WO2015030649A1

WO2015030649A1 - Expansion tank and cooling system comprising such an expansion tank

Info

Publication number: WO2015030649A1
Application number: PCT/SE2014/050955
Authority: WO
Inventors: Zoltan Kardos
Original assignee: Scania Cv Ab
Priority date: 2013-08-27
Filing date: 2014-08-21
Publication date: 2015-03-05
Also published as: SE1350977A1; SE537748C2

Abstract

The invention relates to an expansion tank (1) which is intended to form part of a cooling system of a motor vehicle and which comprises - an outer casing (2), - an expansion chamber (3) enclosed i n the casing, to accommodate coolant, and - an overpressure valve (10) situated in the casing, to limit the pressure in the expansion chamber. The casing (2) comprises a first casing element (2a) and a second casing element (2b), which second casing element is movably connected to the first casing element and can be put into different positions relative to the first casing element in order thereby to allow variation of the volume of the expansion chamber (3). The invention relates also to a cooling system comprising such an expansion tank.

Description

Expansion tank and cooling system comprising such an expansion tank

FIELD OF TH E I NVENTION AN D PR IOR ART

The present invention relates to an expansion tank according to the preamble of claim 1 intended to form part of a cooling system of a motor vehicle. The invention relates also to a cooling system provided with such an expansion tank.

A com bustion engine of a vehicle is cooled by means of coolant which is circulated in a cooling system. When the engine is in operation it gives off heat to the coolant, wh ich is thereby warmed and expands. The resulting total volume increase of the coolant in the vehicle's cooling system may amount to several litres and depends on the original coolant volume and the respective temperature increase. To prevent too much pressure increase in the cooling system , it is provided with an expansion tank which can accommodate the coolant surplus arising from the coolant's expansion . The coolant's boiling point rises with increasing pressure, which makes it desirable to maintain a certain positive pressure in the cooling system when the engine is in operation and thereby prevent boiling. To make this possible and at the same time prevent dangerously high coolant pressure, the expansion tank is provided with an overpressure valve which ensures that the pressure in the tank cannot exceed a predetermined pressure level . When the coolant expands through warming , the air present in the expansion tank is compressed, increasing the pressure in the expansion tank and the rest of the cooling system . When the combustion engine is started, a relatively rapid pressure increase in the cooling system is desirable so that the boiling point of the coolant can quickly reach a suitably high level and boiling be prevented. If the expansion tank contains a large volume of air which needs to be compressed before the desired pressure increase is achieved , the desired raising of the coolant's boiling point will be delayed . For this reason it is therefore appropriate to use as small an expansion tank as possible. It does however need to be large enough to be able to accommodate the expanded coolant so that undesirable coolant leakage to the surroundings via the overpressure valve is prevented. As the volume of coolant in the vehicle's cooling system will vary greatly, depending on vehicle type and what equipment items are connected to the cooling system , different vehicles need expansion tanks of different sizes.

OBJ ECT OF THE I NVENTION The object of the present invention is to propose an expansion tank of the type indicated in the introduction which is of novel and advantageous configuration .

SU MMARY OF TH E I NVENTION

The present invention achieves said object by means of an expansion tank presenting the features defined in claim 1 .

The expansion tank according to the invention comprises an outer casing , an expansion chamber enclosed in the casing and intended to accommodate coolant, and an overpressure valve situated in the casing to limit the pressure i n the expansion chamber. The casing comprises a first element and a second element, which second element is movably connected to, and can be put into different positions relative to, the first element to allow variation of the volume of the expansion chamber. The solution according to the invention makes it easy to adapt the size of the expansion tank to the coolant volume of the cool ing system which the tank is to be part of. Identically configured expansion tanks may be used to achieve expansion chambers with different volumes, and may thus be usable in different cooling systems which have different coolant volumes, resulting in cost savings. It will also be easy, where necessary, for the volume of the expansion chamber to be post-adjusted , i .e. after the expansion tank has been installed in a cooling system , by adjusting the position of the second casing element relative to the first.

One embodiment of the invention is characterised

- in that the second casi ng element takes the form of a hood with a closed end which faces away from the first casing element, and an opposite open end which faces towards the first casing element, and that the second casing element is arranged to be axially movable externally about a cylindrical portion of the first casing element, and

- that said cyl indrical portion has an open end which faces towards the second casing element's closed end and which is surrounded by the second casing element, and the space between the open end of the cylindrical portion and the closed end of the second casing element forms part of the expansion chamber.

