FI ELD OF TH E I NVENTION AN D P RIOR ART The present invention relates to a motor vehicle according to the preamble of claim 1 .

In a motor vehicle there are usually a plu rality of heat-generating components which need cooling , e.g. a combustion engine usually cooled by a water-based cooling medium, or a gearbox usually cooled by oil as cooling mediu m. The heat absorbed by the cooling medium may be given off to the surrou ndings via a radiator device situated at the front of the vehicle and comprising one or more radiator elements for cooling the cooli ng medium. Each radiator element has elongate pipelines with cooling flanges connected to them, and the cooling medium which is to be cooled is led through these pipelines in order to give off heat via their walls and the cooling flanges to ambient air which passes th rough air passages between the pipelines. The cooling medium is thus cooled by the ambient air passi ng between the pipelines. The cooling flow of ambient air th rough the air passages is generated by the vehicle's forward move ment and/or by a fan . The heat absorbed by the cooling medium may also be used to warm the vehicle's d river space and/or passenger space by the cooli ng mediu m being led th rough a heat exchanger, thereby giving off heat to air which passes th rough the heat exchanger. The warmed air is then led into the driver space and/or the passenger space. Modern motor vehicles are often also provided with an air conditioning system to cool thei r driver space and/or passenger space. Such an air conditioning system comprises i nter alia an evaporator i n which the system's working medium is vaporised, thereby absorbing heat from passing air. The air thus cooled is then led into the driver space and/or the passenger space. The air conditioni ng system further comprises a condenser which may be situated at the front of the vehicle and in which the working medium is condensed, thereby giving off heat to passing ambient air.

In certain heavy motor vehicles, e.g. certain types of tractor u nits and trucks, the driver space is situated in a cab u nit which is hingingly con nected to the frame of the vehicle and tiltable relative to the vehicle frame between a lowered state and a raised state. The normal situation is that the cab u nit is in the lowered state and can be tilted forward to the raised state to provide access for servicing or repai r of the engine situated under the cab unit. I n a motor vehicle with tiltable cab u nit it is usually the case that a heat exchanger situated in the cab unit to warm or cool cab air is connected to pipelines situated on the vehicle frame which form part of a cooling circuit or an air conditioning system via flexible hoses which extend between the cab u nit and the vehicle frame. These hoses have to be relatively long to be able to remain con nected between the cab unit and the vehicle frame when the cab unit is tilted forward from the lowered state to the raised state, which means that the hoses occupy a relatively large amou nt of space. They also risk damage by wear and tear during ru nni ng of the vehicle and by wear and tear and buckling during tilting of the cab u nit relative to the vehicle frame.

OBJ ECT OF TH E I NVENTION

The object of the present invention is to propose a solution to the above problem of liability to damage of hose runs between the tiltable cab u nit and the frame of a motor vehicle fitted with it. SUMMARY OF TH E I NVENTION

According to the present invention, said object is achieved by means of a motor vehicle having the features defined in claim 1 . The motor vehicle according to the invention comprises

- a first ci rcuit situated on the vehicle's frame for ci rculation of a first mediu m,

- a second ci rcuit situated in the vehicle's tiltable cab unit for circulation of a second medium , and

- a heat transfer arrangement for transfer of heat between said media.

The heat transfer arrangement comprises a first heat transfer unit fitted on the vehicle frame, faci ng towards the cab unit and incorporated in the first circuit in order to have said first mediu m flowi ng through it, and a second heat transfer unit fitted on the cab u nit, facing towards the vehicle frame and incorporated in the second ci rcuit in order to have said second mediu m flowing th rough it. These heat transfer u nits are arranged to be in heat- transferring contact with one another when the cab unit is in the lowered state and be separate from one another when the cab unit is in the raised state.

