GB2577324A - A HP pump of a fuel injection system provided with a camshaft assembly - Google Patents

A HP pump of a fuel injection system provided with a camshaft assembly Download PDF

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Publication number
GB2577324A
GB2577324A GB1815484.9A GB201815484A GB2577324A GB 2577324 A GB2577324 A GB 2577324A GB 201815484 A GB201815484 A GB 201815484A GB 2577324 A GB2577324 A GB 2577324A
Authority
GB
United Kingdom
Prior art keywords
sleeve
shaft
high pressure
profile
pressure pump
Prior art date
Legal status (The legal status 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 status listed.)
Withdrawn
Application number
GB1815484.9A
Other versions
GB201815484D0 (en
Inventor
Batchelor Kieran
Shariati Meghdad
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Delphi Technologies IP Ltd
Original Assignee
Delphi Technologies IP Ltd
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 Delphi Technologies IP Ltd filed Critical Delphi Technologies IP Ltd
Priority to GB1815484.9A priority Critical patent/GB2577324A/en
Publication of GB201815484D0 publication Critical patent/GB201815484D0/en
Publication of GB2577324A publication Critical patent/GB2577324A/en
Withdrawn legal-status Critical Current

Links

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
    • 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
    • F02M59/44—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
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
    • F04B1/00—Multi-cylinder machines or pumps characterised by number or arrangement of cylinders
    • F04B1/04—Multi-cylinder machines or pumps characterised by number or arrangement of cylinders having cylinders in star- or fan-arrangement
    • F04B1/0404—Details or component parts
    • F04B1/0413—Cams
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
    • F04B1/00—Multi-cylinder machines or pumps characterised by number or arrangement of cylinders
    • F04B1/04—Multi-cylinder machines or pumps characterised by number or arrangement of cylinders having cylinders in star- or fan-arrangement
    • F04B1/053—Multi-cylinder machines or pumps characterised by number or arrangement of cylinders having cylinders in star- or fan-arrangement with actuating or actuated elements at the inner ends of the cylinders
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
    • F04B9/00—Piston machines or pumps characterised by the driving or driven means to or from their working members
    • F04B9/02—Piston machines or pumps characterised by the driving or driven means to or from their working members the means being mechanical
    • F04B9/04—Piston machines or pumps characterised by the driving or driven means to or from their working members the means being mechanical the means being cams, eccentrics or pin-and-slot mechanisms
    • F04B9/042—Piston machines or pumps characterised by the driving or driven means to or from their working members the means being mechanical the means being cams, eccentrics or pin-and-slot mechanisms the means being 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
    • F02M2200/00—Details of fuel-injection apparatus, not otherwise provided for
    • F02M2200/03—Fuel-injection apparatus having means for reducing or avoiding stress, e.g. the stress caused by mechanical force, by fluid pressure or by temperature variations
    • 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
    • F02M2200/80—Fuel injection apparatus manufacture, repair or assembly
    • F02M2200/8061—Fuel injection apparatus manufacture, repair or assembly involving press-fit, i.e. interference or friction fit
    • 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
    • F02M2200/90—Selection of particular materials
    • F02M2200/9053—Metals

Abstract

A high pressure fuel injection pump of an i.c. comprises a plunger (18, figs.1,2) urged to reciprocate in a bore (14) by a camshaft assembly 36 which comprises a shaft 42, and a tubular sleeve 44 engaged on the shaft 42. The inner profile 46 of the sleeve 44 coincides with an exterior surface (50, fig.4) of the shaft 42 and the outer profile 48 provides the cam profile, each of the inner and outer profiles 46, 48 having a noncircular transverse sections, eg oval, rectangular, square or elliptical, to prevent cam slippage. The sleeve 44 may be made of higher grade steel than the shaft 42. An interference fit between the sleeve 44 and the shaft 42 may be small, eg 15µm for reduced hoop stress and reduced risk of failure by hydrogen embrittlement.