The result is a relatively simple constructional solution. In another embodiment of the invention a bladder of flexible material i mpervious to water and air is connected fluid-tightly to said cylindrical portion , is arranged to block the latter's open end and is expandable to be able to fill the space between the cylindrical portion's open end and the second casing element's closed end . The internal volume of the bladder forms part of the expansion chamber. The bladder prevents coolant and air which are in the expansion chamber from coming into contact with the joint between the first and the second casing elements, obviating the need to provide any seal means at this joint.

In another embodiment of the invention the expansion tank is provided with an operating device by means of which the second casing element can automatically be put into different positions relative to the first casing element. The operating device makes it possi ble to vary the volume of the expansion chamber without any manual action , so that the volume can for example be adjusted as appropriate depending on the prevailing temperature or pressure of the coolant in the cooling system which the expansion tank is part of. For example, the position of the second casing element relative to the first casi ng element may be controlled by means of the operating device in such a way that the volume of the expansion cham ber will be smaller when the coolant is at a low temperature and greater when the coolant is at a high temperature. Other advantageous features of the expansion tank according to the invention are indicated by the dependent claims and the description set out below. The invention relates also to a cooling system presenting the features defined in claim 1 2. .

Other advantageous features of the cooling system according to the invention are indicated by the dependent claims and the description set out below.

BR IEF DESCR IPTION OF THE D RAW INGS

The invention is described below in more detail on the basis of em bodiment examples with reference to the attached drawings, in which depicts a schematic sideview of an expansion tank according to a first embodiment of the present invention, depicts a partly cutaway schematic sideview of the expansion tank according to Fig . 1 , with the movable casing element in an extreme position for minimum expansion chamber volume, depicts a partly cutaway schematic sideview of the expansion tank according to Fig . 1 , with the movable casing element in an extreme position for maximum expansion chamber volume, Fig . 4 depicts a schematic sideview of an expansion tank according to a second embodiment of the present invention,

Fig . 5 is a schematic diagram of a cooling system according to a first embodiment of the present invention, and

Fig . 6 is a schematic diagram of a cooling system according to a second embodiment of the present invention .

DETAILED DESCR I PTION OF EM BOD IM ENTS OF THE INVENTION Figs. 1 -3 illustrate an expansion tank 1 according to a first em bodiment of the present invention. This tank is intended to form part of a cooling system of a motor vehicle, e.g . a cooling system 40 of the type depicted in Fig . 5. The tank comprises an outer casing 2 made of rigid material, e.g . plastic, and an expansion chamber 3 delineated by the casing. The casing comprises a first element 2a and a second element 2b. The second casing element is movably connected to, and can be put into different positions relative to, the first casing element to allow variation of the volume of the expansion cham ber 3. The second casing element is with advantage movable telescopically relative to, by being journalled slidingly on , the first casing element.

The first casing element 2a is provided with an outlet aperture 4 which is intended to be connected to a coolant line of a cooling system in order to allow exchange of coolant between the expansion chamber 3 and other parts of the cooling system via this outlet aperture 4. The outlet aperture is situated at the bottom of the expansion cham ber. A stub pipe 5 connected to the outlet aperture protrudes from the underside of the first casing element. Said coolant line is intended to be connected to this stub pipe.

The first casing element 2a is provided with an inlet aperture 6 which is intended to be connected to a venting line of said cooling system to allow inflow of coolant and air from this venting line to the expansion chamber 3 via this inlet aperture 6. In the em bodiment depicted the inlet aperture is situated at the bottom of the expansion chamber. A stub pipe 7 connected to the inlet aperture protrudes from the underside of the first casing element. Said venting line is intended to be connected to this stub pipe. The inlet aperture 6 might alternatively be situated i n a sidewall of the first casing element, and the first casing element might also be provided with two or more inlet apertures 6 for connection to respective venti ng lines of said cooling system .

The first casing element 2a is also provided with a closable fill ing aperture 8 via which coolant may be introduced into the expansion chamber 3 to allow said cooling system to be replenished with coolant. This filling aperture is closed by means of a removable cover 9.

