SE541597C2

SE541597C2 - An expansion tank for the cooling system of a liquid-cooled internal combustion engine

Info

Publication number: SE541597C2
Application number: SE1651510A
Authority: SE
Inventors: Bozidar Stevanovic
Original assignee: Scania Cv Ab
Priority date: 2016-11-18
Filing date: 2016-11-18
Publication date: 2019-11-12
Also published as: DE102017010286A1; SE1651510A1

Abstract

An expansion tank for the cooling system of a liquid-cooled internal combustion engine comprising a housing (15) and an expansion chamber (16) delimited by the housing (15), an inlet connection for connection (8) to a supply of coolant discharged from the engine and an outlet connection (11) for the return of coolant to the engine. The outlet connection (11) comprise a coolant channel (28) and a baffle (34) is arranged in the expansion chamber (16) for damping the movement of coolant. The baffle (34) is a stand-alone insert adapted to be inserted into the coolant channel (28).

Description

AN EXPANSION TANK FOR THE COOLING SYSTEM OF A LIQUID-COOLED INTERNAL COMBUSTION ENGINE TECHNICAL FIELD The present invention generally relates to an expansion tank for the cooling system of a liquid-cooled internal combustion engine and a motor vehicle comprising an expansion tank according to the claims.

BACKGROUND AND PRIOR ART Liquid coolant which circulates in a cooling system for cooling a combustion engine is usually at an operating temperature of 80-100°C.

When the engine is started up from cold, the coolant will be at a significantly lower temperature. The coolant occupies a larger volume in the cooling system when it is warm than when it is cold. To cater for a change of volume of the coolant during operation, the cooling system is provided with an expansion tank. The expansion tank may take the form of a confined vessel which, when the engine is at rest, is only partially filled with coolant. The remainder of the space above the coolant being available for the volumetric expansion of the coolant due to heat. Such an expansion tank also serves as a means of enabling gases dissolved or trapped in the coolant to rise to the coolant surface and escape.

Coolant discharged from the engine flows through an inlet into the expansion tank above the level of coolant and returns from the bottom of the tank through an outlet to join the flow of coolant returned to the engine. The outlet of the expansion tank is normally connected to other parts of the cooling system by a vertical line called the “static line”. The expansion tank is therefore situated at a certain height level above the coolant pump which circulates the coolant in the cooling system. Such a configuration results in a column of coolant extending from the coolant level in the expansion tank to the coolant pump. This column of coolant provides assurance that the coolant close to the inlet of the pump will be at a positive pressure related to the height of the column. The fact that the coolant close to the pump inlet is at a positive pressure decreases the risk of cavitation when the pump is started.

One problem in the design of such expansion tanks is that the coolant level may be quite low above the outlet of the tank at certain vehicle operating conditions when coolant sloshing back and forth in the expansion tank, for example when driving on uneven ground or in a sharp curve. A consequence of this may be that gases and vapours that normally are above the coolant level in the tank may reach the outlet of the tank and follow the coolant to the pump which increases the risk of cavitation.

GB 2 067 919 A shows a cooling circuit with an expansion tank. The tank has an inlet pipe and an outlet pipe for liquid coolant. A vane is provided upstream of the outlet pipe. When the coolant level in the tank decreases, the vane prevents air from being drawn into the circuit by water eddy which normally tends to form at the outlet pipe.

SUMMARY OF THE INVENTION One object of the present invention is to improve the efficiency of a motor vehicle cooling system. Another object is to propose an expansion tank with improved slosh reducing characteristics. Those objects and other objects are achieved by the features mentioned in the claims.

The invention relates to an expansion tank for the cooling system of a liquid-cooled internal combustion engine. The expansion tank comprises a housing and an expansion chamber delimited by the housing and arranged to comprise coolant at a certain level, an inlet connection on the housing for connection to a supply of coolant discharged from the engine and an outlet connection on the housing for the return of coolant to the engine. The outlet connection is connected to a tank return line below the level and discharges into the tank return line through a coolant channel. A baffle is arranged in the expansion chamber for damping the movement of coolant. The baffle is a stand-alone insert adapted to be inserted into the coolant channel and comprises a passage adapted to serve as a coolant inlet passage to the tank return line and coolant openings adapted to allow a coolant flow between the expansion chamber and the passage.

