EP3601777A1

EP3601777A1 - A high pressure fuel pump assembly for an internal combustion piston engine

Info

Publication number: EP3601777A1
Application number: EP17716564.4A
Authority: EP
Inventors: Ossi LAAKSO; Antti VUOHIJOKI; Kjell Eklund; David C. Jay
Original assignee: Wartsila Finland Oy
Current assignee: Wartsila Finland Oy
Priority date: 2017-03-29
Filing date: 2017-03-29
Publication date: 2020-02-05
Anticipated expiration: 2037-03-29
Also published as: CN110691904A; CN110691904B; KR102239680B1; EP3601777B1; WO2018178501A1; KR20190124810A

Abstract

Invention relates to a high pressure fuel pump assembly (100) comprising a number of piston pump units (10) driven by a drive shaft (110) of the pump assembly (100), a drive shaft lubrication system (114) and pump unit lubrication system (116), and at least one inlet (115) for pressurized lubricant, where the pump assembly (100) is provided with a first collector conduit (120) configured to receive lubricant from the pump unit lubrication system (116) and a second collector conduit (122) configured to receive leak fuel from the piston pump units, and a third collector conduit configured to receive fuel mist from the piston pump units.

Description

A high pressure fuel pump assembly for an internal combustion piston engine

Technical field [001 ] The invention relates to a high pressure fuel pump assembly for an internal combustion piston engine according to a preamble of claim 1 .

Background art

[002] Internal combustion piston engines need to be provided with one or more fuel pumps. Particularly the fuel injection in so called common rail systems into the combustion chambers of the engine requires capability of pumping the fuel into high pressure of even above 250 MPa. Since the pumps are typically lubricated by the lubrication medium of the engine the presence of both the fuel and the lubrication medium in the pump may call for special attention particularly re- lating to preventing or minimizing the mixing of the fuel and the lubricant in the pump.

[003] Document EP 0976926 B1 discloses an integrated pump and tappet unit for supplying fuel to an internal combustion engine, such as a large diesel engine, the unit comprising a body part enclosing a tappet member, whose axial move- ment is governed by movement of a cam surface provided on a cam shaft or the like, and a piston member operationally connected to the tappet member and which is arranged to pump fuel under high pressure from a fuel chamber disposed within the body part. The body part is a single member housing both said tappet member and said fuel chamber and the tappet member and the piston member are connected to each other by means of a tappet arm, which is sealed to a flange member fixed to the body part, so that fuel from the fuel chamber is prevented from coming into contact with the tappet member.

[004] Document DE 102015002304 A1 discloses a high pressure fuel pump. Document is silent about the possible leakage of the fuel into the lubrication me- dium but shows a lubrication system of the pump. The pump comprises a pump housing having an inner space, a pump plunger with a guide surface, which is guided in the interior space on the pump housing, wherein the interior space and the pump plunger limits a spring chamber of the high-pressure fuel pump, a lubricant line which opens into the interior space against the guide surface of the plunger, a vent pipe, by means of which the lubricant can be discharged from the spring chamber.

[005] Document DE102008042067 A1 discloses a pump which has a drive shaft provided with an eccentric cam, and a piston accommodated in a cylinder. The document discloses circular membrane seals used for separating the fuel and lubrication systems from each other.

[006] Document DE102006059333 A1 discloses a fuel pump comprising at least one wiper element integrated in the pump piston for removing leakage fuel collecting between the pump cylinder and the pump piston from the cylinder wall. The wiper element is a scraper ring that removes leakage fuel accumulating on the wall of the pump cylinder and guides it into at least one leakage groove.

[007] US7308849 defines a work chamber and driven at least indirectly by a drive shaft in a reciprocating motion, counter to the force of a restoring spring. The pump piston is braced on the drive shaft at least indirectly via a sleeve like tappet, and the restoring spring engages at least the pump piston. A support element in the tappet braces the pump piston toward the drive shaft and is braced at least indirectly on the drive shaft. The restoring spring, via a spring plate, engages the pump piston and the tappet. The spring plate is elastically deformable in the direction of motion of the pump piston in such a way that as a result of its elastic deformation, deviations in the position of its contact faces on the pump piston and on the tappet are compensated for.