An overpressure valve 1 0 for limiting the pressure in the expansion chamber 3, and a return valve 1 1 , are provided on a wal l 1 2 of the first casing element 2a. In the embodiment depicted this wall 1 2 is an upper wall of the first casing element. In the example depicted said valves 1 0, 1 1 are at a distance from one another, each in its respective aperture in said wall , but they might alternatively be close to one another in a common valve unit situated in a larger aperture in said wall . The overpressure valve 1 0 allows air and coolant to flow out from the upper part of the expansion chamber 3 when coolant volume increase results in a higher positive pressure in the expansion chamber than a level set by the overpressure valve. The return valve 1 1 allows air to flow into the upper part of the expansion chamber 3 from the surroundings when coolant volume decrease results in a lower negative pressure in the expansion chamber than a level set by the return valve. In the embodiment depicted in Figs. 1 -3 the second casing element 2b takes the form of a shel l-like hood with a closed end 1 5 which faces away from the first casing element 2a, and an opposite open end 1 6 which faces towards the first casing element. The second casing element 2b is in this case arranged to be axially movable externally about a cylindrical portion 1 7 of the first casing element 2a, and the second casing element has a cylindrical wall 1 8 which abuts slidingly against the outside of the cylindrical portion 1 7, either directly or via a plain bearing. The cross-sectional shape of the cyl indrical wal l 1 8 and the cylindrical portion 1 7 is with advantage circular but might alternatively be elliptical or rectangular. The cylindrical portion 1 7 has an open end 1 9 which faces towards the second casing element's closed end 1 5 and which is surrounded by the second casing element's cylindrical wall 1 8. The space 20 between the cylindrical portion's open end 1 9 and the second casing element's closed end 1 5 forms part of the expansion chamber 3, so the vol ume of the expansion chamber will vary depending on the position of the second casing element at the time. Fig . 2 depicts an extreme position for minimum expansion chamber volume, with the second casing element 2b in a fully retracted position . Fig . 3 depicts an extreme position for maximum expansion chamber volume, with the second casing element in a fully extended position. The second casing element may also be put into intermediate positions between these two extreme positions.

In the example depicted the cylindrical portion 1 7 protrudes in a horizontal direction from the upper part of a base portion 21 of the first casing element 2a.

In the embodiment depicted an expandable bladder 22 made of flexible material impervious to water and air is provided to fill the space 20 between the cylindrical portion's open end 1 9 and the second casi ng element's closed end 1 5. The bladder may for example be made of plastic or rubber material. It is connected fluid-tightly to the cylindrical portion 1 7 and arranged to block the latter's open end 1 9. It may for example be bonded or clamped to the cylindrical portion . It prevents air and coolant in the expansion chamber 3 from coming into contact with the joint between the two casing elements 2a, 2b and thus serves as a seal means to prevent air and coolant from flowing out of the expansion chamber via the joint between the two casing elements. As an alternative to such a bladder, one or more seal means may be provided at the joint between the two casing elements to prevent air and coolant from flowing out of the expansion chamber via this joint.

The second casing element 2b might be configured to be moved manually relative to the first casi ng element 2a, for manual setting of the size of the expansion chamber 3. In the em bodiments depicted , however, the expansion tank 1 is provided with an operating device 30 by means of which the second casing element is automatically movable to different positions relative to the first casing element. The operating devices 30 depicted each have a drive motor 31 with an output shaft 32 and a power transfer mechanism 33 for converting rotary motion of the output shaft to axial linear motion of the second casing element 2b. The drive motor 31 is with advantage an electric motor or a hydraulic motor. In the embodiment depicted in Figs. 1 -3 the power transfer mechanism 33 takes the form of spur gearing with a gearwheel 34 which is connected to, for joint rotation with, the drive motor's output shaft 32, and a toothed rack 35 which is firmly attached to the outside of the second casing element 2b, and the gearwheel 34 is in driving engagement with the toothed rack. In the embodiment depicted in Fig . 4 the power transfer mechanism 33 takes the form of a worm gear with a worm screw 34' which is firmly connected to, for joint rotation with , the drive motor's output shaft 32, and a toothed rack 35 which is firm ly attached to the outside of the second casing element 2b, and the worm screw 34' is in driving engagement with the toothed rack. The embodiment depicted in Fig . 4 corresponds otherwise to that depicted in Figs. 1 -3. The operating device 30 might alternatively be configured otherwise than as depicted in Figs. 1 -4 and might for example comprise one or more hydraulic cyl inders for moving the second casing element 2b relative to the first casing element 2a.

