CN106795845B

CN106795845B - Pumping mechanism

Info

Publication number: CN106795845B
Application number: CN201580055779.XA
Authority: CN
Inventors: P·沃伊特; O·M·坦苏格
Original assignee: Delphi International Operations Luxembourg SARL
Current assignee: Delphi Technologies IP Ltd
Priority date: 2014-10-21
Filing date: 2015-08-24
Publication date: 2020-04-17
Anticipated expiration: 2035-08-24
Also published as: KR102357678B1; CN106795845A; EP3209880B1; WO2016062431A1; GB201418661D0; KR20170072886A; EP3209880A1

Abstract

A seal assembly for a high pressure fuel pumping mechanism comprising a seal and a seal retainer, wherein the seal partially surrounds an extended section of the pump head and partially extends below the pump head toward a cam follower, and wherein the seal is partially disposed within the seal retainer and partially extends from the seal retainer, the cam follower; means, such as a weld, for retaining the seal holder on the pump head are provided.

Description

Pumping mechanism

Technical Field

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

Background

As illustrated in fig. 1, a pumping mechanism 2 of a known high-pressure fuel pump (such as a unit pump) includes a pump head 6, the pump head 6 being provided with a plunger positioning hole 8, and a plunger 10 being partially positioned and restrained in the plunger positioning hole 8 in an axial direction by a guide portion 20 of the hole 8. Plunger 10 extends toward cam follower 12, which includes tappet 14 and 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 reciprocatingly within the pump head 6, thereby pressurizing fuel in an expansion chamber (not shown) provided at the end of the bore 8 remote from the cam follower 12. The 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 the return stroke of the pumping mechanism 2.

The plunger 10 is lubricated by the fuel inside the guide portion 20 of the plunger positioning hole 8, while the lower end of the plunger 10 and the cam follower 12 are lubricated by the engine oil. As the plunger 10 slides reciprocally within the pump head 6, a small amount of oil and fuel mixing may result, thereby generating undesirable contamination.

In fuel systems which comply with the european emission standards above euro 6, in the case of a particulate filter being provided in the exhaust system, the oil in the fuel system has the adverse effect of generating chemical substances which can cause clogging of the filter during the combustion process, and furthermore spray the spray orifices of the injector nozzles.

Fuel contamination of lubricating oils is of increasing concern in the latest high efficiency engines, as lubricating oil viscosity is decreasing to minimize friction losses and all engine manufacturers are increasing maintenance intervals.

In pump assemblies for older applications with less stringent dilution requirements, separation of oil and fuel has previously been achieved by a controllable clearance between the plunger and a leading portion of the bore in which the plunger is able to move. However, with the new generation of diesel fuel injection pumps, the demand of fuel for oil and the control of the dilution ratio of oil and fuel are becoming increasingly strict.

In order to comply with new regulations for acceptable dilution of fuel lubrication (where the allowable amount of fuel is typically 1/20 or 1/100 of the allowable amount under regulations applicable to older pump assembly applications), it is necessary to provide an axial seal 22 as illustrated in FIG. 1. In addition to the seal 22, it is also necessary to provide a metal retainer 24, the metal retainer 24 being attached to the pump head 6 by crimping (at the region 26 indicated in figure 1) to place the seal 22 and the O-ring seal 28 to seal the interface between the retainer 24 and the pump head 6.

A well-known problem with this type of pump is that it is difficult to verify the crimping operation, which must be strong enough to hold the retainer on the pump head, but weak enough not to deform the mating bore or damage the retainer during the crimping operation.

Disclosure of Invention

It is an object of the present invention to provide an improved high-pressure fuel pump which at least alleviates the above-mentioned problems.

Accordingly, in a first aspect, the present invention provides a seal assembly for a high pressure fuel pumping mechanism.

The seal assembly may further comprise means for retaining the seal assembly on the pump head.

The extension section of the pump head may comprise a first portion and a second portion, the second portion being closer to the cam follower than the first portion, wherein a portion of a seal holder surrounds the second portion of the extension section, and the retaining means may comprise a weld between the seal holder and the second portion of the extension section.

The second portion of the extension section may have an outer diameter that is less than an outer diameter of the first portion, wherein an axial surface of the seal retainer abuts a shoulder disposed at a junction of the first and second sections of the extension section, and the weld may include at least a weld between the shoulder of the extension section and the surface of the seal retainer abutting the shoulder.

