GB2597705A

GB2597705A - Filter assembly

Info

Publication number: GB2597705A
Application number: GB2011867.5A
Authority: GB
Inventors: Wade Ben; Mold Alex
Original assignee: Delphi Technologies IP Ltd
Current assignee: Delphi Technologies IP Ltd
Priority date: 2020-07-30
Filing date: 2020-07-30
Publication date: 2022-02-09
Anticipated expiration: 2040-07-30
Also published as: GB2597705B; GB202011867D0

Abstract

A filter assembly 26 for a fuel system of an internal combustion engine comprises a first filter element 28 and a second filter element 30, the first filter element being arranged upstream of the second and each comprising a filter medium for preventing the onward passage of particles of a size determined by a filter dimension for each of the filter elements which is greater for the first than the second, and wherein the filter elements are arranged together in a common housing 62. The assembly preferably comprises one or more additional filter elements 32 having a reduced filter dimension compared to the preceding upstream element. The filter elements may comprise a conical filter body, wherein a filter element is received within the body of the element located immediately downstream to form a stacked filter assembly. A closed tip end 60 of each filter element may collect particles and block the flow of fuel through the end. The common housing is preferably part of a pump housing of the fuel system.

Description

FILTER ASSEMBLY

Field of the invention

The invention relates to a filter assembly for use in a fuel system. In particular, but not exclusively, the invention relates to a filter assembly for use in filtering fuel supplied to a fuel pump of an internal combustion engine. The invention also relates to a fuel system incorporating a filter assembly.

Background to the Invention

It is known to provide filters in fuel injection systems to prevent particles and debris which are present in the fuel flow from causing damage to the component parts of the system. In a compression ignition internal combustion engine, for example, one component that it is important to protect is the high pressure fuel pump which pressurises fuel to a high level suitable for injection. In a common rail fuel injection system, the high pressure fuel pump typically receives fuel from a low pressure circuit, at around 4-7 bar, and increases the pressure to a level in excess of 2000 bar. The pressurised fuel is then supplied to the common rail from where it is supplied to the injectors for injection into the combustion chambers.

The high pressure circuit of the fuel pump is protected from damage caused by particles and debris by means of a filter. There are several places that a filter can be used in such systems; (i) in the pipe between fuel tank and pump inlet; (ii) in the pump inlet connector; (ii) in the inlet metering valve; and (iv) in the area around the inlet valve. When the filter is provided upstream of the inlet valve to the pump it prevents particles with a size in excess of around 150 microns from entering the pump. However, whilst such filters provide a degree of protection for the pump, particles with a size less than the filter size can still pass through the filter and cause damage. Reducing the filter size further is not always straightforward because it results in a reduced flow rate through the pump, which can cause blockages. Furthermore, the situation of the filter at the inlet valve presents a particular problem for pump orientations where the hydraulic head is arranged vertically. In this orientation particles which have managed to pass through the current filters tend to collect at the seal between the inlet valve and the valve seat. The result of debris build up at the valve seat is that there is insufficient pressure generated for the pump to function properly and so the engine cannot be started.

It is against this background that the present invention has been devised.

Summary of the Invention

According to the present invention, there is provided a filter assembly for a fuel system of an internal combustion engine, the filter assembly comprising at least a first filter element and a second filter element, the first filter element being arranged upstream of the second filter element, each of the filter elements comprising a filter medium for preventing the onward passage of particles of a size determined by a filter dimension for each of the filter elements which is greater for the first filter element compared to the second filter element, and wherein the first and second filter elements are arranged together in a common unit or in a common housing.

The invention provides the advantage that a multi-stage filter assembly is provided for particles and other debris in the flow which are gradually filtered from the flow, with larger particles being filtered from the flow initially and then smaller particles being filtered in the downstream stage(s) of the filter assembly. This prevents the smaller openings in the downstream filter element(s) from being blocked by larger particles and ensures that a satisfactory flow rate is maintained through the filter assembly. The filter assembly is particularly suitable for use upstream of an inlet to a high pressure pump or other injection system components, such as fuel injectors.

In embodiments of the invention, the filter assembly further includes one or more additional filter element, arranged downstream of the second filter element, such that the filter medium of each filter element has a reducing filter dimension compared to the preceding upstream filter element. For example, the one or more additional filter elements is arranged in the common housing together with the first and second filter elements.

Conveniently, each of the filter elements includes a conical filter body.

The filter elements may be arranged to form a stacked filter assembly. In one embodiment, all bar one of the filter elements is received within the filter body of the filter element which is located immediately downstream.

