WO2010025982A1 - Pump unit for feeding fuel to an internal-combustion engine - Google Patents

Pump unit for feeding fuel to an internal-combustion engine Download PDF

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Publication number
WO2010025982A1
WO2010025982A1 PCT/EP2009/058976 EP2009058976W WO2010025982A1 WO 2010025982 A1 WO2010025982 A1 WO 2010025982A1 EP 2009058976 W EP2009058976 W EP 2009058976W WO 2010025982 A1 WO2010025982 A1 WO 2010025982A1
Authority
WO
WIPO (PCT)
Prior art keywords
pump
side wall
fuel
chamber
pressure
Prior art date
Application number
PCT/EP2009/058976
Other languages
French (fr)
Inventor
Alessandro De Luca
Gaetano Riglietti
Ruggiero Gissi
Pasquale Cavallera
Original Assignee
Robert Bosch Gmbh
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Robert Bosch Gmbh filed Critical Robert Bosch Gmbh
Publication of WO2010025982A1 publication Critical patent/WO2010025982A1/en

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M59/00—Pumps specially adapted for fuel-injection and not provided for in groups F02M39/00 -F02M57/00, e.g. rotary cylinder-block type of pumps
    • F02M59/02—Pumps specially adapted for fuel-injection and not provided for in groups F02M39/00 -F02M57/00, e.g. rotary cylinder-block type of pumps of reciprocating-piston or reciprocating-cylinder type
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M59/00—Pumps specially adapted for fuel-injection and not provided for in groups F02M39/00 -F02M57/00, e.g. rotary cylinder-block type of pumps
    • F02M59/02—Pumps specially adapted for fuel-injection and not provided for in groups F02M39/00 -F02M57/00, e.g. rotary cylinder-block type of pumps of reciprocating-piston or reciprocating-cylinder type
    • F02M59/10—Pumps specially adapted for fuel-injection and not provided for in groups F02M39/00 -F02M57/00, e.g. rotary cylinder-block type of pumps of reciprocating-piston or reciprocating-cylinder type characterised by the piston-drive
    • F02M59/102—Mechanical drive, e.g. tappets or cams
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M59/00—Pumps specially adapted for fuel-injection and not provided for in groups F02M39/00 -F02M57/00, e.g. rotary cylinder-block type of pumps
    • F02M59/12—Pumps specially adapted for fuel-injection and not provided for in groups F02M39/00 -F02M57/00, e.g. rotary cylinder-block type of pumps having other positive-displacement pumping elements, e.g. rotary
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M59/00—Pumps specially adapted for fuel-injection and not provided for in groups F02M39/00 -F02M57/00, e.g. rotary cylinder-block type of pumps
    • F02M59/44—Details, components parts, or accessories not provided for in, or of interest apart from, the apparatus of groups F02M59/02 - F02M59/42; Pumps having transducers, e.g. to measure displacement of pump rack or piston
    • F02M59/445—Selection of particular materials
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M63/00—Other fuel-injection apparatus having pertinent characteristics not provided for in groups F02M39/00 - F02M57/00 or F02M67/00; Details, component parts, or accessories of fuel-injection apparatus, not provided for in, or of interest apart from, the apparatus of groups F02M39/00 - F02M61/00 or F02M67/00; Combination of fuel pump with other devices, e.g. lubricating oil pump
