GB2061774A

GB2061774A - An arrangement for cleaning induction air to an internal combustion engine

Info

Publication number: GB2061774A
Application number: GB8034962A
Authority: GB
Original assignee: Saab Scania AB
Current assignee: Saab AB
Priority date: 1979-11-06
Filing date: 1980-10-30
Publication date: 1981-05-20
Also published as: IT8068694A0; JPS5681253A; FR2468756A1; GB2061774B; SE416989B; DE3041547C2; DE3041547A1; IT1129373B; BR8007150A; FR2468756B1

Abstract

In an arrangement for cleaning the induction air to an internal combustion engine, a coarse separator (4) is arranged in the induction air pipe (6) of the engine, and a fine separator (7) is arranged downstream of the coarse separator. In the coarse separator the air is imparted a movement such that solid contaminants are separated into a dirt-collecting chamber (18) which, via a suction pipe (20), is connected to a vacuum source (22). The suction pipe is connected to the induction air pipe (6) downstream of the coarse separator (4), said connection in the induction air pipe constituting the vacuum source. A separator (21) in the suction pipe (20) cleans the air flowing through said suction pipe. <IMAGE>

Description

SPECIFICATION An arrangement for cleaning induction air to an internal combustion engine The present invention relates to an arrangement for cleaning induction air to an internal combustion engine, comprising a coarse filter in the induction air pipe of the engine and a fine filter arranged downsteam of the coarse filter, in said coarse filter the air being given a movement such that solid contaminants are separated into a dirt-collecting chamber from which contaminants are sucked out via a suction pipe connected to a vacuum source, while the air cleaned in the coarse filter is passed further through the induction air pipe to the fine filter.

In internal combustion engines working in a dusty environment, e.g. engines in lorries or trucks used on construction sites, more and more complex arrangements are demanded to clean the air flowing into such engines. Filters for cleaning the air must thereby not create too great a pressure drop in the induction air system of the engine, and neither must the filters require too close intervals between changes or cleaning. If the mentioned requirements are to be met utilizing only one filter, this results in very capacious arrangements in the engine room. It is therefore known to provide the induction air system in engines subjected to dirty conditions with two filters coupled in series; a coarse filter and downstream of it a fine filter in the induction air pipe.

It is known to use a so-called cyclone filter as the coarse filter. In such a filter the air obtains a rotating movement, whereby solid contaminants are separated into a dirt-collecting chamber. For use in military vehicles, e.g.

tanks, it is also known to create a vacuum in said chamber by means of an electrically driven fan. This has resulted in an improvement of the cleaning capacity of the coarse filter, but the use of a separate fan for this puspose constitutes a comparatively expensive solution which can furthermore easily be subjected to operational disturbances.

In another known solution, the vacuum is created by means of ejector effect from the exhaust gas pipe of the engine. This solution results in long piping, especially when applied to heavy vehicles with the coarse filter placed above the driver's cabin. Furthermore, an extra sealing problem occurs if the vehicle is equipped with a tippable cabin. The ejector construction also requires the use of relatively expensive material to withstand the corrosive exhaust gases.

The present invention has the task of providing an arrangement which does not have the above-mentioned disadvantages. With this aim, the invention is distinguished in that the suction pipe from the chamber is connected to the induction air pipe downstream of the coarse filter, that said connection to the induction air pipe constitues the vacuum source providing vacuum in the suction pipe, and that the suction pipe between its connections to the coarse filter chamber and the induction air pipe includes a filter for separating solid contaminations from the air flowing through the suction pipe.

In the inventive arrangement, the vacuum source does not require any separate parts and has extremely good operational reliability as a result thereof. The presence of a filter in the suction pipe ensures that the air flowing through the suction pipe is cleaned before it is once again returned to the induction air pipe.

An advantageous embodiment of the invention is applied to a vehicle with a body unit resiliently suspended on a chassis. Here, at least the coarse filter, the suction pipe with its filter and the portion of the induction air pipe constituting the vacuum source are attached to said body unit. The arrangement thus does not require any connections taking up movement between the chassis and the body unit, problems and costs for forming such connections without leakage thereby being avoided.

Further features distinguishing the invention are apparent from the patent claims and the description of an embodiment exemplifying the invention set forth below. The description is made with reference to the attached drawing illustrating a view from behind of an inventive arrangement on the back wall of a driver's cabin on a lorry. The figure has fragmentary sections and cut-away portions to better illustrate the details incorporated in the arrangement.

