DE102010009030A1 - Motor vehicle has internal-combustion engine, transmission oil containing gear box and device for heating up transmission oil by waste heat of internal-combustion engine - Google Patents

Abstract

The invention relates to a motor vehicle with an internal combustion engine (1), a transmission oil (5) containing gearbox (3), and devices (4) for heating the gearbox oil (5) by waste heat of the internal combustion engine (1). So that the transmission oil (5) after a cold start of the internal combustion engine (1) without affecting the heating of the internal combustion engine (1) and without increasing the fuel consumption can be heated to its operating temperature faster, the invention proposes that the devices (4) a heat pipe (10).

Description

The invention relates to a motor vehicle having an internal combustion engine, a transmission oil containing transmission, and means for heating the transmission oil by waste heat of the internal combustion engine.

Motor vehicle transmissions, such as manual transmissions, automatic transmissions or axle transmissions, usually contain a larger quantity of transmission oil, which cools down to ambient temperature after an extended standstill of the motor vehicle. If the ambient temperature is low, then the transmission oil has a relatively high viscosity, which decreases only slowly after the start of the motor vehicle by the frictional heat generated in the transmission. Therefore, without additional heating of the transmission oil, relatively high power losses occur in motor vehicle transmissions until the transmission oil reaches its operating temperature.

To avoid the power losses caused by cold transmission oil, it is for example from the WO 2008/094110 A1 Already known in a motor vehicle of the type mentioned, to heat transmission oil from a transmission of the motor vehicle at low transmission oil temperatures in a heat exchanger by heat exchange with heated engine oil from an internal combustion engine of the motor vehicle. However, this has the disadvantage that the heating of the internal combustion engine is slowed even after a cold start, whereby the pollutant emissions may even increase in undesirable ways.

For heating transmission oil in motor vehicle transmissions, the use of electrical heating rods has also been proposed. As a result of a multiple energy conversion in the generation of electrical energy from engine work in a generator and the generation of heat from the electrical energy, however, results in a poor energy efficiency and possibly even an increase in fuel consumption.

Proceeding from this, the present invention seeks to improve a motor vehicle of the type mentioned in that after a cold start of the engine cold transmission oil without affecting the heating of the engine and without increasing the fuel consumption can be heated faster to its operating temperature.

This object is achieved in that the means for heating the transmission oil comprise a heat pipe.

A heat pipe is known in the art as a heat pipe or heat pipe. A heat pipe usually has the form of a tube with a hermetically sealed, partially filled with a liquid working fluid hollow interior volume. With such a heat pipe, a high heat flux density and thus a high power density of heat transfer can be achieved by heat by evaporation of the working fluid under heat absorption, automatic transport of the vaporized working fluid into another part of the heat pipe and condensation of the vaporized working fluid with heat release very effective, ie with a large heat transfer amount is transported on a small heat transfer cross section, from a heat source to a heat sink. In contrast to a heat exchanger with working fluid no energy is needed for the circulation of the working fluid and thus the fuel consumption is not increased. With such a heat pipe, it is also possible to transfer the waste heat of the exhaust gas generated during operation of the internal combustion engine or an exhaust pipe heated by the exhaust gas with high power density in the transmission oil, so that unlike in the case of a heat exchange with engine oil does not slow down the heating of the internal combustion engine itself becomes.

By means of the measure according to the invention, the power losses caused by cold transmission oil and thus also the fuel consumption and the pollutant emissions of the internal combustion engine of the motor vehicle can be reduced. The term gear oil also includes axle oil, d. H. the oil in axle transmissions.

A preferred embodiment of the invention provides that a first part of the heat pipe is in heat transfer contact with exhaust gas of the internal combustion engine or an exhaust pipe heated by the exhaust gas, and that a second part of the heat pipe is in heat transfer contact with the transmission oil.

The waste heat is preferably withdrawn from the exhaust gas or the exhaust pipe in the flow direction behind a catalyst, where the first part of the heat pipe is in heat transfer contact with the exhaust gas or the exhaust pipe in order to extend the period of time until the light-off is reached after a cold start of the internal combustion engine. Temperature of the catalyst and thus to avoid an increase in pollutant emissions.

A further preferred embodiment of the invention provides that the heat pipe surrounds a working fluid which evaporates in the first part of the heat pipe by the waste heat generated during operation of the internal combustion engine and flows as steam in the second part of the heat pipe where It then condenses by the heat transfer contact of the second part of the heat pipe with the gear oil and thereby releases heat of condensation. From the second part of the heat pipe, the working medium then flows back as liquid by gravity or capillary forces in the first part of the heat pipe.