[008] WO201 1 160908 A1 discloses a pump which comprises at least one pump element which has a pump piston that is at least indirectly driven in a stroke movement by a drive shaft. A plunger having a plunger body is arranged between the drive shaft and the pump piston and is movably guided in a receiving device in the direction of the stroke movement of the pump piston and is supported on the drive shaft by means of a support element. Lubricant is supplied to the receiving device via a supply line and lubricant is conducted out of the receiving device via a discharge line into the plunger body to the support element. An annular gap filter is provided between the plunger body and the receiving device and is arranged between the supply line for supplying lubricant to the receiving device and the discharge line for discharging lubricant into the plunger body.

[009] An object of the invention is to provide a high pressure fuel pump assembly in which the performance is considerably improved compared to the prior art solutions.

Disclosure of the Invention [0010] The objects of the invention can be met substantially as is disclosed in the independent claim and in the other claims describing more details of different embodiments of the invention.

[001 1 ] A high pressure fuel pump assembly for an internal combustion piston engine according to an embodiment of the invention comprises a number of pis- ton pump units driven by a drive shaft of the pump assembly, a drive shaft lubrication system and pump unit lubrication system, and at least one inlet for pressurized lubricant. The pump assembly is provided with a first collector conduit configured to receive lubricant from the pump unit lubrication system and a second collector conduit configured to receive leak fuel from the piston pump units, and a third collector conduit configured to receive fuel mist from the piston pump units.

[0012] According to an embodiment of the invention the first collector conduit, the second collector conduit and a third collector conduit are arranged in a fluid collector block which is releasably attached to the pump units. [0013] According to an embodiment of the invention the first collector conduit is configured to receive lubricant from the drive shaft lubrication system and from the pump unit lubrication system.

[0014] According to an embodiment of the invention the first, the second and the third collector conduits are arranged horizontally at lower position in respect to pump units such that there is a substantially continuous sloping flow passage arranged from the pump unit to said conduits.

[0015] According to an embodiment of the invention the first collector conduit is arranged vertically below an outlet of the drive shaft lubrication system, the sec- ond collector conduit is arranged vertically below an outlet of the piston pump units and the third collector conduit is arranged vertically below an outlet of the piston pump unit.

[0016] According to an embodiment of the invention the assembly comprises a number of piston pump units in-line. [0017] According to an embodiment of the invention the assembly comprises a number of piston pump units in two banks of pistons in v-arrangement and that the fluid collector block is arranged between the two banks.

[0018] According to an embodiment of the invention the fluid collector block is provided with a number of fluid interfaces and the piston pump units are provided with corresponding fluid interface, the fluid interfaces mating with each other such that a sealed fluid communication between the fluid collector block and the piston pump unit is formed when the interfaces are coupled.

[0019] According to an embodiment of the invention the fluid interfaces of the piston pump units are directed to open into direction between the banks and the fluid collector block is provided with a number of fluid interfaces in a two rows such that the fluid interfaces are simultaneously connected to the respective fluid interfaces of the bank of piston pumps.

[0020] According to an embodiment of the invention the fluid collector block is arranged below the drive shaft. [0021 ] The present invention is suitable for use as a high pressure pump unit in a common rail fuel system, i.e. it may be called as a high pressure common rail pump assembly.

[0022] The exemplary embodiments of the invention presented in this patent application are not to be interpreted to pose limitations to the applicability of the appended claims. The verb "to comprise" is used in this patent application as an open limitation that does not exclude the existence of also unrecited features. The features recited in depending claims are mutually freely combinable unless otherwise explicitly stated. The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims.

Brief Description of Drawings

[0023] In the following, the invention will be described with reference to the accompanying exemplary, schematic drawings, in which

Figure 1 illustrates a fuel pump unit according to an embodiment of the invention, and

Figure 2 illustrates a fuel pump assembly according to an embodiment of the invention.

