WO2014081374A1

WO2014081374A1 - Thermostat for a cooling system which cools a combustion engine

Info

Publication number: WO2014081374A1
Application number: PCT/SE2013/051331
Authority: WO
Inventors: Zoltan Kardos
Original assignee: Scania Cv Ab
Priority date: 2012-11-21
Filing date: 2013-11-12
Publication date: 2014-05-30
Also published as: SE1251315A1; SE536719C2

Abstract

The present invention pertains to a thermostat (7) for a cooling system which cools a combustion engine (1). The cooling system comprises a cooler (5) for cooling of coolant, a first pipe (4) which leads coolant from the combustion engine (1) to the cooler (5), a second pipe (8) which leads coolant from the first pipe (4) to the thermostat (7), a third pipe (9) which leads coolant from the cooler (5) to the thermostat (7) and a fourth pipe (10) which leads coolant from the thermostat (7) to the combustion engine (1). The thermostat (7) comprises a thermostat housing (12) which encloses a first valve (17) which controls the flow from the third pipe (9) to the fourth pipe (10), a second valve (19) which controls the flow of coolant from the second pipe (8) to the fourth pipe (10) and a feeler (28) which detects the temperature of the coolant which is led to the fourth pipe (10) and controls the valves (23, 25). The feeler (28) is arranged inside a space (10a) inside the thermostat housing which is located between the first valve (23) and the second valve (25). The valves (23, 25) and the feeler (28) are arranged inside a thermostat device (13) which may be assembled in one continuous piece inside the thermostat housing (12).

Description

Thermostat for a cooling system which cools a combustion engine

BACKGROUND AND PRIOR ART

The present invention relates to a thermostat for a cooling system which cools a combustion engine, according to the preamble of patent claim 1.

The coolant in a cooling system for cooling a combustion engine in a vehicle should have an operative temperature which is normally within the temperature range 80-90°C. The cooling system usually comprises a thermostat which regulates the coolant's temperature in the cooling system. As a rule, the thermostat comprises a feeler which detects the temperature of the coolant after it has cooled the combustion engine. During

operational times, when the thermostat detects that the coolant has a lower temperature than the desired operative temperature, it leads the coolant back to the combustion engine without any cooling. During operational times, when the thermostat detects that the coolant has a higher

temperature than the desired operative temperature, it leads the coolant to a cooler for cooling before it is led to the combustion engine. The cooler is usually arranged at the vehicle's front section where the coolant is cooled by air which is forced through the cooler with the help of a radiator fan.

Conventional thermostats are controlled by the temperature of the coolant after it has cooled the coolant. After the coolant is cooled in the cooler it must circulate through a large part of the cooling system before the thermostat detects that the coolant has obtained a lower temperature. Thus, the regulation of the coolant's temperature takes place with a delay that many times leads to a subsequent temperature cycling where the thermostat abruptly switches between the two modes. Therefore, the cooler and associated devices in the cooling system are exposed to very quick temperature changes resulting in large thermal loads on the material in the cooler. The cooler and associated devices may at one moment have the temperature of the surrounding environment which may be extremely low in winter, and the next moment a temperature around 100°C when the thermostat opens and a large amount of warm coolant circulates through the cooler and associated devices. In this case, the cooler is very frequently subjected to thermal loads which probably shorten the cooler's life. A cooler's life is largely determined by how many times it is heated up and cooled. Coolers in the cooling system of a heavy goods vehicle are rather large and thus relatively expensive to purchase.

US 1 ,31 1 , 809 shows an older cooling system for a combustion engine. The cooling system includes a cooler and a bypass pipe, through which the coolant may be led past the cooler. A thermostat is arranged in the cooling system which, alternatively, leads the coolant from the bypass pipe or the cooler to the combustion engine depending on the temperature of the coolant. In order to avoid that the cooler freezes, the thermostat comprises a small passage so that a certain circulation of coolant through the cooler is always maintained. The thermostat is arranged inside a housing which has a complex construction. To replace only the thermostat is a complex j ob.

SUMMARY OF THE INVENTION

The objective of the present invention is to provide a thermostat controlled by the temperature of the coolant which is led to the combustion engine and which has a relatively simple and reliable construction and is easy to replace if it fails to function in the intended manner.

