GB2287664A

GB2287664A - Air filter assembly

Info

Publication number: GB2287664A
Application number: GB9504429A
Authority: GB
Inventors: Stanley William Kemp; Christopher Cosby
Original assignee: AC DELCO SYSTEMS OVERSEAS CORP
Current assignee: AC DELCO SYSTEMS OVERSEAS CORP
Priority date: 1994-03-22
Filing date: 1995-03-06
Publication date: 1995-09-27
Also published as: GB9405670D0; FR2717707A1; DE19509825A1; GB9504429D0

Description

AIR FILTER ASSEMBLY is 2287664 The present invention relates to an air

filter assembly for filtering, for example, air passing into an engine of a vehicle or into a ventilation system for a passenger compartment of a 5 vehicle.

The use of air filters for filtering air fed into the engine of a vehicle is becoming increasingly important, in particular as a result of the use of electronic engine management systems.

With the increase in amount and accuracy of processing of combustion events in the engine, it is becoming increasingly important to have highly efficient filtration of air which is due to pass into the engine.

In order to obtain highly filtered air, it is necessary to use filters which are able to remove in excess of around 99.5% of particles in the incoming air stream. Such filtration requires the filter medium to be formed with small air passages which can allow the capture of large and small particles.

on the other hand, present trends are to increase the period between vehicle services. However, existing filters having high filtration efficiencies tend to become clogged relatively quickly due to the formation of a layer of particles on the upstream side of the filter medium. As a result, there is a trade-off between the purity of air passing into the engine and filter life to meet servicing requirements.

The present invention seeks to provide improved air filter assembly.

According to an aspect of the present invention, there is provided an air filter assembly for filtering air passing through a vehicle air intake conduit comprising a first filter element; and a 2 pre-filter for filtering air prior to filtration by the first filter element; wherein the first filter element is pleated; wherein the pre-filter is adhered to the apexes of the pleats of the first filter element on one side of the first filter element; and wherein an elastomeric seal is provided around the periphery of the other side of the first filter element.

The pre-filter is designed to collect and hold particles which would otherwise clog the first filter element. In this manner, it is possible to provide very efficient filtration of air by use of a very fine filter element while maintaining and in some cases significantly increasing the operating life of the filter assembly. This is possible because of the pre-filter, which captures and holds a significant proportion of particles which would otherwise contribute to clogging the first filter element. In tests it has been found that the filter assembly can have an operating life up to around four times the operating life of a conventional air filter. In some cases, the filter assembly may last up to around 100,000 kilometres of vehicle use.

Preferably, the pre-filter is in the form of a filter pad having a thickness in the range of substantially 3 to 40 millimetres.

It has been found that this construction of pre-filter can provide relatively high particle capturing efficiency, in part as a result of the depth of the filter, and can retain its permeability for a significant period.

In the preferred embodiment, the pre-filter has arrestance of substantially 60 to 800-.. The pre-filter may be formed from a blown polyester fibre.

It has been found that a pre-filter having such 1 3 characteristics gives optimum pre-filtration of incoming air.

The first filter element may be formed from a cellulose paper, rayon or a micro-fibre filter medium.

The filter assembly can conveniently be treated as a single unit, thereby improving ease of use and reducing overall costs.

In an embodiment, the pre-filter is disposed below the first filter element. It is believed that when the pre-filter is disposed below the first filter element the operating life of the filter assembly may be increased. This may be caused by the manner in which particles eventually settle within the filter is assembly and at what point in the filter assembly the particles are caught and held.

The vehicle air intake conduit may be part of an air intake to a vehicle engine. Alternatively, the vehicle air intake conduit may be part of a ventilation system for supplying air to the passenger compartment of a vehicle. An embodiment of the present invention is described below, by way of illustration only, with reference to the accompanying drawings, in which: 25 Figure 1 is a perspective view of an embodiment of air filter; Figure 2 is an expanded view in perspective of the air filter of Figure 1; and Figure 3 is a cross-sectional view on the line III-III of Figure 1.

Referring to Figures 1 and 2, the embodiment of air filter assembly 10 shown is intended for location in the air intake passage leading to the cylinders of a vehicle engine. The air filter assembly 10 removes particles from the atmospheric air 4 fed through the intake system which would otherwise impair the performance of the engine.

The air filter assembly 10 has a generally rectangular shape and is formed of three parts, a pleated filter sheet or first filter element 12, a seal 14 of elastomeric material and a pre-filter 16. The filter sheet 12 is formed from any suitable woven or non-woven filter medium of a type well known in the art, for example a cellulose paper, a rayon based material, a polyester based material or any combination of such materials. A suitable material may be Toyobo Blitolon Grade EFU-60p (Trade Name) imported by Mitsubishi Corporation (UK) Ltd of Bow Bells House, Bread Street, Cheapside, London (GB). A preferred arrangement is cellulose fibre paper with a phenolic resin coating.

The filter material is folded into substantially parallel pleats 20 (Figure 3) which extend along a transverse axis of the filter element such that two opposing edge walls 22 of the filter element are formed by the ends of the pleats, while each of two opposing end walls 24 of the filter element 12 are formed by one of the pleats.