The baffle creates a barrier to sudden slosh or movement of coolant at the outlet connection, as may be caused for example when driving on uneven ground or in a sharp curve. Further, the baffle may eliminate the coolant water eddy which normally tends to form at the outlet connection. This prevents gases and vapours that normally are above the coolant level in the tank to reach the outlet of the tank and follow the coolant to the pump.

Since the baffle is a stand-alone insert shaped and configured so as to be received within an existing coolant channel a particular expansion tank is not required in order receive improved slosh reducing characteristics, on the contrary the insert can be installed in already existing expansion tanks to improve their characteristics. Further, the insert can easily be manually or automatically inserted and removed from the coolant channel which have been fitted with such baffle. Another advantage is that the insert is simple to manufacture, and can be manufactured in large numbers for subsequent installation in any expansion tank.

According to an embodiment the baffle is a tubular cylinder comprising an envelope surface delimiting the passage, a downstream end adapted to extend into the coolant channel and an upstream end adapted to extend into the expansion chamber above the level. The coolant openings are arranged in the envelope surface. The tubular cylinder is relatively simple to manufacture and assemble during the manufacturing of the tanks and in existing tanks. The baffle may be arranged so that either less or more of its length extends outwardly through the mouth of the coolant channel and into the expansion chamber. By varying the length of the part of the baffle extending outwardly through the mouth, a particular baffle can be tailored so as to produce optimal slosh characteristics desired by the user.

According to an embodiment the coolant openings are adapted to extend around the entire envelope surface in its circumferential direction which makes it possible for coolant to flow into the passage from different direction.

According to an embodiment the baffle comprises a first half and a second half. The upstream end is arranged at the first half and the downstream end at the second half. The coolant openings are adapted to be arranged at the second half which makes it possible to arrange them close to the bottom in the expansion chamber and to arrange at least some of them at substantially the same level as the bottom.

According to an embodiment each coolant opening has a first opening area and the baffle comprises at least one opening with a second opening area at the upstream end. The sum of the first opening areas are at least equal to the sum of the second opening areas. According to another embodiment the sum of the first opening areas are larger than the sum of the second opening areas. The upstream end is adapted to extend into the expansion chamber above the coolant level and the opening is adapted to enable a communication of air between the air filled space above the level and the passage through the baffle. By designing the opening areas in the manner indicated the pressure drop which may arise when coolant passes through the openings 36 from the the expansion chamber 16 to the passage 35 may be reduced.

According to an embodiment each coolant opening has a circular crosssectional shape and according to another embodiment the opening has a circular cross-sectional shape, which makes it relatively simple to manufacture the baffle.

According to an embodiment the baffle is held in place by a press fit.

Hereby the coolant deflector will remain in place in the coolant channel without using any separate fastening means.

According to an embodiment the baffle is held in place by a hose clamp. The tank return line may be slipped on the outlet connection and fixed to it by a hose clamp. Since the baffle is adapted to extend into the coolant channel which in turn extends through the outlet connection it may be advantageous to arrange the hose clamp to press the tank return line against the outlet connection and the outlet connection against the baffle.

Embodiments herein also aim to provide a motor vehicle with an improved cooling system. According to an embodiment this is provided by a motor vehicle which comprises an expansion tank according to embodiments herein.

Other features and advantages of the invention are apparent from the claims, the description of embodiment and the attached figures.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be described in greater detail with reference to the appended drawings in which: Fig. 1 shows a schematic side view of a motor vehicle comprising a cooling system.

Fig. 2 shows schematically a cooling system intended for a motor vehicle.

Fig. 3 shows a vertical cross-section through an expansion tank in fig. 2.

Fig. 4 shows a vertical cross-section through an outlet connection in fig. 3 and a part of the expansion tank.

Fig. 5 shows a vertical cross-section through the outlet connection in fig. 4, a part of the expansion tank and an embodiment of a baffle.

DETAILED DESCRIPTION Fig. 1 shows a schematic side view of a motor vehicle 1 powered by an liquid cooled internal combustion engine 2. The engine 2 may be a diesel engine or an Otto engine cooled by a coolant circulating in a cooling system 3. The vehicle 1 may be a heavy vehicle such as for example a truck, a tractor or a bus or a lighter vehicle such as for example a passenger car. In alternative embodiments, the internal combustion engine 2 may be a separate engine adapted to drive e.g. an electricity generating unit or a boat.

