マーレのキャビンエアフィルタ - 車内の空気を清浄に保つ

キャビンエアフィルタは非常に効率的に機能します。わずか1時間のドライブであっても車内を循環する空気の量は最大10万リットルに達しますので、キャビンエアフィルタの定期交換は非常に重要となってきます。そこでマーレは、走行距離1万5,000キロメートル毎、あるいは最低でも年1回のキャビンエアフィルタの交換を推奨しています。キャビンエアフィルタが故障したり、目づまりが発生した場合、車内の汚染物質の濃度は外気の6倍にも上昇します。マーレのキャビンエアフィルタは、スモッグの発生や多量の花粉が飛散している状態でもドライバーと乗員に清浄な空気を確実に届け、健康や快適性、ドライバーの集中力を守ります。また、キャビンエアフィルタはブロワの負荷の低減、汚染物質からのエアコンの保護、空気循環の改善、危険なウィンドウの曇り防止など、さまざまな役割も担っているだけでなく、ウィンドウの内部やフィッティングもクリーンな状態に保ち、長持ちさせます。

キャビンエアフィルタエレメントのプリーツ形状は、長寿命を実現できるようデザインされています。また、低い流体抵抗はブロワの負荷を最小限に抑えます。ハウジングに正確にフィットしたフィルタエレメントのおかげで、バイパスエアは抑制されます。

マーレの活性炭キャビンエアフィルタLAK 472

活性炭エレメント付きのキャビンエアフィルタは、有害な排出ガス、汚れ、塵埃だけでなく、高濃度のオゾンや不快な臭気も除去します。プリーツ形状のベローズは、不織布材の2層の間に活性炭層が挟まれた3層構造となっています。熱加工によってフィルタ層が結合されるため、溶剤が含まれる接着剤は使われていません。車両タイプに応じて、従来のキャビンエアフィルタの代わりに使用できる活性炭フィルタもあります。

マーレのキャビンエアフィルタ

キャビンエアフィルタが装備されていない車両に、活性炭キャビンエアフィルタを含め、マーレのキャビンエアフィルタを後付けすることができます。その際、マーレの幅広い製品ラインナップの中から、フィルタエレメントを特定の車両に適したハウジングと組み合わせることも可能です。

Car manufacturers have been using cabin air filters for many years now to make sure that the passengers get enough clean air to breathe. Whether passenger cars, trucks, buses or agricultural and construction machinery: almost every vehicle today has a “cleaner”—either as a simple particulate filter or combination filter with activated carbon layer. Particulate filters filter solids out of the air we breathe and protect us against fine particulate, pollen, industrial dusts and other microscopic, respirable particles. Activated carbon filters also absorb smells and toxic gases such as nitrogen oxides, petrol vapours or fertilizers and break down up to 99 % of ozone.

Additional coarse filters are often used in vehicles with a long service life that are operated in heavily polluted areas. This type of filter mat can often be seen in traffic as roof-top structures on buses. Others are fitted in the air intake system before the actual cabin air filter and installed as pre-filters in the heater and air-conditioning casing. These coarse filters are used to ensure the maximum filter service life for the complete filter surface area of the cabin air filter: if a mass of coarse particles hits the fanfold surface of the filter this can lead to a premature clogging of the inlet side of the air filter—even to the dreaded pleat bellows clogging that prevents the passage of any air at all. Upstream coarse filters can reduce one-sided clogging of the surface of the cabin air filter on the inlet side, thus helping to ensure that the entire filter capacity is used before the cabin air filter is changed during routine inspections.

CABIN AIR PRE-FILTER (LAP): FOAM OR FLEECE
Pre-filters are normally made of polyester foams or fleece mats. The choice of material depends on the specifications of the vehicle manufacturer.

FOAMED: A HOMOGENEOUS STRUCTURE
Polyester foams consist of a homogeneous block with uniform pores produced by a special thermophysical process, reticulation. After cooling the foam is cut into slices and shaped by cutting dies.

Reticulation – what’s that?
Reticulation is the term used to describe the subsequent removal of foam membranes in a pressure vessel charged with gas. This process produces a uniform, open pore lattice structure with a minimum flow resistance for gases and fluids.

The filter effect of the reticulated material depends on the pore size PPI (pores per inch, in other words the number of open linear pores per inch = 25.4 mm). The higher the PPI number the smaller the particles that can be filtered. Common foams have between PPI 10 and PPI 80. MAHLE Original and Knecht LAP pre-filters are made using foams with a PPI of 30 since extensive laboratory tests have proven the optimum relationship between service life and coarse particle filtration for this pore size.

