STATE OF THE ART Cooling systems for internal combustion engines may be provided with filters for filtering the coolant circulating between the cooling ducts of the engine and the radiator. Through filtering, contamination, e. g. corrosion products, will be caught, which might otherwise in time cause clogging of the cooling ducts in the interna combustion engine as well as in the radiator. In order not to limit the circulating main flow in the cooling system, the filter is usually located in a so-called bypass line, i. e. a parallel or shunt line over the circulation pump. This extra flow however requires special consideration when sizing the circulation pump, in order to achieve sufficient capacity, entailing costs during manufacture as well as in operation, and space requirements.

DISCLOSURE OF INVENTION The object of the present invention is to provide a device creating savings in space as well as costs, regarding the pump sizing as well as its operating costs, and reduced filter costs.

Said object is achieved by means of a device according to the invention, according to which a filter unit is provided in the coolant reservoir. The filter unit is passed by at least a portion of the coolant flowing through the reservoir. Hereby, the number of

components and sources of errors, such as leaking hose connections, can be reduced.

DESCRIPTION OF DRAWINGS The invention will be explained in further detail below by way of an embodiment example, with reference to the accompanying drawings, in which Fig. 1 schematically illustrates a cooling system in which the device according to the invention can be used ; Fig. 2 illustrates, in a partly cut-through perspective view, the filter device according to the invention in a first embodiment ; Fig. 3 illustrates, in a partly cut-through sectional view, the filter device according to Fig. 2 fitted into a coolant reservoir ; whereas Fig. 4 illustrates, in a schematic sectional view, a filter device according to the invention in a second embodiment, fitted into a coolant reservoir.

PREFERRED EMBODIMENTS In order to explain better the function of the filtering device within a cooling system, an example of such a system, in which the present invention can be used, will ini- tially be described.

Fig. 1 shows, schematically, an internal combustion engine 1, e. g. an Otto type engine, for propulsion of automotive vehicles, ships or other machinery, such as power plants, forest machinery, etc. Further, a cooling system is schematically shown, for cooling the combustion engine 1 by bringing a coolant flow to circulate through cooling ducts in the engine cylinder block and cylinder head, and between the engine and a radiator unit 2 comprised in the cooling system, intended for through flow of the coolant, which is thereby subjected to cooling air. The cooling system further comprises a pump 3, being driven either by the combustion engine 1 or by a separate electric motor, for achieving said coolant flow. The system includes a thermostatic valve 4, functioning to control the coolant flow, in dependence of the coolant temperature, between a cooling circuit, see arrow 5, through the radiator unit 2, or a shunt or bypass circuit, see arrow 6, conducting the coolant past the radiator unit 2. The thermostatic valve 4 exhibits an inlet passage, 7, and two outlet pas- sages 8,9. The inlet passage 7 is connected to the cooling ducts in the combustion

engine 1, whereas one outlet passage, 8, is connected through a cooling line 10 to an inlet 11 of the radiator unit 2, and thus leads to the cooling circuit, whereas the other outlet passage 9 is connected to a bypass or shunt line 12, thus defining the bypass or shunt circuit discussed above. The thermostatic valve 4 is functioning, at temperatures below a selected lower limit value, to direct the coolant flow through the outlet passage 9 to the bypass line 12 and, for a rising temperature, when the selected lower limit value has been exceeded, to successively close the outlet pas- sage 9 and open the outlet passage 8, so as, when exceeding an upper limit value, to direct the flow to the cooling circuit, i. e. via the cooling line 10 and the radiator 2.

For a dropping temperature, when the coolant has reached the upper limit value, the coolant flow is again successively directed from the cooling circuit via the outlet pas- sage 8, to the bypass circuit 6 via the outlet passage 9, until, when the lower limit value has been passed, it is directed entirely through the outlet passage 9.

Depending on the type of thermostat, the temperature regulation may be of the on/off type, with rapid changes between the two end positions of the valve, or of the slow, gradual type with the valve being partly open towards both outlet passages 8, 9.

The cooling system further comprises a coolant reservoir 13, partly functioning as a replenishing reservoir for the coolant, partly as an expansion reservoir, which will be explained further in the following. The coolant reservoir 13 exhibits a removable pressure cap 14, closing off a coolant replenishing opening 15. The coolant reser- voir 13 is provided with a bottom coolant outlet 16 for a replenishing line 17 that is connected to the inlet side 18 of the pump 3.

