Patent Description:
The vehicle industry is striving to reduce CO<NUM> emissions. Various alternatives to diesel and gasoline have been developed for energizing the vehicles. One such alternative is the use of hydrogen gas. The chemical energy of the hydrogen may, for example, be converted into mechanical energy in an internal combustion engine or into electric energy in fuel cells, in order to propel the vehicle. The hydrogen gas is normally stored in storage tanks provided on the vehicle.

<CIT> discloses a hydrogen-powered fuel cell truck with hydrogen gas tanks arranged behind the cab of the truck. A coolant circuit is provided for cooling the fuel cells. The coolant circuit comprises a heat exchanger arranged under the chassis. The available space underneath the chassis is rather limited, and therefore the available heat exchanger area is also rather limited. Fuel cells reject a lot of heat and should normally be cooled to around <NUM> or lower. With increasing cooling demands for newer generations of hydrogen fuel cells, larger heat exchanger areas would be desirable.

An object of the invention is to mitigate the drawbacks of the prior art. This and other object which will become apparent in the following are accomplished by a truck as defined in the accompanying independent claim.

According to a first aspect of the invention, the object is achieved by a truck, comprising.

The invention is based on the insight that by reducing the extension of the storage tanks in the lateral direction of the truck, i.e. by not allowing the storage tank to reach the at least one of the lateral sides of the truck (or to be aligned with at least one of the lateral sides of the cab) a volume behind the rear of the cab is made available for other purposes. In particular, the inventors have realized that such a freed volume, having a large vertical height behind the rear of the cab, may advantageously be used for cooling purposes. Thus, a wall comprising at least a part of a cooling arrangement, such as comprising a heat exchanger, may suitably be provided in the wall. Thus, such a wall enables the provision of a much larger heat exchanger area than in the prior art. Additional benefits, include that the heat exchanger is easier to keep clean and to avoid dirt from clogging any airflow passages extending therethrough. With cleaner air more efficient heat exchanger cores can be used.

It should be understood that in this application the directional term "vertical" is to be related to the vehicle as such, irrespectively if it stands on a flat ground surface or on an inclined surface such as on a hill side. Thus, the wheels will normally form part of the vertically lowest part of the truck. The longitudinal direction of the truck extends from the front of the truck to the rear of the truck. Thus, the front and the rear of the cab are separated from each other along the longitudinal direction. The two lateral sides of the cab are separated from each other in the lateral direction, which extends transversely to the longitudinal and vertical directions. Thus, in for example <FIG>, which will be discussed in more detail below, the wall <NUM> may have a length L extending in the vertical direction of the truck, and a width W extending in the longitudinal direction of the truck. The wall <NUM> also may also have a thickness (perpendicular to the plane of the drawing) which extends in the lateral direction.

As will be discussed in connection with some exemplary embodiments, the truck may be provided with two substantially similar walls with parts of the cooling arrangement of different cooling arrangements. In such case, the two walls are suitably separated in the lateral direction and located on either side of the storage tanks. However, it is also conceivable to have only one such wall.

According to at least one exemplary embodiment, said wall has a length, a width and a thickness, wherein the length is greater than the width, and the width is greater than the thickness, wherein the length of the wall extends in the vertical direction of the truck, and the width of the wall extends in the longitudinal direction of the truck. Since there is no upper physical obstacle on the truck, the vertical extension of the wall may be made quite long, and the available space in the longitudinal direction (the space between the cab and for instance a trailer connected to the truck) is also quite large. Considering the fact that a heat exchanger have a rather small thickness, the wall may house a heat exchanger with quite a large heat exchanger area, thereby providing large cooling capacity to the energy conversion system, be it an internal combustion engine or fuel cells.

According to at least one exemplary embodiment, said wall has an inboard side facing the storage tanks, and an oppositely facing outboard side, wherein the outboard side substantially forms a continuation of one of the lateral sides of the cab. This is advantageous from an aerodynamic point of view, since it reduces the pressure drag which normally is present due to the large surface of the cab facing the main flow direction and the large wake resulting from the bluntness of the rear of the cab. This is further reflected in at least one exemplary embodiment, according to which said wall forms part of the aerodynamic kit of the truck.