Detailed Description of Drawings [0024] Figure 1 depicts schematically a fuel pump 10 configured to supply fuel to an internal combustion piston engine. More particularly the pump is a high pressure pump configured to deliver fuel at a pressure of above 200 MPa. The pump is intended to be used in connection with the high pressure fuel pump assembly as shown in the Figure 2 and therefore it is presented in a position to the position of the pump assembly. The pump 10 is provided with a supply rail 12 and a high pressure rail 14 which are both in connection with a first pump chamber 16 arranged to a body 18 of the pump 10. The body 18 comprising the pump chamber 16 may also be referred to as a barrel of the pump 10. The supply rail 12 is connected to a source of fuel for use in the engine. The high pressure rail 14 contains pressurized fuel for injecting into combustion chambers of the engine. The supply rail 12 is connected to the pump chamber 16 via an intake conduit 20. The high pressure rail is connected to the pump chamber 16 via an outlet conduit 22. The intake conduit 20 is provided with a one-way valve 24 configured to allow fuel to flow only from the supply rail 12 to the pump chamber 16. Re- spectively, the outlet conduit 22 is provided with a one-way valve 26 configure to allow fuel to flow only from the pump chamber 16 to the high pressure rail 14. In the embodiment shown in the figure 1 the supply rail 12 and the high pressure rail 14 are integrated into the body 18 but it is conceivable that the rails may be external to the body 18. [0025] The pump 10 is also provided with a piston member 28 which is arranged into a cylindrical space 30 arranged into the body 18. The cylindrical space 30 has a central axis 32 and the cylindrical space 30 is substantially rotationally symmetrical in respect to the central axis 32. Therefore the piston member 28 is also rotationally symmetrical in respect to the central axis 32. The outer form of the body may be designed according to the needs. The piston member 28 is arranged into the space in reciprocatable manner. The piston member 28 has a first end 28' which borders the cylindrical space 30 at an end thereof forming the first pumping chamber 16. The piston has also a second end 28" opposite to the first end 28'. The piston member 28 is configured to reciprocate in the space 30 provided for the piston member 28 and pump the fuel. This way the reciprocating piston member together with the one-way valves 24, 26 provides the pumping effect of the fuel pump.

[0026] The cylindrical space 30 comprises a first space section 30' which has a first diameter D1. The piston member 28 is at least partly within the first space section 30'. In the first space section 30' the wall of the space section and the wall of the piston member 28 are arranged against each other providing a first sealing gap 34 between the walls, which also guides the piston member 28 in the body 18. Additionally the wall of the first space section guides the piston member in the body 18 while it reciprocates in the space 30. The piston member 28 com- prises a first portion 28' which is arranged into the first space section 30' and has a diameter substantially same as the first diameter such that a desired guidance and sealing is provided.

[0027] At one end of body 18 the cylindrical space 30 comprises a second space section 30" which has a second diameter D2, being greater than the first diameter D1 . The second space section 30" is on same central axis as the first space section 30'. The piston member 28 comprises a second portion 28" which is arranged in the second space section 30" such that a desired guidance and sealing is provided. In the second space section 30" the wall of the second space section and the wall of the piston member 28 are arranged against each other providing a second sealing gap 35 between the walls, respectively. Additionally the wall of the second space section guides the piston member at its second portion in the body 18 while the piston member reciprocates in the space. The piston member 28 is advantageously an assembly of several parts.

[0028] There is a second pump chamber 16' arranged to a body 18 of the pump 10. More particularly the second pump chamber 16' is arranged in connection with the second space section 30" such that second pump chamber 16' is configured to use empty space of the second space section 30" as the pump cham- ber. The piston member 28 is arranged to border both the first and the second pump chamber 16, 16'.

[0029] The piston member 28 and the first and the second pump chambers 16, 16' are configured in the pump shown in the figure 1 such that volumes of the first and the second pump chambers are changing same way i.e. either increas- ing or decreasing, during the piston member is moving to one direction.

[0030] As mentioned above, in the first space section 30' the wall of the space section and the wall of the piston member 28 are arranged against each other providing the first sealing gap 34 between the walls. The first sealing gap 34 separates the first pump chamber 16 and the second pump chamber 16' and it is of annular form. Since the first pump chamber 16 operates as a high pressure pump configured to deliver fuel at a pressure at above 200 MPa the fuel in the first pump chamber tends to flow into the first sealing gap 34 and further to flow through the sealing gap 34. The first sealing gap 34 between the pump chambers 16, 16' is provided with means to collect fuel material flown from the first pump chamber 16 into the first sealing gap 34. Such a means may comprise a fuel scraper ring 68 or alike arranged in a groove in the wall of the first space section. Additionally such a means may comprise a annular space 67 closer to the first pump chamber 16 provided with a conduit to lead the fuel material to further processing. Since the second pump chamber 16' is within the second space sec- tion 30" they may be commonly referred to in the following.