The cab unit is thus provided with an independent circulation circuit which is only in heat-transferring contact with the circulation circuit fitted on the vehicle frame when the cab unit is in the lowered state. I n the cab u nit's lowered state the heat transfer u nits are in heat-transferri ng contact with one another and thus jointly constitute a heat exchanger with one heat transfer u nit servi ng as the primary circuit of the heat exchanger and the other heat transfer unit serving as the secondary circuit of the heat exchanger. Tilting the cab unit forward to the raised state causes the heat transfer u nit fitted on the cab unit to swing away from the vehicle frame jointly with the cab unit and be thereby parted from the heat transfer unit fitted on the vehicle frame, thereby breaking the heat-transferring contact between the cab unit's circulation circuit and the circulation circuit situated on the vehicle frame. The solution according to the invention makes it possible to dispense with the aforesaid hose runs between the cab unit and the vehicle frame, thereby eliminating the aforesaid problem of flexible hoses between the cab u nit and the vehicle frame occupying space and being liable to suffer damage. According to an embodiment of the invention, the first heat transfer u nit is springingly suspended i n the vehicle frame and/or the second heat transfer u nit is springingly suspended i n the cab unit. This makes it possible to maintain a satisfactory abutment force between the heat transfer units while at the same time enabling them to absorb the cab u nit's movements relative to the vehicle frame when the vehicle is in motion .

According to another embodiment of the i nvention, the first heat transfer unit has a profiled, e.g . undulating, contact surface intended for heat-transferring engagement with a corresponding profiled contact surface of the second heat transfer u nit. The profiling of the mutual contact surfaces of the heat transfer u nits makes it possible for there to be a relatively large heat transfer surface between the heat transfer units, while at the same ti me the profiling helps to keep the contact su rfaces in position relative to one another i n horizontal di rections when the cab unit is in the lowered state. According to a further embodiment of the invention, a heat exchanger for warming or cooling of cab air is incorporated in the second circuit in series with the second heat transfer u nit. This makes it possible for the mediu m in the second circuit situated in the cab u nit to absorb heat from the mediu m in the first circuit situated on the vehicle frame via the heat transfer arrangement and to give off this heat for warmi ng of cab air via said heat exchanger, or to be cooled by the mediu m in the first circuit via the heat transfer arrangement and to cool cab ai r via said heat exchanger.

According to a further embodiment of the invention, a radiator device, fitted for example on the cab unit's roof, is incorporated in the second circuit in series with the second heat transfer unit to cool the second mediu m by means of ambient air which passes through this radiator device. By cooling the mediu m in the second circuit situated in the cab unit, this radiator device can indirectly contribute to cooling of the medium in the first circuit situated on the vehicle frame. Other advantageous features of the motor vehicle according to the invention are indicated by the independent claims and the description set out below.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described in more detail below on the basis of embodiment examples with reference to the attached drawings, in which: Fig. 1 is a schematic sideview of a motor vehicle according to an embodiment of the present invention with a tiltable cab unit in a lowered state,

Fig.2 depicts a motor vehicle according to Fig. 1 with the cab unit in a raised state,

Fig.3a is a schematic diagram of parts of the motor vehicle according to Figs. 1 and 2 with its cab unit in a lowered state,

Fig.3b depicts the same parts as Fig.3a with the vehicle's cab unit in a raised state, Fig.4 is a schematic diagram of parts of a motor vehicle according to an alternative embodiment of the invention, Fig.5 is a schematic diagram of parts of a motor vehicle according to a further alternative embodiment of the invention, and

Fig.6 is a schematic diagram of parts of a motor vehicle according to a further alternative embodiment of the invention.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

Figs. 1 and 2 illustrate a motor vehicle 1 according to an embodiment of the present invention. In this case the vehicle is a tractor unit. It comprises a vehicle frame 2 and a cab unit 3 with a driver space. The cab unit 3 is hingingly connected to the vehicle frame 2 and tiltable relative to it between a lowered state (see Fig. 1) and a raised state (see Fig.2). In normal situations, inter alia when the vehicle is in motion, the cab unit 3 is in the lowered state and can be tilted forward to the raised state to allow access for servicing or repair to an engine situated under the cab unit.

