EP3209880B1

EP3209880B1 - Pumping mechanism

Info

Publication number: EP3209880B1
Application number: EP15763502.0A
Authority: EP
Inventors: Peter Voigt; Onur Mehmet Tansug
Original assignee: Delphi Technologies IP Ltd
Current assignee: Delphi Technologies IP Ltd
Priority date: 2014-10-21
Filing date: 2015-08-24
Publication date: 2020-10-28
Anticipated expiration: 2035-08-24
Also published as: CN106795845B; GB201418661D0; EP3209880A1; KR102357678B1; KR20170072886A; WO2016062431A1; CN106795845A

Description

TECHNICAL FIELD

The present invention relates to a high pressure fuel pump, and more specifically to a pumping mechanism of a fuel pump actuated by an oil lubricated cam follower.

BACKGROUND OF THE INVENTION

As illustrated in Figure 1, a pumping mechanism 2 of a known high pressure fuel pump such as a unit pump, comprises a pump head 6, provided with a plunger location bore 8, in which a plunger 10 is partially located and restrained in an axial direction by a guide portion 20 of the bore 8. The plunger 10 extends towards a cam follower 12, the cam follower comprising a tappet 14 and a roller 16. A rotating cam (not shown) provides a force to the plunger 10 via the cam follower 12, causing the plunger 10 to move in a reciprocating motion inside the pump head 6, thereby pressurising fuel in a plumping chamber (not shown) provided at an extremity of the bore 8 remote from the cam follower 12. A coil spring 18 is compressed between the cam follower 12 and the pump head 6, and maintains contact between the roller 16 and the cam during a return stoke of the pumping mechanism 2.
The plunger 10 is lubricated by fuel inside the guide portion 20 of the plunger location bore 8, whilst a lower extremity of the plunger 10, and the cam follower 12, are lubricated by engine oil. As the plunger 10 reciprocally slides within the pump head 6, small quantities of oil and fuel are caused to mix, thereby generating undesirable pollution.
In fuel systems adhering to Euro 6 European emission standard and above, where a particulate filter is provided in the exhaust system, oil in the fuel system has detrimental effect of creating chemicals which leads to filter clogging during the combustion process, and furthermore lacquering of the spray holes of the injector nozzles.
Fuel contamination of lubrication oil is of increasing concern in the latest high efficiency engines, as lubrication oil viscosities are decreasing to minimise frictional losses and service intervals are being increased by all engine manufacturers.
In pump assemblies for older applications with less stringent dilution requirements, separation of oil and fuel has previously been achieved by a controlled clearance between the plunger and the guide portion of the bore in which the plunger is moveable. However, requirements of fuel to oil, and oil to fuel dilution rates are being increasing tightly controlled for new generations of diesel fuel injection pumps.
In order to meet new regulations for acceptable dilution of lubrication with fuel (wherein allowable quantities of fuel are typically 1/20 or 1/100 of the allowable quantity under regulations applied to older pump assembly applications), it has become necessary to provide an axial seal 22 as illustrated in Figure 1. In addition to the seal 22, it is necessary to provide a metal retainer 24, attached to the pump head 6 by crimping (at areas 26 as indicated in Figure 1) for placement of the seal 22, and an O-ring seal 28, to seal the interface between the retainer 24 and the pump head 6.
A known problem with such this type of pump is difficulty in validation of the crimping operation, which must be sufficiently strong to retain the retainer on the pump head, but must also be sufficiently weak so as not distort the match bore, or damage the retainer during the crimping operation.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an improved high pressure fuel pump which at least mitigates the above mentioned problems.
Accordingly the present invention provides, in a first aspect, a pumping mechanism of a fuel pump actuated by an oil lubricated cam follower, the pumping mechanism according to claim 1.
The sealing assembly further comprises means to retain the sealing assembly on the pump head said retaining means comprising a lip provided on the seal which is located in a recess provided on the extension section of the pump head.
The extension section of the pump head may comprise a first portion and a second portion, closer to the cam follower than the first portion, wherein part of the seal retainer surrounds the second portion of the extension section, and the retaining means may comprise a weld between the seal retainer and the second portion of the extension section.
The second portion of the extension section may have an external diameter which is less than that of the first portion, wherein an axial surface of the seal retainer abuts a shoulder provided at a junction of the first and second sections of the extension section, and the weld may comprise at least a weld seam between the shoulder of the extension section and the surface of the seal retainer which abuts the shoulder.
Alternatively or additionally, the weld may comprise a weld seam between an external surface of the second portion of the extension section, and an internal surface of the seal retainer which surrounds the second portion.
The cam follower may comprise a tappet and a roller provided in a recess of the tappet, wherein the first spring seat is provided by an axial surface of the pump head.
The sealing retainer may comprise a deep drawn sheet, or a low carbon tube.
The spring retainer may entirely envelop the extension section of the pump head, and the first spring seat may be provided by an axial face of a flange provided at an end of the seal retainer proximate to the main section of the pump head.
In a further aspect, the present invention comprises a high pressure fuel pumping mechanism comprising a sealing assembly according to the first aspect of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is now described by way of example with reference to the accompanying figures, in which:

Figure 2 is a partial cross-sectional view of a pump assembly in accordance with the embodiment of the present invention;
Figure 3 is a cross-sectional detailed partial view of the pump assembly of Figure 2;
Figure 4 is a partial cross-sectional view of a pump assembly in accordance with an example not covered by the present invention; and
Figure 5 is a cross-section detailed partial view of the pump assembly of Figure 4.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the description of the present below, relative terms such as upper, lower, above, below, top and bottom, are used in relation to the Figures only, and are not intended to be limiting.
Referring to Figures 2 and 3, the embodiment of the present invention comprises a pumping mechanism 102 comprising a pump head 106, comprising a main body section 130, and an extension section 132. At a top end of a plunger location bore 108 provided in the pump head 106, a pumping chamber (not shown) is provided. A pumping element in the form of a plunger 110 is located partially within the plunger location bore 108, the plunger 110 extending from the pumping chamber, along the extension section 132, and protruding from a base surface 134 of the extension section 132. A guide portion 120 of the plunger location bore 108 bore acts to restrain the plunger 110 within the plunger location bore 108 in an axial direction.
Below the plunger 110 is provided a cam follower 112, comprising a tappet 114 and a cam roller 116. A bottom end 140 of the plunger 110 contacts an upper side 150 of the tappet 114, and the cam roller 116 is located in a recess 154 provided on a lower side 152 of the tappet 114.
The extension section 132 of the pump head 106 comprises a first portion 136, and a second portion 138, further away from the main body section 130 of the pump head 106, and of a reduced external diameter relative to that of the first portion 136. A junction of the first portion 136 and the second portion 138 forms a shoulder 137 (indicated in Figure 3).
The pumping mechanism further 102 comprises a sealing assembly 180, comprising a seal 182 and a seal retainer 184, located within a spring chamber 142.
In the embodiment of Figures 2 and 3, the seal retainer 184 envelops both the first portion 136 and the second portion 138 of the extension section 132 of the pump head 106. The seal retainer is shaped so as to abut the outer surfaces of the first portion 136 and the second portion 138 of the extension section 132, i.e. the seal retainer 184 comprises a first, upper tubular section 186 around the first portion 136 of the extension section 132, and a second, lower tubular section 188 of greater cross-sectional area, around the second portion 138 of the extension section 132.
The second, lower tubular section 188 comprises a first, upper portion 190 which surrounds the second portion 138 of the extension section 132, and a second, lower portion 192, which extends below the extension section 132, towards the cam follower 112. The seal 182 is located partially in the lower section 192 of the seal retainer 184, and partially extends below the seal retainer 184, towards the cam follower 112.
The seal retainer 184 further comprises a flange 300, which extends perpendicularly to a longitudinal axis A of the plunger location bore 108, and contacts an axial surface 170 of the pump head 106.
In the embodiment of the present invention, the extension section 132 of the pump head 106 further comprises an end section 350, which is provided with an annular recess 352 at a point adjacent the second portion 138. The seal 182 is provided with an annular lip 360, of a complementary form to the recess 352. Once the sealing assembly has been assembled onto the pump head 106, the annular lip 360 of the seal 182 is urged into the recess 352, thereby acting as a retaining means, to retain the sealing assembly 180 on the pump head 106.
During operation of the pumping mechanism 102 and in a pumping stroke, rotation of a cam (not shown) causes force to be transferred, via the cam roller 116 and tappet 114, to the plunger 110, thereby causing the plunger 110 to move upwardly within the plunger location bore 108, along the longitudinal axis A of the plunger location bore 108, thereby causing fuel in the pumping chamber to become pressurised.
During further operation of the pumping mechanism 102 and in a return stroke, on further rotation of the cam, the cam roller 116, tappet 114 and plunger 110 move downwardly. A coil spring 118 is provided in the spring chamber 142 surrounding the extension section 132 of the pump head 106 and part of the plunger 110 extending from the plunger location bore 108. The outer diameter of the flange 300 of the seal retainer 184 is greater than the outer diameter of the spring 118.
A first, top end 160 of the spring 118 abuts against a first, upper spring seat provided by an axial face 302 of the flange 300 of the seal retainer 184, and a second, bottom end 162 of the spring 118 abuts at a second, lower spring seat 172 adjacent the tappet 114. The spring retainer 184 is formed of a material having a sufficient hardness to enable the axial face 302 of the flange 300 to act as a spring seat.
The spring 118 ensures that, during the return stroke, contact is maintained between the cam roller 116 and the cam.
Subsequent pumping and return strokes cause the plunger 110 to move slidably within the plunger location bore 108 in a reciprocating motion.