[0031 ] The pump 10 is provided with means for transferring fuel material away from the second pump chamber 16'. Therefore firstly the pump 10 is provided with a vent flow path 36. The vent flow path 36 runs through the body 18 of the pump and connects the second pump chamber 16 which is formed into the second space section 30" to outside of the body 18. The vent flow path 36 is configured to allow gas admission into the second space section 30", driven by the reciprocating movement of the piston member. The pump 10 is further provided with a discharge flow path 38 connecting the second pump chamber 16' to outside of the body 18 configured to transfer fuel material entered into the second pump chamber 16' or the second space section 30" via the sealing gap 34 away from the second space section 30" i.e. the second pump chamber 16'.

[0032] In the embodiment shown in the figure 1 the vent flow path 36 is provided with a one-way valve 40 which allows gas flow in the vent flow path 36 in the direction towards the second space section 30" and prevent back flow of the fluid from the second pump chamber 16'. The vent flow path 36 has an inlet which opens into the surroundings of the pump 10. Respectively, the discharge flow path 38 is provided with a one-way valve 42 configured to allow flow away from the second space section 30" via the discharge flow path 38. During compression stroke the volume of the second pump chamber 16" is reduced and due to that it is pressurized. Gases and liquids within the second pump chamber 16" are forced out from the second pump chamber 16" via the discharge one-way valve 42. During suction stroke of the pump the second pump chamber 16" expands causing suction through the vent one-way valve 40.

[0033] In the figure 1 the piston member 28 is at its first extreme position where the first pump chamber 16 has its greatest volume. The piston member 28 is movable by an external force, depicted by an arrow 44, which may be provided directly by the operation of the engine.

[0034] The piston member 28 is provided with a coaxial sleeve member 46 which connects to the second end 28" of the piston member 28 and which has a closed end i.e. a bottom 58. The bottom 58 of the sleeve member 46 extends radially to the piston member 28. The sleeve member 46 may be integral to or separate part from the second end 28" of the piston member 28. The bottom 58 of the sleeve member 46 is therefore common with the piston member 28 and it serves for receiving the force needed for reciprocate the piston member 28 in the pump 10. The sleeve member 46 is arranged such that an annular space is provided between the sleeve member 46 and the piston member 28, which now forms at least partly the second pump space 16'. The sleeve member 46 opens towards the first end 28' of the piston member 28. The sleeve member 46 is aspace section 30" such that the radially inner wall of the second space section 30" and the radially outer wall of the sleeve member 46 are against each other providing a second sealing gap 35. The wall of the second space section 30" guides the sleeve member 46 of the piston member 28 in the body 18 when the piston member 28 and sleeve member are moving along the central axis 32.

[0035] The body 18 of the pump 10 is provided with a cylindrical extension 48 towards the second end of the piston member 28 which extension is coaxial to the first space section 30'. The cylindrical extension 48 has an axial length in the direction of the central axis 32 and an outer diameter smaller than the second diameter D2. The cylindrical extension 48 extends axially into the second space section 30". Now, when installed to an internal combustion engine, the external force 44 is advantageously brought about by a power system of the engine. Therefore the piston member 28 is in mechanical force transmission connection, typically indirectly, with the crankshaft of the engine. In practise this mean that mechanical force transmission is lubricated by the engine lubricant. The pump 10 is provided with means for transferring fuel material away from the second pump chamber 16' any fuel material which escapes through the sealing gap 34 will not find its way into the lubrication medium of the engine.

