GB2248195A

GB2248195A - Filter for cleaning the air supplied through an air duct to the internal space of a motor vehicle

Info

Publication number: GB2248195A
Application number: GB9119361A
Authority: GB
Inventors: Karl-Heinz Weller
Original assignee: Daimler Benz AG; Mercedes Benz AG
Current assignee: Daimler Benz AG; Mercedes Benz AG
Priority date: 1990-09-24
Filing date: 1991-09-11
Publication date: 1992-04-01
Also published as: IT1250104B; DE4030144C1; FR2667021A1; ITRM910707A0; GB9119361D0; ITRM910707A1; JPH04271917A

Abstract

A filter 5 is proposed for cleaning the air supplied through an air duct to the internal space of a motor vehicle, a metallic grid 14 which can be connected to a potential pole being fitted upstream of the filter 5 at the inlet flow end 8. So that the filter 5 retaining the gaseous air impurities can be quickly regenerated again before its maximum absorption capacity is reached, the filter has at least one active carbon layer 12 and the grid 14 consists of a resistance wire (15, 18) which becomes strongly heated when an electrical current is applied, the heat generated in this way being given up to the passing airflow and being transferred to the active carbon layer 12. <IMAGE>

Description

1 Filter for cleaning the air supplied through an air duct to the internal

space of a motor vehicle The invention concerns a filter for cleaning the air supplied through an air duct to the internal space of a motor vehicle, a metallic grid adapted to be connected to an electrical potential and located upstream of-the filter at the inlet flow end.

Such a filter is known from DE-OS2063764 and is designed as a fine filter, a coarse filter being fitted upstream of it and a filter which retains toxic constituents being fitted downstream of it. The fine filter has at both the inlet and outlet flow ends a grid fixing the filter material, each grid being connected to one pole of a voltage source in order to achieve an additional electrical separating effect.

A filter which retains toxic and intensively odorous constituents of the air has, like other filters separating dust-type particles, only a limited absorption capability and must therefore be replaced or regenerated at fixed time intervals.

The present invention seeks to provide in a simple way, using simple means and at small cost, a means of restoring within a short period a filter which retains gaseous air impurities - where the absorption capacity of the filter has been at least partially exhausted - to a condition in which it is again capable of absorbing the impurities so that the time until replacement can be delayed.

According to the present invention there is provided a filter for cleaning the air supplied through an air duct to the internal space of a motor vehicle, including a metallic grid adapted to be connected to an electrical potential and located upstream of the filter at an inlet flow end, wherein the filter has at least one active carbon layer and the grid consists of a resistance wire adapted to be heated by the electrical potential, the heat generated in this way being given up to the passing airflow and transferred to the active carbon layer.

1 2 Although it is already known, from DE-PS3517105, to use a filter with a charge of active carbon for the separation of toxic and intensively odorous constituents of the air and to heat the filter by electrical heating elements for the purpose of better desorption, these heating elements (consisting of individual heating rods) are embedded in the active carbon charge and rotate together with the rotating filter so that it is difficult to arrange zonal switching of the heating elements located in the desorption flow and, furthermore, there is no guarantee that the active carbon layer placed in front of the outer heating elements at the inlet flow end will reach a temperature sufficient to put the desorption process into operation.

In one illustrative example of the invention, the grid consists of a multiplicity of wires running parallel to one another, the wires being connected to one another at their respective ends by means of a collecting wire provided with an electrical connection, the adjacent active carbon layer (usually embedded in a web-type mat) being provided with good support by this means.

It is, however, also possible for the grid to be formed by a wire shaped in the form of a meander, both ends of the wire having an electrical connection. This design is characterised by a particularly even heating of the active carbon layer.

In a further embodiment of the invention, the grid can form a boundary wall of the filter and can be removed together with the filter when a replacement for the latter is fitted. This stabilises the filter. In this respect, it is desirable to design the electrical connections as a plug or coupling, the electrical connection with the relevant mating piece taking place automatically during the course of the insertion of the filter.

A low-cost arrangement satisfying the requirements is one in which the grid forms a boundary wall of the filter, which boundary wall remains in the air duct when the filter is removed for replacement.

0 3 The electric current for heating the grid can be provided by the vehicle battery or the generator and/or an external current source, the latter electricity supply possibility being mainly used when the vehicle is in a workshop for service work.

In a simple illustrative example of the invention, the instruction for switching on the heating of the grid takes place by means of an arbitrarily actuated switching element. It is, however, also possible for the instruction for switching on the heating of the grid to take place automatically at predetermined time intervals and preferably during periods when the vehicle is not in operation. In both types of operation, it is desirable for the heating to be switched on only for a fixed time period. The predetermined time interval between two heating procedures preferably depends on the operational life of the filter; for designs involving filters which can be bypassed or deflected out of the flow, the times when the filter is not in operation are taken into account in the determination of the operating period.

In order to restrict admission to the internal space, the air leaving the filter is passed directly to the outside while bypassing the passenger compartment, at least during the period when the grid is being heated. This can be achieved, while retaining the airflow direction, by providing a flap which releases an opening into, for example, the engine compartment while cutting off the flow path to the internal space.

Another way of avoiding admission to the internal space is to pass the air through the filter, assisted if necessary by a heating fan, against the airflow direction present during the adsorption operation. This can be achieved without modifications to the airflow path if, during the desorption phase, the heating fan runs in the opposite rotational direction.

An example of the invention willl now be described by way of example with reference to the drawing, in which:

4 Fig. 1 shows a greatly simplified side view of a heating device provided with a filter which binds gaseous pollutant and odorous materials, Fig. 2 shows a first illustrative example of a grid design and Fig. 3 shows a second grid design in the form of a meander.