By way of example, at least a tip of at least one of the filter elements is received within the filter body of a filter element which is located immediately downstream.

For example, the tip of each filter element which is received within the filter body of the filter element which is located immediately downstream may be received in a press fit, a screw fit or a shrink fit within said filter body.

In some embodiments, the tip of each filter element may be configured to collect particles and block the flow of fuel through the tip.

Alternatively, in other embodiments, the tip of each filter element may be configured to allow particles which are smaller than the filter dimension to pass through the tip.

The filter body may be formed from a filter mesh formed into a conical body.

In other embodiments, as an alternative to having filter elements of conical form, each of the filter elements may be a planar filter element (e.g. disc) arranged to form a stacked filter assembly.

In one embodiment, the common housing need not be a separate housing part which mounts, for example, within a pump housing, but may itself be a housing part of a pump housing of the fuel system. In this case, during assembly the filter elements are fitted into the pump housing one filter element at a time.

In accordance with another aspect of the invention, there is provided a fuel system including the filter assembly of the preceding aspect of the invention.

By way of example, the fuel system may include a high pressure pump for supplying fuel to a common rail of the fuel system, wherein the high pressure pump has an inlet valve, and wherein the filter assembly is arranged upstream of the inlet valve.

The fuel system may further comprise an inlet metering valve for controlling a metered supply of fuel to the inlet valve of the high pressure fuel pump, and wherein the filter assembly is arranged between the inlet metering valve and the inlet valve.

The inlet metering valve may itself have a filter element (either integral with or upstream of the inlet metering valve), and the filter assembly is provided in addition to any filter which may be provided specifically for the inlet metering valve.

It will be appreciated that preferred and/or optional features of each aspect of the invention may be incorporated alone or in appropriate combination in the other aspects of the invention also.

Brief Description of the Drawings

The invention will now be described, by way of example only, with reference to the accompanying figures in which: Figure 1 shows a high pressure fuel pump system in which the filter assembly of the invention may be used; Figure 2 is a schematic diagram of the high pressure fuel pump system in Figure 1 to illustrate the position of the filter assembly within the system; Figure 3 is a side view of the filter assembly shown in Figure 2; and Figure 4 is a cut away perspective view of the filter assembly in Figure 3.

The skilled reader will appreciate that in practice embodiments of the invention may be oriented differently to the manner depicted in the drawings.

Detailed Description of Embodiments of the Invention Referring to Figure 1, a fuel system including a high pressure fuel pump, referred to generally as 10, includes a filter assembly (not shown in Figure 1) of the invention. The high pressure fuel pump includes a main pump housing 12 to which a hydraulic head 14 is mounted. A drive shaft 16 extends through the main pump housing 12 and drives a pumping plunger (not visible in Figure 1) to perform a pumping cycle as the drive shaft rotates, in use. The hydraulic head 14 is mounted on the main pump housing 12 so that an axis of movement of the pumping plunger is vertically aligned. The hydraulic head 14 comprises an inlet (not visible in Figure 1) to which fuel is delivered from a low pressure fuel system. Fuel delivered to the pump chamber (not visible in Figure 1) is supplied through an inlet valve (also not visible in Figure 1) and a filter assembly of the invention (also not visible in Figure 1) and fuel within the pump chamber is pressurised to a high level suitable for injection. In a compression ignition internal combustion engine, fuel is typically pressurised to a level around or in excess of 2000bar and is delivered through a high pressure outlet 18.

Referring to Figure 2, the components of the high pressure fuel pump 10 in Figure 1 can be seen in more detail. A low pressure feed line 20 supplies fuel to an inlet metering valve (IMV) 22 which regulates the rate of flow of fuel supplied to the pump chamber. The IMV 22 has an associated IMV filter 24 located upstream of the IMV 22 which serves to filter relatively large particles in the fuel flow and prevents them from reaching the IMV 22. The IMV filter 24 is a relatively simple, primary stage filter for the flow of fuel and although it is effective to remove larger particles from the fuel flow it does not in itself provide an ideal level of filtration for the flow to the high pressure pump as smaller particles can still pass through the IMV filter 24, causing damage to the fuel pump.

Downstream of the IMV 22, the fuel therefore passes through a second stage filter arrangement, referred to generally as 26, including first, second and third filter elements, 28, 30, 32 respectively. The first filter element 28 is selected to filter smaller particles than the IMV filter 24. Of the three filters elements 28, 30, 32, the first filter element is selected to filter relatively larger particles compared to the second filter element 30 and the second filter element 30 is selected to filter relatively larger particles compared to the third filter element 32. Thus, the three filter elements provide a multi-stage filter assembly where decreasingly smaller particles are filtered from the flow at each filter stage. By way of example, the first filter element 28 may be selected to filter particles having a dimension of 100 pm, the second filter element 30 may be selected to filter particles having a dimension of 75 pm, and the third filter element 32 may be selected to filter particles having a dimension of 50 pm.

