SE542852C2

SE542852C2 - A thermostat device for a cooling system

Info

Publication number: SE542852C2
Application number: SE1850198A
Authority: SE
Inventors: Ola Hall; Zoltan Kardos
Original assignee: Scania Cv Ab
Priority date: 2018-02-22
Filing date: 2018-02-22
Publication date: 2020-07-21
Also published as: DE102019000836A1; SE1850198A1; DE102019000836B4

Abstract

The present invention relates to a thermostat device for a cooling system. The thermostat device comprises a thermostat valve (7) with a valve body (16) comprising a first valve plate (17) and a second valve plate (18), a thermal expansion element (22) configured to be in thermal contact with coolant entering the thermostat valve (7) and to exert a first force on the valve body (16) in relation to the coolant temperature, pressure means configured to exert a second force on the valve body (16) related to the pressure of the coolant entering the thermostat valve (7) and a main spring (28) configured to exert a third force on the valve body (16) in direction towards the first end position. The valve body (16) is moved to a position defined by the temperature and the pressure of the coolant.

Description

AND PRIOR ART The present invention relates to a therrnostat device for a cooling system according to the preamble of claim l.

It is important to maintain a desired operating temperature of a coolant With a highaccuracy in a cooling system. It is possible to use electrically controlled valves inorder to fulf1l the above mention demand. HoWever, electrically controlled therrnostatsare large and expensive. A conventional Wax therrnostat may comprise a capsuleenclosing a Wax material Which is arranged in heat transfer contact With the coolant ina cooling system. The Wax material changing phase Within a specific temperaturerange Which defmes the regulation temperature of the Wax therrnostat. Waxtherrnostats have a simple design and they are not able to maintain a desired operatingtemperature of a coolant With a high accuracy during all operating conditions.

HoWever, Wax therrnostats are inexpensive.

Heavy vehicles are often equipped With a supplementary brake in the form of ahydraulic retarder. In a conventional hydraulic retarder, an oil is used as Workingmedium. The oil leaving the retarder is cooled in a retarder cooler by coolantcirculating in a cooling system of the vehicle. In another kind of hydraulic retarder, thecoolant is used as Working medium. The cooling demand of the cooling system isusually very high When the retarder is activated. Usually, the coolant is circulated inthe cooling system by a mechanical pump Which is driven by the combustion engine.During activation of the retarder, the combustion engine and the pump are beneficial toachieve a high speed Which increases the coolant pressure in the cooling system. Thus, a high coolant pressure may indicate that the retarder has been activated.

US 2013/0048741 comprises a therrnostatic valve assembly for a cooling system. Thetherrnostatic valve assembly includes a valve body having an inlet from a radiator, aninlet from an engine and an outlet to the engine. A main valve plate opens and closes apathWay of a cooling ﬂuid from the radiator. A Wax element is placed in a chamber ofthe valve body in ﬂuid communication With the inlets and the outlet. The Wax elementhas a piston mechanically connected to the main valve plate. A main spring keeps the main plate closed until a target temperature of the cooling ﬂuid coming from the engine is reached. The main valve plate consists of two separate valve parts. In casethe pressure of the cooling ﬂuid reaches a too high value in the radiator, the valve partsact as a relief valve to allow a little ﬂow of cooling ﬂuid through the therrnostatic valve assembly that decreases the pressure in the radiator.

SUMMARY OF THE INVENTION The object of the present invention is to provide an inexpensive therrnostat device for acooling system for a combustion engine which has capacity to maintain a desired operating temperature of the combustion engine and the coolant with a high accuracy.

The above mentioned object is achieved by the device defined in claim l. Thus, thetherrnostat device comprises a therrnal expansion element to be in therrnal contact withcoolant and to exert a first force on the valve body related to the coolant temperature,pressure means configured to exert a second force on the valve body related to thecoolant pressure and a main spring conf1gured to exert a spring force on the valve bodyin a direction towards the first end position. In this case, it is possible to move thevalve body from the first end position and provide a coolant ﬂow to the radiator duringoperating conditions with a high coolant temperature and/or a high coolant pressure.Thus, the therrnostat device according to the present invention provides a coolant ﬂowto the radiator depending on the coolant temperature as well as the coolant pressure. Itis obvious that a high coolant temperature requires a high coolant ﬂow to the radiatorin order to obtain a required cooling of the coolant. A high coolant pressure may alsoindicate that it is desired to provide a high coolant ﬂow to the radiator. In case thecooling system is used to cool a combustion engine and a hydraulic retarder, highpressure may occur during activation of the hydraulic retarder. A hydraulic retardermay convert a very large portion of the potential and kinetic energy of a vehicle toheat. Consequently, the cooling demand is high during activation of a hydraulicretarder. However, the above mentioned design of the therrnostat device makes itpossible to maintain a desired operating temperature of the coolant and the combustionengine with a high accuracy also during activation of a hydraulic retarder. The therrnostat device may have a simple design and be inexpensive.

