EP2975264A1

EP2975264A1 - Pumping unit for feeding fuel, preferably diesel fuel, from a storage tank to an internal combustion engine

Info

Publication number: EP2975264A1
Application number: EP15173357.3A
Authority: EP
Inventors: Discar RUDINAL; Pasquale Cavallera
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2014-07-16
Filing date: 2015-06-23
Publication date: 2016-01-20
Anticipated expiration: 2035-06-23
Also published as: EP2975264B1

Abstract

A pumping unit for feeding fuel, preferably diesel fuel, to an internal combustion engine (3) is provided with a hydraulic circuit (14) having a first branch (15) for connecting together a storage tank (2) and a pre-feed pump (7), a second branch (16) for connecting together the pre-feed pump (7) and a high-pressure pump (6), a third branch (18) for connecting together the high-pressure pump (6) and the internal combustion engine (3), and a fourth branch (22) which connects together the second branch (16) and the storage tank (2) and is associated with an overflow valve (27) which has a valve body (28) defined by two sleeves (30) coaxial with each other.

Description

The present invention relates to a pumping unit for feeding fuel, preferably diesel fuel, from a storage tank to an internal combustion engine.
In particular, the present invention relates to a pumping unit of the type comprising a pre-feed pump, for example a gear pump, for drawing the fuel from a storage tank; a high-pressure pump, for example a piston pump, for feeding the fuel to an internal combustion engine; and a hydraulic circuit for connecting together the storage tank and the internal combustion engine.
The hydraulic circuit comprises a first branch for connecting together the storage tank and the gear pump; a second branch for connecting together the gear pump and the piston pump; and a third branch for connecting together the piston pump and the internal combustion engine.
Generally, the hydraulic circuit further comprises an electric metering valve arranged along the second branch for selectively controlling the instantaneous fuel flow fed to the piston pump depending on the values of a plurality of operating parameters of the internal combustion engine; and a fourth branch, which connects together the second branch and the storage tank, is connected to the second branch upstream of the electric metering valve in an advancing direction of the fuel along said second branch and allows discharging into the storage tank of at least part of the fuel flow in excess of that fed through the electric metering valve.
The fourth branch is provided with an overflow valve comprising a valve body mounted in the pump body of the piston pump; an inlet for introducing the fuel into the valve body; at least one outlet for discharging the fuel from the valve body; and a closing member movable between a position for closing and a position for opening said outlet.
The outlet is connected to a connector projecting outside the pump body of the piston pump so as to be connected to a pipe for feeding the fuel to the storage tank.
The outlet of the overflow valve and the connector are connected together by a feed duct formed through the pump body of the piston pump or by a plurality of feed holes formed through the valve body.
The known pumping units of the type described above have a number of drawbacks due mainly to the fact that the formation of the feed duct through the pump body of the piston pump or of feed holes through the valve body is relatively complex and costly.
The object of the present invention is to provide a pumping unit for feeding fuel, preferably diesel fuel, from a storage tank to an internal combustion engine, which does not have the abovementioned drawbacks and which is simple and inexpensive to implement.
According to the present invention a pumping unit for feeding fuel, preferably diesel fuel, from a storage tank to an internal combustion engine is provided, as claimed in the accompanying claims.
The present invention will now be described with reference to the accompanying drawings which illustrate a non-limiting example of embodiment thereof in which:

Figure 1 is a hydraulic diagram of a preferred embodiment of the pumping unit according to the present invention; and
Figures 2a and 2b are two schematic side views, with parts cross-sectioned and parts removed for greater clarity, of a detail of the pumping unit according to Figure 1 shown in two different operating positions.