The second part of the heat pipe preferably dips into the transmission oil in order to transfer as completely as possible into the transmission oil the heat of condensation released in the interior of the heat pipe.

As a working medium can advantageously be used water, which is completely unproblematic from an environmental point, can be easily evaporated by the heat transfer contact of the first part of the heat pipe with the exhaust gas or the exhaust gas heated by the exhaust gas, and by the heat transfer contact of the second part of the heat pipe with the transmission oil again can be cooled to condensation, at least as long as the temperature of the transmission oil is below the evaporation temperature of the water. Regardless of which working medium is used, the working medium enclosed by the heat pipe is expediently under a reduced pressure at ambient temperature, so that even at this temperature a small part of the working medium evaporates. This ensures that the heat transfer through the heat pipe already begins shortly after a cold start of the internal combustion engine, as soon as heat from the exhaust gas or the exhaust gas heated by the exhaust gas is introduced into the first part of the heat pipe.

In order to avoid that the transmission oil is excessively heated by the heat pipe or the waste heat transferred through the heat pipe in the transmission oil, another preferred embodiment of the invention provides that the heat transfer is interrupted upon reaching a predetermined transmission oil temperature.

To interrupt the heat transfer through the heat pipe, the supply of exhaust gas to the first part of the heat pipe or in the standing with the first part of the heat pipe in the heat transfer contact exhaust pipe is interrupted according to a first variant of the invention by the exhaust gas after reaching the predetermined transmission oil temperature through another exhaust pipe is directed to the exhaust. In other words, the standing with the first part of the heat pipe in the heat transfer contact exhaust pipe is formed by a bypass line, which is acted upon only with reaching the predetermined transmission oil temperature with the exhaust gas.

Since the exhaust pipe greatly expands and contracts due to high temperature differences, a preferred embodiment of the invention provides that the first part of the heat pipe is in heat transfer contact with the outside of the exhaust pipe. In this way, can be dispensed with an inlet opening for the heat pipe, whereby leakage problems due to a different thermal expansion of the heat pipe and the exhaust pipe can be avoided.

This also makes it possible, upon reaching the predetermined transmission oil temperature to interrupt the heat transfer to move the first part of the heat pipe according to a second variant of the invention away from the exhaust pipe to produce an insulating air gap between the first part of the heat pipe and the outside of the exhaust pipe. It is sufficient to interrupt the heat transfer from an air gap of a few millimeters width.

The movement of the Wärmeleitrohrs, which is required to separate the first part of the heat pipe for the purpose of interrupting the heat transfer from the outside of the exhaust pipe or around the first part of the heat pipe for the purpose of resuming the heat transfer again with the outside of the exhaust pipe in heat transfer contact It is expedient to bring about an axial movement along a longitudinal axis of the heat conduction tube or a rotation about the longitudinal axis of the heat conduction tube, since during this movement a seal of the transmission around an inlet opening of the heat conduction tube can be ensured without difficulties if, according to an advantageous embodiment of FIG Invention has a constant cross section in the region of the inlet opening. Alternatively, however, other movements are possible, such as a tilting or pivoting movement.

The movement of the Wärmeleitrohrs can in principle be made with the aid of an actuator, such as an electromagnetic coil, which is controlled in dependence on the sensed transmission oil temperature. Preferably, however, the movement will take place automatically, advantageously with the aid of an element of a shape memory alloy acting on the heat pipe, the shape of which abruptly changes upon reaching the predetermined transmission oil temperature and thereby moves the heat pipe out of the heat transfer contact with the exhaust pipe. Alternatively, however, it can also be used a consisting of a bimetal or an expansion element that moves by a deformation due to a rising transmission oil temperature, the heat pipe gradually more and more away from the exhaust pipe until it is at Reaching the predetermined transmission oil temperature is not deformed.

The exhaust pipe may be below the transmission, such as a Hinterachsgetriebe run, in which case the heat pipe is appropriately oriented vertically, so that the return transport of the liquid working medium from the standing in heat transfer contact with the transmission oil first part in the heat transfer contact with the exhaust gas or the exhaust pipe standing second part of the heat pipe can be done by gravity. Alternatively, however, the heat pipe may also have a different orientation, in which case suitably provide capillary forces for the return transport of the liquid working medium.