    • F02M63/02—Fuel-injection apparatus having several injectors fed by a common pumping element, or having several pumping elements feeding a common injector; Fuel-injection apparatus having provisions for cutting-out pumps, pumping elements, or injectors; Fuel-injection apparatus having provisions for variably interconnecting pumping elements and injectors alternatively
    • F02M63/0225—Fuel-injection apparatus having a common rail feeding several injectors ; Means for varying pressure in common rails; Pumps feeding common rails
    • F02M63/0265—Pumps feeding common rails
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M2200/00—Details of fuel-injection apparatus, not otherwise provided for
    • F02M2200/16—Sealing of fuel injection apparatus not otherwise provided for
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M37/00—Apparatus or systems for feeding liquid fuel from storage containers to carburettors or fuel-injection apparatus; Arrangements for purifying liquid fuel specially adapted for, or arranged on, internal-combustion engines
    • F02M37/04—Feeding by means of driven pumps
    • F02M37/041—Arrangements for driving gear-type pumps
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M37/00—Apparatus or systems for feeding liquid fuel from storage containers to carburettors or fuel-injection apparatus; Arrangements for purifying liquid fuel specially adapted for, or arranged on, internal-combustion engines
    • F02M37/04—Feeding by means of driven pumps
    • F02M37/043—Arrangements for driving reciprocating piston-type pumps
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M59/00—Pumps specially adapted for fuel-injection and not provided for in groups F02M39/00 -F02M57/00, e.g. rotary cylinder-block type of pumps
    • F02M59/02—Pumps specially adapted for fuel-injection and not provided for in groups F02M39/00 -F02M57/00, e.g. rotary cylinder-block type of pumps of reciprocating-piston or reciprocating-cylinder type
    • F02M59/04—Pumps specially adapted for fuel-injection and not provided for in groups F02M39/00 -F02M57/00, e.g. rotary cylinder-block type of pumps of reciprocating-piston or reciprocating-cylinder type characterised by special arrangement of cylinders with respect to piston-driving shaft, e.g. arranged parallel to that shaft or swash-plate type pumps
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M59/00—Pumps specially adapted for fuel-injection and not provided for in groups F02M39/00 -F02M57/00, e.g. rotary cylinder-block type of pumps
    • F02M59/02—Pumps specially adapted for fuel-injection and not provided for in groups F02M39/00 -F02M57/00, e.g. rotary cylinder-block type of pumps of reciprocating-piston or reciprocating-cylinder type
    • F02M59/08—Pumps specially adapted for fuel-injection and not provided for in groups F02M39/00 -F02M57/00, e.g. rotary cylinder-block type of pumps of reciprocating-piston or reciprocating-cylinder type characterised by two or more pumping elements with conjoint outlet or several pumping elements feeding one engine cylinder

