WO2013178477A1

WO2013178477A1 - Fluid-Dynamic Device And Fuel Feed System Comprising Said Fluid-Dynamic Device

Info

Publication number: WO2013178477A1
Application number: PCT/EP2013/060134
Authority: WO
Inventors: Luigi Fiorentino
Original assignee: Robert Bosch Gmbh
Priority date: 2012-05-30
Filing date: 2013-05-16
Publication date: 2013-12-05
Also published as: IN2014DN07054A; ITMI20120938A1; CN104350273B; CN104350273A

Abstract

Fluid-dynamic device for a fuel feed system; the fluid-dynamic device (50) comprising an inlet conduit (51) extending along an axis (A), an outlet conduit (52) extending along the axis (A), an intake conduit (53), and a connecting conduit (54) into which the inlet conduit (51), the outlet conduit (52) and the intake conduit (53) converge; the connecting conduit (54) defines a constriction between the inlet conduit (51) and the outlet conduit (52) so that, during use, a fuel pressure is created in the intake conduit (53) lower than the pressure in the inlet conduit (51) and the outlet conduit (52).

Description

DESCRIPTION

Title

FLUID-DYNAMIC DEVICE AND FU EL FEED SYSTEM COMPRISING SAID FLUID-DYNAMIC DEVICE

The present invention relates to a fluid-dynamic device and to a fuel feed system comprising said fluid-dynamic device.

In greater detail, the fuel feed system is a system for feeding diesel fuel from a tank to a Diesel engine, an application to which the following description will make specific reference without thereby limiting in any way its general character.

Generally the fuel feed system comprises:

- a low-pressure pump or pre-feed pump;

- a high-pressure pump comprising at least one intake valve;

- a hydraulic circuit comprising a delivery branch for connecting the pre- feed pump to the intake valve of the high-pressure pump; and

- a choke valve located along the delivery branch for supplying a given amount of fuel to the intake valve.

Moreover, the hydraulic circuit comprises a drain branch for recovering surplus fuel, connected to the delivery branch at a point upstream of the choke valve.

Whenever the internal combustion engine is in a condition where it does not require fuel, the choke valve is closed, so as not to supply any flow to the intake valve.

A drawback of the prior art is that, when the choke valve is closed, owing to losses, it provides a minimum flow to the intake valve. The high-pressure pump, therefore, supplies said minimum flow to the internal combustion engine via the delivery valve. Consequently, the internal combustion engine is supplied even in the case where it does not require fuel, thereby resulting in the unnecessary consumption of fuel and unnecessary wear of the internal combustion engine.

One solution could be that of providing the feed system with an overflow valve on a branch communicating with the delivery branch, between the choke valve and the intake valve.

A drawback of this solution is that the intake valve opens at a pressure lower than the opening pressure of the overflow valve, consequently it does not solve completely the drawback mentioned above.

The object of the present invention is to provide a fluid-dynamic device which limits the drawbacks of the prior art.

According to the present invention a fluid-dynamic device for a fuel feed system is provided, the fluid-dynamic device comprising an inlet conduit, an outlet conduit, an intake conduit and a connecting conduit connected to the inlet conduit, the outlet conduit and the intake conduit; and wherein the flow cross- section of the connecting conduit is smaller than the flow cross-section of the inlet conduit and the flow cross-section of the outlet conduit, so that, during use, the fuel pressure in the intake conduit is lower than the fuel pressure in the inlet conduit and the outlet conduit.

During use, the dynamic device is installed along a drain branch of the fuel feed system. The fuel feed system comprises a delivery branch for feeding an intake valve of a high-pressure pump, along which a choke valve is located. The drain branch is connected to the delivery branch at a point upstream of the choke valve. The fluid-dynamic device is installed with the inlet conduit and the outlet conduit which operate along the drain branch. The intake conduit of the fluid-dynamic device is connected to the delivery branch at a point between the choke valve and the intake valve. During use, when the choke valve is closed and, owing to losses, fuel flows along the delivery branch downstream of the choke device, said fuel is drawn in by the intake conduit of the fluid-dynamic device and consequently the intake valve of the high-pressure pump does not open. In fact, owing to the intake conduit connected to the portion of the delivery branch located between the choke valve and the intake valve, when the choke valve is closed, the pressure along said portion of the delivery branch does not reach a value such as to cause the intake valve to open. This effect is due to the fact that the intake conduit creates a negative pressure in said portion of the delivery branch.