The thermostat detects the temperature of the coolant led to the combustion engine. Such a thermostat regulates the coolant's temperature with a significantly smaller delay than a conventional thermostat. It therefore does not need to switch as frequently before the coolant gains a stable operative temperature. The thermostat comprises a feeler which detects the coolant's temperature in an area in the thermostat housing which is located between the first valve and the second valve. Thus, the first valve may lead cooled coolant to the area from one side and the second valve may lead non-cooled coolant to the area from the opposite side. The thermostat thus obtains a relatively simple and reliable construction. Since the first valve, the second valve and the feeler are contained in one cohesive thermostat device, these components may benefit from a simultaneous and simple assembly in the thermostat housing and a similar simple disassembly in the event a fault arises in any of the components of the thermostat device.

According to one embodiment of the present invention, the thermostat device comprises a connection connecting the valves with each other so that they are included in one connected valve body, so that when one valve is moved into a fully open position, the other valve is moved into a closed position. On occasions when the coolant has a higher temperature than the regulating temperature, the first valve is open and the second valve is closed so that cooled coolant is led from the cooler to the combustion engine . On occasions when the coolant has a lower temperature than the regulating temperature, the first valve is closed and the second valve is open so that non-cooled coolant is led from the combustion engine directly back to the combustion engine without being cooled in the cooler. Since the valves are connected with each other, they can be regulated by one and the same feeler.

According to one embodiment of the present invention, the valve device is designed so that the connected valves are capable of being in a partly open position simultaneously. In this case, the valve body is positioned in an intermediate position where a mixture of cooled and non-cooled coolant is led to the combustion engine. Thus the thermostat does not switch as abruptly. If the thermostat detects that the coolant's temperature rises above the regulation temperature, the valves are moved into the

intermediate position. Thus , cooled coolant is also led to the combustion engine which often leads to the thermostat closing again since the feeler detects a lower temperature in the coolant. Thus, the thermostat does not switch as frequently. The cooler in the cooling system may thus achieve a slower heating without quick switches .

According to one embodiment of the present invention, at least one of the valves is designed so that it is not lifted from the closed position if a temporary increase of pressure in an adj oining conduit arises . During the operation of a cooling system, temporary pressure peaks may arise in the cooling system in particular on occasions where the valves are closed. The valves are preferably designed so that local pressure increases in adj oining conduits press the valve against a valve seat which constitutes a stop surface in the closed position. Thus, temperature fluctuations caused by temporary pressure increases in the cooling system are avoided. According to one embodiment of the present invention, the thermostat device includes a first valve plate with an opening for the first valve and a second valve plate with an opening for the second valve. The thermostat device may with the help of the said valve plates create internal walls dividing the thermostat housing into separate spaces which are necessary for the thermostat's function. Thus, the thermostat housing itself does not need to provide such internal wall elements. The thermostat housing may therefore have a relatively large empty internal space to receive the thermostat device. Thus, simple assembly and disassembly of the thermostat device in the thermostat housing is facilitated.

According to one embodiment of the present invention, the feeler is arranged in an intermediate space which is located between the valve plates. The first valve plate preferably consists of a wall element on one side of the space for coolant which is led to the combustion engine. The second valve plate preferably consists of a wall element on the opposite side of the space for coolant which is led to the combustion engine. Thus, cooled coolant may be led to the area from one side and non-cooled coolant may be led to the area from the opposite side. According to one embodiment of the present invention, the two valve plates are fixed with one sealing element each inside the thermostat housing. In order to guarantee that no coolant leakage occurs to the intermediate space when the respective valves are closed, it is appropriate to arrange a sealing element in the connection areas between the valve plates and the thermostat housing.

According to one embodiment of the present invention, the thermostat device includes two valve bodies arranged in parallel. Thus, two parallel flows of coolant may be obtained to the said space between the valve plates. Therefore, the thermostat's function may be maintained in at least a limited scope on occasions when the thermostat bodies lose their function. Thus , damage to components cooled by the cooling system may be avoided. Thus , the combustion engine may be operated at least a short distance to a location where the thermostat may be replaced. According to one embodiment of the present invention, the thermostat housing comprises a first section and a second section which are releasably connectable to each other. In order to assemble the thermostat device inside the thermostat housing, it is appropriate that a part of the thermostat housing be removable. When the said part is disassembled, an opening in the thermostat housing is exposed which means it is possible to assemble or disassemble the thermostat device.