From the radiator unit 2, more particularly from its top end, a degassing line 19 is connected to the coolant reservoir 13 for the release of entrapped air from the radiator unit 2. In this process, a certain amount of coolant waste flow is also released, in the order of about 1% of the pump flow. This flow is limited by means of a flow limiter 20, in the form of a preferably fixed restriction inserted into the degassing line 19. Hereby, a certain partial flow will flow through the coolant reser- voir 13.

For degassing of the remaining parts of the cooling system, such as the cooling ducts inside the combustion engine 1, and the pump 3, a further degassing line 21 is arranged, with one end, 22, thereof connected to the thermostatic valve 4 outlet 9 to the bypass circuit, i. e. the bypass tine 12, and the other end, 23, running into the coolant reservoir 13. The mouth is advantageously located at the top end of the res- ervoir, but, in principle, it might also be located below the coolant level in the reser- voir. The degassing line 21 from the outlet 9 of the thermostatic valve exhibits a flow limiter 24 in the form of a preferably fixed restriction, securing a limitation of the coolant flow to about 2% of the total flow.

The filtering device according to the invention will now be described in detail, in a first embodiment thereof, where the filtering device is shown separate from its oper- ating position in Fig. 2, whereas Fig. 3 shows the filtering device fitted into the cool- ant reservoir 13. The filtering device according to the first embodiment is designed as a separate filter unit 25 in the form of a cartridge, being integrated with a cover member 26 which is functioning, when the filter unit is fitted into the coolant reser- voir, to close off an aperture 27 of the reservoir. To this end, the cover member exhibits a grip portion 28 and an attachment portion with engagement members 29, for example threads, functioning to engage with corresponding engagement mem- bers 30 in the reservoir aperture 27. A sealing ring 31 between the cover member 26 and the reservoir 13 secures a fluid-tight sealing of the aperture 27. The sealing ring 31 is provided either on the cover member 26 and will follow that member when removed, or is permanently arranged at the circumferential edge 32 of the aperture 27. From the cover member, the other portion of the filter unit extends downwards, in the illustrated example being of the radial filter type having a generally cylindri- cally extending filter member 33, encircling a cavity 34. At that end of the filter unit, which is adjacent to the cover member 26, the filter member 33 connects sealingly with one of its circumferential edges, 37, against a closed end surface 38, defining an end wall of the enclosed cavity 34. In the illustrated example, the filter member 33 is folded in order to provide a large filter area, and for example made of a liquid- resistant filter paper. The type of folding is called radial folding, having a multitude of generally radial folds 39.

The filter unit 25 further exhibits a sleeve member 40, having one of its ends fixedly attached to the end wall 38 at the cover member 26, and at its other end 42 carrying an end piece 43, the inside of which defines a second end wall 43'inside the filter unit. The end piece 43, in the example shown in Figs 2 and 3, is removably attached to the filter sleeve 40 at the outer end 42 thereof, by the end piece exhibiting a bore 44 through which the sleeve member 40 extends. This bore preferably exhibits a cylindrical surface co-operating with a corresponding cylindrical surface on the sleeve member 40, providing the end piece 43 with a correct position in a radial plane relative to the geometrical longitudinal axis 45 of the filter cartridge. The end piece 43 is arranged to abut with its end surface against the other circumferential edge of the filter member 39, for closing off, together with the filter member and the opposite end wall 38, the cavity 34, except for a multitude of bores 47 in the sleeve member 41, said bores in the illustrated example being arranged in a number of, for example four, evenly spaced rows, and being countersunk in relation to the cylindri- cal envelope surface 48 of the sleeve member. Each opening exhibits well rounded edges 49 for achieving a highly laminar fluid flow. These bores 47 are directed radi- ally towards the filter member 33 and are communicating with an axial aperture 35 in the end portion 42 of the sleeve member 40, through the sleeve member exhibiting an interior chamber, in the illustrated example being generally cylindrical, extending for generally the entire length of the sleeve member and debouching, at one end thereof, in the aperture 35. Between the axial aperture 35 and the end piece 43, a locking means 50 is provided, in the illustrated example being designed as a resil- ient, open locking ring, functioning in its locking position to be resiliently received in a groove 50'in the sleeve member 40. With the locking ring removed, the end piece 43 can be moved axially outwards, past the end of the sleeve member, whereby the filter member 33 can also be moved axially the same way, in order to be replaced with a new filter member. In the locked position, the filter member is held in place by the two circumferential edge portions, 37,46, being pressed against the end sur- faces, 38,43'.