[0036] As is shown in the figure 1 , the pump 10 is configured to be installed such that the first end 28' of the piston member 28 is horizontally below the second end 28" of the piston member 28 and the central axis 32 is at inclined position. In the figure 1 there is shown that the fuel scraper ring 68 is arranged in an annular space arranged to minimize the flow of fuel into the second space section 30". There is also another annular space 67 closer to the first pump chamber 16 from which a fuel discharge channel 66 is extending to outside the body 18. The discharge channel acts as a fuel recovery point. This arrangement decreases the amount of fuel flow through the first sealing gap 34 to the second pump space 16", since major part of the fuel is directed to the fuel discharge channel 66.

[0037] In the pump 10 the second space section 30" is provided with a bushing 70 which is at its first end attached to the inner surface of the body 18 at the second space section 30" and which is provided with a section having a smaller diameter than the outer surface of the second space section 30" such that an annular space is provided between the bushing 70 and the inner surface of the section space section 30". The bushing is attached at its first end, on the side of the first end 28' of the piston member 28, to the body 18. The piston member 28 comprises a sleeve member 46 which is arranged in the second space section 30" such that a desired guidance and sealing is provided. In the second space section 30" the inner wall of the second space section 30" and the wall of the sleeve member 46 are arranged against each other providing a second sealing gap 35 between the walls, respectively. The sleeve member 46 is arranged to extend into said annular gap 60 formed by the bushing 70 and the wall of the second space section 30". This way the bushing 70 borders the second pump chamber 16" together with the sleeve member 46 and the piston member 28. The fitting of the sleeve member 46 to extend into the annular gap between the bushing 70 and the second space section 30" is such that the radially inner wall of the annular gap i.e. the radially outer wall of the bushing 70 and the radially inner wall of the sleeve member 46 are against each other providing a third sealing gap 37.

[0038] There is a third space section 60 arranged into the annular gap radially between the bushing 70 and the inner wall of the body 18 and the sleeve member 49 which borders the third space section. The third space section 60 serves for purposes of lubrication the pump 10. The third space section is also an annular space. The pump 10 is provided with lubrication medium supply channel 62 and a lubrication medium discharge channel 64. The lubrication medium supply chan- nel 62 is arranged to a position so as to supply lubrication medium, usually oil, to the second sealing gap 35. The lubrication medium discharge channel 64 is positioned to open in to the third space section 60. The minimum volume of the third space section 60 and the locations and/dimensions of the lubrication medium supply channel 62 and the lubrication medium discharge channel 64 are config- ured to allow a formation of a pond of lubrication medium in the third space section 60 but preventing a total filling of the third space section with the lubrication medium. Particularly the lubrication medium supply channel 62 and the lubrication medium discharge channel 64 are dimensioned so that the flow rate of the lubrication medium out from the third space section 60 is at least in the long run greater than the flow rate of the lubrication medium into the third space section 60. The lubrication medium supply channel 62 is connected to lubrication system of the engine and therefore it is configured to receive pressurized lubrication medium. [0039] The sealing effect of the sealing gaps above may be based on qualities of the surface and/or dimension tolerances of parts and/or separate sealing elements, such as an o-ring or a lip seal.

[0040] In the figure 2 there is shown a high pressure pump assembly 100 into which at least two piston pump units 10 are assembled. The pump unit 10 shown in the figure 2 is the high pressure pump according to the figure 1 . The pump units 10 are here in a down facing v-configuration. In case there are more than two pump units they are configured in two in-line banks.

[0041 ] The pump assembly is provided with a drive shaft 1 10 which operates the piston pump units 10 coupled there to. The drive shaft 1 10 is a crank shaft having eccentric parts 1 12 via which the drive shaft 1 10 coupled to the piston member 28 of the pump unit 10. The drive shaft 1 10 of the pump assembly may be driven by the engine or it may be provided with for example an electric motor (not shown) to operate the pump assembly 100. The assembly 100 comprises a housing 102 into which the shaft 1 10 is fit with bearings. [0042] The high pressure pump assembly 100 comprises a drive shaft lubrication system 1 14 which is adapted to deliver lubricant to bearings of the shaft. The pump assembly comprises also a pump unit lubrication system 1 16, and at least one inlet 1 15 for pressurized lubricant, via which the lubrication systems may be connected the lubrication system of the engine to which the high pressure fuel pump is installed. The drive shaft lubrication system 1 14 is, when in use, connected to the lubrication system of the engine to deliver pressurized lubricant.