Alternatively or additionally, the weld may comprise a weld between an outer surface of the second portion of the extension section and an inner surface of the seal holder surrounding the second portion.

The cam follower may include a tappet and a roller disposed in a recess of the tappet, wherein a first spring seat is provided by an axial surface of the pump head.

The seal holder may comprise a deep drawn sheet or a carbon nanotube.

Alternatively, the retaining means may comprise a lip provided on the seal, the lip being located in a recess provided on the extension section of the pump head. The seal retainer may completely enclose 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 the main section of the pump head.

In yet another aspect, the invention comprises a high pressure fuel pumping mechanism comprising a seal assembly according to the first aspect of the invention.

Drawings

The invention will now be described, by way of example, with reference to the accompanying drawings, in which:

FIG. 1 is a partial cross-sectional view of a pumping mechanism of a known high pressure fuel pump;

FIG. 2 is a partial cross-sectional view of a pump assembly according to a first embodiment of the present invention;

FIG. 3 is a cross-sectional detailed partial view of the pump assembly of FIG. 2;

FIG. 4 is a partial cross-sectional view of a pump assembly according to a second embodiment of the present invention; and

FIG. 5 is a cross-sectional detailed partial view of the pump assembly of FIG. 2.

Detailed Description

In the description presented below, relative terms such as upper, lower, above, below, top, and bottom are used with respect to the drawings only and are not limiting.

Referring to fig. 2 and 3, a first embodiment of the present invention includes a pumping mechanism 102, the pumping mechanism 102 including a pump head 106, the pump head 106 including a body section 130 and an extension section 132. At the top end of the plunger positioning hole 108, which is provided in the pump head 106, a pumping chamber (not shown) is provided. A pumping element in the form of a plunger 110 is positioned partially within the plunger positioning bore 108, the plunger 110 extending from the pumping chamber along the extension section 132 and protruding from the base surface 134 of the extension section 132. The guide portion 120 of the plunger positioning bore 108 acts to constrain the plunger 110 within the plunger positioning bore 108 in the axial direction.

A cam follower 112 is provided under the plunger 110, the cam follower 112 including a tappet 114 and a cam roller 116. The bottom end 140 of the plunger 110 contacts an upper side 150 of the tappet 114, and the cam roller 116 is positioned in a recess 154 provided on a lower side 152 of the tappet 114.

The extension section 132 of the pump head 106 includes a first portion 136 and a second portion 138, the second portion 138 being further away from the body section 130 of the pump head 106 and having a reduced outer diameter relative to the first portion 136. The junction of the first portion 136 and the second portion 138 forms a shoulder 137 (indicated in fig. 3).

Pumping mechanism 102 further includes a seal assembly 180, seal assembly 180 including a seal 182 and a seal retainer 184 positioned within spring chamber 142.

In the embodiment of fig. 2 and 3, the seal retainer 184 encloses 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 to abut the outer surfaces of the first and

second portions

136, 138 of the extension section 132, i.e. the seal retainer 184 includes a first upper tubular section 186 surrounding the first portion 136 of the extension section 132 and includes a second lower tubular section 188 surrounding the second portion 138 of the extension section 132 and having a larger cross-sectional area.

The second lower tubular section 188 includes a first upper portion 190 that surrounds the second portion 138 of the extension section 132 and includes a second lower portion 192 that extends below the extension section 132 toward the cam follower 112. The seal 182 is positioned partially in the lower section 192 of the seal retainer 184 and extends partially underneath the seal retainer 184 toward the cam follower 112.

The seal retainer 184 further includes a flange 300, the flange 300 extending perpendicular to the longitudinal axis a of the plunger positioning bore 108 and contacting the axial surface 170 of the pump head 106.

In the first embodiment of the invention, the extension section 132 of the pump head 106 further comprises an end section 350, the end section 350 being provided with an annular recess 352 at a point adjacent the second portion 138. The seal 182 is provided with an annular lip 360, the annular lip 360 having a form complementary to the recess 352. Once the seal assembly has been assembled to the pump head 106, the annular lip 360 of the seal 182 is pushed into the recess 352, thereby acting as a retaining means to retain the seal assembly 180 on the pump head 106.

During operation of the pumping mechanism 102 and during a pumping stroke, rotation of a cam (not shown) causes a force to be transmitted to the plunger 110 via the cam roller 116 and the tappet 114, causing the plunger 110 to move upwardly within the plunger positioning bore 108 along the longitudinal axis a of the plunger positioning bore 108, causing fuel in the pumping chamber to be pressurized.

