GB2549485A

GB2549485A - Pump housing, elastomeric damper, method of making an elastomeric damper, and high pressure fuel pump

Info

Publication number: GB2549485A
Application number: GB1606731.6A
Authority: GB
Inventors: Serenas Karolis
Original assignee: Delphi International Operations Luxembourg SARL
Current assignee: Delphi International Operations Luxembourg SARL
Priority date: 2016-04-18
Filing date: 2016-04-18
Publication date: 2017-10-25
Anticipated expiration: 2036-04-18
Also published as: GB2549485B

Abstract

A pump housing 10 of a high pressure fuel pump comprising a low pressure side and a high pressure side for a diesel engine, the pump housing 10 comprising a fluid inlet for feeding a fluid into the low pressure side and an elastomeric damper 16 arranged within the low pressure side of the pump housing 10. An elastomeric damper, a method of making an elastomeric damper, and a high pressure fuel pump for a diesel engine are also defined. The invention is intended to increase the efficiency of the pump, and increase the durability of drivetrain components.

Description

Pump housing, elastomeric damper, method of making an elastomeric damper, and high pressure fuel pump

The present invention relates to a pump housing of a fuel pump for a diesel engine having an elastomeric damper, to an elastomeric damper, to a method of making an elastomeric damper, and to a high pressure fuel pump for a diesel engine having such a pump housing.

In general high pressure fuel pumps used in diesel passenger cars are driven by the engine. A driveshaft with a cam profile is normally used in the fuel pump to convert the rotational motion to a reciprocating motion. A reciprocating pumping element present within a cylinder bore then compresses the fuel to achieve high pressure which is evacuated through an outlet valve. A pumping chamber is re-filled with fuel through an inlet valve on a stroke of the pumping element.

There is an ongoing requirement to meet compact engine packaging requirements, reduced CO2 emissions, as well as minimising the weight of the pump. What is more, to achieve high volumetric efficiency of the pump, the pumping capacity needs to be close to the maximum high pressure fuel delivery requirements for the engine. This leads to the tendency of using a single reciprocating pumping element in high pressure pumps.

Due to the reciprocating motion of the single reciprocating pumping element, the fuel used for lubrication and cooling within the drivetrain housing (cambox) is subjected to a volume change. Due to this change in volume, the fuel is compressed, which in turn raises and lowers the pressure in the cambox above and below the average inlet pressure. This effect is highly dependent on the stroke of the single reciprocating pumping element stroke and the pumping speed thereof.

The resultant pressure pulsations restrict the ability of maintaining smooth inlet pressures and of re-filling of the pumping chamber which leads to a lower volumetric efficiency and an increased emission of CO2. Additionally pressure excursions from the average inlet pressure decrease the durability of the drivetrain and affect the durability of the low pressure system components on the vehicle.

For this reason it is an object of the invention to provide components of a fuel supply system of a diesel engine in which the problems associated with the pressure pulsations are at least significantly minimized in order to increase the efficiency of the pump of the diesel engine. It is a further object of the invention to increase the durability of the components of a drive train associated with the diesel engine.

This object is satisfied by a pump housing having the features of claim 1.

In particular such a pump housing is for a high pressure fuel pump comprising a low pressure side and a high pressure side for a diesel engine, the pump housing comprising a fluid inlet for feeding a fluid into the low pressure side and an elastomeric damper arranged within the low pressure side of the pump housing.

As the pressure in a cambox increases during the introduction of fuel the pressure acts on the inner surfaces of the walls of the cambox (pump housing). As this pressure exerts a force onto the elastomeric damper, the elastomeric damper is compressed. This allows for a volume compensation in the pump housing. The provision of a volume compensation in the pump housing ensures a smoother introduction of fuel into the high pressure part of the pump and also reduces the pressure pulsations present in the low pressure side of a high pressure pump.

Moreover, this design minimizes the number of components used in a pump, it reduces the cost of machining the pump housing and allows for a more compact pump packaging to be placed on the engine.

The problem of pressure pulsations in a high pressure pump having such a pump housing is solved by providing an elastomeric damper e.g. present in the form of a capsule. This means that pressure pulsations are avoided that can travel from such a high pressure fuel pump to the fuel tank and cause disruptions in the operation of the fuel supply system.

