DE102018222568A1 - Heat exchanger with integrated bypass - Google Patents

Abstract

The invention relates to a multi-flow heat exchanger (1) comprising at least a first region (14) for cooling an operating medium of a transmission and a second region (15) for cooling an operating medium of a hydrodynamic retarder (23) and an insert (16) for Distribution of the equipment to the different areas (14, 15) of the heat exchanger (1). It is provided that the heat exchanger (1) has at least one bypass (18, 20), via which the first region (14) of the heat exchanger (1) and the second region (15) of the heat exchanger (1) are connected to one another.

Description

The present invention relates to a multi-flow heat exchanger according to the preamble of claim 1. Furthermore, the invention relates to a cooling system with at least two operating medium circuits and a transmission comprising the heat exchanger according to the invention or the cooling system according to the invention.

In liquid equipment in vehicles, for example, heating generated in a heat exchanger by energy conversion into heat is given off to a coolant so that the operational capability of the equipment is preserved and the equipment is available for further energy consumption.

Equipment of this type can be lubricants in engines or transmissions that are heated by the movements of the existing components, or it can also affect an oil or water of a hydrodynamic braking device that converts the kinetic energy of the vehicle into heat by means of blading the equipment is transferred.

Heat exchangers are often designed in plate or shell design, with several plates or shells of the same type being fastened, for example soldered, one above the other and to one another, which then form passages which each lead coolant and operating medium to be cooled past one another.

If several items of equipment are to be cooled in a vehicle, several heat exchangers can be provided for this purpose, of which one heat exchanger in each case cools an item of equipment by means of a coolant. If several heat exchangers are used to cool several devices, then these can be optimally adapted according to the device circuit to be cooled and, for example, have different geometrical dimensions. However, the use of several heat exchangers is relatively expensive and a correspondingly large installation or attachment space is required to arrange the heat exchangers.

It is already known that a plurality of operating resources in a vehicle can also be cooled in a common heat exchanger, this heat exchanger then having a plurality of regions, which can each come into contact with a coolant for heat dissipation. Such heat exchangers are also referred to as multi-flow heat exchangers. For example, it is possible to connect a coolant circuit and two operating medium circuits to a 3-pipe heat exchanger. The equipment circuits can be designed, for example, as an equipment circuit of a transmission and as an equipment circuit of a retarder.

Such a multi-flow heat exchanger is for example from the DE 197 12 599 A1 is known, in which a plurality of oil feeds are provided, each of which the associated passages are supplied, in order to come into contact with a coolant for heat transfer which is also supplied to the heat exchanger.

Such multi-flow heat exchangers are tied to a geometric structure in their construction and can therefore only be designed to a limited extent to the equipment circuits to be cooled. Depending on the design of such a multi-flow heat exchanger, pressure losses can occur when the passages of the heat exchanger flow through the equipment circuit, which can lead to a negative influence on the equipment circuit.

Against this background, the invention has for its object to provide a new type of heat exchanger and an improved cooling system with a multi-flow heat exchanger.

This object is achieved by a heat exchanger according to claim 1 and a cooling system according to claim 8. Advantageous further developments are the subject of the subclaims and the following description and the drawings.

According to the present invention, a multi-flow heat exchanger comprising at least a first region, which is used to cool an operating medium of a transmission, and a second region, which is used to cool an operating medium of a hydrodynamic retarder, is proposed. The heat exchanger comprises an insert for distributing the operating media to the different areas of the heat exchanger. Depending on the design of the heat exchanger, the heat exchanger has a corresponding flow resistance in the areas carrying the equipment. The flow resistance of the heat exchanger can lead to an increase in pressure in the equipment circuit in certain operating areas.

To achieve the object, the invention therefore provides that the heat exchanger has at least one bypass via which the first region of the heat exchanger and the second region of the heat exchanger are connected to one another. The fact that the two resource-carrying areas of the multi-flow heat exchanger are connected to one another via a bypass can be a Flow resistance of the heat exchanger can be reduced in certain operating areas.

In one embodiment of the multi-flow heat exchanger, the bypass is integrated in a connection plate of the heat exchanger. The connection plate has connections for connecting the equipment circuits as well as connections for connecting the coolant circuit to the heat exchanger. The connection plate can be connected to an end plate of the heat exchanger, for example soldered.