During further operation of the pumping mechanism 102 and on the return stroke, as the cam rotates further, the cam roller 116, tappet 114 and plunger 110 move downward. The coil spring 118 is disposed in a spring chamber 142, the spring chamber 142 surrounding the extension section 132 of the pump head 106 and the portion of the plunger 110 extending from the plunger positioning bore 108. The outer diameter of the flange 300 of the seal retainer 184 is greater than the outer diameter of the spring 118.

The first top end 160 of the spring 118 abuts a first upper spring seat provided by the axial face 302 of the flange 300 of the seal retainer 184, and the second bottom end 162 of the spring 118 abuts a second lower spring seat 172 adjacent the tappet 114. The seal retainer 184 is formed of a material having sufficient hardness to enable the axial face 302 of the flange 300 to act as a spring seat.

The spring 118 ensures that contact is maintained between the cam roller 116 and the cam during the return stroke.

The subsequent pumping and return strokes cause plunger 110 to slidably move reciprocally within plunger positioning bore 108.

During use of the pumping mechanism 102, the seal assembly 180 acts to prevent the fuel inside the plunger positioning bore 108 that lubricates the plunger 110 from mixing with the oil that lubricates the cam follower 112 and the lower portion 111 of the plunger 110 that extends below the seal 182.

The first embodiment of the present invention is an improvement over the prior art in that a crimping step is not required to hold the seal assembly 180 in place on the pump head 106.

Furthermore, there is no need to seal the lip or additional O-ring used in prior art embodiments, allowing for further cost reduction and simpler manufacturing compared to prior art embodiments.

Extending seal 182 below seal retainer 184 (e.g., beyond seal retainer 184) provides: less material is required to form the seal retainer than prior art embodiments. Additionally, prior art embodiments require tight tolerances between the pump head 106 and the seal retainer 184 to allow for thermal expansion of the steel components and/or extension of the sealing material (such as rubber); the tolerance requirements of the present invention are relaxed compared to prior art embodiments. This can provide additional benefits for achieving optimal packaging of the pump.

The present invention can also provide the seal assembly 180 as a subassembly. Furthermore, during handling and transportation of the subassembly comprising the seal assembly 180 and the pump head 106, a grip is maintained between the pump head 106 and the seal assembly 180 due to the cooperation of the lip 360 in the recess 352 of the end section 350 of the extension section 132.

Fig. 4 and 5 illustrate an alternative embodiment of the present invention. Like the first embodiment, the seal assembly 280 of the second embodiment includes a seal 282 and a seal retainer 284. However, the form and assembly of the packing retainer 284 is different from that of the first embodiment as described below.

The seal retainer 284 includes a tubular section 288, the tubular section 288 including a first top portion 290 surrounding the second portion 138 of the extension section 132 of the pump head 106 and a second lower portion 292 extending below the extension section 132 toward the cam follower 112. The seal 282 is partially disposed in the second lower portion 288 of the seal retainer 284 and extends partially below the seal retainer 284 toward the cam follower 112.

An axial top surface 294 of an upper end of the seal retainer 284 abuts the shoulder 137 formed between the first and

second portions

136, 138 of the extension section 132.

The seal retainer 284 is welded to the second portion 138 of the extension section 132 by a laser weld to act as a retaining device to retain the seal assembly 280 on the pump head 106.

The weld between seal retainer 284 and second portion 138 of extension section 132 is located either between top surface 294 of retainer 284 and shoulder 137 of extension section 132, or between a portion of inner wall 287 of seal retainer 184 and surrounding outer wall portion 139 of second portion 138, or both.

The location and extent of the weld between the seal retainer 284 and the extension section 132 can be selected such that the longitudinal length of the seal retainer 284 (i.e., along the longitudinal axis a of the plunger positioning bore 108) can be minimized. This helps to minimize material costs and maximize the extension of seal 282 from seal retainer 284.

In a manner similar to the first embodiment, during use of the pumping mechanism 102, the seal assembly 280 functions to prevent fuel lubricating the plunger 110 inside the plunger positioning bore 108 from mixing with oil lubricating the cam follower 112 and the lower portion 111 of the plunger 110 extending below the seal 282.