Preferably the elastomeric damper has elastic properties that are selected to compensate an increase in volume of the fluid in the first space on an operation of the fuel pump. Generally speaking, the displaced volume compensation will depend on the difference in pressure between the cam-box and the preferably inert gas pressure of the elastomeric damper. The internal damper pressure can be tuned to suit the mean pressure of the high pressure pump during the manufacture of the elastomeric damper.

Advantageously the elastomeric damper is hollow and filled with a gas, in particular an inert gas, such as argon.

The additional gas volume made available within the elastomeric damper, e.g. present as a capsule, allows for the compensation of the volume change in the pump housing, thus decreasing the amplitude of pressure excursions from the average feed pressure at the low pressure side of the pump.

Moreover, an elastomeric damper filled with argon is easy to handle. Since argon is not volatile the argon will not interact in a negative way with the material of the damper.

Preferably the pump housing comprises at least a first and a second space at the low pressure side of the pump housing, with the elastomeric damper being received in the second space that is adjacent to the first space and that is dedicated solely for the reception of the elastomeric damper. Providing the elastomeric damper in the dedicated second space that is preferably separate from the first space means that the volume of the pump available for pumping remains the same.

It is preferred if the second space is only accessible from within the pump housing. In this way the components of the pump are all present within the pump housing, moreover, no position is introduced at the pump where fuel could leak into the surrounding components.

Preferably the second space is provided in the form of a first recess formed in an inner surface of the pump housing. A recess can be provided in a simple manner during the production of the pump housing, it can either be included e.g. during a casting process or can be machined into the pump housing e.g. in the form of a bore. The provision of such a second space is simple to manufacture. Moreover, by selecting a suitable location of application of the recess, the pump outline dimensions can be minimized.

In this connection it should be noted that the first space can be a fuel reception chamber of the high pressure pump at the low pressure side of the pump, so that the provision of the elastomeric damper in the second space means that it is placed as close as possible to the point where a dampening of the pressure pulsations is required most on an operation of the high pressure pump.

In this connection it is beneficial if the elastomeric damper at least substantially completely fills the second space. In this way no dead space is created where fuel could collect and either degrade in time or cause interactions with the fuel introduced during the pumping phases which could lead to different pressure pulsations.

Preferably the pump housing further comprises retaining means to retain the elastomeric damper at a desired position within the pump housing. Such retaining means could be present in the form of a plate or a support and ensure that the elastomeric damper is retained at a desired position of implementation.

Advantageously the retaining means engage an inner surface of the pump housing. In this way it can be ensured that the location of the elastomeric damper is fixed within the housing.

It is preferred if the retaining means are present in the form of a circlip. A circlip is a relatively cheap component that only requires the provision of e.g. a groove or recess in the pump housing, with the circlip being able to engage in the groove or recess. Moreover, a circlip can provide a supporting function.

Moreover, a recess, such as a bore, can be produced in a cost-effective manner as, e.g. only a bore needs to be machined or a recess has to be cast during a production of the pump housing. Moreover, a groove has to be machined in the pump housing in order to accommodate the elastomeric damper and the circlip. The recess has a fairly minimal impact on pump size. In particular the recess could be provided in a suitable location where it does not come into close contact with other components of the pump or an engine at which the pump is attached.

Also the elastomeric damper can be installed simply on assembly, as after the provision of the elastomeric damper only a circlip is required to be inserted into the pump housing to retain the capsule.

Preferably the position of the retaining means defines a boundary between the first space and the second space. This provides a separation between the first space and the second space, in this way one can ensure that the pump components do not come into contact with the elastomeric damper which could hamper the operation of the pump.

In a further aspect the present invention relates to an elastomeric damper that can be used in a pump housing of a diesel pump as discussed herein, the elastomeric damper comprising two half shells that are bonded to one another to form the elastomeric damper, with the elastomeric damper being filled with a gas.

Advantageously the elastomeric damper comprises a viscoelastic polymer. Such a viscoelastic polymer has inherent elastic properties ensuring that the elastomeric damper can act as a cushion. Moreover, forming the half shells from a viscoelastic polymer also means that a diffusion of gas from within the elastomeric damper is at least substantially prevented.