Definitions

  • the present invention relates to a pump unit for feeding fuel to an internal- combustion engine.
  • the pump unit comprises a high-pressure pump and a pre-feed pump for feeding the fuel to the high-pressure pump.
  • the high-pressure pump is a piston pump which comprises a first pump body with a side wall delimiting a first chamber, and a drive shaft housed partly inside the chamber and extending through the side wall outside of the first pump body.
  • the pre-feed pump is generally a gear pump which comprises a gear keyed onto the drive shaft and a second pump body which defines a second chamber for containing the gear.
  • part of the fuel fed by the pre-feed pump to the high-pressure pump passes through the first chamber so as to lubricate and cool the parts in relative movement contained therein.
  • the pump units of the known type have relatively small dimensions compared to the delivery and the pressure head which they can provide, many car manufacturers require a further reduction in the size of the pump units, while still requiring an increase in their performance.
  • One object of the present invention is to provide a high-pressure pump unit for feeding fuel to an internal-combustion engine, able to minimize the drawbacks of the prior art. Moreover, one object of the present invention is to provide a pump unit which reduces the overall dimensions of the high-pressure pump.
  • a further object of the present invention consists in providing a pump unit which simplifies assembly of the pump unit and which, at the same time, helps reduce the costs of the pump unit.
  • a pump unit for feeding fuel to an internal- combustion engine comprising a high-pressure pump and a pre-feed pump for feeding the fuel to the high-pressure pump
  • the high- pressure pump comprising a pump body with a side wall delimiting a first chamber able to contain part of the fuel fed by the pre-feed pump, and a drive shaft housed partly inside the first chamber and extending through the side wall outside of the pump body
  • the pre-feed pump being a gear pump which comprises a gear keyed onto the drive shaft and a shell which defines a second chamber for containing the gear and the fuel and which is fixed to the side wall.
  • the pump unit is particularly compact and manageable as well as being easy to store and manufacture.
  • the number of components forming the pump unit is particularly small because the second chamber is delimited, at least partly, by the pump body of the high-pressure pump.
  • the side wall has a hole through which the drive shaft extends, the high-pressure pump comprising a seal which is fixed to the side wall in the region of the hole and is arranged in contact with the drive shaft so as to prevent fuel from passing between the first and second chambers.
  • FIG. 1 is a side elevation view, with parts removed for greater clarity, of a pump unit for feeding fuel to an internal-combustion engine, provided according to the present invention
  • FIG. 1 denotes in its entirety with the reference number 1 a pump unit for feeding fuel, in particular diesel fuel, from a tank to an internal-combustion engine, both of which are not shown in the accompanying figures.
  • the pump unit 1 comprises a high-pressure pump and a pre-feed pump 3 which are joined together.
  • the pre-feed pump 3 has the function of increasing the pressure of the fuel from the ambient pressure to a pressure of between 4 and 7 bar, while the high- pressure pump 2 has the function of increasing the pressure of the fuel from the values of 4 and 7 bar to values higher than 2000 bar.
  • the high-pressure pump 2 is a piston pump, while the pre-feed pump 3 is a gear pump.
  • the high-pressure pump 2 comprises a pump body 4 and a drive shaft 5 which is partly housed inside the pump body 4 and partly extends outside of the pump body 4.
  • the drive shaft 5 comprises an end section 6 able to be coupled to a transmission component connected to the internal-combustion engine (not shown in the accompanying figures) so as to receive the movement from the internal-combustion engine and transmit this movement to the active parts of the high-pressure pump 2 and pre- - A -
  • the drive shaft 5 comprises a further end section 7 which extends outside the pump body 4 in order to drive the pre- feed pump 3.
  • the pump body 4 is formed by at least two parts joined together (not identified in the accompanying figures) and comprises a side wall 8 which helps define a chamber 9 formed inside the pump body 4.