According to at least one exemplary embodiment said wall is mounted directly or indirectly on the chassis of the truck, such as mounted to a rack for holding the storage tanks, which rack is attached to the chassis. Thus, the cooling arrangement containing wall may extend vertically upwards from the chassis. By connecting this wall to the chassis (directly or indirectly), the cab, if tiltable, may be tilted without disconnecting the wall. Suitably, the wall is placed at/near the lateral end/edge of the chassis. If two cooling arrangement containing walls are provided, then they may be placed at a respective opposite lateral end/edge of the chassis. A rack for holding the storage tanks may be attached to the chassis and may have an extension in the lateral direction of the truck, so that the outboard sides of cooling arrangement containing walls mounted to the rack are substantially aligned with the lateral ends/edges of the chassis.

According to at least one exemplary embodiment, the thickness of the wall is in the range of <NUM>-<NUM>, such as in the range of <NUM>-<NUM>, for example in the range of <NUM>-<NUM>. This is advantageous, since future safety regulations may potentially stipulate that hydrogen tanks should not extend all the way to the lateral sides of the truck, but for example be positioned at least <NUM> from the lateral sides of truck. It may be conceivable that, in some exemplary embodiments, some components protrude out from the wall on the inboard side. For instance, one or more motors that power one or more fans of a heat exchanger may protrude out from the wall, and even a portion of such fans may in some exemplary embodiments protrude out from the wall.

According to at least one exemplary embodiment, said wall comprises one or more energy absorbing structures forming collision protection for the storage tanks. Suitably, the wall comprises or consists of more yielding material than the material of the storage tanks. Thus, in case of an accidental lateral collision, the collision energy will at least initially be absorbed by the wall, thereby providing increased protection of the storage tanks. Suitably, the wall may comprise a deformable material, wherein collision energy may at least partly be taken up by the deformation of the wall.

According to at least one exemplary embodiment, the truck is configured to tow a trailer, wherein said wall is configured to extend between the rear of the cab and a towed trailer. Thus, the wall may cover completely or at least partly the lateral opening that is normally available between the rear of the cab and the towed trailer. This is advantageous from an aerodynamic perspective. Suitably, there may be two such cooling arrangement containing walls, one on each lateral side of the storage tanks.

According to at least one exemplary embodiment, the energy conversion system comprises fuel cells configured to generate electricity. Although the general inventive principle could be used for cooling other energy converting systems, the modern fuel cells assemblies are particularly advantageous, since they may require high cooling capacity, which the present inventive concept can cater for by means of a cooling arrangement containing wall at the rear of the cab, enabling a large heat exchanger area to be contained therein.

According to at least one exemplary embodiment, the cooling arrangement comprises:.

As already mentioned, the truck may have two cooling arrangement containing walls, one on either side of the storage tanks. This is reflected in at least one exemplary embodiment, according to which said wall is a first wall, the truck further comprising a second wall provided behind the cab and laterally of the storage tanks, so that said first and second walls are located on a respective lateral side of the storage tank, wherein said second wall having its main extension in a vertical plane, wherein said second wall houses at least a part of said cooling arrangement or a different cooling arrangement. Thus, the first and second wall may comprise a respective heat exchanger, which may be connected to a common recirculation loop or may be connected to a respective recirculation loop. It should be understood, that in other exemplary embodiments, the truck may have one cooling arrangement containing wall at one lateral side of the chassis and another wall (for example for aerodynamic and/or crash-protecting purposes) at the opposite lateral side of the chassis.

Furthermore, it should be understood that the present inventive concept may be combined with other means for cooling the energy conversion system, for instance additional cooling arrangements, such as one or more heat exchangers provided under the cab.

<FIG> illustrates a truck <NUM> which comprises a cab <NUM> in which a driver may operate the truck <NUM>. The cab <NUM> has a front <NUM> and a rear <NUM>, and two opposite lateral sides <NUM> interconnecting the front <NUM> and the rear <NUM> of the cab <NUM>. A plurality of storage tanks <NUM> are secured behind the rear <NUM> of the cab <NUM>, wherein the storage tanks <NUM> are configured to contain hydrogen gas. The truck <NUM> comprises an energy conversion system (not shown) configured to receive hydrogen gas from the storage tanks <NUM> and to convert the chemical energy of the hydrogen into mechanical or electric energy.