According to the invention, said-pfessufe-Hiea-ns-eonaiarises-thatﬂi second valve plate is designed to have a larger contact area with the coolant in the therrnostat device than the first valve plate. In this case, the coolant pressure exerts a force on the Valve body in a direction towards the second end position of the valvebody which is related to the coolant pressure. The force derived from the coolantpressure exerts a movement of the valve body against the action of the main spring. ípressure means may alicomprise anadjustable throttle valve arranged in the radiator bypass line. By means of such athrottle valve it is possible to adjust the ﬂow resistance in the radiator bypass line andthus the force acting on the first valve plate of the valve body. An increased pressure inthe bypass line results in a force tending to move the valve body from the first endposition against the action of the main spring. The adjustable throttle valve may bemechanically controlled by the coolant pressure or controlled by a control unit receiving information from a pressure sensor.

According to an embodiment of the invention, the therrnal expansion element exertssaid force on the valve body via a spring member. Thus, therrnal expansion elementacts with a resilient first force on the valve body. In this case, a certain stroke of thetherrnal expansion element does not always results in a specific position of the valvebody. The spring member may be is arranged in a manner such that a longitudinalcentral axis of the spring member coincides with a longitudinal central axis of thevalve body. Such a positioning of the spring member results in a simple design of thetherrnostat device. A movement of the valve body results in a contraction or elongationof the spring member which changes the spring force acting on the valve body. The spring member may be a coil spring.

According to an embodiment of the invention, the therrnal expansion elementcomprises at least a first material body changing phase within a first temperaturerange, and that the therrnal expansion element is configured to exerts a force on thevalve body when the first material body changes phase. The first material body maycomprise a wax material having the property to change phase within said first temperature range.

According to an embodiment of the invention, the therrnal expansion elementcomprises a second material body changing phase within a second temperature range,and that the therrnal expansion element is configured to exert a force on the valve bodywhen the second material body changes phase. The second material body maycomprise a wax material having the property to change phase within said second temperature range.

According to an embodiment of the invention, the highest temperature in the firsttemperature range is lower than the lowest temperature in the second temperaturerange. Thus, the first temperature range and the second temperature range does notoverlap each other. Consequently, the first material body provides a force on the valvebody when the coolant has a relatively low temperature and the second material bodyprovides a force on the valve body when the coolant has a relatively high temperature.The object of the first material body is to provide a force which make it possible tomove the valve body from the first end position by means of the coolant pressure at arelatively low coolant temperatures. The position of the valve body in the firsttemperature range is mainly defined by the coolant pressure. The object of the secondmaterial body is to provide a force which moves the valve body from the first endposition at a relatively high temperature. The position of the valve body in the second temperature range is mainly defined by the coolant temperature.

According to an embodiment of the invention, the width of the first temperature rangeis within the interval l5-25°. It is usually an advantage that the first temperature rangehas a relatively wide width. The first temperature range may be 70 -90°C. The width ofthe second temperature range may be within the interval 5-l5°. It is usually anadvantage that the second temperature range has a relatively small width. The second temperature range may be 100 -l l0°C.

According to an embodiment of the invention, the main spring is arranged in a mannersuch that a longitudinal central axis of the main spring coincides with a longitudinalcentral axis of the valve body. Such a positioning of the main spring results in a simpledesign of the therrnostat device. A movement of the valve body results in a contractionor elongation of the main spring which changes the spring force acting on the valve body. The main spring may be a coil spring.

According to an embodiment of the invention, the first material body and the secondmaterial body is arranged in a common therrnal expansion element. In this case, it ispossible to use a single therrnal expansion element. However, it is possible to use two therrnal expansion element each comprising a material body.