In Fig.1, a motor vehicle 1 (which is only indicated) is provided with a heating system 3 fitted upstream of the passenger compartment 2, the heating system 3 having a filter 5 as well as a heat exchanger 4. In a manner which is not shown, an evaporator could also be provided to support air conditioning equipment. If the motor vehicle 1 is operated in an atmosphere which is free from pollutants or which has only a low level of pollution, external air flows to an air inlet 8 retaining coarse impurities against the airflow direction between the windscreen 6 and the engine bonnet 7 indicated by the arrow "A", a water separator 9, whose presence is indicated, being fitted downstream of the air inlet 8. Bypassing the filter 5, the air - possibly supported by a heating fan 10 reaches the heat exchanger 4 where it divides and flows to the passenger compartment 2 through outlet openings 11 placed at various heights.

If the vehicle 1 is used in a highly polluted atmosphere, the air passes through the filter 5 which, in order to adsorb harmful air constituents, has several active carbon layers 12 fitted in series and deposited, for example, on webbing. In this connection, the switching from operation bypassing the filter to filter operation can be brought about by means of flaps (not shown) - the switching taking place by means of a sensor located at the air inlet end.

Because the adsorption capability of the active carbon layers 12 is exhausted after a certain time, desorption phases have to be inserted at intervals so as to avoid the necessity of prematurely fitting a replacement for the filter 5 by removing the latter upwards through the air duct 13. If the desorption procedure is be undertaken within a short period, 4 i it is necessary to heat and scavenge the active carbon layers 12. A grid 14 consisting of a resistance wire is fitted at the inlet flow end upstream of the first active carbon layer 12 in order to be able to make the necessary heating energy available.

In Fig.2, the grid 14 possesses a multiplicity of wires 15 extending in parallel-to one another, these wires being connected to one another at their respective ends by means of a collecting wire 16, each collecting wire 16 being provided with an electrical connection 17. A different design of the grid 14 may be seen in Fig.3. A wire 18, both of whose ends 19 have an electrical connection 17, is shaped in the form of a meander.

Fig.1 shows that a conductor 20 leads from each connection 17 to a switching device 21 which is supplied with on-board voltage by means of a vehicle battery 22 or a generator 23. In a manner not shown, it is also possible when in a workshop for example - to supply external current in order to preserve the charge in the vehicle battery 22 during a simultaneous desorption process. In order to switch on the heating current for the grid 14, a switching device 24 favourably placed within the passenger compartment can be operated. It is, however, better to have the desorption procedure operate automatically and be initiated by means of a device indicated by the position number 25. It is desirable for the heating, which is limited in time, to occur during periods when the vehicle 1 is not in operation or while the driving takes place in an atmosphere which is free of pollutants or has a low pollution level. The air flowing past the grid 14 is heated and gives up heat to the active carbon layers 12 so that the desorption procedure is accelerated. The air leaving the filter 5 during the regeneration phase is guided to the open air in order to avoid admission to the passenger compartment 2. This is achieved, in a manner not shown, by means of appropriate ducting and simultaneous closure of the outlet openings 11. The same effect is achieved with less complication if the direction of rotation 6 of the heating fan 10 is reversed during desorption operation so that the airflow takes up the course indicated by the arrow "A". In contrast to the first-mentioned possibility, the grid 14 is not then located at the end of the filter 5 facing towards the air inlet 8 but is located on the opposite side of the filter 5.

7

Claims

1. A filter for cleaning the air supplied through an air duct to the internal space of a motor vehicle, including a metallic grid adapted to be connected to an electrical potential and located upstream of the filter at an inlet flow end, wherein the filter has at least one active carbon layer and the grid consists of a resistance wire adapted to be heated by the electrical potential, the heat generated in this way being given up to the passing airflow and transferred to the active carbon layer.

2. A filter according to Claim 1, wherein the grid consists of a multiplicity of wires running parallel to one another, the wires being connected to one another at their respective ends by means of a collecting wire provided with an electrical connection.

3. A filter according to Claim 1, wherein the grid is formed by a wire shaped in the form of a meander, both ends of the wire having an electrical connection.

4. A filter according to any one or more of the preceding claims, wherein the grid forms a boundary wall of the filter and is removed together with the filter when a replacement for the latter is fitted.

5. A filter according to any one or more of the preceding claims, wherein the grid forms a boundary wall of the filter, which boundary wall remains in the air duct when the filter is removed for replacement.

6. A filter according to any one or more of the preceding claims, wherein the electric current for heating the grid is provided by the vehicle battery or the generator and/or an 1 8 external current source.

7. A filter according to any one or more of the preceding claims, wherein the instruction for switching on the heating of the grid takes place by means of an arbitrarily actuated switching element.

8. A filter according to any one or more of the preceding cla.ims, wherein the instruction for switching on the heating of the grid takes place automatically at predetermined time intervals.

9. A filter according to claim 8, wherein said instruction takes place during periods when the vehicle is not in operation.

10. A filter according to Claim 7 8 or 9, wherein the air leaving the filter is passed directly to the outside while bypassing the passenger compartment, at least during the period when the grid is being heated.

11. A filter according to Claim 10, wherein the air is passed through the filter against the airflow direction present during the adsorption operation.

12. A filter according to claim 11, wherein the air is passed through the filter with the assistance of a heating fan.

13. A filter for cleaning the air supplied through an air duct to the internal space of a motor vehicle, substantially as described herein, with reference to, and as illustrated in, the accompanying drawings.