In a further aspect the present invention relates to a method of making an elastomeric damper that can be used in a pump housing as described herein, the method comprising the steps of: - providing two half shells made from an elastomeric material that each define a half of the shape of the elastomeric damper; and - joining the two half shells in a gas chamber possibly on use of an adhesive.

The elastomeric damper in particular is proposed to be provided in the form of a capsule that is made out of the two shells. Each shell is made from an elastomer compound material, such as a viscoelastic polymer. After the forming of the two half shells, these are joined together using an adhesive in an e.g. inert gas chamber. This would allow to permanently seal pressurised gas inside the capsule.

In a further aspect the present invention relates to a high pressure fuel pump for a diesel engine, the fuel pump having a pump housing such as the one discussed herein and/or an elastomeric damper as described herein that could alternatively also be made using a method described herein.

In this connection it should be noted that the high pressure fuel pump is a piston pump and comprises at least one piston.

The advantages described in connection with the pump housing are likewise true in connection with the high pressure fuel pump described herein.

Although the present invention is intended to be comprehensive in terms of its description using embodiments, it will be apparent to those skilled in the art that many alternatives, equivalents and variations of varying degree will fall within the scope of the present invention.

The invention will be described in detail by means of embodiments and with reference to the drawings. These show preferred embodiments of the pump housing. The features described in the dependent claims, in the description and in the drawings may be configured in various combinations, which are encompassed by this document. The drawings show:

Fig. 1 a section through a part of a pump housing.

Fig. 1 shows a section through a part of a pump housing 10. The pump housing 10 houses part of a cambox 12 that is configured to receive a driveshaft having a cam profile (not shown). The driveshaft is generally received in the cambox 12 via different supports and bearings (also not shown) and in operation cooperates with a piston that is used to further compress the fuel so that this is pressurized to the desired degree for the injection into the combustion space (also not shown) of an internal combustion engine in a manner known per se.

At the upper end of the illustration of the pump housing 10 there is provided a buffer space 14 in which a capsule 16 is received. The capsule 16 is filled with a gas 18, such as an inert gas like Argon, with individual gas particles of the gas 18 being indicated within the capsule 16.

In order to retain the capsule 16 in the buffer space 14 a circlip 20 is provided at the end of the buffer space 14 facing the cambox 12. The circlip 20 is installed in a ring groove 22 provided in the pump housing 10.

In the present example the groove 22 is at least substantially of rectangular shape in a cross-section thereof. In this connection it should be noted that the shape of the groove 22 can be arbitrarily selected provided the shape is capable of receiving a circlip 20 or a different form of retaining means.

Likewise the shape of the buffer space 14 is configured so that it at least substantially completely receives the capsule 16 between the retaining means and the pump housing 10. In the present example the capsule 16 has an at least substantially rectangular cross-section in the plane of the section of the pump housing 10.

Consequently the buffer space 14 also has an at least substantially rectangular cross-section in the plane of the section of the pump housing 10 shown in Fig. 1.

The capsule 16 is formed from an elastomeric material, such as a material comprising natural rubber and/or silicone or a viscoelastic polymer.

The capsule 16 can be filled with the gas 18 prior to being installed in the pump housing 10. Alternatively the capsule 16 can be filled with the gas 18 after it has been installed in the pump housing 18. In this event a point of introduction of the gas 18 into the capsule 16 is sealed off using a heat treatment step (not shown).

The shape of the circlip 20 corresponds at least substantially to the shape of the capsule 16 when viewing the capsule 16 from the top. In order to retain the capsule 16 in the buffer space 14, the circlip 20 is dimensioned in such a way that it acts as a support for the capsule 16 when the circlip 20 is installed in the groove 22. A join 24 can be seen at the center of the capsule 16. The join 24 is present at the position at which two half shells 26, 28 of the capsule are joined together during a manufacture of the capsule 16. This is advantageously done in a gas chamber (not shown) in order to fill the capsule 16 with the gas 18.

On use of the pump housing 10, fuel, preferably diesel, is supplied via a fuel supply to the corresponding fuel pump. During an operation of an engine associated with the fuel pump, pressurized fuel is injected from the fuel pump into the engine.