Polyester foam is resistant to ozone and partly resistant to hydrolysis, it withstands ageing and temperatures up to 90 °C and it is free from plasticizers and CFCs. The material can be recycled and poses no problems for thermal disposal.

FLEECE MATS: PROGRESSIVE LAYERS
These fleece mats are based on approx. 10 and 20 mm thick polyester fibre mats that are made up of various, progressive layers so that they become denser and denser on the clean air side. This structure combines a maximum filter performance with optimum dust retention properties.

Filter mats are classified in filter classes according to DIN EN 779.

The filter effect of the reticulated material depends on the pore size PPI (pores per inch, in other words the number of open linear pores per inch = 25.4 mm). The higher the PPI number the smaller the particles that can be filtered. Common foams have between PPI 10 and PPI 80. MAHLE Original and Knecht LAP pre-filters are made using foams with a PPI of 30 since extensive laboratory tests have proven the optimum relationship between service life and coarse particle filtration for this pore size.

Polyester foam is resistant to ozone and partly resistant to hydrolysis, it withstands ageing and temperatures up to 90 °C and it is free from plasticizers and CFCs. The material can be recycled and poses no problems for thermal disposal.

FLEECE MATS: PROGRESSIVE LAYERS
These fleece mats are based on approx. 10 and 20 mm thick polyester fibre mats that are made up of various, progressive layers so that they become denser and denser on the clean air side. This structure combines a maximum filter performance with optimum dust retention properties.

Filter mats are classified in filter classes according to DIN EN 779.

Filter classFiltration efficiency
G2up to 80 %
G3up to 90 %
G4> 90 %

Weights of between 100 g/m² and 200 g/m² are used depending on the requirements. For example, a G2 filter mat with a weight of 100 g/m² will primarily stop coarse particles whereas a G3 filter mat of the same thickness and a weight of 200 g/m² can filter out much finer particles.

Polyester fleece is hardly flammable (classification of inflammability F1), resistant to hydrolysis, withstands ageing and temperatures up to 100 °C. The material is free from silicon, plasticizers and CFCs, can be recycled and is suitable for thermal disposal.

The surface of the cabin air filter can become clogged with coarse dirt particles—right through to pleat bellows clogging (see left)—whereas the lower depths of the pleats remain relatively clean (see right). A pre-filter protects against this premature wear (LAP).

REPLACING CABIN AIR FILTER MATS (LAP)
Since the coarse filters are often located in front of the actual cabin air filters they can usually be replaced with no great effort by the driver. Only a few steps are needed and these are described in detail in the MAHLE fitting instructions (see illustration example).

Image-Galerie

LAP filters are either used as pre-filters in addition to particulate filters (LA) or as combi-filters (LAK). Older commercial vehicles only filter the outside air for the driver’s cab through filter mats. MAHLE Original and Knecht cabin air filter mats (LAP) are also available for a number of these commercial vehicles.

MAHLE is one of the top suppliers of cabin air filter mats on the free aftermarket. Following a successful market launch the range of products is constantly expanded, with a focus on commercial vehicle applications and older passenger cars as of model year 1980. Popular examples include the Renault Truck Midlum or Volvo 760. Cabin air filter mats will also be available as of October 2010 for commercial vehicles from DAF, MAN, Mercedes, Neoplan, Saab, Webasto or cars such as the Mercedes-Benz S-Class.

A TIDY JOB
During only one hour driving, an air volume of up to 100,000 litres is blown into the vehicle interior. All the more important is the regular replacement of the cabin air filters. The MAHLE filter experts recommend: replace filters after every 15,000 km or at least once per year. If the cabin air filter is clogged up or fails completely, the pollutant concentration in the interior of the vehicle can increase up to six times of that of the outside air. MAHLE cabin air filters supply driver and passengers reliably with cleaned air to breathe and safeguard their health, well-being and the driver’s ability to concentrate even in the presence of smog or high pollen count.

HOLDING BACK THE DIRT
Dirt particles such as dust, pollen or soot, harmful exhaust fumes, high ozone concentrations, unpleasant odours and even fine particulate dust: all these are retained by the cabin air filter – provided it is a combi-filter (LAK) that consists of two fleece layers and an active carbon layer, like this one. Due to the sandwich construction of the combi-filter (see also the scanning electron microscope image), two independent functions have been combined in one filter. The gases (mainly hydrocarbons as well as inorganic and harmful gases such as hydrogen sulphide, sulphur dioxide and nitrogen oxides) are here absorbed by the active carbon layer.