Description

A HP PUMP OF A FUEL INJECTION SYSTEM PROVIDED WITH A CAMSHAFT ASSEMBLY
TECHNICAL FIELD
The present invention relates to a high pressure pump of a fuel injection system of an internal combustion engine provided with a camshaft assembly arranged to reduce risk of cam slippage.
BACKGROUND OF THE INVENTION
In a HP pump for a fuel injection system, the fuel enters a compression chamber via an inlet wherein it is compressed from a few bars to thousands of bars then is expelled via an outlet, thanks to a plunger reciprocating in a bore of the pump. The plunger is controlled by a camshaft assembly provided with a cam follower that produces the reciprocating of the plunger in the bore. The camshaft assembly comprises a shaft that may be a bi-component shaft made up of a solid shaft manufactured from a low grade steel and a cam made from a higher grade steel. Such a bi-component shaft is less expensive and ensures a good withstanding of the loading during the pumping cycles thanks to the high grade steel cam. However, a large interference fit is required between the shaft and the cam to provide sufficient torque transmission capability, which can cause brittle fracture due to hydrogen embrittlement as well as high tensile hoop stress. Hydrogen can enter the cam material and generate corrosion when there is water in the fuel. Consequently, meaning failure can happen at any point during the life of the vehicle, and is very hard to detect until total failure.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to resolve the above mentioned problems in providing a high pressure pump of a fuel injection equipment of an internal combustion engine, said pump comprising a body provided with a bore extending along a pumping axis from an first end to a second end, said second end partially defining a compression chamber, a plunger configured to reciprocate within said bore along said pumping axis to alternatively increase and decrease the volume of the compression chamber, and a camshaft assembly, the camshaft assembly cooperating with the plunger to urge the plunger to reciprocating in the bore, wherein the camshaft assembly comprises a shaft extended along a longitudinal axis, and a tubular sleeve, said sleeve being engaged on the shaft and being delimited by an inner profile and an outer profile, wherein the inner profile coincides with an exterior surface of the shaft and the outer profile coincides with a cam profile, each of the inner profile and the outer profile having a noncircular transverse sections.
Thanks to the claimed configuration of the camshaft assembly, the sleeve cannot slip on the shaft. The interference fit can accordingly be dropped considerably, reducing thus any failure risk.
The inner profile of the sleeve may be of an oval shape.
The sleeve may be made of steel that has higher grade than steel of which is made the shaft.
The shaft may be made of 16MnCr66 and the sleeve (44) of M50 tool steel.
The sleeve has a constant thickness measured between the inner profile and the outer profile.
The sleeve has a thickness measured between the inner profile and the outer profile that is not constant.
Said thickness may be comprised between 3 mm and 5 mm.
An interference fit between the sleeve and the shaft may be comprised between 10 jun and 20 Rm.
The invention also relates to a process for manufacturing a camshaft assembly as already described, comprising a step of assembling the sleeve and the shaft, the temperature assembly being smaller than 180°.
The invention also relates to a high pressure pump of a fuel injection equipment of an internal combustion engine, said pump may comprise: a body provided with a bore extending along a pumping axis from an first end to a second end, said second end partially defining a compression chamber, a plunger configured to reciprocate within said bore along said pumping axis to alternatively increase and decrease the volume of the compression chamber, and a camshaft assembly as already described to control the plunger reciprocating in the bore.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention is now described by way of example with reference to the accompanying drawings in which: Figures 1 and 2 are longitudinal sections of a HP pump with a camshaft assembly as per the invention.
Figure 3 is a perspective view of camshaft assembly of figure 1.
Figure 4 is a perspective view of a shaft of the camshaft assembly of figure 3 Figure 5 is a perspective view of a sleeve of the camshaft assembly of figure 3
DESCRIPTION OF THE PREFERRED EMBODIMENTS
A diesel internal combustion engine is provided with a fuel injection equipment arranged to cyclically spray compressed diesel fuel in its cylinders. Said equipment comprises a high pressure pump 10, shown on figures 1 and 2.