In the following the invention will be explained in more detail with reference to two embodiments shown in the drawing. Show it:

1 a partially sectioned view of parts of a transmission and an exhaust tract of a motor vehicle and of a first embodiment of a heat pipe for heating transmission oil by transfer of waste heat from the exhaust system;

2 an enlarged, partially sectioned view of parts of a transmission and an exhaust pipe of a motor vehicle and of a second embodiment of a heat pipe with means for interrupting the heat transfer;

3 an enlarged, partially sectioned view of a contact head between the exhaust pipe and the heat pipe;

4 an enlarged, partially sectional view of parts of a transmission and an exhaust pipe of a motor vehicle and of a third embodiment of a heat pipe with other means for interrupting the heat transfer.

The parts of a motor vehicle shown in the drawing comprise an internal combustion engine 1 , Parts of an exhaust tract 2 the internal combustion engine 1 , one between the internal combustion engine 1 and a drive train (not shown) of the motor vehicle arranged shift or axle drive 3 , as well as facilities 4 for heating transmission oil 5 in the transmission 3 after a cold start by waste heat of the engine 1 ,

The exhaust tract 2 includes one with exhaust gas outlet openings of a cylinder head 6 the internal combustion engine 1 connected exhaust manifold 7 , one in the flow direction of the exhaust gas behind the exhaust manifold 7 arranged catalyst 8th , as well as one from the catalyst 8th to an exhaust (not shown) leading exhaust pipe 9 ,

The facilities 4 for heating the transmission oil 5 include a heat pipe 10 extending through a housing wall 11 a transmission housing 12 extends, with an outside of the transmission case 12 located first part 13 of the heat pipe 10 behind the catalyst 8th in heat transfer contact with the exhaust pipe 9 while standing inside the gearbox 12 second part 14 of the heat pipe 10 in one with the gear oil 5 filled sump 16 of the transmission 3 sticks out, so he always uses the gear oil 5 is in heat transfer contact.

How best in 2 shown, there is the heat pipe 10 from a straight, closed at both ends pipe section of copper or other metal or a metal alloy with high thermal conductivity, the hollow inner volume is hermetically sealed, where it is partially filled with a working fluid and is under a negative pressure, so that at ambient temperature greater part of the working medium in the liquid state and a smaller part of the working medium is in the vapor state.

While that in 1 only schematically illustrated vertically oriented heat pipe 10 may have a smooth inner wall, has the in 2 illustrated horizontally oriented heat pipe 10 inside a fine wire mesh made of copper or another metal or a metal alloy with high thermal conductivity. The distances between the individual fibers of the wire mesh are so small that the wire mesh can transport liquid working medium by capillary action similar to a wick.

How best in 2 and 3 is the first part 13 the Wärmeleitrohrs at its the exhaust pipe 9 facing outer front end with a contact head 17 provided, which serves to transfer heat from the wall 18 of the exhaust pipe 9 on the heat pipe 10 to improve. The in the transmission oil 5 in the oil sump 16 immersing second part 14 of the heat pipe 10 is on its outside with ribs or wings 19 provided to increase the heat transfer surface and thus the heat transfer from the heat pipe 10 in the transmission oil 5 to improve.

The contact head 17 indicates at its the heat pipe 10 facing side a hole 20 on, in which the outer front end of the heat pipe 10 protrudes. As in 3 shown, the hole can 20 around the front end of the heat pipe 10 around with a thermal grease 21 be filled to the contact head 17 to compensate for tolerances, vibrations and / or relative movements between the gearbox 3 and the exhaust pipe 9 radially movable but axially immovable with the heat pipe 10 connect without affecting the heat transfer capacity. To escape the thermal compound 21 out of the hole 20 To prevent an annular gap between the outside of the heat pipe 10 and the wall of the hole 20 near the mouth of the latter with an O-ring seal 22 or the like may be closed. The O-ring seal 22 carries by friction or positive connection with the heat pipe 10 and the wall of the hole 20 at the same time, an axial displacement between the heat pipe 10 and the contact head 17 to prevent.

The contact head 17 widens in the direction of the exhaust pipe and has at its the exhaust pipe 9 facing side of the exhaust pipe 9 opposite part-cylindrical recess 23 , the cross-sectional dimension and the radius of curvature of the cross-sectional dimension and the radius of curvature of the outside of the hollow cylindrical exhaust pipe 9 are adapted to the best possible heat transfer from the exhaust gas heated by the heat of the exhaust pipe 9 on the contact head 17 and via this into the heat pipe 10 to enable.