<FIG> illustrates a truck <NUM> in accordance with at least one exemplary embodiment of the invention. Similarly to the truck <NUM> in <FIG>, the truck <NUM> in <FIG> has a cab <NUM>, with a front <NUM>, a rear <NUM> and two opposite lateral sides <NUM>. A plurality of storage tanks <NUM> are provided behind the rear <NUM> of the cab <NUM>. Suitably the storage tanks <NUM> may be held by a rack (not shown) attached to the chassis <NUM> of the truck <NUM>. The storage tanks <NUM> are configured to contain hydrogen gas. The truck <NUM> comprises an energy conversion system (not shown) configured to receive hydrogen gas from the storage tanks <NUM> and to convert the chemical energy of the hydrogen into mechanical or electric energy. The truck <NUM> comprises a number of road wheels <NUM>, herein illustrated as two pairs of wheels, however, in other embodiments there may be a different number of wheels, such as three pairs, four pairs or more.

The truck <NUM> in <FIG> further comprises a cooling arrangement (not shown in <FIG>) configured to cool the energy conversion system. A wall <NUM> is provided behind the cab <NUM> and laterally of the storage tanks <NUM>. The wall <NUM> has its main extension in a vertical plane (i.e. the plane of the drawing). The wall <NUM> houses at least a part of said cooling arrangement. Although <FIG> is a side view, it should be understood that there may be a corresponding second wall on the other lateral side of the storage tanks <NUM>, also behind the rear <NUM> of the cab <NUM>. Such a second wall may house another part of the cooling arrangement or a part of a separate second cooling arrangement. In the following discussion, reference will only be made to the wall <NUM> shown in <FIG>. However, it should be understood that the features discussed in relation to this wall <NUM>, may be equally applicable to the above mentioned second wall in embodiments having such a second wall.

The wall <NUM> has a length L, a width W, and a thickness T, wherein the length L is greater than the width W and the width W is greater than the thickness T. In other words, L > W > T. As illustrated in <FIG>, since there is no upper obstacle on the truck <NUM>, the length L of the wall <NUM> may suitably extend in the vertical direction of the truck <NUM>. The width W of the wall <NUM> may extend in the longitudinal direction of the truck <NUM>. The thickness T (not shown) of the wall <NUM> may thus extend in the lateral direction of the truck, i.e. perpendicularly to the plane of the drawing.

The wall <NUM> has an inboard side facing the storage tanks <NUM>, and an oppositely facing outboard side. Suitably, the outboard side may form a continuation of one of the lateral sides <NUM> of the cab. Thus, the outboard side of the wall <NUM> may suitably be aligned with the lateral side <NUM> of the cab <NUM> and form part of the aerodynamic kit of the truck <NUM>. The wall is hollow, such that between the inboard side and the outboard side of the wall <NUM>, there is a space for said part of the cooling arrangement.

The wall <NUM> may be directly or indirectly mounted on the chassis <NUM>. For instance, there may be provided a rack for holding the storage tanks <NUM> and the rack may be attached to the chassis <NUM>. The wall <NUM> may in such case suitably be mounted to the rack.

The thickness of the wall <NUM> may be in the range of <NUM>-<NUM>, such as in the range of <NUM>-<NUM>, for example in the range of <NUM>-<NUM>. For instance, from the inboard side to the outboard side, the wall <NUM> may span approximately <NUM>, leaving plenty of space in the lateral direction for the storage tanks <NUM>. As mentioned above, the wall <NUM> may comprise a part of the cooling arrangement for cooling the energy conversion system. The large area available for the wall <NUM>, and inside the wall, is particularly suitable for housing a heat exchanger. The core of a heat exchanger may be very thin, such as <NUM>-<NUM>, which may be held by a thicker frame. Fans may also fit inside the thin wall <NUM>. Thus, the thin wall <NUM> combined with the large available heat exchanger area, is beneficial for creating an efficient cooling of the energy conversion device, without any substantial compromising on the size of the storage tanks <NUM>. It may be conceivable that, in some exemplary embodiments, some components protrude out from the wall <NUM> on the inboard side. For instance, one or more motors that power one or more fans of a heat exchanger may protrude out from the wall <NUM>, and even a portion of such fans may in some exemplary embodiments protrude out from the wall <NUM>.