  • the high-pressure pump 2 comprises three pumping members (not shown in the accompanying figures) designed to compress cyclically the fuel to a pressure higher than 2000 bar and convey the compressed fuel along a delivery line (not shown) to a common rail which, in turn, feeds the internal-combustion engine, these not being shown in the accompanying figures.
  • the high-pressure pump 2 comprises, moreover, a drive mechanism which has the function of imparting a reciprocating movement to pumping members and comprises the drive shaft 5, a cam integral with the drive shaft 5, a polygonal ring, a washer or a cup member and a return spring (not shown in the accompanying figures).
  • a drive mechanism which has the function of imparting a reciprocating movement to pumping members and comprises the drive shaft 5, a cam integral with the drive shaft 5, a polygonal ring, a washer or a cup member and a return spring (not shown in the accompanying figures).
  • the drive mechanism is housed inside the chamber 9 and is lubricated by part of the fuel which the pre-feed pump 3 feeds to the high-pressure pump 2. In other words, a part of the fuel fed by the pre-feed pump 3 passes through the chamber 9 so as to lubricate and cool the parts in contact with each other.
  • the chamber 9 is occupied by the drive shaft 5 and by a sliding-friction bearing 10.
  • the bearing 10 is forced along a cylindrical surface 11 of the chamber 9 and supports the drive shaft 5 about an axis Al of rotation.
  • the wall 8 has a hole 12 for allowing the end section 7 to project outside the pump body 4, an inner side 13 and an outer side 14.
  • the wall 8 has an annular seat 15 which is formed along the inner side 13, is arranged around the hole 12 and is able to seat a seal 16.
  • the seal 16 is forced inside the seat 15 of the wall 8 and has a sealing element
  • the sealing element 17 is preferably made of a material comprising polytetrafluoroethylene (PTFE) or, alternatively, fluoropolymers (FPM) or nitrile butadiene rubber (NBR) or acrylic rubber (ACM).
  • PTFE polytetrafluoroethylene
  • FPM fluoropolymers
  • NBR nitrile butadiene rubber
  • ACM acrylic rubber
  • the pre-feed pump 3 comprises a shell 18 which has the function of enclosing the moving parts and the fuel and is fixed to the pump body 4 by means of screws 19 ( Figure 1), a gear 20 keyed onto the end section 7 and gears 21 and
  • the shell 18 has a central protruding part 23, coaxial with the axis Al, which rotationally supports the gear 21.
  • the shell 18 together with the wall 8 defines a chamber 24 which is able to contain the fuel, the end section 7 and the gears 20, 21 and 22.
  • the pre-feed pump 3 feeds the fuel to the high-pressure pump 2 at a pressure of between 4 and 7 bar.
  • the high-pressure pump compresses the fuel to a pressure higher than 2000 bar.
  • Part of the fuel sent by the pre-feed pump 3 to the high-pressure pump 2 instead of being compressed is fed to the chamber 9 in order to lubricate and cool the drive mechanism.
  • the inevitable loss of head along the path between the pre- feed pump 3 and the high-pressure pump 2 determines a pressure gradient between the chamber 24 inside which the fuel is compressed to the pre-feed pressure (4-7 bar) and the chamber 9.
  • the pressure gradient is particularly high upon start-up of the internal-combustion engine. In fact, in this situation the pressure of the fuel increases firstly inside the chamber 24 and then inside the chamber 9.
  • the transitory phase is therefore particularly critical.
  • the seal 16 prevents fluid from passing from the chamber 24 to the chamber 9 or at least limits the fuel leakages and consequently improves the efficiency of the pre-feed pump 3.
  • the wall 8 has a seat 25 which is formed along the outer side 14 and extends around the drive shaft 5.
  • the seal 16 is embedded inside the seat 25 and has the function of ensuring a hydraulic seal between the chamber 24 and the chamber 9.
  • the side wall comprises two annular seats which are formed along the inner side and along the outer side, respectively, and two seals both fixed to the side wall and forced inside the respective annular seats.
  • the seal is manufactured with forms and using materials different from those shown in the accompanying figures and described.
  • the solution described is particularly advantageous because it allows the overall dimensions of the pump unit to be limited without adversely affecting the performance of the pump unit.
  • the pre-fed pump is connected to the high-pressure pump directly without any connecting flange and the seal is supported directly by the side wall of the high-pressure pump.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Fuel-Injection Apparatus (AREA)