According to an embodiment of the invention, the therrnal expansion element comprises a capsule containing the first material body and the second material body and a piston configured to provide a stroke in relation to the coolant temperature. It ispossible to arrange the first material body and the second material body such theytransfer a movement, via a common piston, to the valve body in proper order. An outerend of the position may be stationary arranged in the valve device and the capsule maybe configured to provide a movement exerting a force on the valve body. The springmember may transfer the movement from the capsule to the valve body. Altematively, the capsule is stationary arranged and the piston connected to the valve body.

According to an embodiment of the invention, valve body comprises connectingelements connecting the first valve plate and the second valve plate. The connectingelements may be arranged at a distance from adj acent connecting elements such that ﬂow passages are formed between adjacent connecting elements to an inner space of thevalvebody. -- -- -- - . -' - -- . -= -- .. .- BRIEF DESCRIPTION OF THE DRAWINGS In the following a preferred embodiments of the invention are described, as examples,with reference to the attached drawings, on which: Fig. l shows a cooling system comprising a therrnostat device according to theinvention, Fig. 2- 4 shows the therrnostat device during different operating conditions, Fig. 5 shows a graph depicting the length of the therrnal expansion element as afunction of the coolant temperature, Fig. 6 shows a graph depicting the coolant ﬂow to the radiator as a function ofthe coolant temperature at three different engine speeds and Fig. 7 shows an altemative embodiment of the therrnostat device.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THEINVENTION Fig. 1 shows a cooling system cooling a combustion engine 2 in a schematicallyindicated vehicle l. The coolant is circulated in the cooling system by means of acoolant pump 3. In this case, the coolant pump 3 is a mechanical pump driven by the combustion engine 2. Thus, the coolant pump provides a coolant ﬂow in the cooling system in relation to the speed of the combustion engine. The coolant pump 3 isarranged in an engine inlet line 4 leading coolant to the combustion engine l. After thecoolant has passed through the combustion engine l it enters an engine outlet line 5. Inthis case, the engine outlet line 5 comprises a retarder cooler 6 in which the coolantcools a retarder oil circulating in a retarder system. A therrnostat Valve 7 is arranged inan end of the engine outlet line 5. The purpose of the therrnostat Valve 7 is to distributethe coolant ﬂow to a radiator bypass line 8 and a radiator inlet line 9 directing thecoolant to a radiator l0. The radiator bypass line 8 directs the coolant back to theengine inlet line 4 and the coolant pump 3. The radiator l0 is arranged at a frontportion of the vehicle l. Other coolers such as a charge air cooler may be arranged infront of the radiator l0. A cooling fan ll forces a cooling air stream through theradiator l0. After that the coolant has been cooled in the radiator 10, it is led, Via a return line l2, back to the engine inlet line 4 and the coolant pump 3.

Fig 2-4 show the therrnostat Valve 7 more in detail during three different operatingconditions. The therrnostat Valve 7 comprises an inlet opening l3 receiVing coolantfrom the engine outlet line 5, a first outlet opening l4 directing coolant to the bypassline 8 and a second outlet opening l5 directing coolant to the radiator inlet line 9 andthe radiator l0. The first outlet opening l4 is defined by a first Valve seat l4a and thesecond outlet opening l5 is defined by a second Valve seat l5a. The therrnostat Valve 7comprises a movably arranged Valve body 16. The Valve body 16 comprises a firstValve plate l7 and a second Valve plate l8. The first end-m plate l7 is arranged at afirst end portion of the Valve body 16 and the second Valve plate l8 is arranged at anopposite second end portion of the Valve body l6. The first Valve plate l7 and thesecond Valve plate l8 are connected to each other by means of a number of elongatedconnecting elements 19 such that the Valve body 16 constitutes a coherent unit. Theconnecting elements l9 are arranged around a longitudinal central axis l6a of the Valvebody l6. The inner surfaces of the Valve plates l7, l8 and the connecting elements l9defines an inner space 20 of the Valve body l6. Flow passages are arranged betweenadj acent connecting elements l9 making it possible for the coolant ﬂow from the engine inlet line 5 to enter the inner space 20 of the Valve body l6.