According to one embodiment of the present invention, the thermostat housing with a fitted thermostat device comprises a first space for receipt of coolant from the second pipe, a second space for receipt of coolant from the third pipe and a third intermediate space which is connected to the fourth pipe. The valve plates of the thermostat device preferably define the walls separating the said spaces from each other. The thermostat housing may be equipped with a connecting section for a coolant pipe for each one of the said spaces .

BRIEF DESCRIPTION OF DRAWINGS

Below is a description, as an example, of a preferred embodiment of the invention with reference to the enclosed drawings , on which :

Fig . 1 shows a cooling system with a thermostat, according to the present invention,

Fig shows a thermostat housing in the thermostat,

Fig shows a thermostat device in the thermostat,

Fig shows the thermostat in a first operating condition

Fig shows the thermostat during a second operating condition and Fig shows the thermostat during a third operating condition. DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION

Fig. 1 shows a cooling system for cooling a combustion engine 1 in a vehicle 2 showed schematically. The coolant circulates in the cooling system with the help of a coolant pump 3. After the coolant has passed through the combustion engine 1 it is led, via a first pipe 4, to an air- cooled cooler 5. The cooler 5 may be fitted to a front section of the vehicle 2. In this case, the first pipe 4 also comprises an oil cooler 6 for a hydraulic retarder. The cooling system may thus be used for cooling other components and media in the vehicle 2, and not only the combustion engine 1. The cooling system comprises a thermostat 7. A second pipe 8 leads the coolant from the first pipe 4 to the thermostat 7. The second pipe 8 thus leads coolant which has not been cooled in the cooler to the thermostat 7. A third pipe 9 leads coolant which has been cooled in the cooler 5 to the thermostat 7. The thermostat 7 detects the coolant's temperature and it leads non-cooled liquid from the second pipe 8 to a fourth pipe 10 and the combustion engine 1 on occasions where the coolant has a temperature below the thermostat's regulation temperature. The thermostat 7 leads cooled coolant from the third pipe 9 to the fourth pipe

10 and the combustion engine 1 on occasions where the coolant has a temperature above the thermostat's regulation temperature. A radiator fan

1 1 sucks a cooling air stream through the cooler 5 so that the coolant provides effective cooling.

Fig. 2 shows a thermostat housing 12 in the thermostat 7. Fig. 3 shows a thermostat device 13 which is adapted to be fitted in the thermostat housing 12. The thermostat housing 12 comprises a first upper section 12a and a second section 12b which are releasably mountable with e.g. bolts that are not displayed. The first section 12a comprises an internal space 9a which has a connection to the third pipe 9. The second section 12b comprises an internal space 8a with a connection to the second pipe 8 and an internal space 10a with a connection to the fourth pipe 10. By releasing the first upper section of the housing 12a from the second lower section 12b, an opening 12c is exposed through which it is possible to insert and assemble the thermostat device 13 in a specific position in the thermostat housing 12. The thermostat device 13 is designed so that it may be assembled and disassembled in one continuous piece in the thermostat housing 12. A first sealing element 14a and a second sealing element 15a are adapted to seal between the thermostat device 13 and the thermostat housing 12 in one assembled condition. The thermostat 7 thus consists of a thermostat housing 12, a thermostat device 13 and two sealing elements 14a and 15a.

The thermostat device 13 comprises a first valve plate 14 and a second valve plate 15. The valve plates 14, 15 are held together with the help of spacers 16 which are only partly visible in the diagrams. The valve plates 14, 15 are thus held at a constant distance from each other with the help of the spacers 16. The first valve plate 14 is equipped with two pervading holes 17. The second valve plate 15 is equipped with two pervading holes 19. A first valve body 21 is fitted in connection with two holes 17, 19 in the valve plates 14, 15 and a second valve body 22 is fitted in connection with the two other holes 17, 19 in the valve plates 14, 15. The first valve body 21 comprises a first valve in the form of a first plate valve 23. A valve spring 24 acts on the plate valve 23. The first plate valve 23 is adapted to be displaced between a closed position where it seals one of the holes 17 in the first valve plate 14 and a more or less open position where it leaves the hole 17 exposed. The first valve body 21 comprises a second valve in the form of a second plate valve 25. A valve spring 26 acts on the plate valve 25. The second plate valve 25 is adapted to be displaced between a closed position where it seals one of the holes 19 in the second valve plate 15 and a more or less open position where it leaves the hole 19 exposed.