Having passed through the three filter elements 28, 30, 32, the flow is then passed to a spring-biassed inlet valve 34 associated with the hydraulic head 14 which allows fuel to flow through the inlet valve only if it exceeds a predetermined pressure level, as determined by the force of the associated spring. The fuel then passes to the pump chamber 35 for pressurisation by the pumping plunger 36 and is delivered through a spring-biassed outlet valve 38 to the downstream parts of the fuel system (e.g. the common rail 40). The filter assembly is sized to ensure an adequate flow (at all reasonably expected fuel temperatures) is received at the inlet to the pump and any particles which are collected within the filter do not provide a blockage to the flow to adversely affect the flow rate through the filter 26.

Referring to Figures 3 and 4, the filter assembly is constructed so that the first, second and third filter elements 28, 30, 32 form a single, integrally formed filter unit which is mounted upstream of the hydraulic head 14. The filter elements 28, 30, 32 are mounted within a common housing, as will be described in further detail below.

Considering the first filter element 28, this takes the form of an elongate filter element comprising a first filter medium or mesh which is formed into a conical body. The first filter medium comprises a plurality of first openings 42 to allow fuel to pass freely therethrough. However, each of the first openings 42 has a dimension that is selected to prevent the passage of particles greater than a certain size. The first openings 42 may be circular and the dimension may be the diameter of the circular opening, although other shapes for the openings, and other dimensions, are also envisaged. Typically, the dimension of each of the first openings 42 for the first filter element 28 is 100 pm in diameter.

The first filter medium is open at one end 44 (the left hand end in the illustration shown) and is closed at the other, tip end 46 (the right hand end in the illustration shown). The closed tip end 46 of the first filter element 28 defines a first collection volume for particles which are not able to pass through the first openings 42 (i.e. the closed end forms a particle trap). For the first filter element 28, the left-hand end of the filter medium includes a tip end region 48 which is not provided with any openings and so does not allow the passage of any fuel through the medium in this region. This tip end region forms a mounting region 48 for the filter assembly, as described in further detail below.

In use, as fuel enters the open end 44 of the first filter element 28, it flows radially outwards through the first openings 42 of the filter medium for onward passage through the filter assembly 26. Any particles which are not small enough to pass through the plurality of first openings 42 continue with the flow through the conical filter body and collect in the first collection volume 46.

The second filter element 30 has the same construction as the first filter element 28, including a second filter medium forming a conical filter body which is provided with a plurality of second openings 50. At its inlet end, the second filter element 30 includes an open end 52 but this does not define a mounting region, as for the first filter element 28, for reasons that will become clear in the following description.

Again, the second filter element 30 has a closed tip end 54 remote from the open end 52 which defines a second collection volume for particles which are too big to pass through the second openings 50 (i.e. the closed end forms a particle trap). The closed tip end 46 of the first filter element 28 is received in the open end 52 of the second filter element 30 in an interference fit.

In a similar manner, the third filter element 32 comprises a third filter medium which forms a conical filter body which is provided with a plurality of third openings 56. The third filter element 32 also has an open tip end 58, which receives the closed tip end 54 of the second filter element 30, and a closed tip end 60 remote from the open tip end 58. The open tip end 58 of the third filter element 32 receives the closed tip end 54 of the second filter element 30 in an interference fit. The closed tip end 60 defines a third collection volume for particles (i.e. the closed end forms a particle trap).

In this way, the first, second and third filter elements 28, 30, 32 form a stacked assembly with all bar an end one of the filter elements (the right hand filter element 32) being received within the hollow filter body of the filter elements which is located immediately downstream. Additional filter elements could be added to the assembly 26 to extend the arrangement to include further filter stages.

Alternatively, the filter assembly may only include two filter elements.

As shown in Figure 4, the first, second and third filter elements 28, 30, 32 are received within a tubular filter housing 62, common to all filter elements, which defines an internal cavity through which fuel flows once it has passed through the openings 42, 50, 56 in the various filter elements. The mounting region 48 of the first filter element 28 forms an interference fit within the filter housing 62 so that fuel is not able to pass between the wall of the internal cavity and the first filter element 28 in this region. The assembly of the first, second and third filter elements28, 30, 32, together within the common housing 62, forms a unitary filter part. The housing 62 may be formed from more than one housing part, without detracting from the unitary nature of the assembly.

