WO2015091264A1

WO2015091264A1 - Pump unit for feeding fuel, preferably diesel fuel, to an internal combustion engine

Info

Publication number: WO2015091264A1
Application number: PCT/EP2014/077567
Authority: WO
Inventors: Alessandro De Luca; Friedrich Boecking; Antonio Diaferia
Original assignee: Robert Bosch Gmbh
Priority date: 2013-12-17
Filing date: 2014-12-12
Publication date: 2015-06-25
Also published as: ITMI20132109A1

Abstract

A pump unit for feeding fuel, preferably, diesel fuel, to an internal combustion engine; the pump unit (1) comprising a head (5) inside which a cylinder (6) extending along an axis (Al) is formed; a pumping piston (7) extending along the axis (Al) and slidably coupled with the cylinder (6); and an intake valve (18) comprising a valve body (22) formed inside the head (5) and in communication with the cylinder (6).

Description

Title

PUMP UNIT FOR FEEDING FU EL, PREFERABLY DIESEL FU EL, TO AN INTERNAL COMBUSTION ENGINE

The present invention relates to a pump unit for feeding fuel, in particular diesel fuel, to an internal combustion engine.

In general, a pump unit comprises a pump body; a head mounted on the pump body; a pumping piston housed inside the head; a shaft, with a cam for actuating the pumping piston; an intake valve; and a delivery valve.

The head comprises a cylinder, inside which the pumping piston of the pump unit moves with a reciprocating motion, and generally has two seats in which the intake valve and the delivery valve are hosued. The head of the cylinder is preferably made by means of forging of a bar of high-quality steel able to withstand the stresses acting on it. The intake valves and the delivery valves are mounted on the head by means of a threaded joint.

One of the drawbacks of the prior art is that, in order to form the seats for the two valves and the threads for the threaded joints in the seats of the head, relatively long and costly precision-machining operations are required. Moreover, in the associated seats, the contact surfaces and the threaded surfaces may give rise to wear and corrosion during the working life of the pump.

One object of the present invention is to provide a pump unit of the type indicated above which is able to limit the aforementioned drawbacks.

According to the present invention a pump unit for feeding fuel, preferably diesel fuel, to an internal combustion engine is provided; the pump unit comprising a head inside which a cylinder extending along an axis is formed; a pumping piston extending along the axis and slidably coupled with the cylinder; and an intake valve comprising a valve body formed inside the head and in communication with the cylinder. As a result of the present invention, the intake valve seat is formed by means of a turning process, avoiding more costly processes, such as milling and grinding, thus reducing production costs and times. Moreover, the pump unit poses fewer wear and corrosion-related problems because the threaded surfaces between the head and the intake valve are not present.

According to another preferred embodiment of the present invention, the valve body and the head are made from a single monobloc part, preferably by means of machining with stock removal.

According to another preferred embodiment of the present invention, the intake valve comprises an intake duct formed inside the head.

According to another preferred embodiment of the present invention, the intake duct comprises a chamber which communicates with the intake duct in order to receive the fuel.

According to another preferred embodiment of the present invention, the intake valve comprises a closing member, which is resiliently supported by the pumping piston via a resilient element arranged between the closing member and the free end of the pumping piston.

According to another preferred embodiment of the present invention, the closing member is movable along the axis so as to allow selectively the flow of fuel.

According to another preferred embodiment of the present invention, the head comprises a seat and a delivery valve housed in the seat.

According to another preferred embodiment of the present invention, the delivery valve is housed inside a connector housed inside the seat and partly making contact with the head.

According to another preferred embodiment of the present invention, the connector of the delivery valve is made of a material having a hardness factor less than that of the material from which the head is made.

As a result of the present invention, the pump unit has a lower cost because different steel types are used depending on the stresses which must be withstood by the various parts of the pump unit.

According to another preferred embodiment of the present invention, comprising a coupling element arranged in the seat between the delivery valve and the head, preferably the coupling element has a frustoconical form. According to another preferred embodiment of the present invention, the coupling element is made of a material having a hardness factor less than that of the material from which the connector is made and that of the material from which the head is made.

According to another preferred embodiment of the present invention, the coupling element is designed to allow automatic centring of the connector inside the seat of the head.

According to another preferred embodiment of the present invention, the delivery valve extends along the axis.

According to another preferred embodiment of the present invention, the intake valve extends along the axis.

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

- Figure 1 is a cross-sectional view, with parts omitted for greater clarity, of the pump unit designed in accordance with the present invention;

- Figure 2 is a view, along the cross-section 11-11, of the pump unit according to Figure 1; and

- Figure 3 is a view, on a larger scale and with parts omitted for greater clarity, along the cross-section Ill-Ill.