The injection pump is one of the essential parts of the engine. The pump is configured to generate a high pressure so that fuel is transmitted to a combustion chamber of the engine.
As can be seen from figures 1 and 2, the pump 10 has a body 12 provided 20 with a bore 14 extending along a pumping axis X from a first end to a second end partially defining a compression chamber 16.
As shown in figures 1 and 2, in the bore 14 is guided a plunger or piston 18 axially X extending from a first end 20 to a second end 22 partially defining the compression chamber 18. The first end 20 is configured to cooperate with a cam, as will be detailed later.
The body 12 further defines an inlet chamber 24 for receiving fuel in the HP pump. The inlet chamber 24 is covered by a cap 26. In use, the inlet chamber 24 is fully filled with fuel from the base to the cap 26.
The body 12 further comprises a fuel inlet 28 controlled by an inlet valve 30. The pump also comprises a fuel outlet 32 controlled by an outlet valve 34.
As can be seen from figures 1 and 2, the pump 10 also comprises a camshaft assembly 36 cooperating with a roller 38 hold by a tappet 40.
As can be particularly seen in figures 3 to 5, the camshaft assembly 36 comprises a shaft 42 and a tubular sleeve 44 engaged on the shaft 42.
The shaft 42 extends along a longitudinal axis L. The sleeve 44 has a thickness T delimited by an inner profile 46 and an outer profile 48.
Advantageously, the thickness T of the sleeve 44 is constant,and has a value for instance between 3 mm and 5 mm, preferably 4 mm.
Alternatively, the thickness T might not be constant, depending on the shape of the outer profile 48 of the shaft.
As shown in figure 3, the inner profile 46 coincides with an exterior surface 50 of the shaft 42 and the outer profile 48 coincides with a cam profile, each of the inner profile 46 and the outer profile 48 having a noncircular shape.
On figures 3 to 5, the inner profile 46 and the outer profile 48 have an oval shape.
The invention is not limited to this shape and the sleeve can be of other noncircular form, like rectangular, squared, oblong or elliptic.
Preferably, the sleeve 44 is made of steel that has higher grade than steel of which is made the shaft 42. For instance, the sleeve 44 is manufactured from M50 tool steel and the shaft 42 of 16kInCir55 (EN ISO HS 0-41).
The oval shape of the sleeve 52 on the oval surface 50 of the shaft 42 ensures an anti-rotation feature in the sense that the sleeve 44 is blocked on the surface 50, thereby preventing any cam slippage.
Since the cam slippage is avoided, an interference fit between the sleeve 44 and the shaft 42 is small, for instance between 10 pm and 20 p.m, preferably 15 25 pm.
The following table compares the hoop stress of a standard M50 cam and the M50 sleeve 44: Hoop stress (MPa) 47 pm 47 pm 15 pm 15 pm (interference fit) sleeve (interference fit) sleeve (interference fit) sleeve (interference fit) sleeve average 273 313 87 100 max 343 352 109 112 min 226 289 72 92 Since the interference fit can be dropped from 47 Jim to 15 pm, which is not feasible for the prior art cam, the hoop stress is greatly reduced, as can be seen from the table above.
With such a low hoop stress, risk of failure by hydrogen embrittlement also drops considerably.
The invention also relates to a process for manufacturing the camshaft assembly 36.
The process comprises a step of assembling the sleeve 44 and the shaft 42 by press fitting the sleeve 44 on the surface 50 of the shaft, the temperature assembly being smaller than 180°. Preferably, the temperature OA is around 130°, according to the following equation: OA = OR Uc aCD where 0R is the room temperature, U, is the total interference and acp is the coefficient of thermal expansion times a nominal joint diameter.
The total interference is determined by the following equation: Uc = Umax + LIA0, where Umax is the interference fit maximum and UA0 is the clearance required between cam and shaft for force free assembly, for instance 10 gm. The process according to the present invention is simplified and less expensive since the temperature assembly is smaller than in the prior art. LIST OF REFERENCES X pumping axis TDC top dead centre BDC bottom dead centre L longitudinal axis of the shaft 10 high pressure pump -HP pump 12 body 14 bore 16 compression chamber 18 piston 20 end of piston 22 other end of piston 24 inlet chamber 26 cap 28 fuel inlet inlet valve 32 fuel outlet 34 outlet valve 36 camshaft assembly 38 roller tappet 42 shaft 44 sleeve 46 inner profile 48 outer profile exterior surface