When in operation of the internal combustion engine 1 hot exhaust gas through the exhaust pipe 9 passed through, heats the exhaust pipe 9 due to the waste heat of the exhaust gas, with a portion of the waste heat through the contact head 17 in the hole 20 projecting front end of the first part 13 of the heat pipe 10 is transmitted. As a result, the wall of the heat pipe heats up in this area 10 on, which begins to evaporate on the inside of the wall working fluid. This causes the outer end of the heat pipe 10 the vapor pressure increases relative to the remainder of the hollow interior volume, resulting in a pressure gradient within the heat pipe 10 leads. As a result, the resulting vapor of the working medium flows through the interior of the heat pipe 10 in the direction of the second part 14 , Because this part 14 in the heat sink forming a cold transmission oil 5 in the oil sump 16 the vapor condenses there, with the previously in the front end of the first part 13 of the heat pipe 10 absorbed heat in the form of heat of condensation is released again.

Because the second part 14 at the in 1 illustrated vertically oriented heat pipe 10 above the first part 13 is located, the condensed liquid working fluid flows by gravity back down into the first part 13 of the heat pipe 10 where it evaporates again. In the horizontally oriented heat pipe 10 in 2 In contrast, the capillary forces of the wire mesh inside the heat pipe ensure 10 for the return transport of the working medium from the second part 14 in the first part 13 of the heat pipe 10 ,

To make it possible, the heat transfer through the heat pipe 10 to interrupt as soon as the transmission oil 5 has reached a predetermined temperature, for example its operating temperature, and thereby overheating of the transmission oil 5 to avoid is the exhaust pipe 9 in 1 formed as a bypass line, which after reaching the predetermined transmission oil temperature by a flap 24 can be closed. The exhaust gas then flows through to the exhaust pipe 9 parallel exhaust pipe 25 , without further heat on the heat pipe 10 is transmitted. To operate the flap 24 may be an actuator (not shown) are used, which is controlled in dependence on the sensed transmission oil temperature.

This in 2 . 3 and 4 illustrated exhaust pipe 9 however, is not designed as a bypass line and is during operation of the internal combustion engine 1 constantly flows through the exhaust. To heat transfer through the heat pipe 10 to interrupt, is the heat pipe 10 in 2 . 3 and 4 movable in its longitudinal direction, so that with the heat pipe 10 connected contact head 17 when the predetermined transmission oil temperature is exceeded by a few millimeters from the outside of the exhaust pipe 9 can move away. By such a movement is between the contact head 17 and the exhaust pipe 9 generates an air gap, whereby a further heat transfer is interrupted or at least very limited.

In contrast to the heat pipe 10 in 1 that is rigid with the gearbox 12 is connected, passes through the heat pipe 10 in 2 . 3 and 4 below the transmission oil level 26 in the oil sump 16 an entrance opening 27 in the to the exhaust pipe 9 adjacent housing wall 11 of the gearbox 12 is arranged.

The axial movement of the heat pipe 10 Here, when the predetermined transmission oil temperature is exceeded by means of an element made of a shape memory alloy 29 triggered automatically. This element 29 is formed so that it below the predetermined transmission oil temperature, a first, in 2 shown in solid lines and has deformed abruptly when exceeding the predetermined transmission oil temperature similar to a crackpot frog, with a second, in 2 takes the form shown in broken lines and the contact head 17 from contact with the exhaust pipe 9 draws. On cooling of the transmission oil 5 takes the element 29 gradually the in 2 shown in solid lines, in which the contact head 17 in contact with the exhaust pipe 9 located.

At the in 2 and 3 illustrated heat pipe 10 is the element 29 opposite the front end of the inner second part 14 of the heat pipe 10 inside the oil sump 16 on the housing wall 11 of the gearbox 12 attached and with the front end of the second part 14 of the heat pipe 10 connected while the inlet opening 27 from a seal 28 is surrounded to during the movement of the heat pipe 10 through the entrance opening 27 around the heat pipe 10 to provide a seal around.