Fig. 2 illustrates schematically a cooling system 3 intended for a motor vehicle. The cooling system 3 comprises a cooling circuit 4 for cooling the combustion engine 2 by means of a liquid coolant flowing in the circuit 4. The cooling circuit 4 comprises a tank feed line 6 adapted to transfer coolant from the engine 2 to an expansion tank 7. For this purpose the one end of the tank feed line 6 is connected to cooling channels (not shown) in the engine 2 and the other end is connected to an inlet connection 8 on the expansion tank 7 for connection to a supply of coolant discharged from the engine 2. The expansion 7 tank is adapted to comprise coolant at a certain level (10) and the tank feed line 6 is connected to the expansion tank 7 above that level 10.

Further, the cooling circuit 4 comprises a tank return line 9, also called the “static line” and which is adapted to transfer coolant to other parts of the cooling system 3. For this purpose the one end of the tank return line 9 is connected to a pump 12 adapted to circulate coolant in the cooling system 3 and the other end is connected to an outlet connection 11 on the expansion tank 7 below the level 10 for the return of coolant to the engine 2. The tank return line 9 extends in a vertical direction and the expansion tank 7 is therefore situated at a certain height level above the pump 12. Such a configuration results in a column of coolant extending from the level 10 to the pump 12. This column provides assurance that the coolant close to the inlet 13 of the pump 12 will be at a positive and static pressure related to the height of the column which decreases the risk of cavitation when the pump 12 is started.

Fig. 3 shows a vertical cross-section through the expansion tank 7 which comprises a housing 15 and an expansion chamber 16 delimited by the housing 15. The housing 15 may be formed by an upper and lower moulded part 17,18 joined at a equatorial joint face 19. The upper part 17 comprises a closable filling aperture 20 via which coolant can be introduced into the expansion chamber 16 to replenish the cooling system 3. The filling aperture 20 may be closed by means of a removable cover 21.

The upper part 17 of the housing 15 comprises the inlet connection 8 for connection to the tank feed line 6 (fig. 2). The inlet connection 8 discharges through an inlet aperture 23 which may be located towards the top of the expansion chamber 16. The lower part 18 of the housing 15 comprises the outlet connection 11 for connection to the tank return line 9 (fig.2). The outlet connection 11 discharges through an outlet aperture 26 which may be located towards the bottom or at the bottom of the expansion chamber 16. The tank feed line 6 and the tank return line 9 may be slipped on its corresponding connection 8,11 and fixed to the connections 8,11 in a suitable way, e.g. by a hose clamp.

Fig. 4 shows a vertical cross-section through the outlet connections 11 which may be shaped as a pipe stub which protrudes from a wall 27 of the housing 15. Only a part of the housing 15 is shown in the figure. A coolant channel 28 extends through the outlet connection 11 in its longitudinal direction. An upstream end 29 of the coolant channel 28 is adapted to receive a coolant flow A from the expansion chamber 16 and a downstream end 30 of the coolant channel 28 is adapted to be connected to, and discharged through, the tank return line 9 (fig. 2). In use, the outlet connection 11 discharges into the tank return line 9 through the coolant channel 28 and the outlet aperture 26 which are arranged to direct a stream B of outgoing coolant into the tank return line 9.

The coolant channel 28 may have any cross-sectional shape that suits the particular application. In a preferred embodiment the cross-sectional shape is circular. In a second embodiment the cross-sectional shape is quadratic. In a third embodiment the cross-sectional shape is rectangular. In a forth embodiment the cross-sectional shape is oval. I addition, an outer surface 31 at the downstream end 30 adapted to receive the tank return line 9 may comprise a bulge 32 which together with a hose clamp or any other suitable attachment means may reduce the risk of the tank return line 9 sliding off the outlet connection 11.

One problem in the design of previously known expansion tanks 7 is, with reference to fig 2, that the coolant level 10 may be quite low above the outlet connection 11 at certain vehicle operating conditions when coolant slashing back and forth in the expansion tank, for example when driving on uneven ground or in a sharp curve. A consequence of this may be that gases and vapours that normally are above the level 10 may reach the outlet connection 11 and follow the coolant to the pump 12 which may increase the risk of cavitation. In order to overcome or at least alleviate this problem a baffle is arranged in the expansion chamber 16 for damping the movement of coolant. The baffle 34 is, which can be seen in fig. 3 adapted to be inserted into the coolant channel 28 and thus, the coolant channel 28 is adapted to receive the baffle 34.