In a further embodiment of the heat exchanger, the bypass is carried out through a channel formed in a connection plate of the heat exchanger, which, when the heat exchanger is mounted on a transmission housing or a retarder housing, is closed by a connection element provided for this purpose or by the transmission housing or the retarder housing itself is sealed.

If the heat exchanger has a connection element by means of which it can be attached to a transmission housing or a retarder housing, then it can be provided in a further embodiment that the bypass is integrated in this connection element of the heat exchanger.

In an advantageous further development it can be provided that the flow through the bypass can be controlled or regulated. For this purpose, a valve can be provided in the bypass. The valve can be designed, for example, as a pressure valve, flow valve, seat valve, directional control valve or as a throttle or orifice valve. The seat valve can be designed, for example, as a check valve, which allows the flowing through of the operating medium to flow in only one direction.

The cooling system according to the invention comprises a coolant circuit, an operating medium circuit of a transmission, an operating medium circuit of a hydrodynamic retarder and a multi-flow heat exchanger. A first area of the heat exchanger is designed to cool an operating medium of the transmission and a second area of the heat exchanger is designed to cool an operating medium of the hydrodynamic retarder. It is provided that a supply line to the first area of the heat exchanger is connected via a bypass to a supply line to the second area of the heat exchanger. Alternatively or additionally, a return line from the first area of the heat exchanger can be connected via a bypass to a return line from the second area of the heat exchanger. In this embodiment, the bypass is not directly integrated in the heat exchanger, as a result of which a conventional multi-flow heat exchanger can be used in the cooling system. Because the two supply lines or the two return lines are connected to one another via a bypass, a flow resistance of the heat exchanger can be reduced in certain operating ranges, as a result of which an increase in pressure in the operating medium circuit in which a multi-flow heat exchanger is used can be avoided.

In this embodiment of the bypass, too, it can be provided that a flow through the bypass can be controlled or regulated. The flow of the bypass can expediently be controlled or regulated as a function of a pressure prevailing in the equipment circuit and / or a temperature of the equipment. A valve can be arranged in the bypass to control or regulate the flow through the bypass. The valve can be designed, for example, as a pressure valve, flow valve, seat valve, directional control valve or as a throttle or orifice valve. The seat valve can be designed, for example, as a check valve, which allows the flowing through of the operating medium to flow in only one direction.

The multi-flow heat exchanger is connected to an operating medium circuit of a transmission and an operating medium circuit of a hydrodynamic retarder in such a way that in an operating state in which the hydrodynamic retarder is not activated, the operating medium of the transmission is also guided through the area of the heat exchanger provided for cooling the operating medium of the retarder and is cooled. Then the area provided for cooling the operating medium of the retarder and the area provided for cooling the operating medium of the transmission are connected in series and the operating medium of the transmission is guided and cooled through both regions of the heat exchanger.

This series connection of the two areas of the heat exchanger intended for cooling equipment results in the heat exchanger having a higher flow resistance, as a result of which there is a corresponding pressure loss at the heat exchanger. The bypass provided can reduce the pressure loss at the heat exchanger accordingly.

A transmission of a motor vehicle comprising a multi-flow heat exchanger according to the invention and / or a cooling system according to the invention is the subject of claim 13.

• 1 einen Ausschnitt eines Kühlsystems mit zwei Betriebsmittelkreisläufen in einem ersten Betriebszustand,
• 2 einen Ausschnitt eines Kühlsystems mit zwei Betriebsmittelkreisläufen in einem zweiten Betriebszustand,
• 3 eine Ansicht eines mehrflutigen Wärmetauschers,
• 4 eine Schnittdarstellung des in 3 dargestellten mehrflutigen Wärmetauschers mit einer Anordnung eines Bypasses gemäß einer ersten Ausführungsform,
• 5 eine Schnittdarstellung des in 3 dargestellten mehrflutigen Wärmetauschers mit einer Anordnung eines Bypasses gemäß einer zweiten Ausführungsform,
• 6 eine Schnittdarstellung des in 3 dargestellten mehrflutigen Wärmetauschers mit einer Anordnung eines Bypasses gemäß einer dritten Ausführungsform.

