least one first projection (63; 64), which extends from the top surface (47) of the disc (36) .

Pump according to Claim 4, wherein the first projection (63; 64) extends along the top side (47) along a second direction (Tl) substantially transverse to the axis (C) .

Pump according to Claim 4 or 5, wherein the disc (36) is provided with at least one first auxiliary opening (51; 52) having a first perimetral edge (65; 66); the first projection (63; 64) extending from the first perimetral edge (65; 66) .

Pump according to any one of Claims 4 to 6, wherein the first projection (63; 64) has at least one curved side (67) designed to cooperate in abutment against the end (56a) of the spring (35) .

Pump according to any one of Claims 2 to 7, wherein the disc (36) comprises at least one second locking element (54; 53) configured to prevent sliding of the disc (36) with respect to the piston (9) along the axis (C) in the direction

(D) from the first lobe (61) to the second lobe

(62) .

Pump according to Claim 8, wherein the first locking element (53; 54) and the second locking element (54; 53) are arranged on opposite sides of the axis (C) .

Pump according to Claim 8 or 9, wherein the first locking element (53; 54) and the second locking element (54; 53) are arranged at the same distance from the centre (c) of the disc (36) . Pump according to any one of Claims 8 to 10, wherein the first locking element (53; 54) and the second locking element (54; 53) are arranged symmetrically with respect to the axis (C) .

Pump according to any one of Claims 8 to 11, wherein the first locking element (53; 54) and the second locking element (54; 53) are substantially identical .

Pump according to any one of Claims 8 to 12, wherein the disc (36) has a top side (47) arranged, during use, abutting against the end (56a) of the spring (35) ; the second locking element (54; 53) comprising at least one second projection (64; 63) which extends from the top side (47) of the disc (36) .

Pump according to Claim 13, wherein the disc (36) is provided with at least one second auxiliary opening (52; 51) provided with a second perimetral edge (66; 65); the second projection (64; 63) extending from the second perimetral edge (66; 65) .

Pump according to any one of the preceding claims, wherein the width (LS) of the constriction (60) is smaller than the maximum width (LI) of the first lobe (61) and smaller than the maximum width (L2) of the second lobe (62) .

Pump according to any one of the preceding claims, wherein the first lobe (61) and the second lobe (62) are substantially circle-shaped and intersect each other. Pump according to any one of the preceding claims, wherein the centre of the second lobe (62) coincides with the centre (c) of the disc (36) .