Figs.3a and 3b illustrate schematically parts of the vehicle 1. In Figs.3a and 3b, as also in Figs.4-6, the vehicle frame 2 and the cab unit 3 are each depicted in respective boxes bounded by broken lines. A first circuit 10 for circulation of a first medium is provided on the vehicle frame 2 and a second circuit 20 for circulation of a second mediu m is provided in the cab unit 3. The vehicle 1 fu rther comprises a heat transfer arrangement 4 for transfer of heat between said media. The heat transfer arrangement comprises a first heat transfer u nit 1 1 fitted on the vehicle frame 2 and facing towards the cab unit 3, and a second heat transfer u nit 21 fitted on the cab unit 3 and facing towards the vehicle frame 2. The fi rst heat transfer u nit 1 1 is incorporated in the first circuit 1 0 in order to have the medium in the first ci rcuit flowing throug h it, and the second heat transfer unit 21 is incorporated in the second circuit 20 in order to have the mediu m in the second circuit flowing th rough it. The heat transfer units 1 1 , 21 are arranged to be in heat-transferring contact with one another when the cab u nit 3 is i n the lowered state as illustrated in Fig. 3a, and to be separate from one another when the cab unit 3 is in the raised state as depicted in Fig . 3b. The second heat transfer unit 21 swings up in conjunction with the cab u nit 3 from the vehicle frame 2 du ring tilting of the cab unit and is thereby parted from the first heat transfer u nit 1 1 , thus breaking the mechanical and thermal contact between these heat transfer units 1 1 , 21 . When the cab unit 3 is in the lowered state, heat may thus be transferred between the medium in the first ci rcuit 1 0 and the medium in the second circuit 20 via the heat transfer arrangement 4, but no such heat transfer is possible when the cab u nit 3 is i n the raised state.

In the embodiment illustrated i n Figs. 3a and 3b, the fi rst heat transfer u nit 1 1 is springingly suspended in the vehicle frame 2 via a suitable springing arrangement 5 which comprises one or more spring means adapted to springingly pressing the first heat transfer unit 11 against the second heat transfer unit 21 when the cab unit 3 is in the lowered state so that the heat transfer units 11, 21 are thereby kept in contact with one another during mutual movements between the cab unit 3 and the vehicle frame 2 when the vehicle 1 is in motion. Alternatively, the second heat transfer unit 21 might be springingly suspended in the cab unit 3 via a springing arrangement comprising one or more spring means adapted to resiliently pressing the second heat transfer unit 21 against the first heat transfer unit 11 when the cab unit 3 is in the lowered state. Similarly, third heat transfer arrangements 31, 31' mentioned below may be springingly suspended in the vehicle frame 2 and a fourth heat transfer arrangement 41' mentioned below may be springingly suspended in the cab unit 3.

The first heat transfer unit 11 has with advantage a profiled, e.g. undulating, contact surface 11a intended for heat-transferring engagement with a corresponding profiled contact surface 21a of the second heat transfer unit 21 when the cab unit 3 is in the lowered state. Third and fourth heat transfer arrangements 31, 31', 41' mentioned below are with advantage similarly provided with profiled contact surfaces.

One or more guide means 6 are with advantage provided close to the heat transfer units 11, 21 to keep them in position relative to one another in horizontal directions when the cab unit 3 is in the lowered state. These guide means 6 are with advantage integrated in the respective heat transfer units 11, 21. Similarly, one or more guide means are with advantage provided close to the third and fourth heat transfer arrangements 31 , 31 ', 41 ' mentioned below.

In the embodiment depicted in Figs. 3a and 3b, the first circuit 1 0 is con nected to, in order to cool, a combustion engine 7 of the vehicle. The mediu m in the first circuit 1 0 takes the form in this case of radiator liquid , and a radiator liquid cooler 1 2 of conventional configuration is incorporated in the first ci rcuit 1 0 to cool this radiator liquid . I n the example illustrated , the first heat transfer unit 1 1 is arranged in series between the radiator liquid cooler 1 2 and the engine 7. I n this situation the radiator liquid flows through , thereby absorbing heat from , the engine 7, then th rough the first heat transfer unit 1 1 , thereby giving off heat to the medium in the second circuit 20, and thereafter through the radiator liquid cooler 1 2, thereby giving off heat to ambient air which passes through the radiator liquid cooler 1 2, after which the radiator liquid returns to the engine 7. A circulation pu mp 1 3 is provided in the first ci rcuit 1 0 to circulate the mediu m in this circuit.

In the embodiment depicted in Figs. 3a and 3b, a radiator device 22 is incorporated in the second circuit 20 in series with the second heat transfer u nit 21 to cool the second mediu m by means of ambient air which passes th rough this radiator device. The radiator device 22 is with advantage fitted on the cab u nit's roof 8, as illustrated in Figs. 1 and 2.