Abstract

A pump unit (1) for feeding fuel to an internal-combustion engine is formed by a high-pressure pump (2) and a pre-feed pump (3) for feeding the fuel to the high-pressure pump (2); the high-pressure pump (2) is provided with a pump body (4) having a side wall (8) delimiting a first chamber (9) able to contain part of the fuel fed by the pre-feed pump (3) and with a drive shaft (5) housed partly inside the first chamber (9) and extending through the side wall (8) outside of the pump body (4), the pre-feed pump (3) being a gear pump which comprises a gear (20) keyed onto the drive shaft (5) and a shell (18) which defines a second chamber (24) for containing the gear (20) and the fuel and which is fixed to the side wall (8).

Description

Description
Title
PUMP UNIT FOR FEEDING FU EL TO AN INTERNAL-COMBUSTION ENGINE
The present invention relates to a pump unit for feeding fuel to an internal- combustion engine.
In particular, the pump unit comprises a high-pressure pump and a pre-feed pump for feeding the fuel to the high-pressure pump.
The high-pressure pump is a piston pump which comprises a first pump body with a side wall delimiting a first chamber, and a drive shaft housed partly inside the chamber and extending through the side wall outside of the first pump body.
The pre-feed pump is generally a gear pump which comprises a gear keyed onto the drive shaft and a second pump body which defines a second chamber for containing the gear.
During operation, part of the fuel fed by the pre-feed pump to the high-pressure pump passes through the first chamber so as to lubricate and cool the parts in relative movement contained therein.
Although the pump units of the known type have relatively small dimensions compared to the delivery and the pressure head which they can provide, many car manufacturers require a further reduction in the size of the pump units, while still requiring an increase in their performance.
One object of the present invention is to provide a high-pressure pump unit for feeding fuel to an internal-combustion engine, able to minimize the drawbacks of the prior art. Moreover, one object of the present invention is to provide a pump unit which reduces the overall dimensions of the high-pressure pump.
A further object of the present invention consists in providing a pump unit which simplifies assembly of the pump unit and which, at the same time, helps reduce the costs of the pump unit.
In accordance with these objects a pump unit for feeding fuel to an internal- combustion engine is provided, the pump unit comprising a high-pressure pump and a pre-feed pump for feeding the fuel to the high-pressure pump, the high- pressure pump comprising a pump body with a side wall delimiting a first chamber able to contain part of the fuel fed by the pre-feed pump, and a drive shaft housed partly inside the first chamber and extending through the side wall outside of the pump body, the pre-feed pump being a gear pump which comprises a gear keyed onto the drive shaft and a shell which defines a second chamber for containing the gear and the fuel and which is fixed to the side wall.
In this way the pump unit is particularly compact and manageable as well as being easy to store and manufacture.
Moreover, the number of components forming the pump unit is particularly small because the second chamber is delimited, at least partly, by the pump body of the high-pressure pump.
According to a particular embodiment of the present invention the side wall has a hole through which the drive shaft extends, the high-pressure pump comprising a seal which is fixed to the side wall in the region of the hole and is arranged in contact with the drive shaft so as to prevent fuel from passing between the first and second chambers.
With this solution it is possible to limit the leakages and therefore the efficiency of the pre-feed pump in a simple and low-cost manner. Further characteristic features and advantages of the present invention will become clear from the following description of non-limiting examples of embodiment thereof with reference to the figures of the accompanying drawings in which: - Figure 1 is a side elevation view, with parts removed for greater clarity, of a pump unit for feeding fuel to an internal-combustion engine, provided according to the present invention;
- Figure 2 is a cross-sectional view, on a larger scale and with parts removed for greater clarity, of a detail of the pump unit shown in Figure 1; and - Figure 3 is a cross-sectional view, on a larger scale and with parts removed for greater clarity, of a detail of a pump unit in accordance with an alternative embodiment of the present invention.
Figure 1 denotes in its entirety with the reference number 1 a pump unit for feeding fuel, in particular diesel fuel, from a tank to an internal-combustion engine, both of which are not shown in the accompanying figures. The pump unit 1 comprises a high-pressure pump and a pre-feed pump 3 which are joined together.
The pre-feed pump 3 has the function of increasing the pressure of the fuel from the ambient pressure to a pressure of between 4 and 7 bar, while the high- pressure pump 2 has the function of increasing the pressure of the fuel from the values of 4 and 7 bar to values higher than 2000 bar.
The high-pressure pump 2 is a piston pump, while the pre-feed pump 3 is a gear pump.