In the following, the invention, which allows several embodiments, is explained in more detail using the examples. Show it:

• 1 a section of a cooling system with two equipment circuits in a first operating state,
• 2nd a section of a cooling system with two equipment circuits in a second operating state,
• 3rd a view of a multi-flow heat exchanger,
• 4th a sectional view of the in 3rd Multi-flow heat exchanger shown with an arrangement of a bypass according to a first embodiment,
• 5 a sectional view of the in 3rd Multi-flow heat exchanger shown with an arrangement of a bypass according to a second embodiment,
• 6 a sectional view of the in 3rd Multi-flow heat exchanger shown with an arrangement of a bypass according to a third embodiment.

Based on 1 and the 2nd In the following, the cooling system according to the invention 24th are explained in more detail. Either 1 as well as 2nd show a section of a cooling system 24th a motor vehicle. The cooling system 24th includes a coolant circuit 28 , a resource cycle 26 of a transmission and a resource cycle 25th a hydrodynamic retarder 23 .

To supply the transmission with pressure oil, an oil pump is advantageously arranged inside the transmission 33 provided, which is coupled to an input shaft of the transmission and can thus be driven by a drive unit. Depending on the speed of the drive unit, there is therefore an oil volume flow for the equipment circuit 26 of the transmission. The oil pump 33 is from an oil sump via a suction line 34 fed, ensuring that there is no contamination in the equipment circuit 26 can reach the oil pump 2nd a suction strainer 35 upstream and an oil filter 36 are connected downstream. A primary pressure circuit is primarily from the intake line 37 and a secondary pressure circuit 38 of the equipment cycle 26 can be supplied with pressure oil.

In the resource cycle 26 of the gearbox are several valves 29 , 30th , 31 , 32 intended. The valve 29 is designed as a main pressure valve, which can be controlled via a pressure control valve, not shown here.

A converter safety valve 30th protects the torque converter 22 against an impermissibly high overpressure by reducing the inlet pressure p0 in front of the torque converter 22 limited. Via the converter safety valve 30th becomes an inlet pressure p0 in front of the torque converter 22 set, with the converter safety valve 30th when a pressure value is reached or exceeded, so that oil flows back towards the intake side of the oil pump 33 or in the oil sump 34 can drain until the desired inlet pressure p0 is reached again.

After the torque converter 22 is a converter back pressure valve in a converter outlet line 31 arranged over which a pressure p1 after the torque converter 22 is set. Exceeds the pressure p1 after the torque converter 22 a predetermined pressure value, then the converter back pressure valve opens 31 , so that gear of the gear can flow in the direction of the cooling circuit or lubrication circuit until the pressure increases p1 after the torque converter 22 resumes.

In the cooling system 24th is a multi-flow heat exchanger 1 provided the two areas 14 , 15 for cooling equipment. A first area 14 of the heat exchanger 1 is for the cooling of an oil as a gear of the transmission and a second area 15 of the heat exchanger 1 is used to cool an oil as the operating fluid of the hydrodynamic retarder 23 educated. In addition to the retarder oil circuit 25th and the transmission oil circuit 26 is on the heat exchanger 1 the coolant circuit 28 connected, for example a coolant circuit 28 of the motor vehicle, comprising a vehicle heat exchanger 27 . The heat exchanger 1 is therefore designed as a so-called 3-pipe heat exchanger.

The valve 32 is controlled depending on a retarder operation. Like in the 1 the retarder is shown 23 not activated in a first operating state and that in the retarder 23 the remaining resources are removed by the line 39 about the valve 32 in the oil sump 34 derived. A supply of resources via a line 40 in the retarder 23 is through the valve 32 prevented. The first operating state is, for example, train operation of the motor vehicle. During the first operating state, the operating medium of the transmission to be cooled is both over the first area 14 as well as over the second area 15 of the heat exchanger 1 guided and consequently through both areas 14 , 15 of the heat exchanger 1 chilled. About the valve 32 and the line 44 the operating fluid cooled in this way is fed to the gear unit for further use.

In a second operating state, which according to 2nd is shown, the retarder 23 activated manually or by a controller and it is via a line 41 Consumables in the working area of the retarder 23 promoted. The valve 32 is then moved to its second position. This allows in the retarder 23 heated equipment via the line 39 in the line 42 passed and over the second area 15 of the heat exchanger 1 be cooled. The now cooled equipment from the second area 15 of the heat exchanger 1 becomes the retarder 23 about the valve 32 and the line 40 fed for further use. The gearbox equipment to be cooled during retarder operation is supplied via the valve 32 and a line 43 the first area 14 of the heat exchanger 1 fed and cooled via this. In the second operating state, the resources of the retarder 23 and consequently the operating medium of the transmission is cooled in two separate coolant circuits. The second operating state is, for example, overrun operation of the motor vehicle.