The exemplified portion of a driver's cabin 1 for a lorry is provided with a rear wall 2 to which the inventive arrangement is attached by means not shown. In the arrangement there is included a coarse filter 4 which has extension over the roof 5 of the cabin 1 in the travelling direction of the vehicle. An induction air pipe 6 leads induction air down along the cabin wall 2 to a fine filter 7 from which the induction air is further led to an internal combustion engine (not shown) via a pipe 8.

The induction air pipe 6 is made in two parts; a lower part 10 being attached to the vehicle chassis 1 2 and an upper part 11 being attached to the cabin 1. The latter is resiliently suspended (not shown) relative to the chassis 12, and taking this into account the parts 10, 11 are connected to each other via a rubber bellows 1 3 which takes up relative movements between the parts 10, 11.

The bellows 1 3 is also formed to provide simple separation of the parts 10, 11 to enable the cabin 1 to be tipped forwards.

The coarse filter 4 is symmetrically constructed about a longitudinal, vertical plane, and each filter half 15, 1 6 includes a plurality of so-called through-cyclones 1 7 in a manner known per se. The cyclones 1 7 have no moving parts and have fixed blades (not shown) which act on the air flowing through to give it a rotating movement. The move ment results in that solid contaminants in the air are forced out to the cylindrical surface of the cyclone by centrifugal force and, via an opening 1 9 in the cyclone wall, further out into a dirt-collecting chamber 18 surrounding the cyclones 1 7. Such cyclones are wellknown in the art and are therefore not subjected to any further description.

Between 20 and 30 cyclones are suitably incorporated in the coarse filter 4, and cleaned air flows out from each cyclone 1 7 further into the induction air pipe 6. From the dirt-collecting chamber 1 8 in the respective filter halves 15, 1 6 a pipe 20 leads to a filter 21 which is also in communication, via a pipe 23, with a Venturi constriction 22 arranged in the induction air pipe 6. This signifies that a vacuum generated in the induction air pipe 6 is taken further through the pipes 20, 23 to the dirt-collecting chamber 18 of the coarse filter. The pipes 20, 23 will hereinafter be commonly denoted suction pipe 20.

The filter 21 includes a plurality of deflecting cyclones 25 arranged in a row or otherwise, of which only one is illustrated in the figure. Even these deflecting cyclones are well-known elements within the art, and the description of them is therefore limited to information required to understand the present invention. In the deflection cyclones 25 the air not only obtains a rotating movement but also a 180 deflection of the flow direction before the air leaves such a deflection cyclone 25. The latter is constructed from two pipes 26, 27 open at the ends, the one concentrically surrounding the other along a portion of their length. In the annular space so formed, there are arranged blades which rigidly connect the two pipes 26, 27 to each other.

In the exemplified embodiment, the deflection cyclones 25 are situated in a row in a middle chamber 28 in the filter 21 and the respective ends of the cyclones 25 are attached to end walls 30, 31 of the middle chamber. Holes in the respective end walls 30, 31 enable flow through the pipes 26, 27, contaminants being led to a lower,dirt-collecting chamber 32 in the filter 21, and cleaned air being led to an upper chamber 33 in the filter 21, said chamber 33 being in communication with the vacuum source 22 via the pipe 23.

Cleaning in the filter 21 is achieved in the following manner. The contaminated air from the dirt-collecting chamber 18 of the coarse filter 4 is led through the suction pipe 20 to the middle chamber 28 of the filter 21. The air is thus sucked, in accordance with an arrow shown in the figure, down through the space provided with blades between the pipes 26, 27 in the deflection cyclone 25. The blades give the air a rotating movement, whereafter the prevailing vacuum in the narrow pipe 26 acts on the air to deflect it 180 and direct it into the upper chamber 33 for further passage into the Venturi constriction 22 in the induction air pipe 6. In the figure, there is at the air pipe a flow arrow which originates at the upper part of the pipe 27.

The rotation of the air together with the deflection results in that solid contaminants in the air precipitate out into the lower chamber 32. In the lower part of the latter there is arranged a so-called dust valve 35 in the form of two mutually opposingly disposed rubber lips. As a result of the vibrations in the vehicle during travel or when the engine is switched off and vacuum is no longer formed in the filter 21, the valve 35 opens and releases any contaminants present into the surroundings.

The Venturi constriction 22 is situated up strearn of the bellows 1 3 whereby the inventive arrangement, incorporating the coarse filter 4, the suction pipe 20 with the filter 21 and the vacuum source 22, constitutes a cohesively constructed unit which is resiliently attached to the vehicle cabin 1. Such a unit is also easily mountable on other types of engine installations, e.g. for engines installed in trucks and construction machines, or for compressors in mobile or stationary use.

The Venturi-type constriction illustrated in the figure provides, in relation to other forms of constriction, an advantageous combination of low pressure drop in the induction air system and a large vacuum at the connection of the suction pipe to the induction air pipe 6.