The first plate valve 23 and the second plate valve 25 are connected with each other through a number of connection elements 27 and a feeler 28 which keep the plate valves 23 , 25 at a constant distance from each other in an unloaded condition. The feeler 28 comprises a sleeve with a closed space which is occupied by a wax substance. The wax substance has the attribute that it increases in volume when it melts and is released in a liquid phase. The closed space of the feeler 28 is defined by a flexible membrane which is fixed on a pointing stick 29. At a lower end, the pointing stick 29 is in contact with a supporting element 30 which in turn is fixed on the second valve plate 15. When the wax melts inside the feeler 28 , the wax increases in volume so that the pointing stick 29 is pushed outward. Since the pointing stick 29 is in contact with the supporting element, it lifts the feeler 28 upwards together with the valve plates 23 , 25 in relation to the holes 17, 19 in the valve plates 14, 15. The second valve body 22 has a construction and function which is identical to the first valve body 21. The component parts of the second valve body 22 have therefore been equipped with the same reference numerals as the corresponding parts in the first valve body 21.

Fig. 4 shows the thermostat device 13 in an assembled condition in the thermostat housing 12. The first valve plate 14 of the thermostat device 13 separates the areas 9a, 10a in the thermostat housing 12 from each other and the second valve plate 15 separates the spaces 8a, 10a from each other. The first plate valve 23 is closed while the second plate valve 19 is open in both valve bodies 21 , 22. This is the case, for example, in the event of cold-starting a combustion engine 1. The wax substance in the feelers 28 is in this case in a solid state and it therefore has a minimal volume which leads to the thermostat bodies 21 , 22 and the plate valves 23, 25 [reaching] the lowest level in relation to the valve plates 14, 15. The coolant received in the pipe 4 from the combustion engine 1 is connected with the space 9a in the thermostat housing 12 via the cooler 5 and the pipe 9 and with the space 8a in the thermostat housing 12 via the pipe 8. Since the first plate valves 23 are closed, they prevent a flow of coolant via the cooler 5 to the pipe 10 and the combustion engine 1. The other plate valves 25 are open so that the coolant in the space 9a is led through the holes 19 in the second valve plate 15 and into the space 10a in the thermostat housing 12. The coolant is led from the space 10a via the pipe 10 to the coolant pump 3 and the combustion engine 1.

The feelers 28 of the thermostat bodies 21 , 22 are in contact with the coolant which circulates in the space 10a. As long as the coolant has a lower temperature than the regulation temperature of the thermostat 7, the wax substance is in the solid state. Since the coolant has been heated to the thermostat's regulation temperature, the wax substance in the feelers 28 begins to melt. The wax substance increases in volume, resulting in the pointing stick 29 being pushed outwards and the feeler upwards to the same degree together with the plate valves 23, 25. Fig. 5 shows the position of the valve bodies 21 , 22 when the wax has partly melted. The volume of the wax substance has increased so that the plate valves 23 have been moved from the closed position to a half-open position. At the same time, the other plate valves 25 have been moved from the fully open position to a half-open position. In this case, cooled coolant is led from the space 9a to the space 10a and non-cooled coolant is led from the space 8a to the space 10a.