In greater detail, the high-pressure pump 2 comprises a pump body 4 and a drive shaft 5 which is partly housed inside the pump body 4 and partly extends outside of the pump body 4. In the example illustrated in Figure 1, the drive shaft 5 comprises an end section 6 able to be coupled to a transmission component connected to the internal-combustion engine (not shown in the accompanying figures) so as to receive the movement from the internal-combustion engine and transmit this movement to the active parts of the high-pressure pump 2 and pre- - A -
feed pump 3. With reference to Figure 2, the drive shaft 5 comprises a further end section 7 which extends outside the pump body 4 in order to drive the pre- feed pump 3.
The pump body 4 is formed by at least two parts joined together (not identified in the accompanying figures) and comprises a side wall 8 which helps define a chamber 9 formed inside the pump body 4.
In general, the high-pressure pump 2 comprises three pumping members (not shown in the accompanying figures) designed to compress cyclically the fuel to a pressure higher than 2000 bar and convey the compressed fuel along a delivery line (not shown) to a common rail which, in turn, feeds the internal-combustion engine, these not being shown in the accompanying figures.
The high-pressure pump 2 comprises, moreover, a drive mechanism which has the function of imparting a reciprocating movement to pumping members and comprises the drive shaft 5, a cam integral with the drive shaft 5, a polygonal ring, a washer or a cup member and a return spring (not shown in the accompanying figures).
The drive mechanism is housed inside the chamber 9 and is lubricated by part of the fuel which the pre-feed pump 3 feeds to the high-pressure pump 2. In other words, a part of the fuel fed by the pre-feed pump 3 passes through the chamber 9 so as to lubricate and cool the parts in contact with each other.
With reference to Figure 2, the chamber 9 is occupied by the drive shaft 5 and by a sliding-friction bearing 10. The bearing 10 is forced along a cylindrical surface 11 of the chamber 9 and supports the drive shaft 5 about an axis Al of rotation.
The wall 8 has a hole 12 for allowing the end section 7 to project outside the pump body 4, an inner side 13 and an outer side 14. In the example illustrated in Figure 2, the wall 8 has an annular seat 15 which is formed along the inner side 13, is arranged around the hole 12 and is able to seat a seal 16.
The seal 16 is forced inside the seat 15 of the wall 8 and has a sealing element
17 arranged in contact with the drive shaft 5.
The sealing element 17 is preferably made of a material comprising polytetrafluoroethylene (PTFE) or, alternatively, fluoropolymers (FPM) or nitrile butadiene rubber (NBR) or acrylic rubber (ACM). The geometrical form of the seal may be different from those forms shown in Figures 2 and 3.
The pre-feed pump 3 comprises a shell 18 which has the function of enclosing the moving parts and the fuel and is fixed to the pump body 4 by means of screws 19 (Figure 1), a gear 20 keyed onto the end section 7 and gears 21 and
22.
The shell 18 has a central protruding part 23, coaxial with the axis Al, which rotationally supports the gear 21.
The shell 18 together with the wall 8 defines a chamber 24 which is able to contain the fuel, the end section 7 and the gears 20, 21 and 22.
During use, the pre-feed pump 3 feeds the fuel to the high-pressure pump 2 at a pressure of between 4 and 7 bar. The high-pressure pump compresses the fuel to a pressure higher than 2000 bar.
Part of the fuel sent by the pre-feed pump 3 to the high-pressure pump 2 instead of being compressed is fed to the chamber 9 in order to lubricate and cool the drive mechanism. The inevitable loss of head along the path between the pre- feed pump 3 and the high-pressure pump 2 determines a pressure gradient between the chamber 24 inside which the fuel is compressed to the pre-feed pressure (4-7 bar) and the chamber 9. The pressure gradient is particularly high upon start-up of the internal-combustion engine. In fact, in this situation the pressure of the fuel increases firstly inside the chamber 24 and then inside the chamber 9. The transitory phase is therefore particularly critical. The seal 16 prevents fluid from passing from the chamber 24 to the chamber 9 or at least limits the fuel leakages and consequently improves the efficiency of the pre-feed pump 3.
With reference to the alternative embodiment shown Figure 3, the wall 8 has a seat 25 which is formed along the outer side 14 and extends around the drive shaft 5. The seal 16 is embedded inside the seat 25 and has the function of ensuring a hydraulic seal between the chamber 24 and the chamber 9.
According to a further alternative embodiment not shown in the accompanying figures, the side wall comprises two annular seats which are formed along the inner side and along the outer side, respectively, and two seals both fixed to the side wall and forced inside the respective annular seats.
According to a variant, the seal is manufactured with forms and using materials different from those shown in the accompanying figures and described.
The solution described is particularly advantageous because it allows the overall dimensions of the pump unit to be limited without adversely affecting the performance of the pump unit. In particular, the pre-fed pump is connected to the high-pressure pump directly without any connecting flange and the seal is supported directly by the side wall of the high-pressure pump.
Finally, it is clear that the pump unit described here may be subject to further modifications and variations without departing from the scope of the accompanying claims.