Figs. 5 and 6 illustrate schematical ly two different variants of a cooling system 40 according to the present invention which is intended for a motor vehicle. This cooling system comprises a cooling circuit 41 for cooling a combustion engine 42 of the vehicle by means of a coolant flowing in the cooling circuit, preferably in the form of water which may contain freezing point lowering additives such as glycol . A coolant pump 43 is incorporated in the cooling circuit 41 to circulate the coolant in the cooling circuit. A radiator 44, e.g . in the form of a conventional coolant radiator, is also incorporated in the cooling circuit 41 to cool said coolant. This radiator has a coolant inlet 45a connected to a coolant outlet 46b of the engine 42 via a first line 47 of the cooling circuit, and a coolant outlet 45b connected to a coolant inlet 46a of the engi ne via a second line 48 of the cooling circuit. In the example depicted the coolant pump 43 is situated in the second line 48. The first line 47 is connected to the second line 48 via a third line 49 of the cooling circuit. This third line is provided to allow coolant to return from the engine's coolant outlet 46b to its coolant inlet 46a without passing through said radiator 44. The third li ne 49 thus serves as a bypass via which the coolant circulating in the cooling circuit 41 can bypass the radiator 44 on its way between the engine's coolant outlet 46b and coolant inlet 46a. Between the inlet 46a and the outlet 46b the coolant circulates through coolant ducts (not depicted) within the engine, in which it absorbs heat from the engine. A thermostat 50 is provided at the connection point between the first line 47 and the third line 49. Depending on the temperature of the coolant, the thermostat will direct the coolant flowing out of the engine either to the radiator 44 for cooling therein before returning to the engine, or directly back to the engine via the third line 49 without passing through the radiator.

The coolant which flows through the radiator 44 is cooled by air which is blown towards the radiator when the vehicle is in motion . The cooling system 40 may also comprise a fan (not depicted) to generate an air flow through the radiator. This fan may be connected to, in order to be driven by, the engine 42.

The cooling system 40 is provided with an expansion tank 1 of the type described above. The tank's outlet aperture 4 is connected to the aforesaid second line 48 via a fourth line 51 of the cooling system . The fourth line 51 is connected to the second line 48 at a point situated between the radiator 44 and the coolant pump 43. The tank's inlet aperture 6 is connected to the radiator 44 via a first venting line 52 and to the coolant ducts in the engine 42 via a second venting line 53. Coolant is led via the venting lines 52, 53 into the expansion chamber 3 within the expansion tank, and is returned from the expansion chamber to the cooling circuit 41 via the aforesaid fourth line 51 . The air which is absorbed by the coolant circulating through the cool ing circuit and which thus accompanies the coolant to the expansion chamber via the venting lines 52, 53 is intended to rise to the surface of the coolant volume in the expansion chamber and accumulate in the air-fi lled space above the liquid level in the expansion chamber. Deaeration of the coolant in the expansion tank is thus achieved . In the embodiments depicted in Figs. 5 and 6 the cooling system 40 comprises an electronic control device 55 arranged to operate the expansion tank's operating device 30 on the basis of values which represent the temperature of the coolant in the cooling circuit 41 or the pressure in the cooling circuit 41 , so that the volume of the expansion chamber 3 is varied through action of the operating device 30 and the control device 55 on the basis of the temperature of the coolant in the cooling circuit or the pressure in the cooling circuit.

In the embodiment depicted in Fig. 5, the control device 55 is arranged to receive measured values from a pressure sensor 56 which is provided to measure the pressure in the cooling circuit 41 . In the example depicted this pressure sensor 56 is situated in the expansion tank 1 .

In the embodiment depicted in Fig. 6, the control device 55 is arranged to receive measured values from a temperature sensor 57 which is provided to measure the temperature of the coolant in the cooling circuit 41 . In the example depicted this temperature sensor 57 is situated i n the engine 42.

The expansion tank according to the invention and the cooling system according to the invention are particularly intended for use in a heavy motor vehicle, e.g . a bus, a tractor vehicle or a truck.