The wall <NUM> may suitably comprise one or more energy absorbing structures forming collision protection for the storage tanks <NUM>. For instance, the hollow wall <NUM> may comprise deformable material which absorbs at least a part of the energy at an impact, so that a reduced amount, or none, of the impact energy reaches the storage tanks <NUM>. Accordingly, the hollow, cooling arrangement containing wall <NUM> has multiple benefits. In addition to providing a large accessible area for efficient cooling, it may also improve the aerodynamic characteristics of the truck <NUM> as well as providing collision protection.

The truck <NUM> comprises a connector <NUM> for connecting and towing a trailer. The wall <NUM> may thus be configured to extend between the rear <NUM> of the cab <NUM> and a towed trailer.

Suitably, the cab <NUM>, the wall <NUM> and the towed trailer may form a substantially continuous contour, with only minor gaps in between, improving the aerodynamic characteristics of the complete combined vehicle.

The energy conversion system may suitably comprise fuel cells configured to generate electricity. However, it should be understood that the general inventive concept, including the wall <NUM> that houses part of the cooling arrangement, may be used for cooling other energy conversion systems as well. In the exemplary embodiment of the energy system comprising fuel cells, the hydrogen gas contained in the storage tanks <NUM> are supplied to the fuel cells for converting the chemical energy of the hydrogen to electric energy.

<FIG> illustrates schematically a cooling arrangement <NUM> of the truck, in accordance with at least one exemplary embodiment of the invention. The illustration is made relative to a schematic outline of certain parts of a truck, however, it should be understood that the specific location of the components may be placed differently than in the exemplary illustration. In the illustration a cab <NUM> of the truck, a connector <NUM> for towing a trailer and a pair of rear wheels <NUM> of the truck have been schematically indicated. At the cab <NUM>, for example under the cab <NUM>, there may be provided an energy conversion system, such as comprising a stack of fuel cells <NUM>. Behind the cab <NUM>, there are provided storage tanks <NUM> for containing hydrogen gas which may be supplied to the stack of fuel cells <NUM>. Although not illustrated, the storage tanks <NUM> may suitably be held by a rack attached to the chassis, as previously mentioned.

The cooling arrangement <NUM> in <FIG> may comprise a heat exchanger <NUM> located within the hollow wall <NUM> illustrated in <FIG>. The cooling arrangement <NUM> also comprises a cooling passage <NUM> for circulating cooling liquid. The cooling passage <NUM> extends from the heat exchanger <NUM>, exits the wall (such as a wall <NUM> in <FIG>), and passes along the stack of fuel cells <NUM> for transporting heat away from the stack of fuel cells <NUM>.

A pump <NUM> is provided to pump water that has taken up heat from the stack of fuel cells <NUM>. Downstream of the pump <NUM> there may be provided a thermostat <NUM> which senses the temperature of the water in the conduit and if the temperature is above a predefined value the water is led back to the heat exchanger <NUM> to be cooled down before returning to the stack of fuel cells <NUM>. If the thermostat <NUM> determines that the temperature of the water is still low enough, it may be returned to the stack of fuel cells <NUM> without being led through the heat exchanger <NUM>.

<FIG> illustrates schematically a cooling arrangement <NUM> of the truck, in accordance with another exemplary embodiment of the invention. In this exemplary embodiment, there are provided two heat exchangers <NUM>, <NUM>. A first heat exchanger <NUM> may be arranged, for instance under the cab <NUM>, and a second heat exchanger <NUM> may be arranged behind the rear of the cab <NUM> within the hollow wall <NUM> of <FIG>, similarly to the heat exchanger <NUM> in <FIG>. As will be explained, the second heat exchanger <NUM> may be used in connection with at least two different modes of operation.