Claims

Claims
1. A pump assembly for feeding fuel to an internal combustion engine; the pump assembly (1) comprising a high-pressure pump (2) and a pre-feed pump (3) for feeding the fuel to the high-pressure pump (2); the high-pressure pump (2) comprising a pump body (4) having a side wall (8) defining a first chamber (9) for containing part of the fuel fed from the pre-feed pump (3); an actuating shaft (5) housed partly in the first chamber (9) and extending out of the pump body (4) through the side wall (8); the pre-feed pump (3) being a gear pump comprising a gear (20) fitted to the actuating shaft (5) and a shell (18), which defines a second chamber (24) for containing the gear (20) and the fuel, and is fixed to the side wall (8).
2. A pump assembly as claimed in claim 1, wherein side wall (8) has a hole (12) through which the actuating shaft (5) extends; the high-pressure pump (2) comprising a seal (16) fixed to the hole (12) in the side wall (8) and contacting the actuating shaft (5) to prevent fuel passage between the first and second chambers (9, 24).
3. A pump assembly as claimed in claim 2, wherein the side wall (8) has an inner face (13), an outer face (14), and an annular first seat (15) formed along the inner face (13); said seal (16) being interference-fitted inside said first seat (15).
4. A pump assembly as claimed in claim 2 o 3, wherein the side wall (8) has an inner face (13), an outer face (14), and an annular second seat (25) formed along the outer face (14); said seal (16) being interference-fitted inside said second seat (25).
5. A pump assembly as claimed in any one of the foregoing claims, wherein said seal (16) comprises a sealing member (17) made of a material comprising polytetrafluoroethylene (PTFE) or fluoropolymers (FPM) or nitrile butadiene rubber (NBR) or acrylic rubber (ACM).
6. A pump assembly as claimed in any one of the foregoing claims, wherein the shell (18) is fixed directly to the pump body (4).
7. A pump assembly as claimed in any one of the foregoing claims, wherein the shell (18) is positioned directly contacting the pump body (4) along the side wall (8).
8. A pump assembly as claimed in any one of the foregoing claims, wherein the side wall (8) has an inner face (13) delimiting the first chamber (9) and an outer face (14) delimiting the second chamber (24).
PCT/EP2009/058976 2008-09-03 2009-07-14 Pump unit for feeding fuel to an internal-combustion engine WO2010025982A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
ITMI2008A001575A IT1391563B1 (en) 2008-09-03 2008-09-03 PUMP UNIT FOR FUEL SUPPLY TO AN INTERNAL COMBUSTION ENGINE
ITMI2008A001575 2008-09-03

Publications (1)

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WO2010025982A1 true WO2010025982A1 (en) 2010-03-11

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PCT/EP2009/058976 WO2010025982A1 (en) 2008-09-03 2009-07-14 Pump unit for feeding fuel to an internal-combustion engine

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IT (1) IT1391563B1 (en)
WO (1) WO2010025982A1 (en)

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20030108443A1 (en) * 2001-12-12 2003-06-12 Masashi Suzuki Fuel injection pump
JP2003184704A (en) * 2001-12-12 2003-07-03 Denso Corp Fuel injection pump
EP1609984A1 (en) * 1998-12-25 2005-12-28 Denso Corporation Fuel injection pump
DE102005050613A1 (en) * 2004-10-22 2006-04-27 Denso Corp., Kariya Fuel injection pump for internal combustion engine, has housing with reception chamber receiving trunk piston and trunk piston drive unit, and oil seal sealing between drive shaft and housing using pressure of fuel provided from chamber
US20080178845A1 (en) * 2007-01-31 2008-07-31 Denso Corporation Fuel injection pump

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1609984A1 (en) * 1998-12-25 2005-12-28 Denso Corporation Fuel injection pump
US20030108443A1 (en) * 2001-12-12 2003-06-12 Masashi Suzuki Fuel injection pump
JP2003184704A (en) * 2001-12-12 2003-07-03 Denso Corp Fuel injection pump
DE102005050613A1 (en) * 2004-10-22 2006-04-27 Denso Corp., Kariya Fuel injection pump for internal combustion engine, has housing with reception chamber receiving trunk piston and trunk piston drive unit, and oil seal sealing between drive shaft and housing using pressure of fuel provided from chamber
US20080178845A1 (en) * 2007-01-31 2008-07-31 Denso Corporation Fuel injection pump

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ITMI20081575A1 (en) 2010-03-04
IT1391563B1 (en) 2012-01-11

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