BACKGROUND TO THE INVENTION AND PRIOR ART

The present invention relates to an arrangement for de-icing of a charge air cooler according to the preamble of claim 1.

The amount of air which can be supplied to a supercharged combustion engine in a vehicle depends on the pressure of the air but also on the temperature of the air.

Supplying as large an amount of air as possible to a supercharged combustion engine entails the compressed air being cooled in a charge air cooler before it is led to the combustion engine. The charge air cooler is generally situated in front of the conventional radiator in a vehicle. A charge air cooler usually comprises two tanks and a plurality of mutually parallel tubular elements which connect the tanks to one another. The parallel tubular elements are disposed at a distance from one another so that surrounding cold air can flow between them and cool the compressed air within them. Depending on the size of the charge air cooler, the compressed air can be cooled to a temperature more or less corresponding to the temperature of the surrounding air.

Charge air coolers in vehicles are usually so dimensioned that they are of relatively good efficiency. In circumstances where a cold ambient temperature prevails and/or the air is at very high humidity, the compressed air may be cooled in charge air coolers to a temperature which is lower than the dew point temperature of the air. The water vapour in the compressed air condenses, with the result that water in liquid form precipitates within the charge air cooler. When the temperature of the surrounding air is very low, there is also risk that the water condensed may freeze to ice within the charge air cooler. In such circumstances, the air flow ducts in the charge air cooler are obstructed by ice and the air supply to the combustion engine becomes deficient or ceases completely, causing the engine to stop. SUMMARY OF THE INVENTION

The object of the present invention is to propose an arrangement which makes rapid and safe de-icing of an air-cooled charge air cooler possible when ice has formed within the charge air cooler.

This object is achieved with the arrangement of the kind mentioned in the introduction which is characterised by the features indicated in the characterising part of claim 1. In situations where surrounding air is at a definitely lower temperature than 0°C and the charge air cooler leads compressed air to a supercharged combustion engine which is running at low load there is risk of ice formation in the charge air cooler. In situations where ice forms within the charge air cooler, a warm liquid medium is led from a medium source to a line disposed close to the tubular element. The liquid medium is with advantage at a temperature over, for example, 50°C when it is led to the charge air cooler. With such a high temperature, the medium effects relatively rapid warming of the tubular element so that the ice within the latter melts. A charge air cooler normally comprises a relatively large number of such mutually parallel tubular elements in which the compressed air is cooled by air which is at the temperature of the surroundings. The line circuit comprises in this case at least one line per tubular element so that ice formation can be prevented in all of the charge air cooler's tubular elements.

According to an embodiment of the present invention, the arrangement comprises at least one sensor adapted to detecting a parameter which is related to whether ice has formed within said tubular elements. One way of detecting whether ice formation occurs in the charge air cooler is to measure the pressure drop of the compressed air when it passes through the charge air cooler. If the pressure drop is unwarrantably large, it may be found that the flow ducts in the charge air cooler have become more or less blocked. If this happens in situations where surrounding air is at a low

temperature, the large pressure drop is probably due to ice formation in the charge air cooler. In this case the arrangement may comprise a sensor adapted to measuring the pressure of the compressed air upstream of the tubular element, and a sensor adapted to measuring the pressure of the compressed air downstream of the tubular element. Alternatively, or in combination, a temperature sensor may be provided downstream of the charge air cooler to measure the temperature of the compressed air when it is led out from the charge air cooler. If the compressed air has cooled to a temperature below 0°C in the charge air cooler, it may be found that there probably is ice formation in the charge air cooler. According to an embodiment of the present invention, the arrangement comprises a control unit adapted to receiving information from said sensor or sensors and to controlling said flow means so that the liquid medium is led to said location close to the tubular element in situations where ice has formed within the tubular elements. The control unit may be a computer unit with suitable software for this purpose. In this case the warm medium is led automatically to the charge air cooler so that the latter is de-iced as soon as the control unit finds that there is ice formation in it.

Alternatively, or in combination, the liquid medium may be led to the charge air cooler by means of a control device operated manually by, for example, a driver in a vehicle when he/she suspects that the charge air cooler needs de-icing.

According to a preferred embodiment of the present invention, said line circuit comprises at least one line which is situated close to the tubular element and which has a substantially parallel extent with the tubular element. The liquid medium may thus be conveyed in a line which has a parallel extent with the whole of the tubular element. When the liquid medium flows through such a line, it effectively warms the tubular element so that the ice within the latter melts. The line at said adjacent location may be disposed in contact within an external surface of the tubular element. With advantage, the tubular element and said line have contact surfaces which are configured complementarily to achieve a relatively large heat transfer surface. The tubular element may be provided with an inward bend where said line is situated.