The cooling arrangement <NUM> in <FIG> may actually be regarded as a combined cooling and water braking system in accordance with at least one exemplary embodiment of the invention. The illustrated exemplary embodiment of the cooling arrangement <NUM> comprises a first water recirculation loop <NUM>. The first heat exchanger <NUM>, which forms part of the first water recirculation loop <NUM>, is configured to cool water flowing in the first water recirculation loop <NUM>. The first water recirculation loop <NUM> comprises a water conduit for transporting heat away from the stack of fuel cells <NUM>.

The illustrated exemplary embodiment of the cooling arrangement <NUM> also comprises a second water recirculation loop <NUM>. The second water recirculation loop <NUM> has said second heat exchanger <NUM> configured to cool water flowing in the second water recirculation loop <NUM>.

Before going into the details of the second water recirculation loop <NUM>, it should be noticed that the illustrated exemplary embodiment of the cooling arrangement <NUM> also comprises a retarder <NUM>. The retarder <NUM> is configured to be coupled the pair of rear wheels <NUM> of the truck. The retarder <NUM> is switchable between an inactive state and an active state. In the inactive state the retarder <NUM> does not affect the rotation speed of the wheels <NUM>. In the active state the retarder <NUM> causes the rotational speed of the wheels <NUM> to be reduced.

Turning back to the details of the second water recirculation loop <NUM>, it comprises a first water conduit portion <NUM> and a second water conduit portion <NUM>. The first water conduit portion <NUM> connects the second heat exchanger <NUM> and the retarder <NUM> for enabling water braking when the retarder <NUM> is in its active state. The second water conduit portion <NUM> extends from the second heat exchanger <NUM> for transporting heat away from the stack of fuel cells <NUM>. The second water conduit portion <NUM> may be closed, for instance by means of a first valve <NUM>. The second water conduit portion <NUM> may suitably also be closed by means of a second valve <NUM>. The first valve <NUM> is located downstream of the second heat exchanger <NUM> and upstream of the stack of fuel cells <NUM>. The second valve <NUM> is located downstream of the stack of fuel cells <NUM> and upstream of the second heat exchanger <NUM>.

The cooling arrangement <NUM> is switchable between a first mode of operation and a second mode of operation. In the first mode of operation the retarder <NUM> is in the inactive state and the second water conduit portion <NUM> of the second water recirculation loop <NUM> together with the water conduit of the first water recirculation loop <NUM> transport heat away from the stack of fuel cells <NUM>. Thus, in the illustrated exemplary embodiment, the first and the second valves <NUM>, <NUM> are open to allow the water to recirculate via the second heat exchanger <NUM> to the stack of fuel cells <NUM>. As illustrated in <FIG>, the first and the second water recirculation loops <NUM>, <NUM> may have a common section <NUM> from the stack of fuel cells <NUM> to the thermostat <NUM> and then downstream of the thermostat <NUM> be divided into two separate sections at a branching point <NUM>. However, in other exemplary embodiments, the first and the second water recirculation loops may exit as separate sections from the stack of fuel cells and two separate pumps and thermostats may be provided for the respective recirculation loop.

In the second mode of operation, the retarder <NUM> is in the active state and the water conduit of the first water recirculation loop <NUM> transports heat away from the stack of fuel cells <NUM>, whereas the second water conduit portion <NUM> of the second water recirculation loop <NUM> is closed, preventing water to flow from the second heat exchanger <NUM> to the stack of fuel cells <NUM>. Thus, in the second mode of operation the first valve <NUM> is closed. Suitably, in the illustrated exemplary embodiment, the second valve <NUM> is also closed, so as to avoid losing water from the first water recirculation loop <NUM> to the second water recirculation loop <NUM>.

Suitably, the cooling arrangement <NUM> may comprise a control unit <NUM> configured to perform the switching between said first mode of operation and said second mode of operation. The control unit <NUM> may thus be operatively connected to the first valve <NUM>, the second valve <NUM> and the retarder <NUM>, in order to control the opening and closing of the first and second valves <NUM>, <NUM>, and the activating and inactivating of the retarder <NUM>. In addition to controlling the just mentioned components, the control unit <NUM> may suitably be operatively connected to control and/or communicate with other components as well, such as for instance the pump <NUM> and/or the thermostat <NUM>.