Fig. 5 shows the outlet connection 11 and a vertical cross-section through an embodiment of a baffle 34. The baffle 34 may have a passage 35 which serves as a coolant inlet passage to the tank return line 9 (fig.2) and a plurality of coolant openings 36 adapted to allow a coolant flow C in both directions between the expansion chamber 16 and the passage 35. The baffle 34 may be a tubular cylinder comprising an envelope surface 37 delimiting the passage 35, a downstream end 38 adapted to extend into the coolant channel 28 and an upstream end 39 adapted to extend into the expansion chamber 16 above the level 10. The coolant openings 36 may be arranged in the envelope surface 37 and may be adapted to extend around the entire envelope surface 37 in its circumferential direction. Further, the baffle 34 comprises a first half 41 and a second half 42. The upstream end 39 is at the first half 41, the downstream end 38 at the second half 42 and the coolant openings 36 may be arranged at the second half 42. Each coolant opening 36 has a first opening area A1 and may have any cross-sectional shape but preferably a circular cross-sectional shape.

The baffle 34 may comprise at least one opening 44 at its upstream end 39. Each opening 44 is adapted to enable a communication of air between an air filled space 43 above the level 10 and the passage 35. Each opening 44 has a second opening area A2 and may have any cross-sectional shape but preferably a circular cross-sectional shape. The at least one opening 44 may be arranged at the end of the baffle 34 with its centre axis aligned with the centre axis X-X of the baffle 34. The opening area A2 may be equal to the cross-sectional area of the passage 35 as shown in fig 5. At an alternative embodiment the opening area A2 may be smaller than the cross sectional area of the passage 35. In another embodiment the at least one opening 44’ may be arranged in the envelope surface 37 with its centre axis offset from the axis x-x of the baffle 34 and preferably perpendicular to that of the baffle 34.

At one embodiment the sum of the first opening areas A1 are at least equal to the sum of the second opening areas A2, but preferably larger than the sum of the second opening areas A2. The reason for this is to reduce the pressure drop which may arise when coolant passes through the openings 36 from the the expansion chamber 16 to the passage 35.

The baffle 34 may be arranged so that either less or more of its length extends into the expansion chamber 16. In a preferred embodiment the baffle 34 may be adapted to extend above the level 10. In another embodiment the baffle 34 may be adapted to extend above the high mark shown in fig 3. In a further embodiment the baffle 34 may be adapted to extend above the equatorial joint face 19, also shown in fig. 3. In further embodiments the baffle 34 may be adapted to extent in line with the high mark or in line with the equatorial joint face 19.

The baffle 34 may have a circular cross-sectional shape but in different embodiments it may have any cross-sectional shape that corresponds to the cross-sectional shape of the coolant channel 28 i.e. if the cross-sectional shape of the cooling channel 28 is circular the cross-sectional shape of the baffle 34 is circular, if the cross-sectional shape of the cooling channel 28 is quadratic the cross-sectional shape of the baffle 34 is quadratic, if the cross-sectional shape of the cooling channel 28 is rectangular the crosssectional shape of the baffle 34 is rectangular and if the cross-sectional shape of the cooling channel 28 is oval the cross-sectional shape of the baffle 34 is oval and so on.

The baffle 34 may be a stand-alone insert adapted to be inserted into the coolant channel 28. The baffle 34 can be manually or automatically inserted and removed, as appropriate, from coolant channels 28 which have been fitted with such baffle 34. Further, the baffle 34 may be manufactured of any suitable material, including metals such as non-ferrous metals, plastic, composite materials or other durable rust resistant materials.

The baffle 34 may be held in position by a press fit and may have a width which at least slightly exceeds the width of the coolant channel 28 so that when the baffle 34 is inserted within the coolant channel 28 it will remain in place and the pressure of the coolant will not cause the baffle 34 to be forced out of the coolant channel 28. At an alternative embodiment the baffle 34 may be held in place by a hose clamp (not shown) which encloses the tank return line 9 (fig. 2) adapted to be slipped on the outlet connection 11 and which is adapted to press the tank return line 9 against the outlet connection 11 and the outlet connection 11 against the baffle 34. At a further embodiment the baffle 34 may have an external thread and the coolant channel 28 an internal thread wherein the baffle 34 may be threaded into the coolant channel 28.