Another object of the present invention is to provide a system for feeding fuel from a tank to an internal combustion engine which limits the drawbacks of the prior art.

According to the present invention a system for feeding fuel from a tank to an internal combustion engine is provided, said system comprising:

- a pre-feed pump;

- a high-pressure pump comprising at least one intake valve;

- a choke valve located along the delivery branch for supplying a given amount of fuel to the intake valve;

the hydraulic circuit comprising a drain branch for recovering surplus fuel; the feed system comprising a fluid-dynamic device according to any one of Claims 1 to 7, wherein the inlet conduit and the outlet conduit are connected along the drain branch and wherein the intake conduit is connected to the delivery branch between the choke valve and the intake valve of the high- pressure pump so as to draw fuel from the delivery branch when the choke valve is closed.

Owing to the present invention, the feed system is able to prevent the supply of fuel when the internal combustion engine does not require it. This results in a reduction in the fuel consumption and a reduction in the unnecessary work load of the internal combustion engine. This reduction in the consumption levels and the work load is achieved owing to the fluid-dynamic device, the intake conduit of which is connected to the delivery branch between the choke valve and the intake valve. In this way, when the choke valve is closed, the intake conduit draws the fuel which passes through the choke valve, and the intake valve does not open. The intake valve is prevented from opening owing to the fact that the intake conduit creates a negative pressure and the pressure of the delivery branch between the intake valve and the choke valve does not reach the opening pressure of the intake valve.

Other characteristic features and advantages of the present invention will emerge clearly from the description which follows of non-limiting examples of embodiment thereof, with reference to the accompanying drawings in which: - Figure 1 is a schematic view, with parts omitted for greater clarity, of a system for feeding fuel from a tank to an internal combustion engine;

- Figure 2 is a cross-sectional view, with parts removed for greater clarity, of a first embodiment of a fluid-dynamic device of the fuel feed system according to Figure 1;

- Figure 3 is a cross-sectional view, with parts removed for greater clarity, of an alternative embodiment of the fluid-dynamic device according to Figure 2.

With reference to Figure 1, the reference number 1 denotes a system for feeding fuel from a tank to an internal combustion engine.

With reference to Figure 1, the reference number 1 denotes in its entirety a system for feeding fuel, diesel fuel in the case in question, from a tank 2 to an internal combustion engine (not shown) of the known type.

In greater detail, the internal combustion engine is a diesel engine which comprises a manifold 4 for distributing the fuel - generally called a "common rail" - which is designed to contain the fuel with a pressure preferably, but not necessarily, greater than 1800 bar; and a series of electrically operated injectors (not shown) which are directly connected to the common rail 4 and are able, when operated, to atomize the fuel inside the various combustion chambers (not shown) of the internal combustion engine.

With reference to Figure 1, the fuel feed system 1 comprises essentially a fuel pump unit 6; a hydraulic circuit 7 which is able to connect the fuel pump unit 6 both to the tank 2 and to the common rail 4 of the internal combustion engine; and a control unit 8.

In greater detail, the fuel pump unit 6 comprises a pre-feed pump 9 and a high-pressure pump 10 with intake valves 11 and delivery valves 12. The pre- feed pump 9 and the high-pressure pump 10 are arranged so that the fuel which reaches the intake valves 11 of the high-pressure pump 10 is supplied by the pre-feed pump 9.

The hydraulic circuit 7 comprises a branch 13 for connecting the tank 2 to the pre-feed pump 9; a delivery branch 14 for connecting the pre-feed pump 9 to the intake valves 11 of the high-pressure pump 10; and branches 15 for connecting the delivery valves 12 of the high-pressure pump 10 to the common rail 4 for distributing the fuel of the internal combustion engine.

Preferably, but not necessarily, the hydraulic circuit 7 is also provided with a fuel filter 16 positioned along the connecting branch 13, upstream of the pre- feed pump 9. Moreover, the hydraulic circuit 7 is provided with a main fuel filter

17 positioned along the delivery branch 14 connecting together the pre-feed pump 9 and the high-pressure pump 10. In an alternative embodiment of the present invention, the fuel filter is omitted and the system comprises a main fuel filter located upstream of the pre-feed pump.