The seal holder 284 of the second embodiment may be formed by deep drawing a sheet of material. In an alternative embodiment, the seal retainer 284 may be formed from a low carbon tube.

Sealing and retention of the seal assembly 280 is provided by welding the seal retainer 284 to the extension section 132 of the pump head 106. A first spring seat that is sufficiently hard and thick is provided by the axial face 302 of the pump head 106.

The present invention also enables cost reduction as compared to prior art embodiments because the packing retainer 284 is a simple component and can be manufactured from a lower grade of steel than is required for the pump head 106.

Similar to the first embodiment, in the second embodiment, there is no need to crimp the seal holder to the pump head, nor is there a need for a sealing lip or additional O-ring as used in prior art embodiments, thereby allowing for further cost reduction and simpler manufacturing compared to prior art embodiments.

Also similar to the first embodiment, extending the seal 282 below the seal retainer 284 (e.g., outside of the seal retainer 284) provides less material to form the seal retainer than prior art embodiments and can relax tolerances between the pump head 106 and the seal retainer 284.

The second embodiment of the present invention can also provide the seal assembly 280 as a subassembly. Further, during handling and shipping of the subassembly including the seal assembly 280 and the pump head 106, a grip is maintained between the pump head 106 and the seal assembly 280 due to the weld.

Reference numerals

The first embodiment:

pumping mechanism 102

Pump head 106

Plunger positioning hole 108

Plunger 110

Hole guide part 120

Cam follower 112

Tappet 114

Cam roller 116

Coil spring 118

Body section 130

Extension section 132

Extended section base surface 134

Plunger bottom end 140

Spring chamber 142

Tappet upper side 150

Tappet undersides 152

Recess 154

First portion 136 of the extension section

Second portion 138

Shoulder 137

Spring first top end 160

Spring second bottom end 162

Second lower spring seat 172

Seal assembly 180

Seal 182

Seal retainer 184

First upper tubular section 186 of seal retainer

Second lower tubular section 188

First upper portion 190 of the lower tubular section

Second lower part 192

Seal retainer flange 300

Flange axial face 302

End section 350 of pump head

Annular recess 352 of the end section

Sealing annular lip 360

Second embodiment:

outer wall portion 139

Seal assembly 280

Seal 282

Seal retainer 284

Inner wall portion 287 of the seal retainer

Tubular section 288 of seal retainer

Top 290 of tubular section

Lower part 292 of the tubular section

Axial top surface (upper end of seal retainer) 294

Claims

1. A seal assembly (180, 280) for a high pressure fuel pumping mechanism (102), the pumping mechanism (102) comprising a pump head (106), a plunger (110) and a cam follower (112) cooperating with a rotating cam, the plunger (110) being positioned partially within a plunger positioning bore (108) provided in the pump head (106) and extending along a longitudinal axis (A) of the plunger positioning 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 a force to be transmitted to the plunger (110) via the cam follower (112) causing the plunger (110) to move along the plunger locating hole (108) into a pumping chamber causing fuel within the pumping chamber to be pressurised; and wherein during a return stroke, a spring disposed in a spring chamber (142) surrounding the extended 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;

wherein the seal assembly (180, 280) comprises a seal (182, 282) and a seal retainer (184, 284);

characterized in that the seal (182, 282) is partially disposed within the seal retainer (184, 284) and extends partially from the seal retainer (184, 284) toward the cam follower (112),

the seal assembly (180, 280) further comprising retaining means for retaining the seal assembly (180, 280) on the pump head (106),

wherein the retaining means comprises a lip (360) provided on the seal (182), the lip (360) being positioned in a recess (352) provided on an end section (350) of the extension section (132) of the pump head (106).

2. The seal assembly (180) of claim 1, wherein the cam follower (112) includes a tappet (114) and a roller (116) disposed 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).

3. The seal assembly (180, 280) of claim 1, wherein the seal retainer (184, 284) comprises a deep drawn sheet of material.

4. The seal assembly (180, 280) of any of claims 1-3, wherein the seal retainer (184, 284) comprises carbon nanotubes.

5. The seal assembly (180) of claim 1 wherein the seal retainer (184) completely encloses the extension section (132) of the pump head (106), and wherein the first spring seat is provided by an axial face (302) of a flange (300) disposed at an end of the seal retainer (184) proximate the main section (130) of the pump head (106).

6. A high-pressure fuel pumping mechanism (102) comprising a seal assembly (180, 280) according to any of the preceding claims.