[0043] The pump assembly 100 according to the invention is configured such that collection of fluids discharged from the pump assembly i.e. so called leaked fuel material and lubrication medium, is taken place by means of the gravity force. By the term leaked fuel it is referred to such fuel which has passed along the first sealing gap 34 to a fuel recovery point. In each one of the pump units, lubricant is used to provide a lubrication effect in the first sealing gap 34 and in the second sealing gap 35. In the pumps the lubricant is collected and conveyed as lubricant return flow by means of gravity draining. Correspondingly, fuel material which is flown through the first sealing gap 34 is collected and conveyed by means of gravity draining. Thus, the pump units 10 are configured to drain the lubricant and fuel material by means of gravity. The pump assembly is provided with a first collector conduit 120 configured to receive lubricant from the drive shaft lubrication system 1 14 and from the pump unit lubrication system 1 16. Further, the pump assembly 100 is provided with a second collector conduit 122 configured to receive leak fuel from the piston pump units, and a third collector conduit 124 configured to receive fuel mist from a second pump chamber 16' of the piston pump unit 10. The first, second and the third collector conduits 120,122,124 are separate from each other and this way the fluids do not mix with each other in undesired manner. The first, the second and the third collector conduits 120,122,124 are arranged at horizontally lower position in respect to pump units such that there is a substantially continuous sloping flow passage from the pump unit to said conduits. The first collector conduit is arranged vertically below an outlet of the drive shaft lubrication system, the second collector conduit is arranged vertically below and outlet of the piston pump units and the third collector conduit is arranged vertically below an outlet of the piston pump unit.

[0044] The first collector conduit, the second collector conduit and a third collector conduit are arranged a fluid collector block 1 18 for receiving the drained fluids and forwarding them to further processing. The further processing advantageously means reusing the fluid in the engine. The collector block is a monolithic structure where the collector conduits are arranged substantially from one end of the collector block to another end thereof.

[0045] In the embodiment of the figure 2 the fluid collector block 1 18, the first collector conduit 120, the second collector conduit 122 and the third collector conduit 124 in the fluid collector block are arranged to extend parallel to the drive shaft 1 10 of the pump assembly 100 from one end of the pump assembly to the other end thereof so that the draining i.e. the outlets of the collector conduits may be arranged at one end of the collector block being collective of for all the pump units 10 in the assembly 100. [0046] A high pressure fuel pump assembly comprises a number of piston pump units 10 in two banks of pistons in v-configuration and that the fluid collector block is arranged between the two banks. It is clear that the pump assembly may comprise only one bank of piston pump units arranged in line. [0047] The fluid collector block 1 18 is provided with a number of fluid interfaces 126 and the piston pump units 10 are provided with corresponding fluid interface 126', in which the fluid interfaces are mating with each other such that a sealed fluid communication between the fluid collector block 1 18 and the piston pump unit 10 is formed. The interfaces are provided with suitable seals, such as o-rings such that the fluids may not leak or mix with each other when connected with each other. The fluid interfaces connect more than one fluid conduits between the pump unit 10 and the fluid collector block 1 18. In connection with each one of the fluid interfaces, the fluid collector block 1 18 is provided with a first passage 121 extending from the first collector conduit 120 to the fluid interface 126, an vice versa, via which interface the first passage is in flow communication with the lubrication medium discharge channel 64 of the fuel pump unit 10. Respectively, the fluid collector block 1 18 is provided with a second passage 123 extending from the second collector conduit 122 to the fluid interface 126 in which the second passage is in flow communication with the fuel discharge channel 66 of the fuel pump unit 10. Also, the fluid collector block 1 18 is provided with a third passage 125 extending from the third collector conduit 124 to the fluid interface 126 in which the third passage is in flow communication with the discharge flow path 38 of the fuel pump unit 10 configured to transfer fuel material entered into the second pump chamber 16' via the sealing gap 34. The fuel material entered in the second pump chamber 16' is typically fuel mist.