With reference to Figure 1, 1 denotes in its entirety a pumping unit for feeding a liquid fuel, preferably diesel fuel, from a storage tank 2 to an internal combustion engine 3.
In the case in question the engine 3 is a diesel combustion engine comprising a manifold 4 for distributing the fuel, commonly referred to by the term "common rail", and a plurality of injectors 5 connected to the manifold 4 and designed to atomize the fuel inside associated combustion chambers (not shown) of said engine 3.
The pumping unit 1 comprises a high-pressure pump 6, in the case in question a piston pump, designed to feed the fuel to the engine 3, and a low-pressure or pre-feed pump 7, in the case in question a gear pump, designed to feed the fuel from the tank 2 to the pump 6.
The pump 6 comprises a pump body 8 which has a given longitudinal axis 10 and at least one cylinder 10 which is formed in the pump body 8 and has a longitudinal axis 11 substantially perpendicular to the axis 9 and is slidably engaged by a piston 12.
The piston 12 is displaced by an actuating device 13 of the known type housed inside the pump body 8 along the cylinder 10 with an alternating rectilinear movement comprising an outward stroke for drawing in the fuel into the cylinder 10 and a return stroke for compressing the fuel contained inside said cylinder 10.
The pumping unit 1 further comprises a hydraulic circuit 14 for feeding the fuel from the tank 2 to the manifold 4.
The circuit 14 comprises a first branch 15 for connecting together the tank 2 and the pump 7; a second branch 39, which connects together the pump 7 and the pump 6, extends through the pump body 8 in order to lubricate the actuating device 13 and is connected to the cylinder 10 by means of an intake valve 17; and a third branch 18, which extends between the pump 6 and the manifold 4 and is connected to the cylinder 10 by means of a delivery valve 19.
The branch 16 is provided with an electric metering valve 20 which is mounted upstream of the valve 17 in an advancing direction 21 of the fuel along the branches 16 and 18, is movable between a position for closing and a position for opening the branch 16 and is designed to control selectively the instantaneous fuel flow fed to the pump 6 depending on the values of a plurality of operating parameters of the engine 3.
The circuit 14 further comprises a fourth branch 22 which connects the branch 16 upstream of the electric valve 20 in the direction 21 to the tank 2 and allows at least part of the fuel flow in excess of that fed through the electric valve 20 to be discharged into the tank 2; and a fifth branch 23 which extends between the manifold 4 and the branch 22 and allows the fuel flow in excess of that required for the injectors 5 to be discharged into the tank 2.
The circuit 14 furthermore has a sixth branch 24 for discharging into the branch 22, and therefore into the tank 2, the fuel fed through the pump body 8 from the branch 16 and seeping through the bearings supporting the actuating device 13; and a seventh branch 25, which is connected to the branch 16 downstream of the electric valve 20 in the direction 21, extends between the branch 16 and the branch 22, is able to take up the fuel flow which seeps through the electric valve 20 when the electric valve 20 is closed and is provided with a calibrated holes 26 having a size such as to limit to below a given threshold value the quantity of fuel taken up by the branch 25 when the electric valve 20 is open.
In accordance with that shown in Figures 1 and 2, the branch 22 is provided with an overflow valve 27 comprising a valve body 28, which has a longitudinal axis 29, and is mounted inside the pump body 8.
The valve body 28 comprises two sleeves 30 which are coaxial with each other and the axis 29 and are locked by means of interference inside one another, one of them (indicated below by 30a) being mounted inside the other one (indicated below by 30b).
The valve body 28 is joined in a fluid-tight manner together with the pump body 8 via two seals 31 mounted on the sleeve 30a and the sleeve 30b, respectively.
The sleeve 30b is screwed into the pump body 8 or is locked by means of interference inside said pump body 8.
Preferably, the sleeve 30a is made of a material, which is different from the material of the sleeve 30b, and has a hardness greater than the hardness of the material of said sleeve 30b.
Each sleeve 30a, 30b comprises an associated portion 32 for coupling together with the other sleeve 30a, 30b and has a free end projecting axially from the other sleeve 30a, 30b.
The portion 32 of the sleeve 30a is limited radially by an outer lateral surface 33 which is substantially cylindrical and coaxial with the axis 29, and the portion 32 of the sleeve 30b is limited radially by an inner lateral surface 34 which is substantially cylindrical and coaxial with said axis 29.
The free end of the sleeve 30a defines an inlet hole 35 for entry of the fuel into the valve 27 and has a plurality of radial outlet holes 36 which are uniformly distributed around the axis 29 and are formed through the sleeve 30a transversely with respect to the axis 29 so as to allow the fuel fed through the hole 35 to come out of said sleeve 30a.
The valve 27 further comprises a closing member 37 which is mounted inside the sleeve 30a coaxially with the axis 29 and is movable axially between a closed position (Figure 2a), in which the hole 35 is hydraulically separated from the holes 36, and an open position (Figure 2a), in which the hole 35 is hydraulically connected to said holes 36.
The closing member 37 is displaced, and normally kept, in its closed position by a spring 38 mounted inside a housing chamber 39 formed in the sleeve 30a and axially limited by the closing member 37 and by an end-of-travel ball 40 which is axially locked inside said sleeve 30a.
The closing member 37 is displaced from its closed position into its open position against the action of the spring 38 by the fuel fed through the hole 35.
The fuel is fed through the holes 36 into an annular receiving chamber 41 which is defined between the pump body 8 and the valve body 28 and is connected to the free end of the sleeve 30b by a plurality of through-channels 42 parallel to the axis 29.
The channels 42 are uniformly distributed around the axis 29 and are formed, in the case in question, on the inner lateral surface 34 of the sleeve 30b.
Obviously, according to variants not shown, the channels 42 may be formed on the outer lateral surface 33 of the sleeve 30a or partly on the surface 33 and partly on the surface 34.
Since the valve body 28 comprises the two sleeves 30a and 30b, the pumping unit 1 offers a number of advantages mainly arising from the fact that the formation of the through-channels 42 on the surface 33 and/or on the surface 34 is relatively simple and low-cost.