During use of the pumping mechanism 102, the sealing assembly 180 acts to prevent mixing of fuel which lubricates the plunger 110 inside the plunger location bore 108, with oil which lubricates the cam follower 112 and a lower part 111 of the plunger 110 extending below the seal 182.
The embodiment of the present invention is improved over the prior art, as a crimping step is not required to retain the sealing assembly 180 in place on the pump head 106.
Furthermore, there is no requirement for additional O-rings which have been used in prior art embodiments, thereby allowing a further cost reduction, and simpler manufacture, compared to prior art embodiments.
Extension of the seal 182 below, e.g. out of, the seal retainer 184, provides that less material is required to form the seal retainer than in prior art embodiments. Additionally, prior art embodiments required a tight tolerance between the pump head 106 and the seal retainer 184, to allow for thermal expansion of steel components and/or extension of the seal material such as rubber; the tolerance requirement in the present invention is relaxed in comparison to prior art embodiments. This can provide an additional benefit in achieving optimum packaging of the pump.
The present invention also enables provision of a the sealing assembly 180 as a sub assembly. Furthermore, during handling and transportation of subassemblies comprising the sealing assembly 180 and the pump head 106, retention is maintained between the pump head 106 and the sealing assembly 180, due to the cooperation of the lip 360 in the recess 352 of the end section 350 of the extension section 132.
Figures 4 and 5 illustrate an example not covered by the present invention. In common with the embodiment, the sealing assembly 280 of the example comprises a seal 282 and a seal retainer 284. However, the form and assembly of the sealing retainer 284 differs from that of the embodiment as described below.
The seal retainer 284 comprises a tubular section 288, comprising a first, top portion 290 which surrounds the second portion 138 of the extension section 132 of the pump head 106, and second, lower portion 292, which extends below the extension section 132, towards the cam follower 112. The seal 282 is provided partially in the second, lower portion 288 of the seal retainer 284, and partially extends below the seal retainer 284, towards the cam follower 112.
An axial top surface 294 of the upper end of the seal retainer 284 abuts the shoulder 137 formed between the first portion 136 and the second portion 138 of the extension section 132.
The seal retainer 284 is welded to the second portion 138 of the extension 132 section by laser weld seam, thereby acting as a retaining means, to retain the sealing assembly 280 on the pump head 106.
The weld between the seal retainer 284 and the second portion 138 of the extension section 132 is either between the top surface 294 of the retainer 284 and the shoulder 137 of the extension section 132, between a portion of an internal wall 287 of the seal retainer 184 and an external wall portion 139 of the second portion 138 which is surrounds, or both.
The location of, and degree of welding between the seal retainer 284 and the extension section 132 can be selected such that the longitudinal length of the seal 284 retainer, i.e. along the longitudinal axis A of the plunger location bore 108, can be minimised. This is advantageous in minimising material costs, and maximising extension of the seal 282 from the seal retainer 284.
In a similar manner to the first embodiment, during use of the pumping mechanism 102, the sealing assembly 280 acts to prevent mixing of fuel which lubricates the plunger 110 inside the plunger location bore 108, with oil which lubricates the cam follower 112 and a lower part 111 of the plunger 110 extending below the seal 282.
The seal retainer 284 of the example could be formed by a deep drawn sheet. In an alternative, the seal retainer 284 could be formed of a low carbon tube.
Sealing and retention of the sealing assembly 280 is provided by the welding of the seal retainer 284 onto the extension section 132 of the pump head 106. A sufficiently hard and thick first spring seat is provided by the axial face 302 of the pump head 106.
The present invention also enables a cost reduction compared to prior art embodiments, as the seal retainer 284 is a simple component, and can be manufactured from a steel of a lower grade than is necessary for the pump head 106.
Similarly to the embodiment, in the example there is no requirement for crimping of the seal retainer to the pump head, nor for sealing lips or additional O-rings which have been used in prior art embodiments, thereby allowing a further cost reduction, and simpler manufacture, compared to prior art embodiments.
Also similarly to the embodiment, extension of the seal 282 below, e.g. out of, the seal retainer 284, provides that less material is required to form the seal retainer than in prior art embodiments, and enables a relaxation of tolerances between the pump head 106 and the seal retainer 284.
The example also enables provision of a the sealing assembly 280 as a sub assembly. Furthermore, during handling and transportation of sub- assemblies comprising the sealing assembly 280 and the pump head 106, retention is maintained between the pump head 106 and the sealing assembly 280, due to the weld seam.