In the embodiment depicted in Figs. 3a and 3b, a heat exchanger 24 to warm cab air is also incorporated in the second circuit 20 in series with the second heat transfer unit 21 and the radiator device 22. This heat exchanger 24 is with advantage situated downstream of the second heat transfer unit 21 and upstream of the radiator device 22. In this situation the medium in the second circuit 20 thus flows through the second heat transfer unit 21, thereby absorbing heat from the medium in the first circuit 10, and then through the heat exchanger 24, thereby giving off heat to air which passes through this heat exchanger and thence into the cab unit's driver space. The medium in the second circuit 20 then flows through the radiator device 22, thereby giving off heat to ambient air which passes through this radiator device, after which the medium returns to the second heat transfer unit 21. A circulation pump 23 is provided in the second circuit 20 to circulate the medium in this circuit. In the embodiment depicted in Fig. 4, the first circuit 10 and the second circuit 20 jointly form an air conditioning system of the vehicle 1. In this case the first heat transfer unit 11 takes the form of an evaporator intended to vaporise the medium in the first circuit 10, thereby absorbing heat from the medium in the second circuit 20 via the second heat transfer unit 21. The first circuit 10, which in this case serves as a cooling circuit to cool the medium in the second circuit 20, further comprises a compressor 14, a condenser 15 and an expansion valve 16 incorporated in series with one another and in series with the first heat transfer unit 11. The medium in the first circuit 10 is in this case a suitable type of refrigerant. The refrigerant is led in liquid form to the evaporator, i.e. the first heat transfer unit 11, in which it is converted to vapour by heat from the medium in the second circuit 20. The vapour is compressed to high pressure by the compressor 14 and then proceeds to the condenser 15, in which it condenses to liquid, thereby giving off heat to ambient air which passes through the condenser. The refrigerant leaves the condenser 15 in the form of liquid at high pressure and returns to the evaporator 11 via the expansion valve 16. During its passage through the expansion valve 16, the pressure and temperature of the refrigerant drop and it enters the evaporator 11 in the form of liquid at high pressure.

In the embodiment depicted in Fig. 4, a heat exchanger 24 for cooling of cab air is incorporated in the second circuit 20 in series with the second heat transfer unit 21. In this case the medium in the second circuit 20 thus flows through the second heat transfer unit 21, thereby giving off heat to the refrigerant in the first circuit 10, and then through the heat exchanger 24, thereby absorbing heat from air which passes through this heat exchanger and thence into the cab unit's driver space, after which the medium in the second circuit 20 returns to the second heat transfer unit 21. In the embodiment depicted in Fig. 5, the vehicle 1 comprises a first circuit 10 situated on the vehicle frame 2 to circulate a first medium, a second circuit 20 situated in the cab unit 3 to circulate a second medium, and a third circuit 30 situated on the vehicle frame 2 to circulate a third medium. The heat transfer arrangement 4 comprises in this case a first heat transfer unit 11 incorporated in the first circuit 10, a second heat transfer unit 21 incorporated in the second circuit 20 and a third heat transfer unit 31 incorporated in the third circuit 30. The first and third heat transfer units 11, 31 are fitted on the vehicle frame 2 and face towards the cab unit 3, and the second heat transfer unit 21 is fitted on the cab unit 3 and faces towards the vehicle frame 2. In this case the first and third heat transfer units 1 1 , 31 are arranged to be in heat-transferring contact with the second heat transfer u nit 21 when the cab u nit 3 is in the lowered state and to be separated from the second heat transfer unit 21 when the cab unit is in the raised state. When the cab unit 3 is in the lowered state, heat may be transferred via the heat transfer arrangement 4 between the media in said first and second circuits 1 0, 20 and between the media in said second and third circuits 20, 30.

In the embodiment depicted in Fig. 6, the vehicle 1 comprises a first circuit 1 0 situated on the vehicle frame 2 to circulate a first medium, a second circuit 20 situated in the cab u nit 3 to circulate a second medium, a third circuit 30 situated on the vehicle frame 2 to circulate a third medium and a fou rth circuit 40 situated in the cab u nit 3 to circulate a fourth medium. The vehicle 1 comprises in this case a first heat transfer arrangement 4 to transfer heat between the media i n the first and second ci rcuits 1 0, 20 and a second heat transfer arrangement 4' to transfer heat between the media in the third and fou rth ci rcuits 30, 40. The fi rst heat transfer arrangement 4 comprises a first heat transfer unit 1 1 incorporated in the first circuit 1 0 and a second heat transfer u nit 21 i ncorporated in the second ci rcuit 20, while the second heat transfer arrangement 4' comprises a heat transfer u nit 31 ', herein called the third heat transfer unit, incorporated in the third circuit 30, and a heat transfer u nit 41 ', herein called the fou rth heat transfer unit, incorporated in the fourth circuit 40. The fi rst and third heat transfer units 1 1 , 31 ' are fitted on the vehicle frame 2 and face towards the cab unit 3, and the second and fou rth heat transfer units 21 , 41 ' are fitted on the cab unit 3 and face towards the vehicle frame 2. In this case the first heat transfer unit 11 is arranged to be in heat- transferring contact with the second heat transfer unit 21, and the third heat transfer unit 31' is arranged to be in heat- transferring contact with the fourth heat transfer unit 41', when the cab unit 3 is in the lowered state, and to be separated from one another when the cab unit is in the raised state. When the cab unit 3 is in the lowered state, heat may be transferred via the first heat transfer arrangement 4 between the media in said first and second circuits 10, 20 and via the second heat transfer arrangement 4' between the media in said third and fourth circuits 30, 40.