In other embodiments, the first filter element 28 may be mounted within the filter body 62 by others means, including screw threading, shrink-fitting or press-fitting.

Likewise, the first filter element 28 may be coupled to the second filter element 30, and the second filter element 30 may be coupled to the third filter element 32, by alternative means such as screw threading, shrink-fitting or press-fitting.

In use, fuel which has passed through the first openings 42 in the first filter element 28 flows radially outwards through the first openings 42 for onward passage through the second filter element 30. Fuel is able to pass through the second openings 50 in the second filter medium and flows radially outwards through the second filter medium for onward passage to the third filter element 32, whilst particles which are larger than the second openings 50 are not able to pass through the filter medium of the second filter element 30 and collect within the second collection volume 54. Importantly, the dimension of the second openings 50 in the second filter medium is smaller than the dimension of the first openings 42 in the first filter medium, so that a progressive filtration effect is provided by these two filter elements, with particles of decreasing size being filtered as the flow moves downstream through the assembly.

Fuel which passes through the second filter element 30 is able to flow through the third openings 56 in the third filter medium and flows radially outward through the third openings 56 to exit the filter assembly 26, whilst particles which are bigger than the dimension of the third openings 56 cannot pass through and collect in the third collection volume 60. Importantly, the dimension of the third openings 56 in the third filter element 32 is smaller than the dimension of the second openings 50 in the second filter element 30 (and hence smaller than the first openings 42 in the first filter element 28 also), so that a progressive filtration effect is provided by the three filter elements 28, 30, 32, with particles of decreasing size being filtered as the flow passes downstream, through the filter assembly.

Because the filter mediums present a large flow area to flow, by virtue of the plurality of openings 42, 50, 56 around the conical bodies of the filter elements, a relatively high flow rate can be achieved through the filter assembly 26 and the pressure drop across the filter assembly is limited. Also, the multi-stage filter process ensures that larger particles are eliminated from the flow by the first filter member 28 and so do not tend to clog the smaller openings of the second and/or third filter elements 30, 32. Likewise, the second openings 50 of the second filter element 30 are sized so that the particles they prevent from passing onwards through the filter assembly cannot clog the smaller openings 56 of the third filter element 32. Overall, the staggered filter assembly provides a good solution for maintaining a desirable flow rate through a filter assembly which does not readily become clogged or blocked with debris. The filter assembly is conveniently formed by assembling the filter elements 28, 30, 32 one inside the other and then receiving the three filter elements combined within the common filter housing 62.

In other embodiments one or more of the closed ends of the filter elements 28, 30, 32 may be provided with openings, in the same way as the conical body section, so that flow can continue through the end of the filter element, as well as via radial flow through the openings 42, 50, 56. The same, staggered filtering process is achieved, but with the exception that particles are not collected at the tip ends but are simply blocked from passing through the openings, depending on their size.

In a further modification, if closed ends are provided for the filter elements 28, 30, 32, the closed ends may be removable from the main filer body so that the filter assembly can be cleaned during service to remove collected debris in the collection volume. Alternatively, the whole filter assembly may be removed completely for replacement.

In other embodiments only the end of one of the filter elements may be closed.

Dimensions for the first, second and third filter elements 28, 30, 32 are typically 100pm, 75 pm and 50 pm, as mentioned above, but other selections of sizes are envisaged. Typically, for example, the second openings 50 in the second filter element 30 may be between 50 and 80 per cent of the size of the first openings 42 in the first filter element 28, and the third openings 56 in the third filter element 32 may be between 50 and 80 per cent of the size of the second openings 50 in the second filter element 30.

If only two filter elements are provided, other arrangements of sizes for the openings are envisaged, but typically the dimensions of the openings in the second filter medium may be between 40 and 80 per cent of the dimensions of the openings in the first filter medium.

Whilst the use of conical filter elements is particularly convenient, the same staggered filtering effect may be achieved by arranging a plurality of filter discs within a common filter housing, with each disc being provided with openings to allow fuel to flow through, but preventing the passage of debris and other particles depending on the dimension of the openings. As described previously, the size of the dimensions in the discs reduces with the downstream flow so that the first filter disc in the series provides a larger dimension to filter relatively large particles, and subsequent filter discs in the series filter decreasingly smaller particles.