When using a 3-pipe heat exchanger 1 where the first area 14 and the second area 15 are manufactured in one component, one is in the construction of the two areas 14 , 15 tied to appropriate specifications. So can the 3-pipe heat exchanger 1 For example, be made in plate construction, the dimensions and the number of plates used for the two areas 14 , 15 cannot be chosen arbitrarily. Depending on the design of the heat exchanger 1 emerges that the heat exchanger 1 has a corresponding flow resistance. This flow resistance creates a corresponding pressure loss at the heat exchanger 1 , which has a negative impact on at least the equipment cycle 26 of the transmission can affect. For example, the function of the converter back pressure valve 31 be overridden, which causes the pressure inside the converter and thus also the pressure p1 after the torque converter 22 no longer through the converter back pressure valve 31 but through the losses of the downstream equipment cycle 26 be determined and consequently increase. The pressure increase has a negative impact on the life of the torque converter 22 and the shift quality of the transmission and also leads to an earlier switching of the converter safety valve 30th , which means the required amount of resources for the torque converter 22 and the cooling or lubrication of the transmission in the oil sump 34 is dissipated and the cooling or lubrication of the transmission and the torque converter 22 is no longer available.

Therefore, in the cooling system 24th according to the invention at least one bypass 18th , 20 provided, due to which the pressure loss at the heat exchanger 1 can be reduced.

According to 1 points the heat exchanger 1 a bypass arranged on the input side 18th and a bypass arranged on the output side 20 on. The bypass arranged on the input side 18th connects the feed line of the first area 14 of the heat exchanger 1 with the supply line of the second area 15 of the heat exchanger 1 . The bypass on the outlet side 20 connects the return line of the first area 14 of the heat exchanger 1 with the return line of the second area 15 of the heat exchanger 1 .

During a train operation of the motor vehicle, the operating medium of the transmission to be cooled is passed over the first area 14 as well as over the second area 15 of the heat exchanger 1 guided and consequently through both areas 14 , 15 of the heat exchanger 1 chilled. Through this series connection of the two areas 14 , 15 of the heat exchanger 1 emerges that the heat exchanger 1 has a higher flow resistance, resulting in a corresponding pressure loss at the heat exchanger 1 arises. Through the bypasses provided 18th , 20 the pressure loss at the heat exchanger 1 be reduced, which in turn has the consequence that the converter pressure or the pressure p1 after the torque converter 22 in the resource cycle 26 limited and the disadvantages mentioned above can be avoided. In the bypass 18th is a valve 19th arranged, which here as a check valve 19th is trained. In the bypass 20 is a valve 21st arranged, which also here as a check valve 21st is trained.

According to the 1 is the pressure in the retarder circuit 25th low because the retarder is not actuated. The valve therefore opens 19th if there is a certain pressure at the connection 7 of the heat exchanger 1 the bypass 18th and part of the transmission oil is bypassing the first area 14 of the heat exchanger 1 directly over the second area 15 of the heat exchanger 1 guided. The valve 21st opens when there is a certain pressure at the connection 8th of the heat exchanger 1 the bypass 20 , causing part of the transmission oil to bypass the second area 15 of the heat exchanger 1 only through the first area 14 of the heat exchanger 1 is cooled.

In the order after 2nd is just a bypass 18th with a check valve 19th to reduce pressure losses at the heat exchanger 1 intended. According to 2nd a push operation of the motor vehicle is shown, in which the retarder 23 is activated and consequently in the retarder circuit 25th a high pressure level prevails. This will make the check valve ball 19th to a valve seat of the check valve 19th pressed, with which the bypass 18th is closed. As a result, the gearbox's operating resource is in the first range 14 of the heat exchanger 1 and the retarder's resource 32 in the second area 15 of Heat exchanger 1 chilled. If the motor vehicle is in overrun mode with activated retarder 23 operated, then the gear to be cooled is only operated in the second area 15 of the heat exchanger 1 led, resulting in a lower flow resistance in the equipment circuit 26 prevails.