Due to the fact that the capsule 16 is arranged in a low pressure side of the pump housing 10 the deviations in pressure within the pump housing 10 at an inlet side of the fuel pump are not as extreme as in a pump housing 10 that is not provided with a damper. This is because the capsule 16 made from an elastomeric material acts like a cushion to dampen the pressure exerted by the fuel present in the fuel pump, i.e. the capsule 16 permits a volume compensation of the fuel present in the fuel pump.

This pressure is present in the fuel pump due to a reciprocating motion of a reciprocating pumping element (not shown) present within a cylinder bore (not shown) that is driven via the driveshaft. The driveshaft is rota-tionally driven e.g. by a belt attached between the driveshaft and an output shaft of the engine. The driveshaft is configured to convert the rotational motion of the engine to the reciprocating motion of the fuel pump. The reciprocating pumping element present within a cylinder bore then compresses the fuel to achieve the high pressure which is evacuated through an outlet valve (not shown) of the outlet to the engine. The pumping chamber is re-filled with fuel through the inlet that typically comprises a valve (not shown) on a stroke of the pumping element.

The capsule 16 is arranged in a low pressure part of the pump housing 10 of the fuel pump. In particular it is arranged in that part of the pump housing 10 that accommodates the driveshaft having the cam profile.

List of reference numerals: 10 pump housing 12 cam box 14 buffer space 16 capsule 18 inert gas 20 circlip 22 groove 24 join 26 half shell 28 half shell

Claims

Claims:

1. A pump housing (10) of a high pressure fuel pump comprising a low pressure side and a high pressure side for a diesel engine, the pump housing (10) comprising a fluid inlet for feeding a fluid into the low pressure side and an elastomeric damper (16) arranged within the low pressure side of the pump housing (10).

2. The pump housing (10) according to claim 1, wherein the elastomeric damper is hollow and filled with a gas.

3. The pump housing (10) according to claim 1 or claim 2, wherein the pump housing (10) comprises at least a first and a second space (14) at the low pressure side of the pump housing, with the elastomeric damper (16) being received in the second space (14) that is adjacent to the first space and that is dedicated solely for the reception of the elastomeric damper (16).

4. The pump housing (10) according to claim 3, wherein the second space (14) is only accessible from within the pump housing (10).

5. The pump housing (10) according to claim 3 or claim 4, wherein the second space (14) is provided in the form of a first recess formed in an inner surface of the pump housing (10).

6. The pump housing (10) according to any one of the claims 3 to 5, wherein the elastomeric damper (16) at least substantially completely fills the second space (14).

7. The pump housing (10) according to at least one of the preceding claims, further comprising retaining means (20) to retain the elastomeric damper (16) at a desired position within the pump housing (10).

8. The pump housing (10) according to claim 7, wherein the retaining means (20) engage an inner surface of the pump housing (10).

9. The pump housing (10) according to claim 7 or claim 8, wherein the retaining means are present in the form of a circlip (20).

10. The pump housing (10) according to any one of the claims 7 to 9, wherein the retaining means (20) are received in a groove (22) or second recess present in the pump housing (10).

11. The pump housing (10) according to any one of the claims 7 to 10 when dependent on claim 3, wherein the position of the retaining means (22) defines a boundary between the first space and the second space (14).

12. An elastomeric damper (16) for use in a pump housing (10) of a diesel pump in accordance with at least one of the preceding claims, comprising two half shells (26, 28) that are bonded to one another to form the elastomeric damper (16), with the elastomeric damper being filled with a gas.

13. The elastomeric damper (16) in accordance with claim 12, wherein the elastomeric damper (16) comprises a viscoelastic polymer.

14. A method of making an elastomeric damper (16), e.g. in accordance with claim 12 or claim 13, for use in a pump housing (10) in accordance with at least one of the preceding claims 1 to 11, the method comprising the steps of: - providing two half shells (26, 28) made from an elastomeric material that each define a half of the shape of the elastomeric damper (16); and - joining the two half shells (26, 28) in a gas chamber possibly on use of an adhesive.

15. A high pressure fuel pump for a diesel engine having a pump housing (10), in particular in accordance with any one of the preceding claims 1 to 11; and comprising an elastomeric damper (16) in accordance with claim 12 or claim 13 or an elastomeric damper that is obtained using a method in accordance with claim 14.