In the embodiments depicted in Figs. 5 and 6, the first circuit 10 is connected to, in order to cool, a combustion engine 7 of the vehicle. The medium in the first circuit takes the form in this case of radiator liquid, and a radiator liquid cooler 12 of conventional configuration is incorporated in the first circuit 10 to cool it. In the examples depicted, the first heat transfer unit 11 is connected in parallel with the radiator liquid cooler 12. In this case the radiator liquid thus flows through, thereby absorbing heat from, the engine 7, and then through the first heat transfer unit 11, thereby giving off heat to the medium in the second circuit 20, or through the radiator liquid cooler 12, thereby giving off heat to ambient air which passes through the radiator liquid cooler 12. A circulation pump 13 is provided in the first circuit 10 to circulate the medium in this circuit. A regulating valve 17 is incorporated in the first circuit 10 in series with the first heat transfer unit 11. This regulating valve 17 may be used to regulate and, when necessary, halt the flow of radiator fluid through the first heat transfer unit 11. A thermostat 18 is also incorporated in a conventional way in the first circuit 10 between the engine 7 and the radiator liquid cooler 12. Radiator liquid is led from the engine 7 to the radiator liquid cooler 12 via this thermostat 18. At an initial stage after starting of the engine 7, when it has not yet become really warm, the thermostat 18 is arranged to direct radiator liquid back to the engine 7 without passing through the radiator liquid cooler 12, to facilitate rapid warming of the engine to desired working temperature.

In the embodiment depicted in embodiment 5, the third heat transfer unit 31 takes the form of an evaporator intended to vaporise the medium in the third circuit 30, thereby absorbing heat from the medium in the second circuit 20 via the second heat transfer unit 21. In the embodiment depicted in Fig. 6, the third heat transfer unit 31' similarly takes the form of an evaporator intended to vaporise the medium in the third circuit 30, thereby absorbing heat from the medium in the fourth circuit 40 via the fourth heat transfer unit 41'. The third circuit 30, which in this case serves as a cooling circuit to cool the medium in the second circuit 20 and in the fourth circuit 40, further comprises a compressor 34, a condenser 35 and an expansion valve 36 incorporated in series with one another and in series with the third heat transfer unit 31, 31'. The medium in the third circuit 30 is in this case a suitable type of refrigerant. The refrigerant is led in liquid form to the evaporator, i.e. the third heat transfer unit 31, 31', in which it is converted to vapour by heat from the medium in the second circuit 20 and fourth circuit 40 respectively. The vapour is compressed to high pressure by the compressor 34 and proceeds to the condenser 35 in which it condenses to liquid, thereby giving off heat to ambient air which passes through the condenser 35. The refrigerant leaves the condenser 35 in the form of liquid at high pressure and returns to the evaporator 31, 31' via the expansion valve 36. During its passage through the expansion valve 36, the pressure and temperature of the refrigerant drop and it enters the evaporator 31, 31' in the form of liquid at low pressure.