REFERENCES

embodiment:

pumping mechanism 102
pump head 106
plunger location bore 108
plunger 110
bore guide portion 120
cam follower 112
tappet 114
cam roller 116
coil spring 118
main body section 130
extension section 132
extension section base surface 134
plunger bottom end 140
spring chamber 142
tappet upper side 150
tappet lower side 152
recess 154
extension section first portion 136
second portion 138
shoulder 137
spring first, top end 160
spring second, bottom end 162
second, lower spring seat 172
sealing assembly 180
seal 182
seal retainer 184
seal retainer first, upper tubular section 186
second, lower tubular section 188
lower tubular section first, upper portion 190
second, lower portion 192
seal retainer flange 300
flange axial face 302
pump head end section 350
end section annular recess 352
seal annular lip 360
to the example : external wall portion 139
sealing assembly 280
seal 282
seal retainer 284
seal retainer internal wall portion 287
seal retainer tubular section 288
tubular section top portion 290
tubular section lower portion 292
axial top surface (upper end of seal retainer) 294

Claims

A pumping mechanism (102) of a diesel fuel pump actuated by an oil lubricated cam follower, the pumping mechanism (102) comprising a pump head (106), a cam follower (112) for cooperating with a rotating cam, and a plunger (110), located partially within a plunger location bore (108) provided in the pump head (106) and extending along a longitudinal axis (A) of the plunger location bore (108);
wherein the pump head (106) comprises a main section (130) and an extension section (132),
wherein a portion (111) of the plunger (110) extends from the extension section (132), and a lower surface at an end (140) of the plunger (110) contacts the cam follower (112);
wherein, in use, during a pumping stroke, rotation of the cam causes force to be transferred to the plunger (110) via the cam follower (112), thereby causing the plunger (110) to move along the plunger location bore (108) and into a pumping chamber, to cause fuel within the pumping chamber to become pressurised; and wherein during a return stroke, a spring provided in a spring chamber (142) surrounding the extension section (132) of the pump head (106), and abutting a first spring seat (170) and a second spring seat (172), maintains contact between the cam follower (112) and the cam;
the pumping mechanism (102) further comprising a sealing assembly (180, 280) comprising a seal (182, 282) and a seal retainer (184, 284), said sealing assembly (180, 280) acting to prevent mixing of fuel which lubricates the plunger (110) inside the plunger location bore (108), with oil which lubricates the cam follower (112) and a lower part (111) of the plunger extending below the seal,
the seal (182, 282) being provided partially within the seal retainer (184, 284), and extending partially from the seal retainer (184, 284), towards the cam follower (112)
the sealing assembly (180, 280) further comprising retaining means to retain the sealing assembly (180, 280) on the pump head (106), characterised in that
the retaining means comprises a lip (360) provided on the seal (182) which is located in a recess (352) provided on an end section (350) of the extension section (132) of the pump head (106).
A pumping mechanism (102) as claimed in claim 1, wherein the cam follower (112) comprises a tappet (114) and a roller (116) provided in a recess (154) of the tappet, and wherein the first spring seat is provided by an axial surface (170) of the pump head (106).
A pumping mechanism (102) as claimed in any preceding claim, wherein the sealing retainer (184) comprises a deep drawn sheet.
A pumping mechanism (102) as claimed in any of claims 1 to 3, wherein the sealing retainer (184) comprises a low carbon tube.
A high pressure fuel pumping mechanism (102) comprising a pumping mechanism (102) according to any one of the preceding claims.