If the coolant which circulates in contact with the feelers 28 inside the space 10a is colder than the regulation temperature, the wax substance becomes solid again and the first plate valve 23 is moved back to the closed position while the second plate valve 25 is moved to the open position. If the coolant which circulates in contact with the feelers 28 is warmer than the regulation temperature, the entire wax substance is released into liquid form. The wax substance thus obtains a maximum volume and the pointing stick 29 is pushed out to a maximum extent toward the supporting element 30 which result in the first plate valve 23 being moved into a fully open position, while the second plate valve 25 is moved to a fully closed position. Fig. 6 shows the thermostat during this operating condition. The valves 23 are arranged externally in relation to the first valve plate 14 in the open position, and they abut to a valve seat in the valve plate, thus creating a stop surface for the valves 23 in the closed position. If a temporary pressure increase arises in the third pipe 9, the valves 23 are pushed toward the said valve seats. Temporary pressure increases in the pipe 9 can thus not open the valves 23. In the same manner, the valves 25 are arranged externally in relation to the second valve plate 15 in the open position, and they abut to a valve seat in the valve plate 15 , thus creating a stop surface for the valves 25 in the closed position. If a temporary pressure increase arises in the second pipe 8 , the valves 25 are pushed toward the said valve seats. Temporary pressure increases in the pipe 8 can thus not open the valves 25. The invention is in no way limited to the embodiment described in the drawing, but may be varied freely within the framework of the patent claims. In this case, the thermostat 7 comprises two thermostat bodies 21 , 22 arranged in parallel. It is sufficient to have one thermostat body, but from a safety perspective it may be favourable to have two in case one should lose its functionality.

Claims

Patent claims

1. Thermostat for a cooling system which cools a combustion engine, where the cooling system comprises a cooler (5) for cooling coolant, a first pipe (4) which leads coolant from the combustion engine ( 1 ) to the cooler (5), a second pipe (8) which leads coolant from the first pipe (4) to the thermostat (7), a third pipe (9) which leads coolant from the cooler (5) to the thermostat (7) and a fourth pipe ( 10) which leads coolant from the thermostat (7) to the combustion engine ( 1 ), and where the thermostat (7) comprises a thermostat housing (12) which encloses a first valve (17) which controls the flow from the third pipe (9) to the fourth pipe ( 10), a second valve ( 19) which controls the flow of coolant from the second pipe (8) to the fourth pipe ( 10) and a feeler (28) which detects the temperature of the coolant which is led to the fourth pipe ( 10) and controls the valves (23 , 25), characterised by the fact that the feeler (28) is arranged inside a space ( 10a) in the thermostat housing which is located between the first valve (23) and the second valve (25), where the valves (23, 25) and the feeler (28) are arranged inside a thermostat device ( 13) which may be assembled in one continuous piece inside the thermostat housing (12).

2. Thermostat according to claim 1 , characterised by the fact that the thermostat device (13) comprises a connection (27, 28) which links the valves (23, 25) with each other so that they are enclosed inside one continuous valve body (21 , 22), causing the second valve (23 , 25) to be moved into a closed position when the first valve (23, 25) is moved into a fully open position.

3. Thermostat according to claim 2, characterised by the fact that the valve unit ( 13) is designed so that the valves (23 , 25) are capable of being partly open at the same time.

4. Thermostat according to claim 2 or 3 , characterised by the fact that at least one of the valves (23 , 25) is designed so that it is not lifted from the closed position if a temporary pressure increase arises in an adjoining pipe (8 , 9).

5. Thermostat according to any of the previous claims, characterised by the fact that the thermostat device (13) comprises a first valve plate ( 14) with an opening ( 17) for the first valve (23) and a second valve plate ( 15) with an opening ( 19) for the second valve (25).

6. Thermostat according to claim 5, characterised by the fact that the feeler (28) is arranged in an intermediate space (10a) which is located between the valve plates ( 14, 15).

7. Thermostat according to claim 5 or 6, characterised by the fact that the two valve plates (14, 15) are fixed with one sealing element (14a, 15a) each inside the thermostat housing ( 12).

8. Thermostat according to any of the previous claims, characterised by the fact that the thermostat device (13) comprises two valve bodies arranged in parallel (21 , 22).

9. Thermostat according to any of the previous claims, characterised by the fact that the thermostat housing ( 12) comprises a first section ( 12a) and a second section ( 12b) which are releaseably connectable to each other.

10. Thermostat according to any of the previous claims, characterised by the fact that the thermostat (7) comprises a first space (8a) to receive coolant from the second pipe (8), a second space (9a) to receive coolant from the third pipe (9) and a third intermediate space ( 10a) which is connected to the fourth pipe ( 10).