The Valve body 16 is movably arranged to different Valve positions in a steplessmanner along a path extending between a first end position and a second end position.Fig. 2 shows the valve body 16 in the first end position. In the first end position, thefirst valve plate 17 is at a maximum distance from first valve seat l4a. In this position,the first opening 14 is maximally open at the same time as the second valve plate 18 isin contact with the second valve seat 15a such that the second outlet opening 15 isclosed. Thus, in the first end position, the entire coolant ﬂow from the engine outlet line 5 is directed, via the first opening 14, to the radiator bypass line 8.

Fig. 3 shows the valve body 16 in the second end position. In the second end position,the first valve plate 17 is in contact with the first valve seat l4a. In this position, thefirst opening 14 is closed at the same time as the second valve plate 18 is at amaximum distance from the second valve seat 15a such that the second outlet opening15 is maximally open. Thus, in the second end position, the entire coolant ﬂow fromthe engine outlet line 5 is directed, via the second outlet opening 15, to the radiator inlet line 9.

However, during most operating conditions of the therrnostat device, the valve body 16is in a position between said end positions. Fig. 4 shows the therrnostat device in suchan operating condition. In this case, a part of the coolant ﬂow from the engine outletline 5 is directed to the radiator bypass line 8 via the first outlet opening 14 and aremaining part of the coolant ﬂow is directed to the radiator 10 via the second outletopening 15. The therrnostat valve 7 comprises pressure means in the form of that thesecond valve plate 18 has a larger contact area with the coolant than the first valveplate 17. Thus, the coolant pressure in the therrnostat valve 7 exerts a force on thevalve body 16 in direction towards the second end position. The magnitude of this force is related to the magnitude of the coolant pressure.

A therrnal expansion element 21 is arranged in the inner space 20 of the valve body 16.The therrnal expansion element comprises a capsule 22 and a piston 23. The capsule 22comprises an inner space that contains a first material body 24a and a second material body 24b. The material bodies 24a, 24b have the property that they increases in Volume when they change from solid phase to liquid phase. The first material body 24amay consist of a material mixture changing phase within a relatively large temperaturerange. The second material body 24b may consist of a material changing phase withina relatively small temperature range. The first material body 24a and the secondmaterial body 24b may consist of a suitable Wax material. In this embodiment, the firstmaterial body 24a changes phase within a first temperature range of 70- 90°C and thesecond material body 24b changes phase within a second temperature range of 100- 110°C.

Flexible membranes or the like may be arranged between the material bodies 24a, 24band an inner end of the piston 23. When the material bodies 24a, 24b are in a solidphase, the piston 23 is in a retracted state and the therrnal expansion element 21 has aminimum length in a longitudinal direction. When the first material body 24a melts,the expanded volume of the first material body 24a results in a first stroke of the piston23 in which the therrnal expansion element 21 is elongated in a first step. When thesecond material body 24b melts, the expanded volume of the second material body 24bresults in a second stroke of the piston 23 in which therrnal expansion element 21 iselongated in a second step. A spring member 25 is attached between a contact surfaceof the capsule 22 and an inner surface of the second valve plate 18. The spring member25 provides a resilient connection between the therrnal capsule 22 of the expansionelement 21 and the second valve plate 18. A further purpose of the spring member 25is to provide a force moving the piston 23 back to its initial position when the material bodies 24a, 24b change phase from liquid to solid.

A first stationary first bracket 26 is arranged adj acent to the first outlet opening 14. Anouter end of the piston 23 is connected to the first stationary bracket 26. When thepiston 23 is elongated or retracted, it provides a movement of the capsule 22 in relationto the stationary first bracket 26. The movement of the capsule 22 results in amovement of the valve body 16 since it is connected to the capsule 22 via the springmember 25. When the piston 23 is elongated, it exerts a force on the valve body 16 in a direction towards the second end position.

The therrnostat device comprises a main spring 28. The main spring 28 is attachedbetween a second stationary bracket 27 and an outer surface of the second valve plate18. The main spring 28 exerts a force on the valve body 16 in a direction towards thefirst end position. Thus, the main spring exerts a force on the valve body 16 in anopposite direction to the forces exerted by the coolant pressure and the expansion element 21.

Fig. 5 shows a curve defining the length L of the therrnal expansion element 21 as a function of the coolant temperature.