Sandwich construction under the scanning electron microscope: combi-filter (LAK), consisting of two fleece layers with an active carbon layer between them.

BAD SMELLS FROM OLD FILTERS
A saturated filter reduces the blower output and therefore delays significantly clearing of steamed up windows. If the filter change is postponed for too long, moisture binds to the accumulated dust: the filter becomes a breeding ground for bacteria and mould, which settle in the ducts of the ventilation and air conditioning system and lead to extremely unpleasant odours and harmful emissions into the vehicle interior. We like to give you therefore some tips for fast and safe filter change.

CLEAN AIR IS ALWAYS IN SEASON
Spring, summer, autumn and winter: the cabin air filter during the course of the year:

Spring may be the main time for changing cabin air filters, but a look at the filter fleece shows: there is always plenty to collect.

Spring

Summer

Autumn

Winter

In spring, for instance, one can recognise pollen, grass seed and relatively coarse dirt particles. These can even lead to clogging on the surface of the pleat bellows – while the pleats further down remain comparatively clean.

In summer, significantly more soot and fine dust can be found in the filter.

In autumn, the situation is similar to that of summer – however, due to the high air humidity, even more dust and other particles are collected more quickly.

Winter: the year reaches its end and so does the air filter. The filter is so dirty that it can no longer fulfil its intended purpose and will have to be replaced.

USEFUL: THE ENCLOSED FITTING INSTRUCTIONS
Depending on the vehicle type, the cabin air filters are located in different areas. To avoid searching for the fitting location, we recommend a look at the CD-ROM “Filter product range” or straight inside the packaging for the MAHLE Filter and Knecht cabin air filters. This is where you can find the printed fitting instructions – clear and always available, saving time and money in the workshop. For easy access, a tear-open strip is integrated in the packaging.

THE DIRECTION IS IMPORTANT
One of the most frequent fitting errors is placing the filter the wrong way round. The correct fitting orientation is exactly described in the vehicle specific instructions. In addition, the flow direction of the filter is indicated with small arrows at the side strip. Also the correct positioning of recesses and fixing projections should be observed.

THIS IS HOW TO FIT A FILTER CORRECTLY – A STEP-BY-STEP INSTRUCTION BY THE EXAMPLE OF THE LA 71/LAK 71
In order to assure correct fitting of the cabin air filter, several things need to be observed during fitting. The MAHLE filter experts have chosen the LA 71 or LAK 71 as graphic example. These cabin air filters are supplied by MAHLE as original equipment and are fitted, for instant, in the DAF CF85 and XF95 from model 01/01 or 09/02 onward.

The frame of the LA 71 behind the front panel of the DAF CF85/XF95. The flow direction should be observed during fitting (see arrows, which point here in direction vehicle).

At first, the filter is slid under the two plastic retainers, while the two grip strips (1) point here downwards.

The filter is then carefully pushed into the frame until the plastic tab clicks into the intended recess. Care should here be taken to avoid damage to the plastic foam seal.

This is the correct position of the filter: the plastic tabs are engaged correctly, the frame seals perfectly and keeps out particles including fine particulate dust.

An obvious fitting error: the plastic tab is not at the intended position (1). The result: the frame bends sharply and the pleats deform (2). This bends also the foam seal – and a gap is formed, allowing dirt to enter freely the interior (arrow).

The commercial vehicle market is booming. This will also enhance the sales prospects for cabin air filters in lorries, transporters and building vehicles. Air conditioning systems with suitable filters have become all but standard equipment in the meantime. However, when a vehicle is used with a clogged cabin air filter, severe consequences for heating and air conditioning systems may be the result. The replacement intervals stipulated by the vehicle manufacturers must therefore be strictly observed. Generally this means: about every 12,000 to 15,000 km. For a lorry that travels an annual distance of 250,000, this would be at least every 3 weeks.

While some years ago only passenger cars were equipped with cabin air filters, there is practically no commercial vehicle today that is not fitted with a filter that protects drivers from polluted air entering the cabin. And that is a good development. Without cabin air filters, drivers in their cabins would be subjected to pollutant concentrations 6 times higher than at the roadside. This is mainly due to the so-called tunnel effect, which means that the exhaust fumes of the vehicles in front are directly drawn into the vehicle interior. But also irritant gases such as ozone, toxic gases such as fertilizers and diesel exhaust particulate and other irritants such as pollen and annoying smells would get straight into the interior without cabin air filters. MAHLE Filter and Knecht cabin air filters are both available as particulate and combination filters. Particulate filters protect from fine dust, but also from pollen, industrial fallout and other very fine particulates that can reach the lungs. In addition, active carbon filters absorb smells and gases and reduce up to 99 % of ozone.