Said connection is located where the Venturi 22 constricts the induction air pipe 6 the most. For achieving the desired effect, the throat of the Venturi should have an area in the order of between 25 and 75 percent of the flow area of the induction air pipe.

With coarse filters of the type described above, suited to diesel engines in heavy vehicles, it has been found, however, that the constriction utilized as a vacuum source should not cause a pressure drop in the induction air pipe which exceeds the pressure drop prevailing across the coarse filter. A heavier pressure drop across the constriction and a resulting increased vacuum in the dirtcollecting chamber of the coarse filter do not give rise'to such an increase of the cleaning degree in the coarse filter that this is capable of compensating the reduction of the permitted pressure drop range of the filter. Said reduction is a result of the increased pressure drop in the constriction, since the induction' air system in its entirety is constructed for a given highest pressure drop, which must not be exceeded. The interval between exchanges and/or cleaning of the fine filter will thus be closer, since the time which passes before the fine filter has reached the highest permitted pressure drop value, which has been set relatively low, will be shorter than previously; this in spite of the cleaning degree of the coarse filter having been increased and the fine filter thus supplied cleaner air than previously.

Good results in respect to increased cleaning degree in the coarse filter, low pressure drop in the constriction and thereby longer change intervals for the fine filter have been achieved with the inventive arrangement when the vacuum source has been able to pass through the suction pipe 20 about six percent of the airflow supplied to the cyclones 1 7. In practical attempts, this has been achieved when the Venturi constriction reduces the flow area of the induction air pipe by about 45 percent. The above-mentioned partial flow of six percent through the suction pipe 20 results in that the cleaning degree for a given, described coarse filter increases from 70 percent without vacuum in the pipe 20, to 90 percent with said vacuum in the pipe 20.

In order that a notably increased cleaning degree shall be achieved in the coarse filter 4, the partial flow through the suction pipe 20 should be at least two percent of the total airflow supplied to the coarse filter 4.

Within the scope of the following patent claims, other more or less specially formed constrictions can constitute the vacuum source. Utilization of the ejector action in the induction air pipe can in this case also be used to create vacuum in the suction pipe 20.

Neither is the invention limited to the described types of filter, since even other filter structures can be used.

Claims

1. An arrangement for cleaning induction air to an internal combustion engine, comprising a coarse filter in the induction air pipe of the engine and a fine filter arranged downstream of the coarse filter, in said coarse filter the air being given a movement such that solid contaminants are separated into a dirtcollecting chamber from which contaminants are sucked out via a suction pipe connected to a vacuum source, while the air cleaned in the coarse filter is passed further through the induction air pipe to the fine filter, characterized in that the suction pipe from the dirtcollecting chamber is connected to the induction air pipe downstream of the coarse filter, that said connection to the induction air pipe constitutes the vacuum source providing vacuum in the suction pipe, and that the suction pipe, between its connections to the coarse filter chamber and the induction air pipe, includes a filter for separating solid contaminants from the air flowing through the suction pipe.

2. An arrangement as claimed in claim 1, where the engine is installed in a vehicle with a body unit suspended on a chassis, characterized in that at least the coarse filter, the suction pipe with the filter arranged therein and the portion of the induction air pipe constituting the vacuum source are fixed to said body unit.

3. An arrangment as claimed in claim 1 or 2, characterized in that the connection of the suction pipe to the induction air pipe opens out in a constriction arranged in the latter.

4. An arrangement as claimed in claim 3, characterized in that the constriction is of the Venturi type and has a throat area the size of which constitutes a reduction of the flow area of the induction air pipe by at least 25 percent.

5. An arrangement as claimed in claim 3 or 4, characterized in that the vacuum created by the vacuum source is capable of diverting at least two percent of the airflow coming into the coarse filter.

6. An arrangement as claimed in any one of claims 3, 4 or 5, characterized in that the vacuum source causes an increased pressure drop in the induction air pipe, said increased pressure drop being smaller than a pressure drop induced in the coarse filter.

7. An arrangement as claimed in claim 1 or 2, characterized in that the filter in the suction pipe is of a kind known per se, where the air is given a movement such that solid contaminants are separated into a lower, dirtcollecting chamber having a bottom valve which automatically unloads contaminants out to the surroundings.

8. An arrangement as claimed in any one of the preceding claims, characterized in that the coarse filter comprises a plurality of through-cyclones, known per se, and that the filter in the suction pipe comprises a plurality of deflection cyclones known per se.

9. An arrangement for cleaning induction air to an internal combustion engine, substantially as hereinbefore described with reference to and as shown in the accompanying drawing.