With reference to Figure 1 in particular, the pre-feed pump 9 is a pump which has the function of conveying to the high-pressure pump 10, at a particular instant, an amount of fuel from the tank 2. The high-pressure pump 10 is a high- pressure piston pump, in particular a volumetric piston pump which has an outer casing or pump body (not shown) defining a closed compartment 18 inside the pump body and a mechanism for moving movable parts 19 arranged at least partially inside the closed compartment 18.

Moreover, the pre-feed pump 9 may be a vane pump, an internal or external gear pump, or an electric pump.

In greater detail, with reference to Figure 1, the high-pressure pump 10 has a plurality of pistons or pumping members 20 which are housed inside respective cylindrical cavities 21 (only two of which are visible in the

accompanying figures) and are angularly distributed around the compartment 18.

The moving parts are the pistons 20 of the high-pressure pump 10.

The mechanism for moving the moving parts 19 instead comprises a rotating shaft which is designed to be rotationally driven by the driving shaft (not shown) of the internal-combustion engine, and is provided with a cam 22 which actuates the pistons 20.

Alternatively, the present invention can be used with high-pressure pumps having, for example, roller guides or a shaft which moves along a polygonal ring.

The delivery branch 14 flows into the compartment 18 of the high- pressure pump 10 via an inlet 23 and emerges from this compartment 18 via an outlet 24. In this way, owing to the forced flow of the fuel inside the compartment

18 of the high-pressure pump 10, lubrication and cooling of the mechanism for moving the moving parts is ensured.

The hydraulic circuit 7 comprises a choke valve 25 arranged along the delivery branch 14 for supplying a given amount of fuel to the intake valve 11. The choke valve 25 is arranged between the pre-feed pump and the intake valve 11. In greater detail, the choke valve 25 is arranged along a portion of the delivery branch 14 which extends between the outlet 24 of the compartment 18 and the intake valve 11. In other words, the choke valve 25 is arranged along the delivery branch 14 downstream of the compartment 18 of the intake pump.

Moreover, the choke valve 25 is arranged along the delivery branch 4 upstream of the intake valve 11.

The choke valve 25 is a valve controlled by the control unit 8 so as to regulate the flow of fuel along the delivery branch 14 towards the intake valves 11.

The intake valve 11 is a non-return valve designed to regulate the flow of the fuel from the delivery branch 14 of the hydraulic circuit 7 towards the cylindrical cavities 21 of the high-pressure pump 10.

The delivery valve 12 is a non-return valve designed to regulate the flow of the fuel from the cylindrical cavity 21 of the high-pressure pump 10 to the branch 15 of the hydraulic circuit 7.

During use, the intake valves 11 remove the fuel from the delivery branch 14 and convey it into the respective cylindrical cavity 21, each piston 20 raises the pressure of the fuel inside the respective cylindrical cavity 21 and finally the delivery valves 12 supply the high-pressure fuel to the branch 15.

The intake valves 11 and the delivery valves 12 are inset in the pump body and will not be further described because they are already widely known in the sector.

In connection with that illustrated above, it should be pointed out that the structure of the high-pressure pump 10 has been shown and described only by way of explanation and that any other type of high-pressure pump may be effectively used for the purposes of the present invention.

The control unit 8 is configured to determine, at a particular instant, the fuel requirement of the internal combustion engine and control some of the components of the fuel feed system 1 so as to convey to the common rail 4 an amount of fuel substantially the same as the fuel requirement of the internal combustion engine.

The hydraulic circuit 7 comprises a drain branch 30 configured to recover surplus fuel in the delivery branch 14 and connected to the delivery branch 14 at a point upstream of the choke valve 25. In other words, the drain branch 30 is connected to the portion of the delivery branch 14 arranged between the outlet 24 of the compartment 18 and the choke valve 25. The drain branch 30 extends as far as the tank 2.

The system 1 comprises an overflow valve 32 arranged along the drain branch 30.

The overflow valve 32 comprises an inlet 33 and two outlets 34 and 35. The inlet 33 is connected to the drain branch 30 so that the fuel from the delivery branch 14 flows into the inlet 33 of the overflow valve 32.