THE STRUCTURE OF A CABIN AIR FILTER WITH ACTIVE CARBON
A layer of special active carbon granules is sandwiched between two fleece layers. The unpleasant smells are deposited in the pores of the active carbon. Active carbon consists mainly of carbon (mostly > 90 %) with an extremely porous structure. The pores are interconnected like in a sponge. Just 2 grams of active carbon are roughly equivalent to the surface area of a football pitch – a standard filter containing about 200 g carbon has therefore a filter surface of about 100 football pitches.

CABIN AIR FILTERS FOR COMMERCIAL VEHICLES: THE FINE AND THE COARSE
In contrast to passenger vehicles, commercial vehicles are often used in dusty environments such as building sites. Their cabin air filters must therefore not only eliminate smallest particulate from the cabin, but also coarse particulate. However, the finer the filtration, the more dirt is removed – and the faster the dirt absorption capacity is exhausted. It is the task of the R&D engineers to combine the required fine filtration with a long service life. When the coarse particulate load is extremely high as, for instance, at a building site or a quarry, the filter must be replaced more often – or there needs to be a way of cleaning it. During the development of the LA 43, the decision was made in favour of cleaning.

The fleece of the LA 43 is supported and protected by a grid on both sides.

FOR EXTREME COARSE PARTICULATE LOAD: THE CLEANABLE MAHLE FILTER
The higher the degree of air pollution, the sooner the filter will clog. In extremely dusty environments, the cabin air filter can become so dirty in a few hours that the ventilation system practically ceases working. For such extreme situation, MAHLE has developed the filter element LA 43 in cooperation with Mercedes- Benz. The filter can be cleaned by knocking out the dirt manually and is used as original equipment in the building site versions of the Actros and Actros II models.

The design of the filter has been modified to make it resilient to the cleaning process that is required several times daily under extreme dust loads. From the outside, the special filter differs from other MAHLE cabin air filters in its more robust construction, with stable aluminium side members and massive end-mouldings made from plastic. Optimum sealing is achieved with a so-called blade location in the end pleat of the fleece and a plastic foam seal all around. A corrosion-resistant wire grid at both sides supports and protects the filter fleece. The filter medium consists of a synthetic filter fleece that has been designed for a significantly higher dust take-up capacity for this application.

The LA 43: robust design with side members of plastic (1) and aluminium (2) as well as a foam seal all around (3).

SERVICE INTERVALS: ONLY A GUIDELINE
Cabin air filters are mostly located in front of the vehicle's heating or air conditioning system, where the polluted outside air is drawn in and blown into the vehicle interior after cleaning – this can be up to 150 l air per second when the filter is in optimum condition. For clogged filters, this air volume is reduced. This can be noted clearly, when only a limited amount of air reaches the passenger compartment, although the blower is set to maximum (if in doubt, a visual check of the filter will help). When the filter is clogged, it is high time for replacement, or in case of the LA 43 for cleaning – regardless of the distance covered since the last filter change. If this is not done, expensive consequential damage of heating or air conditioning can result.

The cleaning process for the LA 43 can be repeated up to 80 times. Tests in laboratory and practice have shown that even after 80 cleaning procedures (tapping out and blowing out) the initial conditions of a new filter are almost reached again. However afterwards, the filter should be replaced as the performance can deteriorate rapidly.

KNOCKING OUT THE DIRT: TIPS FOR CLEANING THE LA 43
Pre-cleaning: tapping the filter on an even surface releases most of the dirt located at the dirty side.

Also for the LA 43, the fitting orientation must be observed the same way as for any other filter.

Main cleaning: If compressed air is available, the filter can be blown out afterwards. However, this should only be done from the clean side, which means in opposite direction to the arrows at the outer moulding (see picture). Otherwise, the dust particles are blown through the material and the collection efficiency, especially for smaller particles, is significantly reduced, making the filter useless. Also the choice of air pressure is important: to maintain the long service life of the filter and to avoid damage, the air pressure generally used in workshops should not be applied. Less is better here, in particular in respect of service life. This means: do not hold the air nozzle too close to the filter, but keep a distance of about 10 to 15 cm and blow out the filter with low air pressure (max. 0.5 bar).

If there is no compressed air available, it is quite sufficient to tap the dust out of the filter and at the next opportunity clean it with compressed air as described above. When the filter is installed again, observe the correct fitting orientation – as indicated by the arrows at the side mouldings.

Note: although the cleanable filter is robustly constructed, it should be checked for possible damage before refitting and be changed when in doubt.