In operation with a cold engine 2 and cooling system 3 the coolant level 10 in the expansion chamber 16 will be between the high and low marks shown in fig. 3. Coolant is pumped by the pump 12 out of the engine 2 into the tank feed line 6 and into the expansion chamber 16 as a stream of coolant. The coolant collected in the expansion chamber 16 flows through the openings 36 and the axial passage 35, shown in fig 5, as a stream C of coolant and is delivered back to the pump 12 through the tank return line 9 as a stream D. While the baffle 34 is not a barrier to the stream C of coolant it do create a barrier to a sudden slosh or movement of collected coolant in the axial passage 38, as may be caused when for example driving on uneven ground or in a sharp curve. Coolant flows slowly through the openings 36, but cannot slosh out quickly which ensures that there is enough coolant at the outlet connection 11 to ensure that gases and vapours that normally are above the coolant level 10 may not reach the outlet connection 11 and follow the coolant to the pump.

The invention is not restricted to the embodiments described above, but many possibilities to modifications thereof will be apparent to those skilled in the art without thereby deviating from the scope of the following claims.

Claims

1. An expansion tank for the cooling system (3) of a liquid-cooled internal combustion engine (2), the expansion tank (7) comprises a housing (15) and an expansion chamber (16) delimited by the housing (15) and arranged to comprise coolant at a certain level (10), an inlet connection (8) on the housing (15) adapted to connect to a supply of coolant discharged from the engine (2), an outlet connection (11) on the housing (15) adapted to provide return of coolant to the engine (2), the outlet connection (11) is connected to a tank return line (9) below the level (10) and discharges into the tank return line (9) through a coolant channel (28) wherein a baffle (34) is arranged in the expansion chamber (16) for damping the movement of coolant, the baffle (34) is a stand-alone insert adapted to be inserted into the coolant channel (28), the baffle (34) comprises a passage (35) adapted to serve as a coolant inlet passage to the tank return line (9) and coolant openings (36) adapted to allow a coolant flow (C) between the expansion chamber (16) and the passage (35), characterised in that the baffle (34) is a tubular cylinder comprising an envelope surface (37) delimiting the passage (35), a downstream end (38) adapted to extend into the coolant channel (28), an upstream end (39) adapted to extend into the expansion chamber (16) above the level (10) and that the coolant openings (36) are arranged in the envelope surface (37).

2. An expansion tank according to claim 1, characterised in that the coolant openings (36) are adapted to extend around the entire envelope surface (37) in its circumferential direction.

3. An expansion tank according to any one of claims 1-2, characterised in that the baffle (34) comprises a first half (41) and a second half (42), that the upstream end (39) is arranged at the first half (41) and the downstream end (38) at the second half (42) and that the coolant openings (36) are adapted to be arranged at the second half (42).

4. An expansion tank according to any one of claims 1-3 characterised in that each coolant opening (36) has a circular cross-sectional shape.

5. An expansion tank according to any one of claims 1-4, characterised in that each coolant opening (36) has a first opening area (A1), that the baffle (34) comprises at least one air opening (44) with a second opening area (A2) at the upstream end (39) and in that the sum of the first opening areas (A1) are at least equal to the sum of the second opening areas (A2).

6. An expansion tank according to claims 1-4, characterised in that each coolant opening (36) has a first opening area (A1), that the baffle (34) comprises at least one air opening (44) with a second opening area (A2) at the upstream end (39) and in that the sum of the first opening areas (A1) are larger than the sum of the second opening areas (A2).

7. An expansion tank according to claim 5 or 6, characterised in that the at least one air opening (44) has a circular cross-sectional shape.

8. An expansion tank according to any one of claim 1-7, characterised in that the baffle (34) is held in position by a press fit.

9. An expansion tank according to any one of claim 1-7, characterised in that the baffle (34) is held in place by a hose clamp.

10. A motor vehicle comprising an expansion tank (7) according to any one of claims 1-9.