The hydraulic circuit 7 comprises a drain branch 35 which connects the outlet 34 to the branch 13 at a point upstream of the pre-feed pump 9. In this way, the surplus fuel from the delivery branch 14 is conveyed back upstream of the pre-feed pump 9 and then recirculated inside the system 1.

The outlet 35 is connected to the drain branch 30 and connects the overflow valve 32 to the tank 2.

In other words, the overflow valve is arranged along the drain branch 30 via the inlet 33 and the outlet 35.

Moreover, the system 1 comprises a fluid-dynamic device 50 arranged along the drain branch 30 downstream of the overflow valve 32. The fluid- dynamic device 50 is arranged upstream of the tank 2.

The fluid-dynamic device 50 comprises an inlet conduit 51, an outlet conduit 52 and an intake conduit 53.

The inlet conduit 51 extends along an axis A. The inlet conduit 51 is connected to the outlet 35 of the overflow valve 32 by means of the drain branch 30.

The outlet conduit 52 extends along an axis B. In the example illustrated in Figure 2, the axis A and the axis B coincide. The outlet conduit 52 is connected to the tank 2 by means of the drain branch 30.

The intake conduit 53 extends along an axis C transverse to the axis A. The axis C is transverse to the axis B. In particular, the axis C lies in a plane perpendicular to the axis A. The axis C lies in a plane perpendicular to the axis B.

The hydraulic circuit 7 comprises a branch 49 which connects the intake conduit 53 to the delivery branch 14 downstream of the choke valve 25 and upstream of the intake valve 11. In other words, the intake conduit 53 is connected by means of the branch 49 to a portion of the delivery branch 14 located between the choke valve 25 and the intake valves 11.

The fluid-dynamic device 50 comprises a connecting conduit 54, inside the fluid-dynamic device 50 itself, connected to the inlet conduit 51, the outlet conduit 52 and the intake conduit 53. The connecting conduit 54 extends along an axis D. In the example shown in Figures 2 and 3, the axis D coincides with the axis A and with the axis B and is transverse to the axis C. The connecting conduit 54 defines a constriction between the inlet conduit 51 and the outlet conduit 52 so that, during use, the fuel pressure inside the intake conduit 53 is lower than the fuel pressure inside the inlet conduit 51 and the outlet conduit 52. In greater detail, the flow cross-section SI of the connecting conduit 54 is smaller than the flow cross-section S2 of the inlet conduit 51 and the flow cross-section

53 of the outlet conduit 52. The connecting conduit 54 comprises a first frustoconical portion 54a, a second frustoconical portion 54b and an intermediate portion 54c. The first frustoconical portion 54a has a flare angle Al greater than 25°. The second frustoconical portion 54b has a flare angle A2 greater than 25°.

The inlet conduit 51 and the outlet conduit 52 have respective cylindrical inlet and outlet portions. The intermediate portion 54c of the connecting conduit

54 comprises a first cylindrical portion 60 connected to the first frustoconical portion 54a. The flow cross-section SI relates to the first cylindrical portion 60. The intermediate portion 54c of the connecting conduit 54 comprises a second cylindrical portion 61. In greater detail, the flow cross-section SI of the first cylindrical portion 60 is greater than the flow cross-section S4 of the second cylindrical portion 61. Moreover, the second cylindrical portion 61 is connected to the second frustoconical portion 54b.

In greater detail, the intake conduit 53 is connected to the first cylindrical portion 60.

Moreover, in a preferred embodiment, the flow cross-section of the intake conduit 53 is smaller than the flow cross-section SI of the connecting conduit 54, the flow cross-section S2 of the inlet conduit 51 and the flow cross-section S3 of the outlet conduit 52.

During use, the fuel which flows from the inlet conduit 51 undergoes further throttling due to the second cylindrical cross-section 61, as a result of which the speed of the fuel increases greatly and the fluid-dynamic device 50 improves the performance characteristics.

According to an alternative embodiment of the present invention shown ^' Figure 3, the fluid-dynamic device 50 comprises a further intake conduit 153 connected to the connecting conduit 54.