With reference to Figures 1 and 2, 1 denotes in its entirety a pump unit for feeding fuel, preferably diesel fuel, to an internal combustion engine (not shown).

The pump unit 1 comprises a high-pressure pump 4 with pumping pistons, which is designed to feed the fuel to the said internal combustion engine (not shown); and a gear pump (known and not shown) which is designed to feed the fuel to the pump 4. The pump 4 and the gear pump are moved by a shaft (not shown in the accompanying drawings).

The pump 4 comprises a pump body 2; a head 5 mounted on the pump body 2; a pumping piston 7 which extends along an axis Al and is coupled with the head 5; an intake duct 13 formed partly in the head 5; an intake valve 18 in communication with the delivery duct 13; a compression chamber 20 in communication with the intake valve 18; a delivery duct 19 formed partly inside the head 5 and in communication with the compression chamber 20; and a delivery valve 21 for selectively stopping the fuel along the delivery duct 19. The head 5 comprises a cylinder 6 which extends along the axis Al. The cylinder 6 is slidably engaged by the pumping piston 7 and is coaxial with the pumping piston 7.

The head 5 has a central hole 11 which is formed through the head 5 coaxially with the axis Al and is in communication with the cylinder 6. The hole 11 has a funnel-shaped form which defines a seat 12.

With reference to Figure 2, the compression chamber 20 is arranged between the pumping piston 7 and the delivery valve 21. The pumping piston 7 is displaced by an actuating device (not shown in the accompanying figures) along the cylinder 6 with a rectilinear reciprocating motion comprising an intake stroke for drawing in the fuel inside the cylinder 6 and a compression stroke for compressing the fuel contained inside said cylinder 6 so as to compress the fuel drawn into the compression chamber 20.

With reference to Figures 2 and 3, the delivery valve 18 is designed to control selectively feeding of the fuel into said cylinder 6 from the intake duct 13. The intake duct 13 is formed inside the head 5 and transverse to the axis Al. The intake duct 13 connects the gear pump to the intake valve 18.

The intake valve 18 extends along the axis Al and comprises a valve body 22 which is formed inside the head 5 and is communication with the cylinder 6. In other words, a portion of the head 5 defines the valve body 22 of the intake valve 18. Moreover, the valve body 22 and the head 5 are made from a single monobloc part, preferably by means of machining with stock removal.

Moreover, the intake valve 18 comprises a closing member 23 movable along the axis Al so as to allow selectively the fuel flow. The closing member 23 is resiliently supported on the pumping piston 7. In greater detail, the intake valve 18 comprises a resilient element 26 which extends along the axis Al and is arranged between the closing member 23 and the free end of the pumping piston 7. In greater detail the intake valve 18 comprises a coupling element 28 which on one side is coupled with the closing member 23 and on the other side engages with the resilient element 26. The resilient element 26 in the non-limiting embodiment shown in the accompanying figures is a helical spring engaged between the free end of the pumping piston 7 and the coupling element 28. The closing member 23 in a preferred non-limiting embodiment is a ball. In an alternative embodiment of the present invention, not shown in the

accompanying figures, the closing member is a flat disc or has a conical form.

The intake valve 18 comprises a cylindrical chamber 24 which

communicates with the intake duct 13 in order to receive the fuel; and a frustoconical chamber 27 communicating with the cylindrical chamber 24. The chambers 24 and 27 extend along the axis Al. The frustoconical chamber 27 is in communication with the compression chamber 20 and defines a seat for the closing member 23. When the pumping piston 7 performs the compression stroke, it pushes the closing member 23 towards the frustoconical chamber 27, and consequently the closing member 23 is in the closed position. In this case, since the frustoconical chamber 27 is engaged by the closing member 23, it does not allow the fuel to pass from the cylindrical chamber 24 of the delivery valve 18 to the compression chamber 20 of the high-pressure pump 1. When the pumping piston 7 performs the intake stroke, the closing member 23 is pushed by the pressure inside the chamber 24 along the axis Al towards said pumping piston 7. In this case, the closing member 20 is in the open position and, consequently, the cylindrical chamber 24 is in communication with the compression chamber 20 via the frustoconical chamber 27. In this case, therefore, the fluid flows from the intake valve 18 to the compression chamber 20.

The pump unit 1 comprises connection ducts 25 which connect the compression chamber 20 to the seat 12 and consequently to the delivery valve 21. The connection ducts 25 extend along an axis parallel to the axis Al. The connection ducts 25 in the accompanying figure are six in number, but may consist of any number greater or smaller than 6.

The pump unit 1 comprises a connector 32 for housing the delivery valve 21 inside the seat 12 and a coupling element 34. The delivery valve 21 is housed along the delivery duct 19 and is able to control selectively feeding of the fuel to the said internal combustion engine (not shown).