Alternatively, said line may be disposed within the tubular element, in which case the whole external surface of the line may be used to supply heat within the tubular element. To render the de-icing of the tubular element more effective, a plurality of lines containing the liquid medium may be disposed externally about or within the tubular element.

According to a preferred embodiment of the present invention, said source comprises a cooling system with a circulating coolant. Vehicles may be provided with one or more cooling systems with a circulating coolant. After the coolant has been used to cool one or more components in the vehicle, the warm coolant is cooled in a radiator or the like. Using such existing warm coolant to de-ice a charge air cooler is relatively simple, involving only a few components. Said cooling system is with advantage an existing cooling system for cooling a combustion engine. The coolant in the engine's cooling system is at a temperature within the range 70-90°C during normal operation. The de- icing of a charge air cooler with coolant at that temperature will be very effective. In this case said line circuit comprises a line for receiving warm coolant from the cooling system at a location upstream of a radiator element of the cooling system, and a line which leads the coolant back to the cooling system at a location downstream of the radiator element after the coolant has been used for de-icing. The radiator element of the cooling system is usually situated behind the charge air cooler at a front portion in a vehicle, in which case relatively short lines are required for conveying warm coolant to and from the charge air cooler. Said source need not take the form of a cooling system with a circulating coolant, as it may take the form of an accumulator tank with a warming device which effects warming of a liquid medium in the accumulator tank to a suitable temperature. When de-icing is required, the warm liquid medium is led from the accumulator tank to the charge air cooler.

Although the object of the invention is to de-ice a charge air cooler, said warm liquid medium may also be used in other situations where it is advantageous to reduce the cooling of the compressed air in the charge air cooler. Such a situation is where the exhaust gases are at such a low temperature that they do not undergo desired cleaning in an exhaust-cleaning component. When a vehicle is being set in motion from cold or is in a low-load state, the exhaust gases from the engine may be at too low a temperature to be effectively cleaned in, for example, a catalyst. In such cases the control unit may direct the warm liquid medium to the charge air cooler to reduce the cooling of the compressed air in the charge air cooler. The air led to the engine may thus be at a higher temperature, as also exhaust gases, which thereby warm catalysts to a desired temperature.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention are described below by way of example with reference to the attached drawings, in which:

Fig. 1 depicts a charge air cooler with an arrangement according to the present

invention,

Fig. 2 depicts a cross-sectional view in the plane A-A in Fig. 1 and Fig. 3 depicts an alternative embodiment of the tubular elements in Fig. 2.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION Fig. 1 depicts a charge air cooler 1 which may be fitted at a front portion of a vehicle which is powered by an undepicted supercharged combustion engine. A supercharged combustion engine needs to be supplied with compressed air. The purpose of the charge air cooler 1 is to cool the compressed air before it is led to the engine. The cooling results in the air becoming more compact and hence in it being possible for a larger amount of air to be supplied to the engine. The charge air cooler 1 comprises an inlet tank 2 which, via an inlet aperture 2a, receives warm compressed air from an undepicted compressor. The charge air cooler comprises a radiator package 3 extending between the inlet tank 2 and an outlet tank 4 which receives the compressed air after cooling in the radiator package 3. The radiator package 3 comprises a plurality of tubular elements 5 extending in a substantially rectilinear manner in a common plane between the inlet tank 2 and the outlet tank 4.

The tubular elements 5 are disposed parallel at substantially uniform spacing from one another so that regular gaps 6 are formed between adjacent tubular elements 5.

Surrounding air can therefore flow through the gaps 6 between the tubular elements 5. The gaps 6 are provided with folded heat transfer elements to increase the heat transfer surface between the surrounding air and the tubular elements 5. The flow of surrounding air through the radiator package 3 is provided by the vehicle's movement and/or by an undepicted radiator fan which draws air through the radiator package 3. The surrounding air cools the compressed air led through the tubular elements 5. The cooled compressed air is led out from the outlet tank 4 via an outlet aperture 4a. The compressed air may where applicable be mixed thereafter with recirculating exhaust gases before it is led to the supercharged combustion engine.

A first pressure sensor 7a is provided in the inlet tank 2 to detect the pressure of the compressed air there before it is led into the radiator portion 3. A second pressure sensor 7b is so arranged in the outlet tank 4 as to detect the pressure of the compressed air there after it has passed through the radiator portion 3. A control unit 8 is adapted to receiving information from said sensors concerning the prevailing pressures in the inlet tank 2 and the outlet tank 4. The control unit uses this information to calculate the pressure drop of the compressed air when it is led through the tubular elements 5. If the compressed air undergoes a pressure drop exceeding a predetermined threshold value, the control unit 8 may find that ice has formed within the tubular elements and is blocking the air flow through the tubular elements 5. The air supply to the engine will thereby be reduced, causing operational malfunctions of the engine. If the tubular elements 5 are substantially completely obstructed by ice, the engine stops.