Fig. 6 shows the coolant flow m to the radiator as a function of the coolant temperatureat three different engine speeds. During operating conditions when the engine speed islow, the coolant pump 3 is driven at a low speed and it provides a low coolant ﬂow inthe cooling system which results in a low coolant pressure in the cooling system. Afirst curve 31 defines the coolant ﬂow m to the radiator 10 when the engine speed islow. During operating conditions when the engine speed is medium, the coolant pump3 is driven at a medium speed and it provides a medium coolant ﬂow in the coolingsystem which results in a medium coolant pressure in the cooling system. A secondcurve 32 defines the coolant ﬂow m to the radiator 10 when the engine speed ismedium. During operating conditions when the engine speed is high, the coolant pump3 is driven at a high speed and it provides a high coolant ﬂow in the cooling systemwhich results in a high coolant pressure in the cooling system. A third curve 33 defines the coolant ﬂow m to the radiator 10 when the engine speed is high.

During operation of the combustion engine 2, the pump 3 circulates a coolant ﬂowthrough the cooling system. The coolant entering the inner space 20 of the valve body16 comes in heat transfer contact with the first material body 24a and the secondmaterial body 24b in the capsule 22 of the therrnal expansion element 21. During aninitial period after a cold start of the combustion engine 2, the coolant temperature iswithin a first temperature interval I below 70°C. In the first temperature interval I, thefirst material body 24a and the second material body 24b in the capsule 22 are in solid phase and the therrnal expansion element 21 has a minimum length Lmin. The main spring 28 is designed to exert a significantly larger force on the valve body 16 towardsthe first end position than the spring member 25 which exerts a force on the valve body16 towards the second end position. Since the second valve plate 18 has a largercontact area with the coolant than the first valve plate 17, the coolant exerts a pressureforce on the valve body 16 towards the second end position. However, the main spring28 is designed to exert a larger force on the valve body 16 than the sum of the oppositedirected forces from the spring member 25 and the coolant pressure even when theengine speed and the coolant pressure are high. Such a main spring 28 makes sure thatthe valve body 16 is maintained in the first end position, which is shown in Fig. 2,when the coolant temperature is below 70°C independent of the engine speed and thecoolant pressure, which is indicated by the curves 31, 32, 33. Thus, there is no coolantﬂow to the radiator 10 when the coolant temperature is within the first temperature interval I.

During further operation of the vehicle, the coolant is heated by the combustion engine2. At a second temperature interval II in which the coolant temperature in between 70-80°C, a smaller proportion than half of the first material body 24a in the capsule 22 haschanged phase from solid to liquid. This results in a stroke of the piston 23 and anelongation of the therrnal expansion element 21 which is in relation to the proportionof liquid material in the first material body 24a. The elongation of the therrnalexpansion element 21 compresses the spring member 25. As a result, the springmember 25 exerts an increased force on the valve body 16. If the engine is driven at amedium speed or a low speed when the coolant temperature is within the secondtemperature interval II, the sum of the forces from the spring member 25 and thecoolant pressure is still lower than the force exerted by the main spring 28. Thus, whenthe coolant temperature is within the second temperature interval II and thecombustion engine 2 is driven with a medium or a low speed there is no coolant ﬂow to the radiator 10 which is indicated by the first curve 31 and the second curve 32.

If the engine is driven at a high speed when the coolant temperature is within thesecond temperature interval II, the coolant pressure is high. In this case, the sum of theforces from the spring member 25 and the coolant pressure will be higher than theforce exerted by the main spring 28. This difference results in a movement of the valvebody 16 from the first end position to a new position in which the sum of the forces from the spring member 25 and the coolant pressure will be equal to the force exerted 11 by the main spring 28. In the new position of the valve body 16, the therrnostat device directs a small coolant ﬂow to the radiator 10 which is indicated by the third curve 33.

At a third temperature interval III in which the coolant temperature is between 80-90°C, a larger proportion than half of the first material body 24a in the capsule 22 haschanged phase to liquid. Thus, the piston 23 has received a further stroke and thetherrnal expansion element 21 a further elongation to a length L which is related to theactual proportion of molten material in the first material body 24a. This additionalstroke of the piston 23 compresses the spring member 25 further. As a result, thespring member 25 exerts a further increased force on the valve body 16. If the engineis driven at a low speed when the coolant temperature is within the third temperatureinterval III, the sum of the forces from the spring member 25 and the coolant pressureis still lower than the force exerted by the main spring 28. Thus, the valve body 16 ismaintained in the first end position and there is no coolant ﬂow to the radiator 10 which is indicated by the first curve 31.