3rd shows the multi-flow heat exchanger 1 in a top view. On an end plate 2nd of the heat exchanger 1 are the connections for connecting the equipment circuits 25th , 26 and the coolant circuit 28 to the heat exchanger 1 . The heat exchanger 1 has in this embodiment two connection plates 3rd , 4th on. In the connection plate 3rd is a connection 7 for the supply of the gearbox equipment to be cooled, a connection 9 for the supply of the retarder's equipment to be cooled 23 as well as a connection 5 provided for returning the heated coolant. Correspondingly, in the connection plate 4th a connection 8th for the return of the cooled gear of the gearbox, a connection 10 for the return of the cooled equipment of the retarder 23 as well as a connection 6 provided for supplying the coolant. The connection plates 3, 4 are with the end plate 2nd of the heat exchanger connected, for example soldered.

The pin assignment shows that the plate heat exchanger shown here works according to the so-called counterflow principle, in which the flow direction of the operating medium flows to be cooled and the coolant flow are opposite. The fact that the operating medium flows and the coolant flow flow towards one another and ultimately past one another makes large heat transfer possible. Of course, the pin assignment can also be such that the plate heat exchanger works according to the so-called direct current principle, in which the operating agent flows to be cooled and the coolant flow flow through the heat exchanger in the same direction.

The 4th to 6 show in a sectional view a multi-flow heat exchanger 1 , which is constructed in a known manner as a plate heat exchanger. Several superimposed plates are arranged between two end plates and form a plate package, which is flowed through by the equipment to be cooled and the coolant. The passages carrying the coolant occur 11 in heat transfer contact with passages 12th or 13 which are traversed by equipment. Through the connection 7 gear oil enters the passages as the operating medium of the gear 12th of the first area 14 of the heat exchanger 1 a. This is shown by the corresponding arrows. Through the connection 9 retarder oil reaches the retarder 23 in the passages 13 of the second area 15 of the heat exchanger 1 a, which is also shown by corresponding arrows. In the connection plate 3rd is the connection 7 for the supply of the gear oil to be cooled, the connection 9 for the supply of the retarder oil to be cooled and the connection 5 provided for returning the heated coolant. Furthermore is in the connection plate 3rd and the heat exchanger 1 in the connection 9 an insert 16 to distribute the equipment to the different areas 14 , 15 of the heat exchanger 1 brought in.

According to the invention, it is now provided that the heat exchanger 1 at least one bypass 18th over which the first area 14 of the heat exchanger 1 and the second area 15 of the heat exchanger 1 are interconnected.

According to 4th is the bypass 18th in a connection element 17th arranged, via which the heat exchanger 1 can be attached to a gearbox or retarder housing. The bypass 18th is preferably directly in the connection element 17th integrated. For example, the bypass 18th in the connection element 17th be poured or in any other way into the connection element 17th be incorporated. In an alternative embodiment, the bypass 18th be arranged in a gear housing or a retarder housing. This can be advantageous, for example, if the heat exchanger 1 without an intermediate connection element 17th to be attached to a gearbox or retarder housing. In the bypass 18th is a valve 19th arranged, which is designed here as a check valve. Is a pressure in the equipment circuit 25th of the retarder 23 low because of the retarder 23 is not actuated, then the check valve 19th due to the pressure in the equipment circuit 26 open the transmission, causing a portion of the transmission oil to the first area 14 of the heat exchanger 1 over and into the second area 15 of the heat exchanger 1 is directed.

According to 5 becomes an alternative way of arranging the bypass 18th shown. Here is the bypass 18th directly into the connection plate 3rd integrated. For example, the bypass 18th into the connection plate 3rd be cast in or in any other way in the connection plate 3rd be incorporated. Here too is in the bypass 18th a valve designed as a check valve 19th arranged. Regarding the mode of operation, the 4th referred.

According to 6 will be another alternative way of arranging the bypass 18th shown. Here is the bypass 18th both through the connection plate 3rd as well as the connection element 17th educated. To connect the first area 14 of the heat exchanger 1 with the second area 15 of the heat exchanger 1 is in the connection plate 3rd a channel worked in, which with the connection element installed 17th sealed and sealed by this. Again, in the bypass 18th a valve designed as a check valve 19th be provided. The one in the connection plate 3rd The built-in duct can also be closed and sealed by a gearbox or a retarder housing if the heat exchanger does not have an intermediate connection element 17th mounted on a gearbox or retarder housing. Regarding the mode of operation is again on the 4th referred.