Claims

Pumping unit for feeding fuel, preferably diesel fuel, from a storage tank (2) to an internal combustion engine (3), the pumping unit comprising a high-pressure pump (6) for feeding the fuel to the internal combustion engine (3); a pre-feed pump (7) for feeding the fuel from the storage tank (2) to the high-pressure pump (6); and a hydraulic circuit (14) comprising, in turn, a first branch (15) for connecting together the storage tank (2) and the pre-feed pump (7), a second branch (16) for connecting together the pre-feed pump (7) and the high-pressure pump (6), a third branch (18) for connecting together the high-pressure pump (6) and the internal combustion engine (3), a fourth branch (22) for connecting together the second branch (16) and the storage tank (2), and an overflow valve (27), which is mounted along the fourth branch (22) and comprises a valve body (28) having a longitudinal axis (29) and a closing member (37) movable along the valve body (28) between a position for opening and a position for closing said overflow valve (27); and being characterized in that the valve body (28) comprises a first sleeve (30a) and a second sleeve (30b) which are coaxial with each other and with the said longitudinal axis (29) and are coupled together angularly and axially fixed together.
Pumping unit according to Claim 1, wherein the said first and second sleeves (30a, 30b) are locked by means of interference inside one another.
Pumping unit according to Claim 1 or 2, wherein each sleeve (30a, 30b) has a free end projecting axially from the other sleeve (30a, 30b).
Pumping unit according to any one of the preceding claims, wherein each sleeve (30a, 30b) comprises a coupling portion (32) for joining together with the coupling portion (32) of the other sleeve (30a, 30b); each coupling portion being limited by an associated lateral surface (33, 34) substantially coaxial with the longitudinal axis (29).
Pumping unit according to Claim 4, wherein the valve body (28) has a plurality of through-channels (42) for the fuel; each through-channel (42) being formed in at least one of the said lateral surfaces (33, 34).
Pumping unit according to Claim 5, wherein the through-channels (42) extend parallel to the longitudinal axis (29).
Pumping unit according to any one of the preceding claims, wherein the valve body (28) is screwed into a pump body (8) of the high-pressure pump (6).
Pumping unit according to any one of Claims 1 to 6, wherein the valve body (28) is locked by means of interference inside a pump body (8) of the high-pressure pump (6).
Pumping unit according to any one of the preceding claims, wherein each sleeve (30a, 30b) is made of a material different from the material of the other sleeve (30a, 30b).
Pumping unit according to any one of the preceding claims, wherein the first sleeve (30a) is slidably engaged by the closing member (37) and the second sleeve (30b) is joined together with a pump body (8) of the high-pressure pump (6).
Pumping unit according to Claim 10, wherein the first sleeve (30a) is made of a material having a hardness greater than the hardness of the material of the second sleeve (30b).
Pumping unit according to Claim 10 or 11, wherein the first sleeve (30a) has an inlet (35) for introducing the fuel into the first sleeve (30a) and at least one outlet (36) for drawing the fuel from said first sleeve (30a); the closing member (37) being configured to close the outlets (36) following displacement thereof into the closed position and to open the outlets (36) following a displacement thereof into the open position.