If the engine is driven at a medium speed when the coolant temperature is within thethird temperature interval III, the coolant pressure is medium. In this case, the sum ofthe forces from the spring member 25 and the coolant pressure will be higher than theforce exerted by the main spring 28. This difference results in a movement of the valvebody 16 to a new position in which the sum of the forces from the spring member 25and the coolant pressure will be equal to the force exerted by the main spring 28. In thenew position of the valve body 16, the therrnostat device directs a small coolant flow to the radiator 10 which is indicated by the second curve 32.

If the engine is driven at a high speed when the coolant temperature is within the thirdtemperature interval III, the increased forces from the spring member 25 and thecoolant pressure moves the valve body 16 against the force from the main spring 28 toa new position in which the sum of the forces from the spring member 25 and thecoolant pressure will be equal to the force from the main spring 28. In the new positionof the valve body 16, the therrnostat device directs an increased coolant ﬂow to the radiator 10 which is indicated by the third curve 33. 12 At a fourth temperature interval IV in which the coolant temperature in between 90-100°C, the entire first material body 24a has changed phase to liquid. However, thesecond material body is still in solid phase. Thus, the piston 23 does not provide afurther stroke in this temperature interval IV and the length L of the therrnal expansionelement 21 is constant. Thus, if the combustion engine 2 is driven at a low speed, thereis still no coolant ﬂow to the radiator 10. If the combustion engine 2 is driven at amedium speed, there is constant small coolant ﬂow m1 to the radiator 10. If thecombustion engine 2 is driven at a high speed, there is constant larger coolant ﬂow m2 to the radiator 10.

At a f1fth temperature interval V in which the coolant temperature in between 100-110°C, a part of the second material body 24b has changed phase to liquid. Thus, thepiston 23 has received a further stroke and the therrnal expansion element 21 a further elongation to a length L which is in relation to the molten material in the first material body 24a and the actual proportion of molten material in the second material body 24b.

This additional stroke of the piston 23 compresses the spring member 25 further.Furthermore, the capsule 22 of the therrnal expansion element 21 has come in directcontact with the second valve plate 18 when the coolant temperature achieves asuitable temperature in the f1fth temperature interval V, which is shown in Fig.3. Inthis state, the position of the capsule 22 defines the position of the second valve plate18 independent of the spring member 25. Thus, the length L of the therrnal expansionelement 21 defines the new position of the valve body 16 independent of the coolantpressure. In the new position of the valve body 16, the therrnostat device directs acoolant flow between mo - m2 at low engine speeds to the radiator 10 which isindicated by the first curve 31, a coolant flow between m1 - ms at medium enginespeed to the radiator 10 which is indicated by the second curve 32 and a coolant flowbetween m2 - m4 at high engine speed to the radiator 10 which is indicated by the third curve 33.

At a sixth temperature interval VI in which the coolant temperature in above 110°C, the entire first material body 24a and the entire second material body 24b are in liquid 13 phase. The therrnal expansion element 21 has a maximum length Lmax and the valvebody 16 has been moved to the second end position. If the combustion engine 2 isdriven at a low speed, there is a constant coolant ﬂow m2 to the radiator 10, if thecombustion engine 2 is driven at a medium speed, there is higher coolant flow ms tothe radiator 10 and if the combustion engine 2 is driven at a high speed, there is maximum coolant ﬂow m4 to the radiator 10.

Fig. 7 shows a cooling system comprising a therrnostat device according to analtemative embodiment. In this case the therrnostat device comprises pressure meansin form of an adjustable throttle way-m 34 by which it is possible to control theﬂow resistance in the radiator bypass line 8. A control unit 35 controls the throttlevalve 34 by means of information from a pressure sensor 36 sensing the coolantpressure in the engine outlet line 5. The throttle valve 34 makes it is possible to adjustthe ﬂow resistance in the radiator bypass line 8 and thus the pressure force acting onthe first valve plate 17 of the valve body 16. In this case, it is possible to exert a pressure force on the valve body 16 related the coolant pressure in the engine outlet line 5. This pressure means may be used together with a valve body 16 in whichthe first valve plate 17 and the second valve plate 18 has-have different contact areas with the coolant.