Because the gear oil flowing through the bypass still passes through part of the heat exchanger 1 cooled and not passed directly into the oil sump, an inadmissible increase in the oil sump temperature can be avoided.

Reference list

1

Heat exchanger

2nd

End plate

3rd

Sub-base

4th

Sub-base

5

Coolant connection

6

Coolant connection

7

Connection equipment circuit gearbox

8th

Connection equipment circuit gearbox

9

Connection of the retarder equipment circuit

10th

Connection of the retarder equipment circuit

11

Passage of coolant

12th

Passage leading equipment

13

Passage leading equipment

14

first area

15

second area

16

commitment

17th

Connecting element

18th

bypass

19th

Valve

20

bypass

21

Valve

22

Torque converter

23

Primary retarder

24th

Cooling system

25th

Retarder equipment cycle

26

Equipment circuit gearbox

27

Heat exchanger

28

Coolant circuit

29

Valve

30th

Valve

31

Valve

32

Valve

33

Oil pump

34

Oil sump

35

Suction strainer

36

Oil filter

37

Primary pressure circuit

38

Secondary pressure circuit

39

management

40

management

41

management

42

management

43

management

44

management

QUOTES INCLUDE IN THE DESCRIPTION

This list of documents listed by the applicant has been generated automatically and is only included for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• DE 19712599 A1 [0007]

Claims (13)

Multi-flow heat exchanger (1) comprising at least a first area (14) for cooling an item of equipment of a transmission and a second area (15) for cooling an item of equipment of a hydrodynamic retarder (23) as well as an insert (16) for distributing the items of equipment to the different areas (14, 15) of the heat exchanger (1), characterized in that the heat exchanger (1) has at least one bypass (18, 20) via which the first region (14) of the heat exchanger (1) and the second region (15) of the heat exchanger (1) are interconnected. Heat exchanger (1) after Claim 1 , characterized in that the bypass (18, 20) is integrated in a connection plate (3, 4) of the heat exchanger (1). Heat exchanger (1) after Claim 1 , characterized in that the bypass (18, 20) is implemented through a channel formed in a connection plate (3, 4) of the heat exchanger (1), which is closed by a connection element (17), a gear housing or a retarder housing. Heat exchanger (1) after Claim 1 , characterized in that the bypass (18, 20) is integrated in a connection element (17) of the heat exchanger (1), via which the heat exchanger (1) can be attached to a gearbox housing or a retarder housing. Heat exchanger (1) according to one of the preceding claims, characterized in that a flow of the bypass (18, 20) can be controlled or regulated. Heat exchanger (1) after Claim 5 , characterized in that a valve (19, 21) is arranged in the bypass (18, 20) to control or regulate the flow through the bypass (18, 20). Heat exchanger (1) after Claim 6 , characterized in that the valve (19, 21) is designed as a pressure valve, flow valve, seat valve, directional control valve or throttle or orifice valve. Cooling system (24) comprising a coolant circuit (28), an operating medium circuit (26) of a transmission, an operating medium circuit (25) of a hydrodynamic retarder (23) and a multi-flow heat exchanger (1), a first area (14) of the heat exchanger (1) for cooling an operating medium of the transmission and a second region (15) of the heat exchanger (1) for cooling an operating medium of the hydrodynamic retarder (23), with a feed line to the first region (14) of the heat exchanger (1) via a bypass ( 18) is connected to a feed line to the second area (15) of the heat exchanger (1) and / or a return line from the first area (14) of the heat exchanger (1) via a bypass (20) to a return line from the second area ( 15) of the heat exchanger (1) is connected. Cooling system (24) after Claim 8 , characterized in that a flow of the bypass (18, 20) can be controlled or regulated. Cooling system (24) after Claim 9 , characterized in that a valve (19, 21) is arranged in the bypass (18, 20) to control or regulate the flow through the bypass (18, 20). Cooling system (24) after Claim 10 , characterized in that the valve (19, 21) is designed as a pressure valve, flow valve, seat valve, directional control valve or throttle or orifice valve. Cooling system (24) according to one of the preceding claims, characterized in that when the retarder (23) is not actuated, the operating medium of the transmission is also passed through the second region (15) of the heat exchanger (1) provided for cooling the operating medium of the retarder (23) and is cooled. Gearbox of a motor vehicle comprising a multi-flow heat exchanger (1) according to at least one of the Claims 1 to 7 and / or a cooling system (24) according to at least one of the Claims 8 to 12th .

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