The connector 32 has a central hole 36 for housing inside it the delivery valve 19. The connector 32 is housed inside the seat 12 and partly makes contact with the head 5. Moreover, the pump unit 1 comprises fixing means 42 for fixing the connector 32 to the seat 12 by means of a threaded joint. In particular, the threads for the threaded joint are formed along an outer surface of the head 5.

The coupling element 34 is positioned between the connector 21 and the head 5 along the axial direction of the axis Al. The coupling element 34 has a frustoconical form and is designed to allow automatic centring of the connector 32 inside the seat 12 of the head 5. In other words, during assembly of the delivery valve 19, the delivery valve 19 is inserted inside the connector 32, the coupling element 34 is inserted inside the seat 12 and then the connector 32 is inserted inside the seat 12. In this way, the axis, along which the delivery valve 19 extends, is positioned so as to coincide with the axis Al in a simply and automatic manner. The delivery valve 19 is then coaxial with the axis Al.

The delivery valve 19 comprises a closing member 38 movable along the axis Al under the thrust of the fluid pressure; and a fixed element 40 rigidly connected to the connector 32. In particular, the closing member 38 is resiliently constrained to the fixed element 40 of the delivery valve 19. When the piston 7 moves upwards, it compresses the fuel until the pressure inside the compression chamber 20 is greater than the pressure inside the delivery duct 18.

Consequently, the closing member 38 moves along the axis Al and allows the fuel to pass into the delivery duct 19 from the compression chamber 20.

The head 5 is made of a material, preferably high-quality steel, having a high hardness factor.

Moreover, the connector 32 is made of a material, preferably high-quality steel, having a hardness factor less than the hardness factor of the material of the head 5.

The coupling element 34 is made of a material, preferably steel, having a hardness factor less than that of the material from which the connector 32 is made and less than that of the material from which the head 5 is made. In this way lower costs are achieved.

As already mentioned, the head 5 consists of a cylindrical monobloc part which is made by means of machining with stock removal, preferably by means of a turning process. Consequently the costs are low.

As a result of the present invention, the intake valve 18, being formed inside the head 5, does not require the use of considerable force in order to fix the intake valve 18 on the head 5. In fact, in this way a high physical stress and interface area is eliminated and there are no problems of sealing the intake valve with the head. Moreover, owing to the fact that the intake valve is incorporated in the head, there is no relative movement of the intake valve and the head and, consequently, the problems of wear and corrosion are reduced in comparison to the prior art.

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

Claims

Pump unit for feeding fuel, preferably diesel fuel, to an internal combustion engine; the pump unit (1) comprising a head (5) inside which a cylinder (6) extending along an axis (Al) is formed; a pumping piston (7) extending along the axis (Al) and slidably coupled with the cylinder (6); and an intake valve (18) comprising a valve body (22) formed inside the head (5) and in communication with cylinder (6).

Pump unit according to Claim 1, wherein the valve body (22) and the head (5) are made from a single monobloc part, preferably by means of machining with stock removal.

Pump unit according to Claims 1 or 2, comprising an intake duct (13) formed inside the head (5).

Pump unit according to any one of the preceding claims, wherein the intake valve (18) comprises a chamber (24) which communicates with the intake duct (13) in order to receive the fuel.

Pump unit according to any one of the preceding claims, wherein the intake valve (18) comprises a closing member (23) which is resiliently supported by the pumping piston (7) via a resilient element (26) arranged between the closing member (23) and the free end of the pumping piston (7).

Pump unit according to Claim 4 or 5, wherein the closing member (23) is movable along the axis (Al) so as to allow selectively the fuel to flow. Pump unit according to any one of the preceding claims, wherein the head (5) comprises a seat (12) and a delivery valve (21) housed inside the seat (12).

Pump unit according to Claim 7, wherein the delivery valve (21) is housed inside a connector (32) housed inside the seat (12) and partly making contact with the head (5).

Pump unit according to Claim 7 or 8, wherein the connector (32) of the delivery valve (21) is made of a material having a hardness factor less than that of the material from which the head (5) is made.

Pump unit according to one of Claims 7 to 9, comprising a coupling element (34) arranged inside the seat (12) between the delivery valve (21) and the head (5); preferably the coupling element (34) has a frustoconical form.

Pump unit according to Claim 10, wherein the coupling element (34) is made of a material having a hardness factor less than that of the material from which the connector (32) is made and less than that of the material from which the head (5) is made.

Pump unit according to one of Claims 7 to 11, wherein the coupling element (34) is designed to allow automatic centring of the connector inside the seat (12) of the head (5).

Pump unit according to one of Claims 7 to 12, wherein the delivery valve (21) extends along the axis (Al).

Pump unit according to any one of the preceding claims, wherein the intake valve (18) extends along the axis (Al).