During use, when the choke valve 25 is closed and owing to losses, fuel flows along the delivery branch 14 downstream of the choke valve 25, said fuel drawn in by the intake conduit 53 of the fluid-dynamic device 50 and

consequently the intake valve 11 of the high-pressure pump 10 does not open. In fact owing to the intake conduit 53 connected to the portion of the delivery branch located between the choke valve 25 and the intake valve 11, when the choke valve 25 is closed, the pressure along said portion of the delivery branch 14 does not reach a value such as to cause the intake valve 11 to open. This effect is due to the fact that the intake conduit creates a negative pressure insid the said portion of the delivery branch 14.

The feed system 1 therefore does not supply fuel when it is not required by the internal combustion engine. This results in a reduction in the fuel consumption and reduction in the unnecessary work load of the internal combustion engine.

It is also evident that the present invention may be subject to variations without thereby departing from the scope of protection as defined in the accompanying claims.

Claims

1) Fluid-dynamic device for a fuel feed system; the fluid-dynamic device (50)

comprising an inlet conduit (51), an outlet conduit (52), an intake conduit (53), and a connecting conduit (54) connected to the inlet conduit (51), the outlet conduit (52), and the intake conduit (53); and wherein the flow cross-section (SI, S4) of the connecting conduit (54) is smaller than the flow cross-section (S2) of the inlet conduit (51) and the flow cross-section (S3) of the outlet conduit (52), so that, in use, the fuel pressure in the intake conduit (53) is lower than the fuel pressure in the inlet conduit (51) and the outlet conduit (52).

2) Fluid-dynamic device according to Claim 1, wherein the connecting conduit (54) comprises a cylindrical intermediate portion (54c), a first frustoconical portion (54a), and a second frustoconical portion (54b); the first and second frustoconical portions (54a, 54b) converging towards the cylindrical intermediate portion (54c).

3) Fluid-dynamic device according to Claim 2, wherein the first and second

frustoconical portions (54a, 54b) have a flare angle greater than 25°.

4) Fluid-dynamic device according to Claim 3, wherein the inlet conduit (51) and outlet conduit (52) have respective cylindrical portions.

5) Fluid-dynamic device according to any one of the foregoing claims, wherein the intermediate portion (54c) of the connecting conduit (54) comprises a first cylindrical portion (60) adjacent to the first frustoconical portion (54a); and a second cylindrical portion (61) adjacent to the second frustoconical portion (54b); the flow cross-section (SI) of the first cylindrical portion (60) being larger than the flow cross-section (S4) of the second cylindrical portion (61).

6) Fluid-dynamic device according to any one of the foregoing claims, comprising a further intake conduit (154) connected to the connecting conduit (54).

Fluid-dynamic device according to Claim 5, wherein the intake conduit (53) is connected to the first cylindrical portion (60).

Feed system for feeding fuel from a tank (2) to an internal combustion engine, comprising :

- a pre-feed pump (9);

- a high-pressure pump (10) comprising at least one intake valve (11);

- a hydraulic circuit (7) comprising a delivery branch (14) for connecting the pre- feed pump (9) to the intake valve (11) of the high-pressure pump (10); and

- a choke valve (25) located along the delivery branch (14) for supplying a given amount of fuel to the intake valve (11);

- the hydraulic circuit (7) comprising a drain branch (30) for recovering surplus fuel;

- the feed system (1) comprising a fluid-dynamic device (50) according to any one of the foregoing claims, wherein the inlet conduit (51) and outlet conduit

(52) are connected along the drain branch (30) and wherein the intake conduit

(53) is connected to the delivery branch (14), between the choke valve (25) and the intake valve (11) of the high-pressure pump (10), so as to draw fuel from the delivery branch (14) when the choke valve (25) is closed.

Feed system according to Claim 8, wherein the drain branch (30) is connected to the delivery branch (14) at a point upstream of the choke valve (25).

Feed system according to Claim 8 or 9, comprising an overflow valve (32) located along the drain branch (30), upstream of the fluid-dynamic device (50).

Feed system according to one of Claims 8 to 10, wherein the high-pressure pump (10) comprises moving parts (20), and an inner compartment (18) housing the moving parts (20); and wherein the delivery branch (14) extends through the inner compartment (18) so as to force fuel into the inner compartment (18) for lubricating and cooling.