Adhered to the apexes 26 of the pleats 20 on one side 28 of the filter element 12 is the pre-filter 16, which is formed of a mass of intertwined fibres. In this example, the pre-filter is formed from a blown polyester fibre pad, for example Lockertex LT105 (trade name), and has a thickness of approximately 3 to 40 millimetres and preferably substantially 20 millimetres. The properties and in particular the filtration efficiency of the filter 16 are determined by its depth, its permeability and the type and diameter of its fibres. Preferably, the pre-filter 16 is chosen to have a relatively high filtration of the particles which would clog the filter element 12 while providing little resistance to air flow. In this example, the pre-filter 16 has an arrestance measured according to BS6540/DIN24185 between about 60 and 95- 0. and most preferably of about 930-.. The preferred filter medium has a filter classification of BU4, and a dust holding capacity of about 699 g/M2.

The pre-filter 16 is adhered to the filter element 12 so as to cover substantially the whole of the associated side 28 of the filter element 12.

The seal 14, which is preferably moulded from a urethane foam, extends around the periphery of the side 30 of the filter element 12 remote from the pre-filter 16, so as to have the form of a frame corresponding to the side 30 of the filter element 12, and is secured thereto in any suitable manner. In the example shown, the seal 14 includes four frame members 18 coupled to one another in the form of the frame. Each frame member 18 is formed of two substantially 20 perpendicular walls 32,34, one 32 extending over part of the side 30 of the filter element 12, the other 34 extending over an edge or end wall 22, 24 of the filter element 12. The construction of the seal 14 is such as to provide support for the filter element 12 and to provide a seal for sealing the edges and ends of the filter 10 to the housing of the vehicle air intake passage.

Air flow through the filter 10 is in the direction of the arrows A shown in Figure 1. Air is first filtered by the pre-filter 16 and then passed to and filtered by the pleated filter element 12 prior to passage to the vehicle engine By virtue of its effective filtration depth and the structure and type of its fibres, the pre-filter 16 captures and holds a 6 significant proportion of particles in the air stream which would otherwise contribute to clogging the filter element 12. The filter element 12 then completes the filtration of the in-coming air to provide the desired degree of air purity.

In an example, a filter assembly 10 of the above-described construction included a filter element 12 of cellulose paper having 106 folds and an effective filtration area of 16748 CM2. A pre-filter 16 of Lockertex LT105 (trade name) having a thickness of 20 mm and an effective area of 600 CM2 was secured to the filter element 12 by adhesion to the apexes 26. At an air test flow rate of 5 M3/min the filter assembly 10 was found to generate a pressure drop thereacross of 9.0 mm water gauge (WG). Air including coarse test dust having a concentration of 1000 Mg/M3 was then passed through the filter assembly 10 until the pressure drop across the filter assembly 10 increased by 200 mm WG. During the test, the filter 20 assembly 10 had a filtration efficiency of 99.94-0o. On weighing the filter assembly 10 after the test, it was found that it had captured 535. 72 g of dust. This equates to a dust load of 0.032 g/CM2 of the filter element 12, several times the dust load of a filter without the prefilter 16. It has been found in tests that the above-described filter assembly 10 can provide very high filtration efficiency while having a filter life up to four times that of a filter which does not include the pre-filter 16.

In a full test, the filter assembly 10 was placed in a vehicle with the pre-filter 16 lying below the filter element 12 and with the incoming air passing upwardly through the filter assembly 10. It 1 7 is believed this arrangement may increase the operating life of the filter.

In alternative embodiments, the pre-filter 16 may be used in a cabin filter assembly designed to filter air passing into the passenger compartment of a vehicle. In such embodiments, the filter element may be of cellulose paper, rayon, or a micro filter medium.

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Claims

Claims:

1. An air filter assembly for filtering air passing through a vehicle air intake conduit comprising a first filter element; and a pre-filter for filtering air prior to filtration by the first filter element; wherein the first filter element is pleated; wherein the pre-filter is adhered to the apexes of the pleats of the first filter element on one side of the first filter element; and wherein an elastomeric seal is provided around the periphery of the other side of the first filter element.

2. An air filter assembly according to claim 1, wherein the pre-filter is in the form of a filter pad having a thickness in the range of substantially 3 to 40 millimetres.

3. An air filter assembly according to claim 1 or 2, wherein the prefilter has an arrestance of substantially 60 to 80%.

4. An air filter assembly according to any one of claims 1 to 3, wherein the pre-filter is formed from a blown polyester fibre.

5. An air filter assembly according to any one of claims 1 to 4, wherein the first filter element is formed from a cellulose paper, rayon or a micro- fibre filter medium.

6. An air filter assembly according to any one of claims 1 to 5, wherein the vehicle air intake conduit is part of an air intake to a vehicle engine.

7. An air filter assembly according to any one of claims 1 to 5, wherein the vehicle air intake conduit is part of a ventilation system for supplying air to the passenger compartment of a vehicle.

8. An air filter assembly substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

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