In the heat pipe in 4 forms the element consisting of a shape memory alloy 29 a part 30 to the exhaust pipe 9 adjacent housing wall 11 of the gearbox 12 that sealingly into a wall opening 31 the housing wall 11 used and around the heat pipe 10 around tight and tightly connected to it. The wall part 30 is on its outside with an insulation 32 provided so that the element 29 only as a function of the internal temperature in the gearbox 12 deformed. The heat pipe 10 is there with the front end of the inner second part 14 in a blind hole 33 in the housing wall 11 of the gearbox 12 guided.

In addition, in the heat pipe 10 in 4 at the exhaust pipe 9 adjacent side of the contact head 17 nor an elastically deformable in cross-section arcuate compensating element 34 attached, with the vibrations of the exhaust pipe 9 without equalizing a noise. As 4 shows, is located for better heat transfer from metal spring elastic compensation element 34 also above the predetermined transmission oil temperature, ie in the in 4 shown retracted position of the heat pipe 10 still in line or point contact with the exhaust pipe 9 while being flat below the predetermined transmission oil temperature against the outside of the exhaust pipe 9 is applied.

LIST OF REFERENCE NUMBERS

1

Internal combustion engine

2

exhaust tract

3

transmission

4

Devices for heating transmission oil

5

transmission oil

6

cylinder head

7

exhaust manifold

8th

catalyst

9

exhaust pipe

10

heat pipe

11

Housing wall Transmission housing

12

gearbox

13

first part heat pipe

14

second part heat pipe

16

oil sump

17

contact head

18

Wall exhaust pipe

19

Ribs or wings

20

Bore contact head

21

Thermal Compounds

22

poetry

23

Partial cylindrical contact head

24

flap

25

exhaust pipe

26

oil level

27

inlet opening

28

poetry

29

Element of shape memory alloy

30

wall part

31

wall opening

32

insulation

33

Blind hole

34

compensation element

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely 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.

Cited patent literature

• WO 2008/094110 A1 [0003]

Claims (10)

Motor vehicle with an internal combustion engine, a gear oil containing transmission, and means for heating the transmission oil by waste heat of the internal combustion engine, characterized in that the devices ( 4 ) a heat pipe ( 10 ). Motor vehicle according to claim 1, characterized in that a first part ( 13 ) of the heat pipe ( 10 ) in the heat transfer contact with exhaust gas of the internal combustion engine ( 1 ) or an exhaust gas flow through the exhaust gas ( 9 ) and that a second part ( 14 ) of the heat pipe ( 10 ) in heat transfer contact with the transmission oil ( 5 ) stands. Motor vehicle according to claim 2, characterized in that the first part ( 13 ) of the heat pipe ( 10 ) in the flow direction of the exhaust gas behind a catalyst ( 8th ) in the heat transfer contact with the exhaust gas or the exhaust gas flowed through by the exhaust gas ( 9 ) stands. Motor vehicle according to claim 2 or 3, characterized in that the first part ( 13 ) of the heat pipe ( 10 ) via a contact head ( 17 ) with the outside of the exhaust pipe ( 9 ) stands. Motor vehicle according to one of claims 2 to 4, characterized in that the second part ( 14 ) of the heat pipe ( 10 ) in the transmission oil ( 5 immersed). Motor vehicle according to one of claims 2 to 5, characterized in that the heat pipe ( 10 ) encloses a working medium, which in the first part ( 13 ) of the heat pipe ( 10 ) evaporates as steam in the second part ( 14 ) of the heat pipe ( 10 ), in the second part ( 14 ) of the heat pipe ( 10 condensed and as a liquid by gravity or capillary forces in the first part ( 13 ) of the heat pipe ( 10 ) flows back. Motor vehicle according to one of the preceding claims, characterized by devices ( 24 . 29 ) for interrupting the heating of the transmission oil ( 5 ) upon reaching a predetermined transmission oil temperature. Motor vehicle according to claim 7, characterized in that the devices ( 24 . 29 ) Medium ( 24 ) for interrupting the supply of exhaust gas to the first part ( 13 ) of the heat pipe ( 10 ) or in the first part ( 13 ) of the heat pipe ( 10 ) Exhaust pipe in heat transfer contact ( 9 ). Motor vehicle according to claim 7, characterized in that the devices ( 24 . 29 ) Medium ( 29 ) to include the first part ( 13 ) of the heat pipe ( 10 ) in and out of the heat transfer contact with the exhaust gas of the internal combustion engine ( 1 ) or the exhaust gas flowed through by the exhaust gas ( 9 ) to move. Motor vehicle according to claim 9, characterized in that the means ( 29 ) depending on the temperature of the transmission oil.

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