In a still further embodiment, instead of the arranging the filter elements 28, 30, 32 of Figure 3 in a common housing 62, which is a separate housing part from the pump housing 12, the filter elements 28, 30, 32 may be received directly within the pump housing 12 without the need for an additional component. In this case the two or more filter elements may be shrink fitted, interference fitted, press fitted or screw threaded directly into the main pump housing 12, inserting each filter element into the housing 12 one at a time. In this embodiment reference to a "common housing" for the filter elements is therefore taken to mean the main pump housing itself, or a housing part carried by the main pump housing.

It will be appreciated that various modifications to the aforementioned embodiments may be made without departing from the scope of the invention.

References used: -fuel pump 12-main pump housing 14-hydraulic head 16 -drive shaft 18-high pressure outlet 20-low pressure feed line 22-inlet metering valve (IMV) 24-inlet metering valve (IMV) filter 26 -second stage filter assembly 28 -first filter element -second filter element 32-third filter element 34 -inlet valve -pump chamber 36-pumping plunger 38 -outlet valve 40-common rail 42 -plurality of first openings 44 -open end of first filter element 46-closed tip end of first filter element 48 -end region of first filter element 50-plurality of second openings 52 -open end of second filter element 54 -closed tip end of second filter element 56 -plurality of third openings 58 -open end of third filter element 60-closed tip end of third filter element 62 -filter housing

Claims

Claims: 1. A filter assembly (26) for a fuel system of an internal combustion engine, the filter assembly (26) comprising: at least a first filter element (28) and a second filter element (30), the first filter element (28) being arranged upstream of the second filter element (30), each of the filter elements (28, 30) comprising a filter medium for preventing the onward passage of particles of a size determined by a filter dimension for each of the filter elements which is greater for the first filter element (28) compared to the second filter element (30), and wherein the first and second filter elements are arranged together in a common housing (62).
2. The filter assembly (26) as claimed in claim 1, wherein the filter assembly (26) further includes one or more additional filter element (32), arranged downstream of the second filter element (30), such that the filter medium of each filter element (28, 30, 32) has a reducing filter dimension compared to the preceding upstream filter element.
3. The filter assembly (26) as claimed in claim 2, wherein the one or more additional filter elements (32) is arranged in the common housing (62) together with the first and second filter elements (28, 30).
4. The filter assembly (26) as claimed in any of claims 1 to 3, wherein each of the filter elements (28, 30, 32) includes a conical filter body.
5. The filter assembly (26) as claimed in claim 4, wherein the filter elements (28, 30, 32) are arranged to form a stacked filter assembly wherein all bar an end one of the filter elements (32) is received within the filter body of the filter element which is located immediately downstream.
6. The filter assembly (26) as claimed in claim 4 or claim 5, wherein at least a tip (46, 54) of at least one of the filter elements (28, 30) is received within the filter body of a filter element which is located immediately downstream.
7. The filter assembly (26) as claimed in claim 6, wherein the tip (46, 54) of each filter element (28, 30) which is received within the filter body of a filter element which is located immediately downstream is received in a press fit or a shrink fit or a screw fit within said filter body.
8. The filter assembly (26) as claimed in claim 6 or claim 7, wherein the tip (46, 54) of each filter element (28, 30) which is received within the filter body of a filter element which is located immediately downstream is configured to collect particles and block the flow of fuel through the tip.
9. The filter assembly (26) as claimed in claim 6 or claim 7, wherein the tip (46, 54) of each filter element (28, 30) which is received within the filter body of a filter element which is located immediately downstream is configured to allow particles which are smaller than the filter dimension to pass through the tip (46, 54).
10. The filter assembly (26) as claimed in any of claims 4 to 9, wherein the filter body comprises a filter mesh formed into a conical body.
11. The filter assembly (26) as claimed in any of claims 1 to 3, wherein each of the filter elements (38, 30, 32) is a planar filter element arranged to form a stacked filter assembly.
12. The filter body as claimed in any of claims 1 to 4, wherein the common housing is a housing part of a pump housing (12) of the fuel system.
13. A fuel system including the filter assembly (26) as claimed in any of claims 1 to 12.
14. The fuel system as claimed in claim 13, comprising a high pressure pump (10) for supplying fuel to a common rail of the fuel system, wherein the high pressure pump (10) has an inlet valve (34), and wherein the filter assembly (26) is arranged upstream of the inlet valve.
15. The fuel system as claimed in claim 14, further comprising an inlet metering valve (22) for controlling a metered supply of fuel to the inlet valve (34) of the high pressure fuel pump (10), and wherein the filter assembly (26) is arranged between the inlet metering valve (22) and the inlet valve (34).