In the embodiment depicted in Fig. 5, a heat exchanger 24 to warm or cool cab air is incorporated in the second circuit 20 in series with the second heat transfer unit 21. When the regulating valve 17 is open and the compressor 34 is switched off while the engine 7 is running, radiator liquid flows through the first heat transfer unit 11 but no refrigerant flows through the third heat transfer unit 31. In this case the medium in the second circuit 20 flows through the second heat transfer unit 21, thereby absorbing heat from the radiator liquid in the first circuit 10, and then through the heat exchanger 24, thereby giving off heat to air which passes through this heat exchanger and thence into the cab unit's driver space. Warming of the cab air is thus effected. When the regulating valve 17 is closed and the compressor 34 is running, refrigerant flows through the third heat transfer unit 31 but no radiator liquid flows through the first heat transfer unit 11. In this case the medium in the second circuit 20 thus flows through the second heat transfer unit 21, thereby giving off heat to the refrigerant in the third circuit 30, and then through the heat exchanger 24, thereby absorbing heat from air which passes through this heat exchanger and thence into the cab unit's driver space. Cooling of the cab air is thus effected. In the embodiment depicted in Fig. 6, a heat exchanger 24 to warm cab air is incorporated in the second circuit 20 in series with the second heat transfer unit 21, and a heat exchanger 44 to cool cab air is incorporated in the fourth circuit 40 in series with the fourth heat transfer unit 41'. A radiator device 22 is also incorporated in the second circuit 20 in series with the second heat transfer unit 21 to cool the second medium by means of ambient air which passes through this radiator device. A circulation pump 23 is provided in the second circuit 20 to circulate the medium in this circuit, and a circulation pump 43 is provided in the fourth circuit 40 to circulate the medium in this circuit.

When the regulating valve 17 is open and the engine 7 is running, radiator liquid flows through the first heat transfer unit 11 and the medium in the second circuit 20 flows through the second heat transfer unit 21, thereby absorbing heat from the radiator liquid in the first circuit 10, and then through the heat exchanger 24, thereby giving off heat to air which passes through this heat exchanger and thence into the cab unit's driver space. Warming of the cab air is thus effected.

When the compressor 34 is running, refrigerant flows through the third heat transfer unit 31' and the medium in the fourth circuit 40 flows through the fourth heat transfer unit 41', thereby giving off heat to the refrigerant in the third circuit 30 and then through the heat exchanger 44, thereby absorbing heat from air which passes through this heat exchanger and thence into the cab unit's driver space. Cooling of the cab air is thus effected.

The embodiment according to Fig.6 makes it possible to use the third and fourth circuits 30, 40 to dry the cab air via the heat exchanger 44 of the fourth circuit and then to warm this dried cab air via the heat exchanger 24 in the second circuit. Alternatively, the heat exchanger 24 i n the second circuit 20 and the heat exchanger 44 in the fourth circuit 40 may be used one at a ti me to respectively warm the cab ai r and cool/dry the cab air.

An adjustable fan 9 is provided close to the aforesaid heat exchangers 24, 44 i n the cab unit 3 to drive air th rough each of them. The air driven th rough each of the heat exchangers 24, 44 comes either via an air intake from the vehicle's surrou ndings or via an air intake from the d river space.

The aforesaid radiator liquid cooler 1 2 is with advantage situated at the front of the vehicle and comprises one or more radiator elements for cooli ng the radiator liquid. Each radiator element has elongate pipelines, with cooling flanges connected to them, and the radiator liquid is led through these pipeli nes in order to give off heat via the pipeline walls and the cooling flanges to ambient air which passes th rough air passages between the pipelines. The radiator liquid is thus cooled by the ambient air passing between the pipeli nes. The cooling flow of ambient air th rough the air passages is generated by the vehicle's forward movement and/or by a fan. The aforesaid condensers 1 5, 35 are with advantage situated at the front of the vehicle and the cooling flow of ambient air th rough them is generated by the vehicle's forward movement and/or by a fan. In the embodiments according to Figs. 3a, 3b, 5 and 6, the first circuit 1 0 might alternatively be connected to, in order to cool , a gearbox of the vehicle instead of being connected to the vehicle's engi ne, in which case the medium in the first circuit would take with advantage the form of a cooling mediu m in the form of oil.

Each heat transfer unit 1 1 , 21 , 31 , 31 ' , 41 ' is provided with one or more pipelines or ducts made of material with good heat conductivity and a contact su rface which is intended for heat transfer to a cooperating heat transfer u nit and which is situated close to said pipelines/ducts to enable it with good effectiveness to receive heat from/give off heat to a mediu m which flows th rough the pipelines/ducts.

The motor vehicle according to the invention is preferably a heavy vehicle, e.g . a tractor unit or truck.

The invention is of cou rse in no way restricted to the embodiments described above, since many possibilities for modifications thereof are likely to be obvious to a specialist in the field without havi ng thereby to depart from the invention's basic concept such as defined in the attached claims.