According to the present invention, the filter unit 25 is arranged inside the coolant reservoir 13 and functioning to be flowed through by at least a portion of the circu- lating coolant flow in the cooling system. In the example shown in Figs 2 and 3, the filter unit is arranged inside the external housing 51 of the coolant reservoir, but is

separated from a main space 52 of the reservoir by an intermediate wall 53. Hereby, a separate space 54 is created inside the coolant reservoir 13, into which the filter unit 25 extends through its cover member 26 being arranged in the aperture 27, in this case being provided at the top end of the space 54. The intermediate wall 53 extends between top portion 55 and the bottom portion 56 of the coolant reservoir 13 and is delimited outwards, in the sideways directions, by the side walls of the reservoir, of which one side wall 57 is shown in Fig. 3. From the exterior of the res- ervoir, a passage 58 leads into the separate space 54, said passage for example consisting of an inlet passage in the form of a connection stud 59, to which a hose may be connected. According to an advantageous embodiment, this passage is defined by one of the degassing lines, preferably the degassing line 21. More pre- cisely, the passage 58 leads into a partial space 60 of the separate space 54, which is divided by the end piece 43 into said partial space 60, in which the filter member 33 resides and a further partial space 61 into which the axial aperture 35 debouches. Furthermore, the first partial space 60 communicates with the main space 52 of the reservoir by means of a bypass bore 62 in the intermediate wall 53, through which a limited flow of coolant will be allowed also when the filter is clogged. The other partial space 61 provides the normal communication with the main space by means of at least one passage 63, handling the main flow and exhibiting a larger area than the bore 62. The outlet 16 of the coolant reservoir 13, shown schemati- cally in Fig. 1, is also shown in Fig. 2, and is arranged in the bottom portion 15 of the reservoir and communicates with the main space 52 of the reservoir.

Through the arrangement discussed above, with the location of the filter unit 25 inside the reservoir 13 and at least partly immersed in the coolant, see the level indicated at 66, at least a partial flow of the coolant circulating in the cooling system is created, which is brought to pass the filter unit. In the example illustrated by Figs 2 and 3, the coolant flowing into the inlet passage 58 is brought to pass from the par- tial space 60 into the filter through the filter member 33. After passing the filter member 33, the filtered fluid is directed to flow, fairly evenly distributed over the height of the filter member 33, into the sleeve member 40 through the bores 47 and then to exit through the axial aperture 35, which serves as an outlet opening. As indicated by the arrow 65 in Fig. 3, the filtered coolant flows on through the passage

63 into the main space 52 of the reservoir, and will, at least periodically, depending on the pressure conditions in the cooling system, flow on through the outlet 16.

In the device for coolant filtering, according to an advantageous embodiment, an anti-corrosion agent is also provided in association with the filter unit. For example, inhibitors in the shape of pellets may be placed in one of the spaces at the filter unit, e. g. inside the filter member 33.

Fig. 4 shows an alternative embodiment of the filter unit 125, the filter member 133 of which is affixed between the cover member 126 and the bottom portion 156 of the coolant reservoir 113. In this example, the reverse flow direction has been selected, the passage 158 defining an axial inlet and the coolant being brought to pass the filter member 33 from the inside out into the coolant reservoir, as indicated by the arrows. A screen 170 is arranged inside the inlet 158 in order to distribute the flow in the cavity 134 inside the filter member 133. A bypass duct 171 having a not shown restriction will allow, in the known manner, through flow of coolant when the filter is clogged.

The invention will not be limited to the embodiment examples described above and depicted in the drawings, but may be varied within the scope of the accompanying patent claims. For example, it would be conceivable, in principle, that degassing through the line 19 from the radiator 2 is excluded. The detail construction of the filter could be made in several different ways. The filter could have, for example, a square cross section shape.