The control unit <NUM> may comprise or may be comprised in a processing circuitry. The processing circuitry may include a microprocessor, microcontroller, programmable digital signal processor or another programmable device. The processing circuitry may also, or instead, include an application specific integrated circuit, a programmable gate array or programmable array logic, a programmable logic device, or a digital signal processor. Where the processing circuitry includes a programmable device such as the microprocessor, microcontroller or programmable digital signal processor mentioned above, the processor may further include computer executable code that controls operation of the programmable device. It should be understood that all or some parts of the functionality provided by means of the processing circuitry may be at least partly integrated with the control unit <NUM>.

Because the temporary water braking (i.e. the second mode of operation) causes a strong rise in temperature of the water in the first water conduit portion <NUM> of the second recirculation loop <NUM>, it may be recommendable to postpone the opening of the second water conduit portion <NUM> of the second recirculation loop <NUM> until the temperature has fallen sufficiently to be able to once again be used for cooling the stack of fuel cells <NUM>. Therefore, the cooling arrangement <NUM> may suitably be further operable in a third mode of operation, which is an intermediate mode of operation before switching back from the second mode of operation to the first mode of operation. In the third mode of operation, the retarder <NUM> is, or has been, switched from the active state (used in the second mode of operation) to the inactive state, and the second water conduit portion <NUM> of the second water recirculation loop <NUM> is maintained closed. Thus, the second heat exchanger <NUM> is allowed to cool down the high temperature water circulating in the first water conduit portion <NUM> before the second water conduit portion <NUM> is opened again (and thus before the first valve <NUM> and the second valve <NUM> is opened again in <FIG>).

The control unit <NUM> may be configured to switch from the third mode of operation when the temperature of the water in the second water recirculation loop <NUM>, in particular in the first water conduit portion <NUM>, has fallen to or below a predetermined value. Suitably, a temperature sensor (not shown) may be provided in the first water conduit portion, and such a temperature sensor may suitably be operatively connected to the control unit <NUM>.

In at least some exemplary embodiments, during said third mode of operation, the retarder <NUM> may operate in a pumping mode, without providing water braking. Thus, after water braking, in the inactive state (i.e. inactive with respect to affecting the rotational speed of the wheels) the retarder <NUM> may pump the heated water in said first water conduit portion <NUM> of the second water recirculation loop <NUM> so that the water is recirculated through the second heat exchanger <NUM> for cooling. When the recirculated water has cooled down sufficiently, the system <NUM> may once again operate in the first mode of operation, opening the closed second water conduit portion <NUM>. In other exemplary embodiments, there may be provided a separate pump (not illustrated) in the first water conduit portion <NUM> of the second water recirculation loop <NUM> for pumping the water during the third mode of operation of the system. According to at least some exemplary embodiments, there may be provided a separate pump for providing water to the retarder <NUM> also in the second mode of operation of the system <NUM>, i.e. when the retarder <NUM> is in its water braking active state. Thus, the retarder <NUM> itself does not necessarily need any pumping functionality at all, but may in exemplary embodiments rely upon a separate pump in the first water conduit portion <NUM> of the second water recirculation loop <NUM>. The control unit <NUM> may suitably be operatively connected to control such a separate pump.

Claim 1:
A truck (<NUM>), comprising
- a cab (<NUM>, <NUM>, <NUM>) having a front (<NUM>) and a rear (<NUM>), and further having two opposite lateral sides (<NUM>) interconnecting the front and the rear of the cab,
- a plurality of storage tanks (<NUM>, <NUM>, <NUM>) secured behind the rear of the cab, wherein the storage tanks are configured to contain hydrogen gas,
- an energy conversion system (<NUM>, <NUM>) configured to receive hydrogen gas from the storage tanks and to convert the chemical energy of the hydrogen into mechanical or electric energy,
- a cooling arrangement (<NUM>, <NUM>) configured to cool the energy conversion system, characterized by
- a wall (<NUM>) provided behind the cab and laterally of the storage tanks, the wall having its main extension in a vertical plane, wherein said wall houses at least a part of said cooling arrangement, wherein the wall has an inboard side facing the storage tanks, and an oppositely facing outboard side, wherein the wall is hollow, such that between the inboard side and the outboard side of the wall, there is a space for said part of said cooling arrangement.