Claims (9)

  1. CLAIMS: 1. A high pressure pump of a fuel injection equipment of an internal combustion engine, said pump comprising a body (12) provided with a bore (14) extending along a pumping axis (X) from an first end to a second end, said second end partially defining a compression chamber (16), a plunger (18) configured to reciprocate within said bore (14) along said pumping axis (X) to alternatively increase and decrease the volume of the compression chamber (16), and a camshaft assembly (36), the camshaft cooperating with the plunger to urge the plunger (18) to reciprocating in the bore (14), wherein the camshaft assembly comprises a shaft (42) extended along a longitudinal axis (L), and a tubular sleeve (44), said sleeve (44) being engaged on the shaft and being delimited by an inner profile (46) and an outer profile (48), wherein the inner profile (46) coincides with an exterior surface (50) of the shaft (42) and the outer profile (48) coincides with a cam profile, each of the inner profile (46) and the outer profile (48) having a noncircular transverse sections.
  2. 2. A high pressure pump as claimed in claim 1, wherein the inner profile (46) of the sleeve (44) is of an oval shape.
  3. 3. A high pressure pump as claimed in any of the preceding claims, wherein the sleeve (44) is made of steel that has higher grade than steel of which is made the shaft (42).
  4. 4. A high pressure pump as claimed in the preceding claim, wherein the shaft (42) is made of 16MnCr66 and the sleeve (44) of M50 tool steel.
  5. 5. A high pressure pump as claimed in any of the preceding claims, wherein the sleeve (44) has a constant thickness (T) measured between the inner profile (46) and the outer profile (48).
  6. 6. A high pressure pump as claimed in any of claims 1-4, wherein the sleeve (44) has a thickness (T) measured between the inner profile (46) and the outer profile (48) that is not constant.
  7. A high pressure pump as claimed in claims 5 and 6, wherein said thickness (T) is comprised between 3 mm and 5 mm.
  8. 8. A high pressure pump as claimed in the preceding claims, wherein an interference fit between the sleeve (44) and the shaft (42) is comprised between 10 10 pm and 20 pm.
  9. 9. A process for manufacturing a camshaft assembly as claimed in any of the preceding claims, comprising a step of assembling the sleeve (44) and the shaft (42), the temperature assembly being smaller than 180°.
GB1815484.9A 2018-09-24 2018-09-24 A HP pump of a fuel injection system provided with a camshaft assembly Withdrawn GB2577324A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB1815484.9A GB2577324A (en) 2018-09-24 2018-09-24 A HP pump of a fuel injection system provided with a camshaft assembly

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB1815484.9A GB2577324A (en) 2018-09-24 2018-09-24 A HP pump of a fuel injection system provided with a camshaft assembly

Publications (2)

Publication Number Publication Date
GB201815484D0 GB201815484D0 (en) 2018-11-07
GB2577324A true GB2577324A (en) 2020-03-25

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GB1815484.9A Withdrawn GB2577324A (en) 2018-09-24 2018-09-24 A HP pump of a fuel injection system provided with a camshaft assembly

Country Status (1)

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GB (1) GB2577324A (en)

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20150093265A1 (en) * 2012-05-09 2015-04-02 Delphi International Operations Luxembourg, S.A.R.L. Driveshaft lubrication

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20150093265A1 (en) * 2012-05-09 2015-04-02 Delphi International Operations Luxembourg, S.A.R.L. Driveshaft lubrication

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Publication number Publication date
GB201815484D0 (en) 2018-11-07

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WAP Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1)