[0048] The fluid interfaces 126' of the piston pump units 10 are directed to open into direction between the banks of the pump units 10 and the fluid collector block is provided with a number of fluid interfaces 126 in a two rows such that the fluid interfaces are simultaneously connected to the respective fluid interfaces of the bank of pistons.

[0049] In the figure 2 the fluid collector block 1 18 is arranged below the drive shaft 1 10 and between the banks of the pump units 10. [0050] As is also shown in the figure 2, the fluid collector block 1 18 is provided with a fluid coupling 128 between the collector block 1 18 and the housing 102 of the pump assembly. The housing of the assembly 100 is provided with corresponding fluid coupling 128', in which the fluid couplings 128,128' are mating with each other such that a sealed fluid communication between the fluid collector block 1 18 and the pump assembly housing 102 is formed. There is a fourth passage 129 in the collector block 1 18 extending from the first collector conduit 120 to the fluid coupling 128 wherein the fourth passage 129 is in flow communication with the lubrication medium discharge channel of the housing of the fuel pump assembly 100.

[0051 ] While the invention has been described herein by way of examples in connection with what are, at present, considered to be the most preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but is intended to cover various combinations or modifications of its features, and several other applications included within the scope of the invention, as defined in the appended claims. The details mentioned in connection with any embodiment above may be used in connection with another embodiment when such combination is technically feasible.

Claims

1 . A high pressure fuel pump assembly for an internal combustion piston engine (100) comprising a number of piston pump units (10) driven by a drive shaft (1 10) of the pump assembly (100), a drive shaft lubrication system (1 14) and pump unit lubrication system (1 16), and at least one inlet (1 15) for pressurized lubricant, characterized in that the pump assembly (100) is provided with a first collector conduit (120) configured to receive lubricant from the pump unit lubrication system (1 16) and a second collector conduit (122) configured to receive leak fuel from the piston pump units, and a third collector conduit configured to receive fuel mist from the piston pump units.

2. A high pressure fuel pump assembly (100) according to claim 1 , characterized in that the first collector conduit (120), the second collector conduit (122) and a third collector conduit (124) are arranged in a fluid collector block (1 18) which is releasably attached to the pump units (10).

3. A high pressure fuel pump assembly (100) according to claim 1 , characterized in that the first collector conduit (120) is configured to receive lubricant from the drive shaft (1 10) lubrication system and from the pump unit lubrication system (1 16).

4. A high pressure fuel pump assembly (100) according to claim 1 , characterized in that the first, the second and the third collector conduits (120,122,124) are arranged horizontally at lower position in respect to pump units (10) such that there is a substantially continuous sloping flow passage arranged from the pump unit (10) to said conduits (120,122,124).

5. A high pressure fuel pump assembly (100) according to claim 1 , characterized in that the first collector conduit (120) is arranged vertically below an outlet of the drive shaft lubrication system (1 10), the second collector conduit (122) is arranged vertically below an outlet of the piston pump units (10) and the third collector conduit (124) is arranged vertically below an outlet of the piston pump unit (10).

6. A high pressure fuel pump assembly (100) according to claim 1 , characterized in that the assembly (100) comprises a number of piston pump units (10) in-line.

7. A high pressure fuel pump assembly (100) according to claim 1 , charac- terized in that the assembly (100) comprises a number of piston pump units (10) in two banks of pistons in v-arrangement and that the fluid collector block is arranged between the two banks.

8. A high pressure fuel pump assembly (100) according to claim 1 , characterized in that the fluid collector block is provided with a number of fluid interfaces (126) and the piston pump units (10) are provided with corresponding fluid interface (126'), the fluid interfaces mating with each other such that a sealed fluid communication between the fluid collector block (1 18) and the piston pump unit (10) is formed when the interfaces are coupled.

9. A high pressure fuel pump assembly (100) according to claim 7 and 8, characterized in that the fluid interfaces (126') of the piston pump units (10) are directed to open into direction between the banks of the pump units (10) and the fluid collector block (1 18) is provided with a number of fluid interfaces (126) in a two rows such that the fluid interfaces are simultaneously connected to the respective fluid interfaces of the bank of piston pumps (10).

10. A high pressure fuel pump assembly (100) according to claim 7 and 8, characterized in that the fluid collector block is arranged below the drive shaft (1 10).