The charge air cooler 1 is here with advantage fitted in front of a schematically depicted radiator element 9 at a front portion of the vehicle. The coolant in the cooling system which cools the combustion engine is led to the radiator element 9 via a line 10 and from the radiator element 9 via a line 11. During normal operation, the coolant is at a temperature within the range 70°-90°C when it is conveyed in the line 10 to the radiator element 9 in order to be cooled. In this case a line circuit 12a-g is connected to the engine's cooling system. The line circuit 12a-g comprises a line 12a connected to the cooling system line 10. The line 12a comprises a valve means 13 which in a closed position prevents coolant from the line 10 from being led to the line 12a, and in an open position allows coolant from the line 10 to be led to the line 12a. The line 12a extends into the inlet tank 2, where it joins at least one vertical line 12b extending in the vertical direction within the inlet tank 2 close to the inlet apertures of the tubular elements 5.

Fig. 2 depicts a cross-sectional view in the plane A-A of three of the tubular elements 5. The tubular elements 5 are provided with internal turbulators 14 to enhance the cooling of the compressed air within the tubular elements 5. In this case two parallel vertical lines 12b are used to lead coolant to respective horizontal parallel lines 12c. The tubular elements 5 are here provided with inward bends at a front surface and a rear surface. One of the horizontal lines 12c is in contact with the external surface of the tubular elements 5 at the forward inward bend, and the other horizontal line 12c is in contact with the external surface of the tubular elements 5 at the rear inward bend. The respective horizontal lines 12c each lead into a respective vertical line 12d. The vertical lines 12d are connected to a line 12e which is itself connected to the line 11 in the coolant system. During operation of the combustion engine, compressed air is led through the charge air cooler 1. At the same time, coolant circulates in the cooling system which cools the engine. The control unit 8 receives information from a temperature sensor 15 concerning the temperature of the surrounding air. In cases where the surrounding air which cools the compressed air in the charge air cooler 1 is at a temperature over 0°C, the control unit 8 finds that there is no risk of ice formation in the charge air cooler 1. In situations where the surrounding air is at a lower temperature than 0°C, the control unit 8 finds that there is risk of ice formation. This risk depends inter alia on the temperature of the surrounding air and the load upon the engine. Ice formation in the charge air cooler 1 occurs primarily in situations where surrounding air is at a very low temperature and at the same time the engine is running at low load. In situations where surrounding air is at a lower temperature than 0°C, the control unit 8 receives in this case information from the pressure sensors 7a, 7b. The control unit 8 uses this information to calculate the pressure drop when the compressed air passes through the tubular elements 5. The control unit compares the calculated pressure drop with a threshold value. If the calculated pressure drop value exceeds the threshold value, the control unit 8 finds that ice has formed within the tubular elements 5 in such an amount that the charge air cooler 1 needs de-icing.

The control unit 8 thereupon opens the valve means 13 so that part of the warm coolant in the line 10 is led to the line 12a. The coolant is led from the line 12a to the two vertical lines 12b. The coolant in the two vertical lines 12b is led to the horizontal lines 12c in each of the tubular elements 5. The horizontal lines 12c are in contact with the external surface of the respective tubular elements 5. The tubular elements 5 are thus warmed by the warm coolant flowing within the horizontal lines 12c. Ice which has formed close to or in contact with the internal surfaces of the tubular elements 5 therefore melts. When the coolant has passed through the horizontal lines 12c, it is received in the two vertical lines 12d. The coolant is thereafter conveyed in the line 12e back to the cooling system which cools the combustion engine.

During the course of the de-icing process, the control unit 8 substantially continuously, or at suitable intervals, receives information from the pressure sensors 7a, 7b so that it can calculate the pressure drop of the compressed air across the tubular elements 5. When it receives pressure values from the pressure sensors 7a, 7b which indicate that the pressure drop has fallen below a predetermined threshold value, the control unit 8 may find that the ice in the charge air cooler has melted. The control unit 8 thereupon closes the valve means 13 so that the coolant flow through the line circuit 12a-d ceases. Fig. 3 depicts an alternative way of arranging the horizontal lines 12c relative to the tubular elements 5. In this case the vertical lines 12b are disposed within the tubular elements 5. The vertical lines are here disposed in flow ducts defined by the internal turbulators 14. In this case the tubular elements 5 have a conventional external surface. The invention is in no way limited to the embodiment described with reference to the drawing but may be varied freely within the scopes of the claims. For example, any desired number of horizontal lines 12c may be disposed in contact with or inside the tubular elements 5.