The invention is of course in no way restricted to the em bodiments described above, since numerous possibilities for modifications thereof are likely to be obvious to one skilled in the art, without thereby deviating from the invention's basic concept such as is defined in the attached claims.

Claims

1 . An expansion tank intended to form part of a cooling system of a motor vehicle, which tank (1 ) comprises

- an outer casing (2),

- an expansion chamber (3) enclosed in the casing (2), to accommodate coolant, and

- an overpressure valve (1 0) situated in the casing (2), to li mit the pressure in the expansion chamber (3),

characterised in that the casing (2) comprises a first element (2a) and a second element (2b), which second element (2b) is movably connected to the first element (2a) and can be put into different positions relative to the first element in order thereby to allow variation of the volume of the expansion chamber (3).

2. An expansion tank according to claim 1 , characterised in that the second casing element (2b) is movable telescopically relative to the fi rst casing element (2a) .

3. An expansion tank according to claim 1 or 2, characterised

- in that the second casing element (2b) takes the form of a hood with a closed end ( 1 5) which faces away from the first casing element (2a), and an opposite open end ( 1 6) which faces towards the first casing element (2a), which second element (2b) is arranged to be axially movable externally about a cylindrical portion ( 1 7) of the first element (2a), and

- that said cylindrical portion (1 7) has an open end (1 9) which faces towards the second casing element's closed end (1 5) and which is surrounded by the second casing element (2b) , and the space (20) between the cylindrical portion's open end ( 1 9) and the second casing element's closed end ( 1 5) forms part of the expansion chamber (3).

An expansion tank according to claim 3, characterised in that a bladder (22) made of flexible material impervious to water and air is fluid-tightly connected to said cylindrical portion ( 1 7), is arranged to block the latter's open end (1 9) and is expandable to be able to fill the space (20) between the cylindrical portion's open end (1 9) and the second casing element's closed end (1 5).

An expansion tank according to any one of claims 1 -4, characterised in that the second casing element (2b) is journalled slidingly on the first casing element (2a).

An expansion tank according to any one of claims 1 -5, characterised in that the first casing element (2a) is provided with an outlet aperture (4) which is intended to be connected to a coolant line of said cooling system in order to allow exchange of coolant between the expansion chamber (3) and other parts of the cooling system via this outlet aperture (4).

An expansion tank according to any one of claims 1 -6, characterised in that the first casing element (2a) is provided with an inlet aperture (6) which is intended to be connected to a venting line of said cooli ng system in order to allow inflow of coolant and air from this venting line to the expansion chamber (3) via this inlet aperture (6).

8. An expansion tank according to any one of claims 1 -7, characterised in that a return valve ( 1 1 ) is provided in the casing (2) and is arranged to allow air to flow into the expansion chamber (3) from the surroundings when a negative pressure lower than a level set by the return valve occurs in the expansion chamber.

9. An expansion tank according to any one of claims 1 -8, characterised in that the expansion tank (1 ) [ERRONEOUS "(3) "] is provided with an operating device (30) by means of which the second casing element (2b) is automatically movable to different positions relative to the first casing element (2a).

1 0. An expansion tank according to claim 9, characterised in that the operating device (30) comprises

- a drive motor (31 ) with an output shaft (32) , and

- a power transfer mechanism (33) for converting rotary motion of the drive motor's output shaft (32) to linear motion of the second casing element (2b).

1 1 . An expansion tank according to claim 1 0, characterised in that the power transfer mechanism (33) takes the form of a worm gear or spur gear.

1 2. A cooling system for a motor vehicle comprising a cool ing circuit (41 ) for cooling a combustion engine (42) of the vehicle by means of a coolant flowing in the cooling circuit, characterised in that the cooling circuit (41 ) comprises an expansion tank ( 1 ) according to any one of claims 1 -1 1 .

3. A cooling system according to claim 1 2, characterised

- in that the cooling circuit (41 ) comprises an expansion tank ( 1 ) according to any one of claim 9-1 1 and

- that the cool ing system (40) comprises an electronic control device (55) adapted to controlling the expansion tank's operating device (30) on the basis of values which represent the temperature of the coolant in the cooling circuit (41 ) or the pressure in the cooling circuit (41 ).