The invention is not restricted to the described embodiment but may be varied freelywithin the scope of the claims. An altemative to design the capsule 22 such that itcomes in direct contact with the second valve plate 18, it is to design the springmember 25 such that it is fully contracted when the coolant temperature achieves asuitable temperature in the f1fth temperature interval V. Furthermore, it is also possibleto design the therrnostat valve such that the therrnal expansion element 21 exerts aresilient force, via the spring member 25, on the second valve plate 18 during all temperature intervals.

Claims

14 Claims

1. A therrnostat device for a cooling system, Wherein the therrnostat device comprises atherrnostat valve (7) provided With an inlet opening (13) via Which coolant enters thetherrnostat valve (7), a f1rst outlet opening (14) arranged to direct coolant to a radiatorbypass line (8) of the cooling system and a second outlet opening (15) arranged todirect coolant to a radiator (10) of the cooling system, a valve body (16) comprising afirst valve plate (17) and a second valve plate (18), Wherein the valve body (16) ismovably arranged between a f1rst end position, in Which the first valve plate (17)exposes the first outlet opening (14) maximally at the same time as the second valveplate (18) closes the second outlet opening (15), and a second end position, in Whichthe first valve plate (17) closes the f1rst outlet opening (14) at the same time as thesecond valve plate (18) exposes the second outlet (15) opening maximally, and atherrnal expansion element (21) arranged inside an inner space (20) of the valve body(16) and conf1gured to be in therrnal contact With coolant and to exert a f1rst force onthe valve body (16) related to the coolant temperature, characterized in that thetherrnostat device comprises pressure means configured to exert a second force on thevalve body (16) related to the pressure of the coolant entering the therrnostat valve (7)and that the therrnostat valve (7) comprises a main spring member (28) conf1gured toexert a third force on the valve body (16) in a direction towards the f1rst end position,Wherein the f1rst and second valve plates (17, 18) form part of said pressure means, thesecond valve plate (18) being designed to have a larger contact area With the coolant entering the therrnostat valve (7) than the f1rst valve plate (17).

2. A therrnostat device according to claim 1, characterized in that the pressure means comprises an adjustable throttle valve (34) arranged in the radiator bypass line (8).

3. A therrnostat device according to claim 1 or 2, characterized in that the therrnalexpansion element (21) exerts said force on the valve body (16) via a spring member(25).

4. A therrnostat device according to claim 3, characterized in that the spring member(25) is arranged in a manner such that a longitudinal central axis of the spring member(25) coincides With a longitudinal central axis (16a) of the valve body (16).

5. A therrnostat device according to any one of the preceding claims, characterized inthat the therrnal expansion element (21) comprises at least a first material body (24a)changing phase Within a first temperature range, and that the therrnal expansionelement is configured to exert a force on the valve body (16) When the first material body changes phase from solid to liquid.

6. A therrnostat device according to claim 5, characterized in that the therrnalexpansion element (21) comprises a second material body (24b) changing phase Withina second temperature range, and that the therrnal expansion element (21) is configuredto exert a force on the valve body (16) When the second material body (24b) changes phase from solid to liquid.

7. A therrnostat device according claim 6, characterized in that the loWest temperaturein the second temperature range is higher than the highest temperature in the first temperature range.

8. A therrnostat device according to claim 5, characterized in that the Width of the first temperature range is Within the interval 15-25°.

9. A therrnostat device according to claim 6, characterized in that the Width of the second temperature range is Within the interval 5- 1 5°.

10. A therrnostat device according to any one of the preceding claims, characterized inthat the main spring (28) is arranged in a manner such that a longitudinal central axis of the main spring coincides With a longitudinal central axis (16a) of the valve body (16).

11. 1 1. A therrnostat device according to claim 6 or 7, characterized in that the therrnalexpansion element (21) comprises a capsule (22) containing the first material body(24a) and the second material body (24b) and a piston (23) configured to provide a stroke in relation to the coolant temperature.

12. A therrnostat device according to any one of the preceding claims, characterized inthat valve body (16) comprises connecting elements (19) connecting the first valveplate (17) and the second valve plate (18). 16

13. A Cooling system, characterized in that the coo1ing system coniprises a therrnostat device according to any one of the preceding c1ain1s 1-12.

14. A vehicle (1), characterized in that the vehicle (1) coniprises a coo1ing system according to c1ain1 13.